Platform Events Developer Guide

Platform Events Developer Guide
Delivering Custom Notifications with Platform Events
Defining Your Custom Platform Event
Publishing Platform Events
Subscribing to Platform Events
Set Up Debug Logs
Flows
Processes
Apex Triggers
Configure the User and Batch Size for Your Platform Event Trigger with PlatformEventSubscriberConfig
Resume a Platform Event Trigger After an Uncaught Exception
Retry Event Triggers with EventBus.RetryableException
Email Notifications for Triggers in Error State
Comparing setResumeCheckpoint() and EventBus.RetryableException
Lightning Components
Pub/Sub API
CometD
Group Your Event Streams
Filter Your Event Streams
Obtain a Platform Event’s Subscribers
Identify and Match Event Messages with the EventUuid Field
Testing Your Platform Event in Apex
Encrypting Platform Event Messages at Rest in the Event Bus
Monitor Platform Event Publishing and Delivery Usage
Considerations
Examples
Reference
PDF

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Resume a Platform Event Trigger After an Uncaught Exception

Set a checkpoint in the event stream for where the platform event trigger resumes execution in a new invocation. If an Apex governor limit is hit or another uncaught exception is thrown, the checkpoint is used during the next execution of the trigger. Trigger processing resumes after the last successfully checkpointed event message. You can also set a checkpoint to explicitly control the number of events processed in one trigger execution. However, you can configure the trigger batch size more easily using Metadata API or Tooling API. For more information, see Configure the User and Batch Size for Your Platform Event Trigger with PlatformEventSubscriberConfig.

By processing fewer event messages, your trigger is less likely to hit Apex governor limits. The maximum batch size of a platform event trigger is 2,000, while the maximum of an Apex object trigger is 200. Therefore, platform event triggers are more likely to reach limits and can benefit from this feature.

To set a checkpoint for trigger resumption, set the replay ID of the last successfully processed event message using this method call.

When the trigger stops its flow of execution, either intentionally or because of an unhandled exception, such as a limit exception, it fires again with a new batch (the sObject list in Trigger.New). The new batch starts with the event message after the one with the replay ID that you set. The setResumeCheckpoint(replayId) method doesn’t cause the trigger execution to stop, but you can end the execution explicitly. For example, to control the batch size, end the execution flow after some event messages are processed.

If the supplied Replay ID isn’t valid, the method throws an EventBus.InvalidReplayIdException. An invalid Replay ID is a replay ID that isn’t in the current trigger batch of events in the Trigger.new list.

Resuming a batch in one trigger doesn’t affect another trigger on the same event object. However, having multiple triggers on the same object isn’t a best practice because we can't guarantee the order of execution, so we recommend that you add only one trigger per object.

Note

Example

This example trigger sets the replay ID of the last processed event message in each iteration. If a limit exception occurs, the trigger is fired again and resumes processing starting with the event message after the one with the set replay ID.

Example

This example controls the platform event trigger batch size and matches it with the 200 batch size of Apex object triggers. The trigger counts the number of event messages processed. The setResumeCheckpoint(replayId) is called in each iteration of the loop after each event message that is successfully processed. The loop is exited if you exceed the count of 200 events, and the trigger stops execution. If you have unprocessed event messages, the trigger fires again. The list of event messages sent to the new trigger invocation starts with the event message after the one with the set replay ID.

Starting in API version 51.0, you can configure the trigger batch size by using PlatformEventSubscriberConfig in Metadata API or Tooling API. For more information, see Configure the User and Batch Size for Your Platform Event Trigger with PlatformEventSubscriberConfig.

Note

The TestBatchSizeTriggerResumption test class contains a test for the ControlBatchSizeTrigger. The test method in the class publishes 201 event messages. Next, it calls the deliver() method twice to fire the trigger twice. The first invocation processes 200 event messages. The second invocation processes the last event message. The test verifies that the trigger was invoked by inspecting the EventBusSubscriber.Position property, which holds the replay ID of the last processed event message.