Store user metadata

The Signaling storage service enables you to store and share contextual user data in your app, such as name, date-of-birth, avatar, and connections. When user metadata is set, updated, or deleted, the SDK triggers a storage event notification. Other users in the channel receive this notification within 100ms and use the information according to your business logic.

Understand the tech

Use metadata enables you to store and share user level information. A set of user metadata facilitates business-level data storage and real-time notifications. Each user has only one set of user metadata, but each set may contain multiple metadata items. For relevant restrictions, refer to the API usage restrictions. Each metadata item has key, value, and revision properties.

User metadata is stored permanently in the Signaling database. The data persists even after a user logs out. You must explicitly delete it to remove it from the database. This feature impacts your storage billing. Refer to Pricing for details.

Prerequisites

Ensure that you have:

• Integrated the Signaling SDK in your project .
• Implemented the framework functionality from the SDK quickstart page.
• Enabled storage in Storage configuration.

Implement user metadata storage

The section shows you to implement user metadata storage in your Signaling app.

Set user metadata

To create a new metadata item for the user, or to update the value of am existing item, call setUserMetadata. This method creates a new item in the user metadata if the specified key does not exist, or overwrites the associated value if a metadata item with the specified key already exists.

The following example saves a set of metadata items for a specified user. It configures the options parameter to add timestamp and modifier information to each metadata item.

const Name = {
    key : "Name",
    value : "Tony"
};

const Age = {
    key : "Age",
    value : "40"
};

const Avatar = {
    key : "Avatar",
    value : "https://your-domain/avatar/tong.png"
};

const data = [Name, Age, avatar];

const options = { userId : "Tony", addTimeStamp : ture, addUserId : true };

try {
    const result = await rtm.storage.setUserMetadata(data, options);
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

The sample code relies on the await/async programming model. Enclose it within an asynchronous function for proper execution. When the call is successful, the SDK returns the following data structure:

{
    timestamp : 18770098911,   // Timestamp of successful operation
    userId : "Tony",           // Username
    totalCount : 3             // Number of Metadata Items
}

Additionally, Signaling triggers a storage event notification of event type UPDATE within 100 ms to inform all users who have subscribed to the this user's metadata.

Get user metadata

To retrieve all metadata items associated with a specific user, call getUserMetadata. Refer to the following example:

try {
    const result = await rtm.storage.getUserMetadata({ userId: "Tony" });
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

You can also leave the userId parameter blank to get the local user's metadata:

try {
    const result = await rtm.storage.getUserMetadata();
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

Signaling SDK returns the following data structure:

{
    majorRevision: 734874892,
    metadata:{
        {
            key:"Name",
            value:"Tony",
            revision:734874872,
            updateTs:1688978391900,
            authorUid:"Tony"
        },
        {
            key:"Age",
            value:"40",
            revision:734874862,
            updated:1688978390900,
            authorUid:"Tony"
        },
        {
            key:"Avatar",
            value:"https://your-domain/avatar/tony.png",
            revision:734874812,
            updated:1688978382900,
            authorUid:"Tony"
        }
    }
}

Update user metadata

To modify existing metadata items, call updateUserMetadata. If the metadata item does not exist, the SDK returns an error. This method is useful for business use-cases that require permission control on creating new metadata items. For example, the admin defines the user metadata fields and users may only update the values.

The following example updates the value of an existing metadata item:

const Age = {
    key : "Age",
    value : "45"
};

const data = [Age];
const options = { userId : "Tony", addTimeStamp : ture, addUserId : true };

try {
    const result = await rtm.storage.updateUserMetadata(data, options);
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

When the call is successful, the SDK returns the following data structure:

{
    timestamp : 18770098911,   // Timestamp of successful operation
    userId : "Tony",           // Username
    totalCount : 3             // Number of Metadata Items
}

Additionally, Signaling triggers a storage event notification of event type UPDATE within 100 ms to inform all users who have subscribed to the this user's metadata.

Delete user metadata

To delete metadata items that are no longer required, call removeUserMetadata. Refer to the following sample code:

const Age = {
    key : "Age",
};

const data = [Age];

const options = { userId: "Tony", data : data };

try {
    const result = await rtm.storage.removeUserMetadata(options);
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

Setting the value for a metadata item that is being deleted has no effect.

Signaling triggers a storage event notification of event type UPDATE within 100 ms to inform all users who have subscribed to the this user's metadata.

To delete the entire set of metadata for a user, do not add any metadata items when calling removeUserMetadata. Refer to the following sample code:

try {
    const result = await rtm.storage.removeUserMetadata();
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

Receive storage event notifications

To receive storage event notifications, implement an event listener. See event listeners for details. You only receive user metadata update notifications for users that you have subscribed to.

Event notification mode

Currently, Signaling only supports the full data update mode. This means that when a user's metadata is updated, the data field in the event notification contains all the metadata of the user.

Subscribe to a user's metadata

To monitor updates to a user's metadata, you subscribe to their metadata. Refer to the following sample code:

try {
    const result = await rtm.storage.subscribeUserMetadata("Tony");
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

When there are changes in the user metadata, Signaling triggers a storage event notification of event type UPDATE within 100 ms to inform all users who have subscribed to this user's metadata.

Unsubscribe from a user's metadata

When you no longer need to receive notifications about a user's metadata updates, unsubscribe from the users's metadata. Refer to the following sample code:

try {
    const result = await rtm.storage.unsubscribeUserMetadata("Tony");
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

Version control

Signaling integrates compare-and-set (CAS) version control to manage metadata updates. CAS is a concurrency control mechanism to ensure that updates to a shared resource occur only if the resource is in an expected state. The mechanism works as follows:

1. The client reads the current version of a data item.
2. Before making an update, the client compares the current version with the last read version number.
3. If the versions match, the client proceeds with the update and increments the version number. If they do not match, the update is aborted.

CAS version control is useful in use-cases that require concurrency management. For instance, consider a dating application where only one user may engage in a chat session with a host. When multiple users attempt to join, only the first request is successful.

The CAS version control feature provides two independent version control parameters. Set one or more of these values according to the needs of your business use-case:

• majorRevision property in MetadataOptions method: Enable version number verification of the entire set of channel metadata.

• revision property of a MetadataItem[]: Enable version number verification of a single metadata item.

When setting user metadata, or a single user metadata item, use the revision attribute to enable or disable version control as follows:

• To disable CAS verification, use the default value of -1 for the revision parameter.

• To enable CAS verification, set the majorRevision or the revision parameter to a positive integer. The SDK updates the corresponding value after successfully verifying the revision number. If the specified revision number does not match the latest revision number in the database, the SDK returns an error.

