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Message Persistence API for Kotlin SDK

Breaking changes in v9.0.0

PubNub Kotlin SDK version 9.0.0 unifies the codebases for Kotlin and Java SDKs, introduces a new way of instantiating the PubNub client, and changes asynchronous API callbacks and emitted status events. These changes can impact applications built with previous versions (< 9.0.0 ) of the Kotlin SDK.

For more details about what has changed, refer to Java/Kotlin SDK migration guide.

Message Persistence gives you real-time access to the history of messages published to PubNub. Each message is timestamped to the nearest 10 nanoseconds and stored across multiple availability zones in several geographic locations. You can encrypt stored messages with AES-256 so they are not readable on PubNub’s network. For details, see Message Persistence.

You control how long messages are stored through your account’s retention policy. Options include: 1 day, 7 days, 30 days, 3 months, 6 months, 1 year, or Unlimited.

You can retrieve the following:

Messages
Message reactions
Files (using the File Sharing API)

Request execution

Most PubNub Kotlin SDK method invocations return an Endpoint object, which allows you to decide whether to perform the operation synchronously or asynchronously.

You must invoke the .sync() or .async() method on the Endpoint to execute the request, or the operation will not be performed.

1val channel = pubnub.channel("channelName")
2

3channel.publish("This SDK rules!").async { result ->
4    result.onFailure { exception ->
5        // Handle error
6    }.onSuccess { value ->
7        // Handle successful method result
8    }
9}

Batch history

Requires Message Persistence

Enable Message Persistence for your key in the Admin Portal. See how to enable add-on features.

Fetch historical messages from multiple channels. Use includeMessageActions or includeActions to include message actions.

You can control how messages are returned and in what order.

If you specify only start, you receive messages older than that timetoken. start is the newer boundary of the query (exclusive).
If you specify only end, you receive messages newer than or equal to that timetoken. end is the older boundary of the query (inclusive).
If you specify both start and end, start must be a higher timetoken than end. Results contain messages between those timetokens, excluding the message at start and including the message at end.

How to use the start and end parameters

PubNub retrieves messages by searching backward through time (newest to oldest). Because of this, the parameter names are the reverse of their intuitive meaning:

start is the newer boundary (higher timetoken value) - search begins here, exclusive
end is the older boundary (lower timetoken value) - search stops here, inclusive

When you provide both parameters, start must be a higher timetoken than end.

9:00 AM10:00 AM11:00 AM11:59 AM

Results are always returned in oldest-first order.

You can receive up to 100 messages for a single channel. For multiple channels (up to 500), you can receive up to 25 messages per channel. If more messages match the time range, make iterative calls and adjust the start timetoken to page through the results.

Method(s)

Use the following method(s) in the Kotlin SDK:

1pubnub.fetchMessages(
  channels: List<String>,
  page: PNBoundedPage,
  includeMeta: Boolean,
  includeMessageAction: Boolean,
  includeMessageType: Boolean,
  includeCustomMessageType: Boolean,
8).async { result -> }

* required

Parameter	Description
`channels` * Type: `List<String>` Default: n/a	Channels to return history messages from.
`page` Type: `PNBoundedPage` Default: n/a	The paging object used for pagination. Set `limit` to specify the number of historical messages to return per channel. If `includeMessageActions` is `false`, then `100` is the default (and maximum) value. Otherwise it's `25`. Set `start` to the newer boundary (exclusive) — retrieval begins here and moves backward in time. Set `end` to the older boundary (inclusive) — retrieval stops here. `start` must be a higher timetoken than `end` when both are provided.
`includeMeta` Type: `Boolean` Default: `false`	Whether to include the message metadata in the response.
`includeMessageActions` Type: `Boolean` Default: `false`	Whether to retrieve history messages with message actions. If `true`, limited to one channel only.
`includeMessageType` Type: `Boolean` Default: `true`	Whether to pass `true` to include message type. Default is `true`.
`includeCustomMessageType` Type: `Boolean` Default: `false`	Whether to retrieve messages with the custom message type. See Retrieving Messages.

Sample code

Reference code

This example is a self-contained code snippet ready to be run. It includes necessary imports and executes methods with console logging. Use it as a reference when working with other examples in this document.

