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
Apex Trigger Best Practices
Platform Event Processing at Scale with Parallel Subscriptions for Apex Triggers
Order of Events in Parallel Subscriptions
Choosing a Partition Key
Parallel Subscription Limits
Parallel Subscription Configuration Examples in Tooling API and Metadata API
Apex Trigger Repartitioning
Configure Parallel Subscriptions for an Apex Trigger
Testing an Apex Trigger Configured with Parallel Subscriptions
Parallel Subscriptions Considerations
Configure the User and Batch Size for Your Platform Event Trigger with PlatformEventSubscriberConfig
Find Uncaught Exceptions in Event Log Files
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 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

Parallel Subscriptions Considerations

Keep in mind these considerations about parallel subscriptions.

Active Apex Trigger

You can configure only an active Apex trigger for parallel subscriptions. If you try to configure an inactive trigger, you get an error.

Deactivating an Apex trigger or deleting PlatformEventSubscriberConfig

If you deactivate an Apex trigger or delete its corresponding PlatformEventSubscriberConfig component, the trigger's parallel subscriptions are deleted. The original subscription is resumed, starting from the earliest Replay ID that one of the parallel subscriptions last processed. As a result, some events can be processed more than once. See "ReplayId System Field" in Platform Event Fields.

Modifying the platformEventConsumer field

You can't modify the platformEventConsumer field in a PlatformEventSubscriberConfig of a trigger that’s configured with parallel subscriptions. To set up parallel subscriptions on another trigger, remove the parallel subscriptions by updating numPartitions to 1 in PlatformEventSubscriberConfig. After the trigger has finished repartitioning, make a separate update to change the platformEventConsumer and numPartitions fields.

We don't recommend deleting and recreating PlatformEventSubscriberConfig because it can result in duplicate event processing.

Deleting an event field

You can't delete a platform event custom field that’s referenced as a partition key in an active Apex trigger.

EventUuid as the default partition key due to corrupt schema

If the system can't resolve a custom partition key field due to a corrupt schema, it uses the EventUuid field to partition incoming event batches. This can result in out-of-order events delivered to partitions, because the hash value of the EventUuid field is probably different than the one for the custom partition key field. In later event batches, the system reverts to the partition key field if the schema is resolved and it can get the partition key value.

Changing the Partition Key Field to Be Optional

If the partition key field is edited to no longer be a required field after the parallel subscriptions feature is enabled for a trigger, the system can't guarantee deterministic distribution of events to the partitions. When you configure parallel subscriptions, the partition key field must be a required field.