The following code snippet demonstrates how to employ majorRevision and revision for updating user metadata and metadata items:

const avatar = {
    key : "Avatar",
    value : "https://your-domain/avatar/tony.png",
    revision : 734874812
};

const data = [sessionRequest];

const options = {
    userId : "Tony",
    addTimeStamp : ture,
    addUserId: true,
    majorRevision : 734874892
};

try {
    const result = await rtm.storage.updateUserMetadata(data, options);
    console.log(JSON.stringify(result));
} catch (status) {
    console.log(JSON.stringify(status));
}

In this example, CAS verification for user metadata and metadata items is enabled by setting majorRevision and revision parameters to positive integers. Upon receiving the update call request, Signaling first verifies the provided major revision number against the latest value in the database. If there's a mismatch, it returns an error; if the values match, Signaling verifies the revision number for each metadata item using a similar logic.

Reference

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

API reference

• setUserMetaData

• getUserMetadata

• removeUserMetadata

• updateUserMetadata

• subscribeUserMetadata

• unsubscribeUserMetadata

• Metadata

• Event listeners

The Signaling storage service enables you to store and share contextual user data in your app, such as name, date-of-birth, avatar, and connections. When user metadata is set, updated, or deleted, the SDK triggers a storage event notification. Other users in the channel receive this notification within 100ms and use the information according to your business logic.

Understand the tech

Use metadata enables you to store and share user level information. A set of user metadata facilitates business-level data storage and real-time notifications. Each user has only one set of user metadata, but each set may contain multiple metadata items. For relevant restrictions, refer to the API usage restrictions. Each metadata item has key, value, and revision properties.

User metadata is stored permanently in the Signaling database. The data persists even after a user logs out. You must explicitly delete it to remove it from the database. This feature impacts your storage billing. Refer to Pricing for details.

Prerequisites

Ensure that you have:

• Integrated the Signaling SDK in your project .
• Implemented the framework functionality from the SDK quickstart page.
• Enabled storage in Storage configuration.

Implement user metadata storage

The section shows you to implement user metadata storage in your Signaling app.

Set user metadata

To create a new metadata item for the user, or to update the value of am existing item, call setUserMetadata. This method creates a new item in the user metadata if the specified key does not exist, or overwrites the associated value if a metadata item with the specified key already exists.

The following example saves a set of metadata items for a specified user. It configures the options parameter to add timestamp and modifier information to each metadata item.

Metadata metadata = new Metadata();
metadata.getItems().add(new MetadataItem("Name", "Tony"));
metadata.getItems().add(new MetadataItem("Age", "40"));
metadata.getItems().add(new MetadataItem("Avatar", "https://your-domain/avatar/tony.png"));

MetadataOptions options = new MetadataOptions();
options.setRecordTs(true);
options.setRecordUserId(true);

mRtmClient.getStorage().setUserMetadata("Tony", metadata, options, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "Set user metadata success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, "Failed to set user metadata: " + errorInfo.toString());
    }
});

val metadata = Metadata().apply {
    items.add(MetadataItem("Name", "Tony"))
    items.add(MetadataItem("Age", "40"))
    items.add(MetadataItem("Avatar", "https://your-domain/avatar/tony.png"))
}

val options = MetadataOptions().apply {
    setRecordTs(true)
    setRecordUserId(true)
}

mRtmClient.getStorage().setUserMetadata("Tony", metadata, options, object : ResultCallback<Void> {
    override fun onSuccess(responseInfo: Void) {
        log(CALLBACK, "Set user metadata success")
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, "Failed to set user metadata: " + errorInfo.toString())
    }
})

The onSuccess callback notifies you of the successful completion of the storage operation. Additionally, Signaling triggers an onStorageEvent notification of event type UPDATE within 100 ms to inform all users who have subscribed to the this user's metadata.

Get user metadata

To retrieve all metadata items associated with a specific user, call getUserMetadata. Refer to the following example:

mRtmClient.getStorage().getUserMetadata("Tony", new ResultCallback<Metadata>() {
    @Override
    public void onSuccess(Metadata data) {
        log(CALLBACK, "Get user metadata success");
        log(INFO, "Major revision: " + data.getMajorRevision());
        for (MetadataItem item : data.getItems()) {
            log(INFO, item.toString());
        }
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, "Failed to get user metadata: " + errorInfo.toString());
    }
});

mRtmClient.getStorage().getUserMetadata("Tony", object : ResultCallback<Metadata> {
    override fun onSuccess(data: Metadata) {
        log(CALLBACK, "Get user metadata success")
        log(INFO, "Major revision: " + data.majorRevision)
        data.items.forEach { item ->
            log(INFO, item.toString())
        }
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, "Failed to get user metadata: " + errorInfo.toString())
    }
})

You can also leave the userId parameter blank to get the local user's metadata:

mRtmClient.getStorage().getUserMetadata("", new ResultCallback<Metadata>() {
    @Override
    public void onSuccess(Metadata data) {
        log(CALLBACK, "Get user metadata success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

mRtmClient.getStorage().getUserMetadata("", object : ResultCallback<Metadata> {
    override fun onSuccess(data: Metadata) {
        log(CALLBACK, "Get user metadata success")
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, errorInfo.toString())
    }
})

Signaling SDK returns the following data structure:

{
    majorRevision: 734874892,
    metadata:{
        {
            key:"Name",
            value:"Tony",
            revision:734874872,
            updateTs:1688978391900,
            authorUid:"Tony"
        },
        {
            key:"Age",
            value:"40",
            revision:734874862,
            updated:1688978390900,
            authorUid:"Tony"
        },
        {
            key:"Avatar",
            value:"https://your-domain/avatar/tony.png",
            revision:734874812,
            updated:1688978382900,
            authorUid:"Tony"
        }
    }
}

Update user metadata

To modify existing metadata items, call updateUserMetadata. If the metadata item does not exist, the SDK returns an error. This method is useful for business use-cases that require permission control on creating new metadata items. For example, the admin defines the user metadata fields and users may only update the values.

The following example updates the value of an existing metadata item:

Metadata metadata = new Metadata();
metadata.getItems().add(new MetadataItem("Age", "45"));

mRtmClient.getStorage().updateUserMetadata("Tony", metadata, new MetadataOptions(true, true), new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "update user metadata success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

val metadata = Metadata().apply {
    items.add(MetadataItem("Age", "45"))
}

mRtmClient.getStorage().updateUserMetadata("Tony", metadata, MetadataOptions(true, true), object : ResultCallback<Void> {
    override fun onSuccess(responseInfo: Void?) {
        log(CALLBACK, "update user metadata success")
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, errorInfo.toString())
    }
})

The onSuccess callback notifies you of the successful completion of the storage operation. Additionally, Signaling triggers an onStorageEvent notification of event type UPDATE within 100 ms to inform all users who have subscribed to the this user's metadata.