Returns

The fetchMessages() operation returns a map of channels and List<PNFetchMessagesResult> and PNBoundedPage object.

Method	Description
`channels` Type: `HashMap<String, List<PNFetchMessageItem>>`	Map of channels and their respective lists of `PNFetchMessageItem`. See PNFetchMessageItem for more details.
`page` Type: `PNBoundedPage`	If exists indicates that more data is available. It can be passed directly to another call of `fetchMessages` to retrieve this remaining data.

PNFetchMessageItem

Method	Description
`message` Type: `JsonElement`	Message
`timetoken` Type: `Long`	`Timetoken` of the message. Always returned by default.
`meta` Type: `JsonElement?`	Metadata of the message. Is `null` if not requested, otherwise an empty string if requested but no associated metadata.
`actions` Type: `Map<String, HashMap<String, List<Action>>>?`	The message actions associated with the message. Is `null` if not requested. The key of the map is the action type. The value is another map, which key is the actual value of the message action, and the key being a list of actions, ie. a list of UUIDs which have posted such a message action. See Action for more details.
`customMessageType` Type: `String`	The custom message type.

Action

Method	Description
`uuid` Type: `String`	The UUID of the publisher.
`actionTimetoken` Type: `String`	The publish timetoken of the action.

Other examples

Paging history responses

Delete messages from history

Requires Message Persistence

Enable Message Persistence for your key in the Admin Portal. See how to enable add-on features.

Remove messages from the history of a specific channel.

Required setting

Enable Delete-From-History for your key in the Admin Portal and initialize the SDK with a secret key.

How to use the start and end parameters

PubNub retrieves messages by searching backward through time (newest to oldest). Because of this, the parameter names are the reverse of their intuitive meaning:

start is the newer boundary (higher timetoken value) - search begins here, exclusive
end is the older boundary (lower timetoken value) - search stops here, inclusive

When you provide both parameters, start must be a higher timetoken than end.

9:00 AM10:00 AM11:00 AM11:59 AM

Results are always returned in oldest-first order.

Method(s)

To deleteMessages() you can use the following method(s) in the Kotlin SDK.

1pubnub.deleteMessages(
2    channels: List<String>,
3    start: Long,
4    end: Long
5).async { result -> }

* required

Parameter	Description
`channels` * Type: `List<String>` Default: n/a	Channels to delete messages from.
`start` Type: `Long` Default: n/a	Newer boundary of the query (exclusive). Must be a higher timetoken value than `end` when both are provided.
`end` Type: `Long` Default: n/a	Older boundary of the query (inclusive). Must be a lower timetoken value than `start` when both are provided.

Sample code

Other examples

Delete specific message from history

To delete a specific message, pass the publish timetoken (received from a successful publish) in the End parameter and timetoken +/- 1 in the Start parameter. For example, if 15526611838554310 is the publish timetoken, pass 15526611838554309 in Start and 15526611838554310 in End parameters respectively as shown in the following code snippet.

Message counts

Requires Message Persistence

Enable Message Persistence for your key in the Admin Portal. See how to enable add-on features.

Return the number of messages published since the given time. The count is the number of messages with a timetoken greater than or equal to channelsTimetoken.

Unlimited message retention

Only messages from the last 30 days are counted.

Method(s)

Use the following method(s) in the Kotlin SDK:

1pubnub.messageCounts(
2    channels: List<String>,
3    channelsTimetoken: List<Long>
4).async { result -> }

* required

Parameter	Description
`channels` * Type: `List<String>` Default: n/a	Channels to fetch the message count.
`channelsTimetoken` * Type: `List<Long>` Default: n/a	Array in the same order as channels; a single timetoken applies to all channels; otherwise, lengths must match exactly.

Sample code

Returns

Method	Description
`channels` Type: `Map<String, Long>`	A map with values of Long for each channel. Channels without messages have a count of 0. Channels with 10,000 messages or more have a count of 10000.

Other examples

History (deprecated)

Requires Message Persistence

This method requires that Message Persistence is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

Deprecated

This method is deprecated and will be removed in a future version. Please use the fetchHistory() method instead.

