Package org.zalando.nakadiproducer.eventlog

Interface EventLogWriter

  • All Known Implementing Classes:
    EventLogWriterImpl
    public interface EventLogWriter
    The main user interface for this library. Autowire an instance of this interface into your service, and call one of the methods whenever you want to send an event.

    All the methods are supposed to be called inside the same database transaction which also contains the corresponding changes to your business objects. This way it is made sure that the events are persisted if and only if the containing transaction is successful, sidestepping the distributed transaction problem.

    The library will later try to submit all those persisted events to Nakadi.

    • Method Detail

      • registerCompactionKeyExtractor

        <X> void registerCompactionKeyExtractor​(String eventType,
                                        Class<X> dataType,
                                        CompactionKeyExtractor<X> extractor)
        Registers a function for extracting compaction keys for events sent in the future.

        When an event for this event type is sent out, and its `data` (or `payload`) object matches the type, the extractor is used to set the partition_compaction_key in the event to be sent out. For all other objects (or if the extractor returns null), no compaction key is set.

        (If multiple extractors are registered for the same event type, their data type is checked in reverse order of registering, until a fitting one is found. The first with matching dataType is used.)

        Note
        Nakadi-Producer does not guarantee event ordering, which is fundamentally incompatible with Nakadi's log-compaction mechanism, as Nakadi will always keep just the last submitted event for the same compaction key, which might not be the last produced one. Still, in some special cases (e.g. when there is normally a long time between production of events with the same compaction key, so all events will be sent out before the next group) it is possible without problems (and these are also cases where the compaction is most useful). This feature is meant just for these special cases.

        Parameters:
        eventType - the event type for which this is used.
        dataType - the Java type of the objects for which the extractor is used.
        extractor - a function which will extract the compaction key from an object.

      • fireCreateEvent

        void fireCreateEvent​(String eventType,
                     String dataType,
                     Object data)
        Fires a data change event about a creation of some resource (object).
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        dataType - the content of the data_type field of the Nakadi event.
        data - some POJO that can be serialized into JSON (required parameter). This is meant to be a representation of the resource which was created. It will be used as content of the data field of the Nakadi event.

      • fireCreateEvents

        void fireCreateEvents​(String eventType,
                      String dataType,
                      Collection<?> data)
        Fires data change events about the creation of some resources (objects), see fireCreateEvent for more details.
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        dataType - the content of the data_type field of the Nakadi event
        data - some POJOs that can be serialized into JSON (required parameter). This is meant to be a representation of the current state of the resource. It will be used as content of the data field of the Nakadi event.

      • fireUpdateEvent

        void fireUpdateEvent​(String eventType,
                     String dataType,
                     Object data)
        Fires a data change event about an update of some resource (object).
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        dataType - the content of the data_type field of the Nakadi event.
        data - some POJO that can be serialized into JSON (required parameter). This is meant to be a representation of the new state of the resource which was updated. It will be used as content of the data field of the Nakadi event.

      • fireUpdateEvents

        void fireUpdateEvents​(String eventType,
                      String dataType,
                      Collection<?> data)
        Fires data change events about the update of some resources (objects), see fireUpdateEvent for more details.
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        dataType - the content of the data_type field of the Nakadi event
        data - some POJOs that can be serialized into JSON (required parameter). This is meant to be a representation of the current state of the resource. It will be used as content of the data field of the Nakadi event.

      • fireDeleteEvent

        void fireDeleteEvent​(String eventType,
                     String dataType,
                     Object data)
        Fires a data change event about the deletion of some resource (object).
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        dataType - the content of the data_type field of the Nakadi event.
        data - some POJO that can be serialized into JSON (required parameter). This is meant to be a representation of the last state (before the deletion) of the resource which was deleted. It will be used as content of the data field of the Nakadi event.

      • fireDeleteEvents

        void fireDeleteEvents​(String eventType,
                      String dataType,
                      Collection<?> data)
        Fires data change events about the deletion of some resources (objects), see fireDeleteEvent for more details.
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        dataType - the content of the data_type field of the Nakadi event
        data - some POJOs that can be serialized into JSON (required parameter). This is meant to be a representation of the current state of the resource. It will be used as content of the data field of the Nakadi event.

      • fireSnapshotEvent

        void fireSnapshotEvent​(String eventType,
                       String dataType,
                       Object data)
        Fires a data change event with a snapshot of some resource (object).

        This notifies your consumers about the current state of a resource, even if nothing changed. Typical use cases include initial replication to new consumers or hotfixes of data inconsistencies between producer and consumer.

        Normally applications don't have to call this themselves, instead they should implement the SnapshotEventGenerator interface to add support for snapshot creation via the actuator endpoint.

        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        dataType - the content of the data_type field of the Nakadi event.
        data - some POJO that can be serialized into JSON (required parameter). This is meant to be a representation of the current state of the resource. It will be used as content of the data field of the Nakadi event.

      • fireSnapshotEvents

        void fireSnapshotEvents​(String eventType,
                        String dataType,
                        Collection<?> data)
        Fires data change events, see fireSnapshotEvent for more details.
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        dataType - the content of the data_type field of the Nakadi event
        data - some POJOs that can be serialized into JSON (required parameter). This is meant to be a representation of the current state of the resource. It will be used as content of the data field of the Nakadi event.

      • fireBusinessEvent

        void fireBusinessEvent​(String eventType,
                       Object payload)
        Fires a business event, i.e. an event communicating the fact that some business process step happened. The payload object will be used as the main event content (just metadata will be added). Same as for data change events, you should call this method in the same transaction as you are storing related changes into your database.
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        payload - some POJO that can be serialized into JSON (required parameter)

      • fireBusinessEvents

        void fireBusinessEvents​(String eventType,
                        Collection<Object> payloads)
        Fires business events, see fireBusinessEvent for more details
        Parameters:
        eventType - the Nakadi event type of the event. This is roughly equivalent to an event channel or topic.
        payloads - some POJOs that can be serialized into JSON (required parameter)