Delete user metadata

To delete metadata items that are no longer required, call removeUserMetadata. Refer to the following sample code:

Metadata metadata = new Metadata();
MetadataItem age = new MetadataItem();
age.setKey("Age");
metadata.getItems().add(age);

mRtmClient.getStorage().removeUserMetadata("Tony", metadata, new MetadataOptions(true, true), new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "remove user metadata success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

val metadata = Metadata().apply {
    val age = MetadataItem().apply { key = "Age" }
    items.add(age)
}

mRtmClient.getStorage().removeUserMetadata("Tony", metadata, MetadataOptions(true, true), object : ResultCallback<Void> {
    override fun onSuccess(responseInfo: Void?) {
        log(CALLBACK, "remove user metadata success")
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, errorInfo.toString())
    }
})

Setting the value for a metadata item that is being deleted has no effect.

The onSuccess callback notifies you of the successful completion of the storage operation. Additionally, Signaling triggers an onStorageEvent notification of event type UPDATE within 100 ms to inform all users who have subscribed to the this user's metadata.

To delete the entire set of metadata for a user, do not add any metadata items when calling removeUserMetadata. Refer to the following sample code:

Metadata metadata = new Metadata();

mRtmClient.getStorage().removeUserMetadata("Tony", metadata, null, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "remove user metadata success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

val metadata = Metadata()

mRtmClient.getStorage().removeUserMetadata("Tony", metadata, null, object : ResultCallback<Void> {
    override fun onSuccess(responseInfo: Void?) {
        log(CALLBACK, "remove user metadata success")
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, errorInfo.toString())
    }
})

Receive storage event notifications

A storage event notification returns the StorageEvent data structure, which includes the RtmStorageEventType parameter.

To receive storage event notifications, implement an event listener. See event listeners for details. You only receive user metadata update notifications for users that you have subscribed to.

Event notification mode

Currently, Signaling only supports the full data update mode. This means that when a user's metadata is updated, the data field in the event notification contains all the metadata of the user.

Subscribe to a user's metadata

To monitor updates to a user's metadata, you subscribe to their metadata. Refer to the following sample code:

mRtmClient.getStorage().subscribeUserMetadata("Tony", new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "subscribe user metadata success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

mRtmClient.getStorage().subscribeUserMetadata("Tony", object : ResultCallback<Void> {
    override fun onSuccess(responseInfo: Void?) {
        log(CALLBACK, "subscribe user metadata success")
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, errorInfo.toString())
    }
})

When there are changes in the user metadata, Signaling triggers an onStorageEvent notification of event type UPDATE within 100 ms to inform all users who have subscribed to this user's metadata.

Unsubscribe from a user's metadata

When you no longer need to receive notifications about a user's metadata updates, unsubscribe from the users's metadata. Refer to the following sample code:

mRtmClient.getStorage().unsubscribeUserMetadata("Tony", new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "unsubscribe user metadata success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

mRtmClient.getStorage().unsubscribeUserMetadata("Tony", object : ResultCallback<Void> {
    override fun onSuccess(responseInfo: Void?) {
        log(CALLBACK, "unsubscribe user metadata success")
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, errorInfo.toString())
    }
})

Version control

Signaling integrates compare-and-set (CAS) version control to manage metadata updates. CAS is a concurrency control mechanism to ensure that updates to a shared resource occur only if the resource is in an expected state. The mechanism works as follows:

1. The client reads the current version of a data item.
2. Before making an update, the client compares the current version with the last read version number.
3. If the versions match, the client proceeds with the update and increments the version number. If they do not match, the update is aborted.

CAS version control is useful in use-cases that require concurrency management. For instance, consider a dating application where only one user may engage in a chat session with a host. When multiple users attempt to join, only the first request is successful.

The CAS version control feature provides two independent version control parameters. Set one or more of these values according to the needs of your business use-case:

• majorRevision parameter in the setMajorRevision method: Enable version number verification of the entire set of user metadata.

• revision parameter of a MetadataItem: Enable version number verification of a single metadata item.

When setting user metadata, or a single user metadata item, use the revision attribute to enable or disable version control as follows:

• To disable CAS verification, use the default value of -1 for the revision parameter.

• To enable CAS verification, set the majorRevision or the revision parameter to a positive integer. The SDK updates the corresponding value after successfully verifying the revision number. If the specified revision number does not match the latest revision number in the database, the SDK returns an error.

The following code snippet demonstrates how to employ majorRevision and revision for updating user metadata and metadata items:

Metadata metadata = new Metadata();
metadata.setMajorRevision(734874892);
metadata.getItems().add(new MetadataItem("Avatar", "https://your-domain/avatar/tony.png", 734874812));

MetadataOptions options = new MetadataOptions();
options.setRecordTs(true);
options.setRecordUserId(true);
mRtmClient.getStorage().updateUserMetadata("Tony", metadata, options, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "update user metadata success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

val metadata = Metadata()
metadata.majorRevision = 734874892
metadata.items.add(MetadataItem("Avatar", "https://your-domain/avatar/tony.png", 734874812))

val options = MetadataOptions()
options.recordTs = true
options.recordUserId = true
mRtmClient.getStorage().updateUserMetadata("Tony", metadata, options, object : ResultCallback<Void> {
    override fun onSuccess(responseInfo: Void?) {
        log(CALLBACK, "update user metadata success")
    }

    override fun onFailure(errorInfo: ErrorInfo) {
        log(ERROR, errorInfo.toString())
    }
})

In this example, CAS verification for user metadata and metadata items is enabled by setting majorRevision and revision parameters to positive integers. Upon receiving the update call request, Signaling first verifies the provided major revision number against the latest value in the database. If there's a mismatch, it returns an error; if the values match, Signaling verifies the revision number for each metadata item using a similar logic.

Reference

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

API reference

• setUserMetaData

• getUserMetadata

• removeUserMetadata

• updateUserMetadata

• subscribeUserMetadata

• unsubscribeUserMetadata

• Metadata

• Event listeners

The Signaling storage service enables you to store and share contextual user data in your app, such as name, date-of-birth, avatar, and connections. When user metadata is set, updated, or deleted, the SDK triggers a storage event notification. Other users in the channel receive this notification within 100ms and use the information according to your business logic.

