Platform Events Developer Guide

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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 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

Configure Parallel Subscriptions for an Apex Trigger

Referencing this multiple-step example, configure an Apex trigger with three partitions and a custom field partition key. Then verify the trigger parallel subscriptions in Setup.

Step 1: Create an Apex trigger

Create an Apex trigger for the Order_Event__e platform event.

User Permissions Needed
To create a platform event: Customize Application
To create an Apex trigger: Author Apex

Prerequisites:

To define the Order_Event__e platform event, follow the steps in Platform Event Fields. Use the label of Order Event, and add the Order Number field of type Text(18) with the Required option enabled.

  1. Click the quick access menu (Quick access menu).
  2. Click Developer Console.
  3. Click File | New | Apex Trigger.
  4. For Name, enter MyOrderEventTrigger.
  5. For sObject, select the platform event Order_Event__e.
  6. Click Submit.
  7. Replace the trigger body with this code.
    This sample trigger prints out to the debug log the total count of the batch of events received in the trigger and the order number in each event.
    trigger MyOrderEventTrigger on Order_Event__e (after insert) {
    System.debug('Count of events in the trigger:' + Trigger.New.size());
    for(Order_Event__e evt : Trigger.New) 
    {
        System.debug('Processed Order Number: ' + evt.Order_Number__c);
    }
}

Step 2: Configure Parallel Subscriptions

Configure parallel subscriptions for the trigger by using Tooling API.

User Permissions Needed
To use Tooling API: API Enabled

Prerequisites:

This step uses REST in Tooling API. To complete this step, you can use your favorite REST API tool. We recommend using Postman with the Salesforce API Collection, which contains handy templates for Salesforce API calls, including calls for creating channels and channel members. See Quick Start: Connect Postman to Salesforce in Trailhead.

  1. Get the Apex trigger ID that you use to fill the PlatformEventConsumerId field. To issue a Tooling API query in the Developer Console, in the Query Editor tab of the Developer Console, enter the query: 
    SELECT Id FROM ApexTrigger WHERE Name='MyOrderEventTrigger'
  2. Make sure that the Use Tooling API option is selected.
  3. Click Execute.
  4. Copy the returned ID for the Apex trigger.
  5. Now that you have the ID of the Apex trigger, use Tooling API to send a POST request to this URI: 
    /services/data/v64.0/tooling/sobjects/PlatformEventSubscriberConfig
  6. Supply this request body, replacing Apex_Trigger_Id with the trigger ID value that you just queried. If you’re using Postman, expand Tooling | Post Tooling SObject. For the SOBJECT_API_NAME parameter, specify PlatformEventSubscriberConfig, and this request body. 
    {
  "DeveloperName":"MyOrderEventTriggerConfig",
  "MasterLabel":"MyOrderEventTriggerConfig",
  "PlatformEventConsumerId": "Apex_Trigger_Id",
  "PartitionKey": "Order_Event__e.Order_Number__c",
  "NumPartitions": "3"
}

    In this example, we chose the Order_Number__c custom field to be the partition key. This field meets the criteria for a partition key because it’s a required field. In addition, the order number field value is unique and spans a wide range of values, ensuring even distribution of events in the partitions. See Choosing a Partition Key.

    Note

Step 3: Set Up Debug Logs for the Apex Trigger

To make sure that debug logs are generated for trigger runs, set up a trace flag. The platform event Apex trigger runs under the Automated Process user by default.
  1. To set up debug logs for the Automated Process user, follow the instructions in Add a Trace Flag Entry for the Default Automated Process User.
  2. Make sure the time range that you select for Automated Process covers the time that you want to collect logs for.

You can override the default running user to another user in PlatformEventSubscriberConfig. See Configure the User and Batch Size for Your Platform Event Trigger with PlatformEventSubscriberConfig. For instructions on setting up debug logs for a specific user, see Add a Trace Flag Entry for the Overridden User.

Note

Step 4: Publish Events

Publish some events so the Apex trigger can process them in parallel.

User Permissions Needed
To publish platform events: Create permission for the platform event
To execute anonymous Apex in the Developer Console: Author Apex
  1. In the Developer Console, click Debug | Open Execute Anonymous Window, and replace the body of the window with this sample code. This sample code publishes 10 events. 
    // Publish events
List<Order_Event__e> events = new List<Order_Event__e>();
for(Integer i=0;i<10;i++) {
    Order_Event__e evt = new Order_Event__e(
     Order_Number__c=String.valueOf(i));
    events.add(evt);
}
List<Database.SaveResult> results = EventBus.publish(events);

// Inspect publishing result for each event
for (Database.SaveResult sr : results) {
    if (sr.isSuccess()) {
        System.debug('Successfully published event.');
    } else {
        for(Database.Error err : sr.getErrors()) {
            System.debug('Error returned: ' +
                        err.getStatusCode() +
                        ' - ' +
                        err.getMessage());
        }
    }       
}
  2. Click Execute.

Step 5: Monitor Parallel Subscriptions

Verify that the Apex trigger is executing with parallel subscriptions.

User Permissions Needed
To view debug logs: View All Data
To manage a trigger subscription: Customize Application

AND

Author Apex
  1. From Setup, in the Quick Find box, enter Platform Events, and then select Platform Events.
  2. On the Platform Events page, click the platform event name: Order Event.
  3. On the platform event detail page, verify that the Apex trigger is listed in the Parallel Subscriptions related list.
    Parallel subscriptions related list
  4. You can verify the trigger's execution by checking the debug output in the debug logs.
    In this case, three debug log entries are created, one for each Apex trigger invocation, which corresponds to one partition.
    Debug logs generated for the parallel subscriptions