Collecting data with Trackers and Webhooks

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  6. Migration guide: v0.12

Migration guide: v0.12

Several new features were added in v0.12. See the Github changelog for full details. Unfortunately, these improvements involve multiple breaking changes. See below for a guide to the changes.


The BatchEmitter.Builder configuration options have changed.


  • bufferSize has been renamed batchSize.
  • requestExecutorService() now requires a ScheduledExecutorService, rather than just ExecutorService.


  • requestCallback() is gone, since events that fail to send will now be automatically retried.

Added (these are not breaking changes):

  • eventStore(). It’s now possible to design your own event buffer using the EventStore interface. This is an optional setting, with a default of InMemoryEventStore.
  • bufferCapacity(). Set the maximum capacity of the default InMemoryEventStore. Again, this setting is optional. The default is Integer.MAX_VALUE (the maximum capacity of the queue used).

Example: creating a BatchEmitter with the relevant options
Old API:

BatchEmitter batchEmitter = BatchEmitter.builder() .url("http://collector.url") .bufferSize(20) .requestCallback( {{ A callback }} ) .requestExecutorService(ExecutorService) .build();
Code language: Java (java)

Version 0.12:

BatchEmitter batchEmitter = BatchEmitter.builder() .url("http://collector.url") .batchSize(20) .eventStore(EventStore) .bufferCapacity(1000000) // this won't do anything since eventStore is specified .requestExecutorService(ScheduledExecutorService) .build();
Code language: Java (java)


SimpleEmitter has been deprecated. Please use BatchEmitter instead, or create your own Emitter using the provided interface. Like SimpleEmitter, the BatchEmitter sends events asynchronously. However, requests are made using POST, rather than GET. We strongly recommend sending events in batches, but to mimic SimpleEmitter in sending events one-by-one, use a batchSize of 1.

Example: replacing SimpleEmitter with BatchEmitter
Old API:

SimpleEmitter simpleEmitter = SimpleEmitter.builder() .url("http://collector.url") .build(); Tracker tracker = new Tracker.TrackerBuilder(simpleEmitter, "namespace", "appId") .build();
Code language: Java (java)

Version 0.12:

BatchEmitter batchEmitter = BatchEmitter.builder() .url("http://collector.url") .batchSize(1) .build(); Tracker tracker = new Tracker.TrackerBuilder(batchEmitter, "namespace", "appId") .build();
Code language: Java (java)

Emitter interface

Every method in the Emitter interface has been updated!

setBufferSize() and getBufferSize() have been renamed setBatchSize() and getBatchSize().

getBuffer() now returns a list of TrackerPayload objects rather than TrackerEvent objects (which no longer exist).

Finally, emit() is now more accurately called add(), as in "add to buffer". It takes a TrackerPayload object, not a TrackerEvent, and has a new return type: a boolean, used to confirm that the TrackerPayload has been successfully added to the buffer.

Getting an event’s eventId

We are aware of some use cases involving exporting the eventIds of tracked Events to third-party apps. The eventId is now returned from Tracker.track(). It’s returned in a list to allow for EcommerceTransaction events, which generate multiple payloads. If the event buffer is full, the event is lost. In this case, null will be returned instead of the eventId.

Example: getting the eventId
Old API:

PageView pageView = PageView.builder() .pageUrl("") .build(); String eventId = pageView.getEventId();
Code language: Java (java)

Version 0.12:

PageView pageView = PageView.builder() .pageUrl("") .build(); List<String> eventIds = tracker.track(pageView); String eventId = eventIds.get(0);
Code language: Java (java)

Event, AbstractEvent, and child classes

Several methods have been removed: the Event interface and AbstractEvent methods getDeviceCreatedTimestamp(), and getEventId(); and the AbstractEvent.Builder methods deviceCreatedTimestamp(), and eventId(). The deprecated timestamp() and getTimestamp() methods have been removed from these classes too.

Having discovered them, we deleted these methods immediately (rather than deprecating) as we considered them very dangerous. Allowing custom UUIDs can accidentally lead to non-unique "unique" identifiers, which causes big problems for pipelines, and risks data loss.

Despite the name, Event objects are no longer associated with an eventId ; this is generated when the Payload object is made. The main purpose of the eventId is to provide a UUID for events once they have been received by the collector and are in the pipeline.

Example: creating a PageView with all the options
Old API:

PageView pageViewEvent = PageView.builder() .pageTitle("Snowplow Analytics") .pageUrl("") .referrer("") .customContext(SelfDescribingJson) .subject(Subject) .trueTimestamp(1646834667343L) .deviceCreatedtimestamp(1646834667123L) .eventId("UUID") .build();
Code language: Java (java)

Version 0.12:

PageView pageViewEvent = PageView.builder() .pageTitle("Snowplow Analytics") .pageUrl("") .referrer("") .customContext(SelfDescribingJson) .subject(Subject) .trueTimestamp(1646834667343L) .build();
Code language: Java (java)

TrackerEvent and callbacks

This class no longer exists. It was a wrapper around tracked Event objects to allow request callbacks. Events were stored in the buffer as TrackerEvent until event sending, when a TrackerPayload would be extracted. TrackerPayload objects are now stored directly.

Callbacks allowed developers to re-track events that failed to send – if a HTTP response code other than 2xx was received. This put the burden on users to handle retry. Now that the tracker automatically retries, callbacks are no longer necessary, and have been removed.

If you’d like to learn more about Snowplow BDP you can book a demo with our team, or if you’d prefer, you can try Snowplow technology for yourself quickly and easily.