Understand the tech

Use metadata enables you to store and share user level information. A set of user metadata facilitates business-level data storage and real-time notifications. Each user has only one set of user metadata, but each set may contain multiple metadata items. For relevant restrictions, refer to the API usage restrictions. Each metadata item has key, value, and revision properties.

User metadata is stored permanently in the Signaling database. The data persists even after a user logs out. You must explicitly delete it to remove it from the database. This feature impacts your storage billing. Refer to Pricing for details.

Prerequisites

Ensure that you have:

• Integrated the Signaling SDK in your project .
• Implemented the framework functionality from the SDK quickstart page.
• Enabled storage in Storage configuration.

Implement user metadata storage

The section shows you to implement user metadata storage in your Signaling app.

Set user metadata

To create a new metadata item for the user, or to update the value of am existing item, call setUserMetadata. This method creates a new item in the user metadata if the specified key does not exist, or overwrites the associated value if a metadata item with the specified key already exists.

The following example saves a set of metadata items for a specified user. It configures the options parameter to add timestamp and modifier information to each metadata item.

let metadata = AgoraRtmMetadata()!

let name = AgoraRtmMetadataItem()
name.key = "Name"
name.value = "Tony"

let age = AgoraRtmMetadataItem()
age.key = "Age"
age.value = "40"

let avatar = AgoraRtmMetadataItem()
avatar.key = "Avatar"
avatar.value = "https://your-domain/avatar/tong.png"

let itemArray = [name, age, avatar]
metadata.items = itemArray

let metadataOpt = AgoraRtmMetadataOptions()
metadataOpt.recordUserId = true
metadataOpt.recordTs = true

rtm.getStorage()?.setUserMetadata(userId: "Tony", data: metadata, options: metadataOpt) { response, errorInfo in
    if errorInfo == nil {
        print("setUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("setUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];

AgoraRtmMetadataItem* Name = [[AgoraRtmMetadataItem alloc] init];
Name.key = @"Name";
Name.value = @"Tony";
AgoraRtmMetadataItem* Age = [[AgoraRtmMetadataItem alloc] init];
Age.key = @"Age";
Age.value = @"40";
AgoraRtmMetadataItem* Avatar = [[AgoraRtmMetadataItem alloc] init];
Avatar.key = @"Avatar";
Avatar.value = @"https://your-domain/avatar/tony.png";

NSArray *item_array = [NSArray arrayWithObjects:Name, Age, Avatar];
metadata.items = item_array;

AgoraRtmMetadataOptions* metadata_opt = [[AgoraRtmMetadataOptions alloc] init];
metadata_opt.recordUserId = true;
metadata_opt.recordTs = true;
[[rtm getStorage] setUserMetadata:@"Tony" data:metadata options:metadata_opt completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"setUserMetadata success!!");
    } else {
        NSLog(@"setUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Get user metadata

To retrieve all metadata items associated with a specific user, call getUserMetadata. Refer to the following example:

// Retrieve user metadata
rtm.getStorage()?.getUserMetadata(userId: "Tony") { response, errorInfo in
    if errorInfo == nil {
        print("getUserMetadata success!!")
        if let data = response?.data {
            print("Retrieved metadata: \\(data)")
        }
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("getUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

[[rtm getStorage] getUserMetadata:@"Tony" completion:^(AgoraRtmGetMetadataResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"getUserMetadata success!!");
        AgoraRtmMetadata* data = response.data; //get storage data;
    } else {
        NSLog(@"getUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

You can also leave the userId parameter blank to get the local user's metadata:

rtm.getStorage()?.getUserMetadata(userId: "") { response, errorInfo in
    if errorInfo == nil {
        print("getUserMetadata success!!")
        if let data = response?.data {
        }
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("getUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

[[rtm getStorage] getUserMetadata:@"" completion:^(AgoraRtmGetMetadataResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"getUserMetadata success!!");
        AgoraRtmMetadata* data = response.data; //get storage data;
    } else {
        NSLog(@"getUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Signaling returns the following data structure:

{
    majorRevision: 734874892,
    metadata:{
        {
            key:"Name",
            value:"Tony",
            revision:734874872,
            updateTs:1688978391900,
            authorUid:"Tony"
        },
        {
            key:"Age",
            value:"40",
            revision:734874862,
            updated:1688978390900,
            authorUid:"Tony"
        },
        {
            key:"Avatar",
            value:"https://your-domain/avatar/tony.png",
            revision:734874812,
            updated:1688978382900,
            authorUid:"Tony"
        }
    }
}

Update user metadata

To modify existing metadata items, call updateUserMetadata. If the metadata item does not exist, the SDK returns an error. This method is useful for business use-cases that require permission control on creating new metadata items. For example, the admin defines the user metadata fields and users may only update the values.

The following example updates the value of an existing metadata item:

let metadata = AgoraRtmMetadata()!

let age = AgoraRtmMetadataItem()
age.key = "Age"
age.value = "45"

let itemArray = [age]
metadata.items = itemArray

let metadataOpt = AgoraRtmMetadataOptions()
metadataOpt.recordUserId = true
metadataOpt.recordTs = true

rtm.getStorage()?.updateUserMetadata(userId: "Tony", data: metadata, options: metadataOpt) { response, errorInfo in
    if errorInfo == nil {
        print("updateUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("updateUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];

AgoraRtmMetadataItem* Age = [[AgoraRtmMetadataItem alloc] init];
Age.key = @"Age";
Age.value = @"45";
NSArray *item_array = [NSArray arrayWithObjects:Age];
metadata.items = item_array;

AgoraRtmMetadataOptions* metadata_opt = [[AgoraRtmMetadataOptions alloc] init];
metadata_opt.recordUserId = true;
metadata_opt.recordTs = true;

[[rtm getStorage] updateUserMetadata:@"Tony" data:metadata options:metadata_opt completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"updateUserMetadata success!!");
    } else {
        NSLog(@"updateUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Delete user metadata

To delete metadata items that are no longer required, call removeUserMetadata. Refer to the following sample code:

let metadata = AgoraRtmMetadata()!

let age = AgoraRtmMetadataItem()
age.key = "Age"

let itemArray = [age]
metadata.items = itemArray

rtm.getStorage()?.removeUserMetadata(userId: "Tony", data: metadata, options: nil) { response, errorInfo in
    if errorInfo == nil {
        print("removeUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("removeUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];

AgoraRtmMetadataItem* Age = [[AgoraRtmMetadataItem alloc] init];
Age.key = @"Age";
NSArray *item_array = [NSArray arrayWithObjects:Age];
metadata.items = item_array;

[[rtm getStorage] removeUserMetadata:@"Tony" data:metadata options:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"removeUserMetadata success!!");
    } else {
        NSLog(@"removeUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

To delete the entire set of metadata for a user, do not add any metadata items when calling removeUserMetadata. Refer to the following sample code:

let metadata = AgoraRtmMetadata()!