Method(s)

Use the following method(s) in the Kotlin SDK:

1pubnub.history(
  channel: String,
  reverse: Boolean,
  includeTimetoken: Boolean,
  includeMeta: Boolean,
  start: Long,
  end: Long,
  count: Int
9).async { result ->  }

* required

Parameter	Description
`channel` * Type: `String` Default: n/a	Channel to return history messages from.
`reverse` Type: `Boolean` Default: `false`	Traverse from oldest to newest when set to `true`.
`includeTimetoken` Type: `Boolean` Default: `false`	Whether to include message timetokens in the response.
`includeMeta` Type: `Boolean` Default: `false`	Include the meta object (if provided at publish time) in the response.
`start` Type: `Long` Default: n/a	Newer boundary of the query (exclusive). Retrieval begins at this timetoken and moves backward in time. Must be a higher timetoken value than `end` when both are provided.
`end` Type: `Long` Default: n/a	Older boundary of the query (inclusive). Retrieval stops at this timetoken. Must be a lower timetoken value than `start` when both are provided.
`count` Type: `Int` Default: `100`	Number of historical messages to return.

Using the reverse parameter:

Messages are always returned sorted in ascending time direction from history regardless of reverse. The reverse direction matters when you have more than 100 (or count, if it's set) messages in the time interval, in which case reverse determines the end of the time interval from which it should start retrieving the messages.

Sample code

Retrieve the last 100 messages on a channel:

Returns

The history() operation returns a PNHistoryResult which contains the following operations:

Method	Description
`messages` Type: `List<PNHistoryItemResult>`	List of messages of type `PNHistoryItemResult`. See PNHistoryItemResult for more details.
`startTimetoken` Type: `Long`	Start `timetoken`.
`endTimetoken` Type: `Long`	End `timetoken`.

PNHistoryItemResult

Method	Description
`timetoken` Type: `Long?`	`Timetoken` of the message. Is `null` if not requested.
`entry` Type: `JsonElement`	Message
`meta` Type: `JsonElement?`	Metadata of the message. Is `null` if not requested, otherwise an empty string if requested but no associated metadata.

Other examples

Use `history()` to retrieve the three oldest messages by retrieving from the time line in reverse

Use `history()` to retrieve messages newer than a given timetoken by paging from oldest message to newest message starting at a single point in time (exclusive)

Use `history()` to retrieve messages until a given timetoken by paging from newest message to oldest message until a specific end point in time (inclusive)

Breaking changes in v9.0.0

Request execution

Batch history​

Requires Message Persistence

How to use the start and end parameters

Method(s)​

Sample code​

Reference code

Returns​

PNFetchMessageItem​

Action​

Other examples​

Paging history responses​

Delete messages from history​

Requires Message Persistence

Required setting

How to use the start and end parameters

Method(s)​

Sample code​

Other examples​

Delete specific message from history​

Message counts​

Requires Message Persistence

Unlimited message retention

Method(s)​

Sample code​

Returns​

Other examples​

History (deprecated)​

Requires Message Persistence

Deprecated

Method(s)​

Using the reverse parameter:

Sample code​

Returns​

PNHistoryItemResult​

Other examples​

Use history() to retrieve the three oldest messages by retrieving from the time line in reverse​

Use history() to retrieve messages newer than a given timetoken by paging from oldest message to newest message starting at a single point in time (exclusive)​

Use history() to retrieve messages until a given timetoken by paging from newest message to oldest message until a specific end point in time (inclusive)​

History paging example​

Include timetoken in history response​

Batch history

Method(s)

Sample code

Returns

PNFetchMessageItem

Action

Other examples

Paging history responses

Delete messages from history

Method(s)

Sample code

Other examples

Delete specific message from history

Message counts

Method(s)

Sample code

Returns

Other examples

History (deprecated)

Method(s)

Sample code

Returns

PNHistoryItemResult

Other examples

Use `history()` to retrieve the three oldest messages by retrieving from the time line in reverse

Use `history()` to retrieve messages newer than a given timetoken by paging from oldest message to newest message starting at a single point in time (exclusive)

Use `history()` to retrieve messages until a given timetoken by paging from newest message to oldest message until a specific end point in time (inclusive)

History paging example

Include `timetoken` in history response