// Remove user metadata
rtm.getStorage()?.removeUserMetadata(userId: "Tony", data: metadata, options: nil) { response, errorInfo in
    if errorInfo == nil {
        print("removeUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("removeUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];
[[rtm getStorage] removeUserMetadata:@"Tony" data:metadata options:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"removeUserMetadata success!!");
    } else {
        NSLog(@"removeUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Receive storage event notifications

A storage event notification returns the AgoraRtmStorageEvent data structure, which includes the AgoraRtmStorageEventType parameter.

To receive storage event notifications, implement an event listener. See event listeners for details. You only receive user metadata update notifications for users that you have subscribed to.

Event notification mode

Currently, Signaling only supports full data update mode. This means that when a user's metadata is updated, the data field in the event notification contains all the metadata of the user.

Subscribe to a user's metadata

To monitor updates to a user's metadata, you subscribe to their metadata. Refer to the following sample code:

rtm.getStorage()?.subscribeUserMetadata(userId: "Tony") { response, errorInfo in
    if errorInfo == nil {
        print("subscribeUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("subscribeUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

[[rtm getStorage] subscribeUserMetadata:@"Tony" completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"subscribeUserMetadata success!!");
    } else {
        NSLog(@"subscribeUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Unsubscribe from a user's metadata

When you no longer need to receive notifications about a user's metadata updates, unsubscribe from the users's metadata. Refer to the following sample code:

rtm.getStorage()?.unsubscribeUserMetadata(userId: "Tony") { response, errorInfo in
    if errorInfo == nil {
        print("unsubscribeUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("unsubscribeUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

[[rtm getStorage] unsubscribeUserMetadata:@"Tony" completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"unsubscribeUserMetadata success!!");
    } else {
        NSLog(@"unsubscribeUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Version control

Signaling integrates compare-and-set (CAS) version control to manage metadata updates. CAS is a concurrency control mechanism to ensure that updates to a shared resource occur only if the resource is in an expected state. The mechanism works as follows:

1. The client reads the current version of a data item.
2. Before making an update, the client compares the current version with the last read version number.
3. If the versions match, the client proceeds with the update and increments the version number. If they do not match, the update is aborted.

CAS version control is useful in use-cases that require concurrency management. For instance, consider a dating application where only one user may engage in a chat session with a host. When multiple users attempt to join, only the first request is successful.

The CAS version control feature provides two independent version control parameters. Set one or more of these values according to the needs of your business use-case:

• majorRevision parameter in the setMajorRevision method: Enable version number verification of the entire set of user metadata.

• revision parameter of a MetadataItem: Enable version number verification of a single metadata item.

When setting user metadata, or a single user metadata item, use the revision attribute to enable or disable version control as follows:

• To disable CAS verification, use the default value of -1 for the revision parameter.

• To enable CAS verification, set the majorRevision or the revision parameter to a positive integer. The SDK updates the corresponding value after successfully verifying the revision number. If the specified revision number does not match the latest revision number in the database, the SDK returns an error.

The following code snippet demonstrates how to employ majorRevision and revision for updating user metadata and metadata items:

let metadata = AgoraRtmMetadata()!

let sessionRequest = AgoraRtmMetadataItem()
// Set user avatar URL as metadata
sessionRequest.key = "Avatar"
sessionRequest.value = "https://your-domain/avatar/tony.png"
sessionRequest.revision = 734874812

// Create an array of metadata items
let itemArray = [sessionRequest]
metadata.items = itemArray
metadata.majorRevision = 734874892 // Set major revision

let metadataOptions = AgoraRtmMetadataOptions()
// Enable recording of user ID and timestamp
metadataOptions.recordUserId = true
metadataOptions.recordTs = true

// Update user metadata
rtm.getStorage().updateUserMetadata(userId: "Tony", data: metadata, options: metadataOptions) { response, errorInfo in
    if errorInfo == nil {
        print("updateUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("updateUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];
AgoraRtmMetadataItem* sessionRequest = [[AgoraRtmMetadataItem alloc] init];
sessionRequest.key = @"Avatar";
sessionRequest.value = @"https://your-domain/avatar/tony.png";
sessionRequest.revision = 734874812;
NSArray *item_array = [NSArray arrayWithObjects:sessionRequest];
metadata.items = item_array;
metadata.majorRevision = 734874892; //set major revision

AgoraRtmMetadataOptions* metadata_opt = [[AgoraRtmMetadataOptions alloc] init];
metadata_opt.recordUserId = true;
metadata_opt.recordTs = true;
[[rtm getStorage] updateUserMetadata:@"Tony" data:metadata options:metadata_opt completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"updateUserMetadata success!!");
    } else {
        NSLog(@"updateUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

In this example, CAS verification for user metadata and metadata items is enabled by setting majorRevision and revision parameters to positive integers. Upon receiving the update call request, Signaling first verifies the provided major revision number against the latest value in the database. If there's a mismatch, it returns an error; if the values match, Signaling verifies the revision number for each metadata item using a similar logic.

Reference

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

API reference

• Event listeners

The Signaling storage service enables you to store and share contextual user data in your app, such as name, date-of-birth, avatar, and connections. When user metadata is set, updated, or deleted, the SDK triggers a storage event notification. Other users in the channel receive this notification within 100ms and use the information according to your business logic.

Understand the tech

Use metadata enables you to store and share user level information. A set of user metadata facilitates business-level data storage and real-time notifications. Each user has only one set of user metadata, but each set may contain multiple metadata items. For relevant restrictions, refer to the API usage restrictions. Each metadata item has key, value, and revision properties.

User metadata is stored permanently in the Signaling database. The data persists even after a user logs out. You must explicitly delete it to remove it from the database. This feature impacts your storage billing. Refer to Pricing for details.

Prerequisites

Ensure that you have:

• Integrated the Signaling SDK in your project .
• Implemented the framework functionality from the SDK quickstart page.
• Enabled storage in Storage configuration.

Implement user metadata storage

The section shows you to implement user metadata storage in your Signaling app.

Set user metadata

To create a new metadata item for the user, or to update the value of am existing item, call setUserMetadata. This method creates a new item in the user metadata if the specified key does not exist, or overwrites the associated value if a metadata item with the specified key already exists.

The following example saves a set of metadata items for a specified user. It configures the options parameter to add timestamp and modifier information to each metadata item.

let metadata = AgoraRtmMetadata()!

let name = AgoraRtmMetadataItem()
name.key = "Name"
name.value = "Tony"

let age = AgoraRtmMetadataItem()
age.key = "Age"
age.value = "40"

let avatar = AgoraRtmMetadataItem()
avatar.key = "Avatar"
avatar.value = "https://your-domain/avatar/tong.png"

let itemArray = [name, age, avatar]
metadata.items = itemArray

let metadataOpt = AgoraRtmMetadataOptions()
metadataOpt.recordUserId = true
metadataOpt.recordTs = true

rtm.getStorage()?.setUserMetadata(userId: "Tony", data: metadata, options: metadataOpt) { response, errorInfo in
    if errorInfo == nil {
        print("setUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("setUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];

AgoraRtmMetadataItem* Name = [[AgoraRtmMetadataItem alloc] init];
Name.key = @"Name";
Name.value = @"Tony";
AgoraRtmMetadataItem* Age = [[AgoraRtmMetadataItem alloc] init];
Age.key = @"Age";
Age.value = @"40";
AgoraRtmMetadataItem* Avatar = [[AgoraRtmMetadataItem alloc] init];
Avatar.key = @"Avatar";
Avatar.value = @"https://your-domain/avatar/tony.png";

NSArray *item_array = [NSArray arrayWithObjects:Name, Age, Avatar];
metadata.items = item_array;

AgoraRtmMetadataOptions* metadata_opt = [[AgoraRtmMetadataOptions alloc] init];
metadata_opt.recordUserId = true;
metadata_opt.recordTs = true;
[[rtm getStorage] setUserMetadata:@"Tony" data:metadata options:metadata_opt completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"setUserMetadata success!!");
    } else {
        NSLog(@"setUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Get user metadata

To retrieve all metadata items associated with a specific user, call getUserMetadata. Refer to the following example:

// Retrieve user metadata
rtm.getStorage()?.getUserMetadata(userId: "Tony") { response, errorInfo in
    if errorInfo == nil {
        print("getUserMetadata success!!")
        if let data = response?.data {
            print("Retrieved metadata: \\(data)")
        }
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("getUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

[[rtm getStorage] getUserMetadata:@"Tony" completion:^(AgoraRtmGetMetadataResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"getUserMetadata success!!");
        AgoraRtmMetadata* data = response.data; //get storage data;
    } else {
        NSLog(@"getUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

You can also leave the userId parameter blank to get the local user's metadata:

rtm.getStorage()?.getUserMetadata(userId: "") { response, errorInfo in
    if errorInfo == nil {
        print("getUserMetadata success!!")
        if let data = response?.data {
        }
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("getUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

[[rtm getStorage] getUserMetadata:@"" completion:^(AgoraRtmGetMetadataResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"getUserMetadata success!!");
        AgoraRtmMetadata* data = response.data; //get storage data;
    } else {
        NSLog(@"getUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Signaling returns the following data structure:

{
    majorRevision: 734874892,
    metadata:{
        {
            key:"Name",
            value:"Tony",
            revision:734874872,
            updateTs:1688978391900,
            authorUid:"Tony"
        },
        {
            key:"Age",
            value:"40",
            revision:734874862,
            updated:1688978390900,
            authorUid:"Tony"
        },
        {
            key:"Avatar",
            value:"https://your-domain/avatar/tony.png",
            revision:734874812,
            updated:1688978382900,
            authorUid:"Tony"
        }
    }
}

Update user metadata

To modify existing metadata items, call updateUserMetadata. If the metadata item does not exist, the SDK returns an error. This method is useful for business use-cases that require permission control on creating new metadata items. For example, the admin defines the user metadata fields and users may only update the values.

The following example updates the value of an existing metadata item:

let metadata = AgoraRtmMetadata()!

let age = AgoraRtmMetadataItem()
age.key = "Age"
age.value = "45"

let itemArray = [age]
metadata.items = itemArray

let metadataOpt = AgoraRtmMetadataOptions()
metadataOpt.recordUserId = true
metadataOpt.recordTs = true

rtm.getStorage()?.updateUserMetadata(userId: "Tony", data: metadata, options: metadataOpt) { response, errorInfo in
    if errorInfo == nil {
        print("updateUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("updateUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];

AgoraRtmMetadataItem* Age = [[AgoraRtmMetadataItem alloc] init];
Age.key = @"Age";
Age.value = @"45";
NSArray *item_array = [NSArray arrayWithObjects:Age];
metadata.items = item_array;

AgoraRtmMetadataOptions* metadata_opt = [[AgoraRtmMetadataOptions alloc] init];
metadata_opt.recordUserId = true;
metadata_opt.recordTs = true;

[[rtm getStorage] updateUserMetadata:@"Tony" data:metadata options:metadata_opt completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"updateUserMetadata success!!");
    } else {
        NSLog(@"updateUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Delete user metadata

To delete metadata items that are no longer required, call removeUserMetadata. Refer to the following sample code:

let metadata = AgoraRtmMetadata()!

let age = AgoraRtmMetadataItem()
age.key = "Age"

let itemArray = [age]
metadata.items = itemArray

rtm.getStorage()?.removeUserMetadata(userId: "Tony", data: metadata, options: nil) { response, errorInfo in
    if errorInfo == nil {
        print("removeUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("removeUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];

AgoraRtmMetadataItem* Age = [[AgoraRtmMetadataItem alloc] init];
Age.key = @"Age";
NSArray *item_array = [NSArray arrayWithObjects:Age];
metadata.items = item_array;

[[rtm getStorage] removeUserMetadata:@"Tony" data:metadata options:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"removeUserMetadata success!!");
    } else {
        NSLog(@"removeUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

To delete the entire set of metadata for a user, do not add any metadata items when calling removeUserMetadata. Refer to the following sample code:

let metadata = AgoraRtmMetadata()!

// Remove user metadata
rtm.getStorage()?.removeUserMetadata(userId: "Tony", data: metadata, options: nil) { response, errorInfo in
    if errorInfo == nil {
        print("removeUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("removeUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];
[[rtm getStorage] removeUserMetadata:@"Tony" data:metadata options:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"removeUserMetadata success!!");
    } else {
        NSLog(@"removeUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Receive storage event notifications

A storage event notification returns the AgoraRtmStorageEvent data structure, which includes the AgoraRtmStorageEventType parameter.

To receive storage event notifications, implement an event listener. See event listeners for details. You only receive user metadata update notifications for users that you have subscribed to.

Event notification mode

Currently, Signaling only supports full data update mode. This means that when a user's metadata is updated, the data field in the event notification contains all the metadata of the user.

Subscribe to a user's metadata

To monitor updates to a user's metadata, you subscribe to their metadata. Refer to the following sample code:

rtm.getStorage()?.subscribeUserMetadata(userId: "Tony") { response, errorInfo in
    if errorInfo == nil {
        print("subscribeUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("subscribeUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

[[rtm getStorage] subscribeUserMetadata:@"Tony" completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"subscribeUserMetadata success!!");
    } else {
        NSLog(@"subscribeUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Unsubscribe from a user's metadata

When you no longer need to receive notifications about a user's metadata updates, unsubscribe from the users's metadata. Refer to the following sample code:

rtm.getStorage()?.unsubscribeUserMetadata(userId: "Tony") { response, errorInfo in
    if errorInfo == nil {
        print("unsubscribeUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("unsubscribeUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

[[rtm getStorage] unsubscribeUserMetadata:@"Tony" completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"unsubscribeUserMetadata success!!");
    } else {
        NSLog(@"unsubscribeUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

Version control

Signaling integrates compare-and-set (CAS) version control to manage metadata updates. CAS is a concurrency control mechanism to ensure that updates to a shared resource occur only if the resource is in an expected state. The mechanism works as follows:

1. The client reads the current version of a data item.
2. Before making an update, the client compares the current version with the last read version number.
3. If the versions match, the client proceeds with the update and increments the version number. If they do not match, the update is aborted.

CAS version control is useful in use-cases that require concurrency management. For instance, consider a dating application where only one user may engage in a chat session with a host. When multiple users attempt to join, only the first request is successful.

The CAS version control feature provides two independent version control parameters. Set one or more of these values according to the needs of your business use-case:

• majorRevision parameter in the setMajorRevision method: Enable version number verification of the entire set of user metadata.

• revision parameter of a MetadataItem: Enable version number verification of a single metadata item.

When setting user metadata, or a single user metadata item, use the revision attribute to enable or disable version control as follows:

• To disable CAS verification, use the default value of -1 for the revision parameter.

• To enable CAS verification, set the majorRevision or the revision parameter to a positive integer. The SDK updates the corresponding value after successfully verifying the revision number. If the specified revision number does not match the latest revision number in the database, the SDK returns an error.

The following code snippet demonstrates how to employ majorRevision and revision for updating user metadata and metadata items:

let metadata = AgoraRtmMetadata()!

let sessionRequest = AgoraRtmMetadataItem()
// Set user avatar URL as metadata
sessionRequest.key = "Avatar"
sessionRequest.value = "https://your-domain/avatar/tony.png"
sessionRequest.revision = 734874812

// Create an array of metadata items
let itemArray = [sessionRequest]
metadata.items = itemArray
metadata.majorRevision = 734874892 // Set major revision

let metadataOptions = AgoraRtmMetadataOptions()
// Enable recording of user ID and timestamp
metadataOptions.recordUserId = true
metadataOptions.recordTs = true

// Update user metadata
rtm.getStorage().updateUserMetadata(userId: "Tony", data: metadata, options: metadataOptions) { response, errorInfo in
    if errorInfo == nil {
        print("updateUserMetadata success!!")
    } else {
        if let errorCode = errorInfo?.errorCode, let reason = errorInfo?.reason {
            print("updateUserMetadata failed, errorCode: \\(errorCode), reason: \\(reason)")
        }
    }
}

AgoraRtmMetadata* metadata = [[AgoraRtmMetadata alloc] init];
AgoraRtmMetadataItem* sessionRequest = [[AgoraRtmMetadataItem alloc] init];
sessionRequest.key = @"Avatar";
sessionRequest.value = @"https://your-domain/avatar/tony.png";
sessionRequest.revision = 734874812;
NSArray *item_array = [NSArray arrayWithObjects:sessionRequest];
metadata.items = item_array;
metadata.majorRevision = 734874892; //set major revision

AgoraRtmMetadataOptions* metadata_opt = [[AgoraRtmMetadataOptions alloc] init];
metadata_opt.recordUserId = true;
metadata_opt.recordTs = true;
[[rtm getStorage] updateUserMetadata:@"Tony" data:metadata options:metadata_opt completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"updateUserMetadata success!!");
    } else {
        NSLog(@"updateUserMetadata failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

In this example, CAS verification for user metadata and metadata items is enabled by setting majorRevision and revision parameters to positive integers. Upon receiving the update call request, Signaling first verifies the provided major revision number against the latest value in the database. If there's a mismatch, it returns an error; if the values match, Signaling verifies the revision number for each metadata item using a similar logic.

Reference

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

API reference

• Event listeners

The Signaling storage service enables you to store and share contextual user data in your app, such as name, date-of-birth, avatar, and connections. When user metadata is set, updated, or deleted, the SDK triggers a storage event notification. Other users in the channel receive this notification within 100ms and use the information according to your business logic.

Understand the tech

Use metadata enables you to store and share user level information. A set of user metadata facilitates business-level data storage and real-time notifications. Each user has only one set of user metadata, but each set may contain multiple metadata items. For relevant restrictions, refer to the API usage restrictions. Each metadata item has key, value, and revision properties.

User metadata is stored permanently in the Signaling database. The data persists even after a user logs out. You must explicitly delete it to remove it from the database. This feature impacts your storage billing. Refer to Pricing for details.

Prerequisites

Ensure that you have:

• Integrated the Signaling SDK in your project .
• Implemented the framework functionality from the SDK quickstart page.
• Enabled storage in Storage configuration.

Implement user metadata storage

The section shows you to implement user metadata storage in your Signaling app.

Set user metadata

To create a new metadata item for the user, or to update the value of am existing item, call setUserMetadata. This method creates a new item in the user metadata if the specified key does not exist, or overwrites the associated value if a metadata item with the specified key already exists.

The following example saves a set of metadata items for a specified user. It configures the options parameter to add timestamp and modifier information to each metadata item.

var Name = MetadataItem.fromJson({
    'key' : 'Name',
    'value' : 'Tony'
});

var Age = MetadataItem.fromJson({
    'key' : 'Age',
    'value' : '40'
});

var Avatar = MetadataItem.fromJson({
    'key' : 'Avatar',
    'value' : 'https://your-domain/avatar/tong.png'
});

var metadata = [Name,Age,Avatar];

try{
    var (status,response) = await rtmClient.getStorage.setUserMetadata(
        'Tony',
        metadata,
        recordTs: true,
        recordUserId: true);

    if (status.error == true) {
        print(status);
    } else {
        print(response);
    }
} catch (e) {
    print('something went wrong: $e');
}

If the operation is successful, Signaling returns the following data structure:

{
    userId : "Tony",
}

Signaling also triggers a storage event notification within 100 ms of type update to notify other users subscribed to this user's metadata. For details, see event listeners.

Get user metadata

To retrieve all metadata items associated with a specific user, call getUserMetadata. Refer to the following example:

try{
    var (status,response) = await rtmClient.getStorage.getUserMetadata('Tony');

    if (status.error == true) {
        print(status);
    } else {
        print(response);
    }
} catch (e) {
    print('something went wrong: $e');
}

Signaling SDK returns the following data structure:

{
    userId: 'Tony',
    data: {
        majorRevision: 734874862,
        itemCount: 3,
        items: [
            {
                key: 'Name',
                value: 'Tony',
                revision: 734874888,
                updateTs: 1688978391900,
                authorUserId: 'Tony'
            },
            {
                key: 'Age',
                value: '40',
                revision: 734874862,
                updated: 1688978390900,
                authorUid: 'Tomas'
            },
            {
                key: 'Avatar',
                value: 'https://your-domain/avatar/tong.png',
                revision: 734874812,
                updated: 1688978382900,
                authorUid: 'Adam'
            }
        ]
    }
}

Update user metadata

To modify existing metadata items, call updateUserMetadata. If the metadata item does not exist, the SDK returns an error. This method is useful for business use-cases that require permission control on creating new metadata items. For example, the admin defines the user metadata fields and users may only update the values.

The following example updates the value of an existing metadata item:

var Age = MetadataItem.fromJson({
    'key' : 'Age',
    'value' : '45'
});
var metadata = [Age];
try{
    var (status,response) = await rtmClient.getStorage.updateUserMetadata(
        'Tony',
        metadata,
        recordTs: true,
        recordUserId: true);

    if (status.error == true) {
        print(status);
    } else {
        print(response);
    }
} catch (e) {
    print('something went wrong: $e');
}

Signaling triggers a storage event notification within 100 ms of type update to notify other users subscribed to this user's metadata. For details, see event listeners.

Delete user metadata

To delete metadata items that are no longer required, call removeUserMetadata. Refer to the following sample code:

var Age = MetadataItem.fromJson({ 'key' : 'Age' });

var metadata = [Age];
try{
    var (status,response) = await rtmClient.getStorage.removeUserMetadata(
        'Tony',
        metadata:metadata);

    if (status.error == true) {
        print(status);
    } else {
        print(response);
    }
} catch (e) {
    print('something went wrong: $e');
}

Setting the value for a metadata item that is being deleted has no effect.

To delete the entire set of metadata for a user, do not add any metadata items when calling removeUserMetadata. Refer to the following sample code:

try{
    var (status,response) = await rtmClient.getStorage.removeUserMetadata('Tony');
    if (status.error == true) {
        print(status);
    } else {
        print(response);
    }
} catch (e) {
    print('something went wrong: $e');
}

Signaling triggers a storage event notification within 100 ms of type update to notify other users subscribed to this user's metadata. For details, see event listeners.

Receive storage event notifications

A storage event notification returns the StorageEvent data structure, which includes the RtmStorageEventType parameter.

To receive storage event notifications, implement an event listener. See event listeners for details. You only receive user metadata update notifications for users that you have subscribed to.

Event notification mode

Currently, Signaling only supports the full data update mode. This means that when a user's metadata is updated, the data field in the event notification contains all the metadata of the user.

Subscribe to a user's metadata

To monitor modifications to a user's metadata, you subscribe to their metadata. Refer to the following sample code:

try{
    var (status,response) = await rtmClient.getStorage.subscribeUserMetadata('Tony');

    if (status.error == true) {
        print(status);
    } else {
        print(response);
    }
} catch (e) {
    print('something went wrong: $e');
}

When there are changes to the user metadata, Signaling triggers a storage notification of event type update within 100 ms to inform all users who have subscribed to this user's metadata.

Unsubscribe from a user's metadata

When you no longer need to receive notifications about a user's metadata updates, unsubscribe from the users's metadata. Refer to the following sample code:

try{
    var (status,response) = await rtmClient.getStorage.unsubscribeUserMetadata('Tony');

    if (status.error == true) {
        print(status);
    } else {
        print(response);
    }
} catch (e) {
    print('something went wrong: $e');
}

Version control

Signaling integrates compare-and-set (CAS) version control to manage metadata updates. CAS is a concurrency control mechanism to ensure that updates to a shared resource occur only if the resource is in an expected state. The mechanism works as follows:

1. The client reads the current version of a data item.
2. Before making an update, the client compares the current version with the last read version number.
3. If the versions match, the client proceeds with the update and increments the version number. If they do not match, the update is aborted.

CAS version control is useful in use-cases that require concurrency management. For instance, consider a dating application where only one user may engage in a chat session with a host. When multiple users attempt to join, only the first request is successful.

The CAS version control feature provides two independent version control parameters. Set one or more of these values according to the needs of your business use-case:

• majorRevision parameter in the setMajorRevision method: Enable version number verification of the entire set of user metadata.

• revision parameter of a MetadataItem: Enable version number verification of a single metadata item.

When setting user metadata, or a single user metadata item, use the revision attribute to enable or disable version control as follows:

• To disable CAS verification, use the default value of -1 for the revision parameter.

• To enable CAS verification, set the majorRevision or the revision parameter to a positive integer. The SDK updates the corresponding value after successfully verifying the revision number. If the specified revision number does not match the latest revision number in the storage, the SDK returns an error.

The following code demonstrates how to employ majorRevision and revision for updating user metadata and metadata items:

var Name = MetadataItem.fromJson({
    'key' : 'Name',
    'value' : 'Tony',
    'revision' : 734874812
});

var metadata = [Name];

try{
    var (status,response) = await rtmClient.getStorage.setUserMetadata(
        'Tony',
        metadata,
        majorRevision: 734874892,
        recordTs: true,
        recordUserId: true);

    if (status.error == true) {
        print(status);
    } else {
        print(response);
    }
} catch (e) {
    print('something went wrong: $e');
}

In this example, CAS verification for user metadata and metadata items is enabled by setting majorRevision and revision parameters to positive integers. Upon receiving the update call request, Signaling first verifies the provided major revision number against the latest value in storage. If there's a mismatch, it returns an error; if the values match, Signaling verifies the revision number for each metadata item using a similar logic.

Reference

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

API reference

• setUserMetaData

• getUserMetadata

• removeUserMetadata

• updateUserMetadata

• subscribeUserMetadata

• unsubscribeUserMetadata

• MetadataItem

• Event listeners