As of MongoDB 3.6, Change Streams allow application to get notified about changes without having to tailing the oplog.
NOTE: Change Stream support is only available with replica sets or a sharded cluster.
Change Streams can be subscribed to with both the imperative and the reactive MongoDB java driver. It is highly recommended to use the reactive variant as it is less resource intensive. However if you do not feel comfortable using the reactive API for whatever reason, you can sill obtain the change events via a Messaging concept already common in the Spring ecosystem.
== Change Streams - Sync ==
Listening to a Change Stream using a Sync Driver is a long running, blocking task that needs to be delegated to a separate component.
In this case we need to create a MessageListenerContainer first which will be the main entry point for running the specific SubscriptionRequests.
Spring Data MongoDB already ships with a default implementation that operates upon MongoTemplate and is capable of creating and executing Tasks for a ChangeStreamRequest.
MessageListenerContainer container = MessageListenerContainer.create(template);
container.start();
MessageListener<ChangeStreamDocument<Document>, User> listener = System.out::println;
ChangeStreamRequestOptions options = new ChangeStreamRequestOptions("user", ChangeStreamOptions.empty());
Subscription subscription = container.register(new ChangeStreamRequest<>(listener, options), User.class);
== Change Streams - Reactive ==
Subscribing to Change Stream via the reactive API is clearly more straight forward. Still the building blocks like ChangeStreamOptions remain the same.
Aggregation filter = newAggregation(User.class, match(where("age").gte(38));
Flux<ChangeStreamEvent<User>> flux = reactiveTemplate.changeStream(filter), User.class, ChangeStreamOptions.empty());
== Tailable Cursors - Sync ==
This commit also adds support for tailable cursors using the synchronous driver to be used with capped collections:
MessageListenerContainer container = MessageListenerContainer.create(template);
container.start();
TailableCursorRequestOptions options = TailableCursorRequestOptions.builder()
.collection("user")
.filter(query(where("age").is(7)))
.build()
container.register(new TailableCursorRequest<>(messageListener, options, User.class));
Original pull request: #528.
The benchmarks module does not produce a JAR by default which let's our Maven Central deployment fail as a module has to produce one according to their rules. We're now only including the benchmark module when the benchmarks profile is active.
Run the benchmark via the maven profile "benchmarks":
mvn -P benchmarks clean test
Or run them customized:
mvn -P benchmarks -DwarmupIterations=2 -DmeasurementIterations=5 -Dforks=1 clean test
Origin pull request: #483.
Added MongoDB 3.4 profile to pom.xml and upgraded to MongoDB 3.4 on travis-ci.
Delete assertion checking property that has been removed in MongoDB 3.4 (see: https://jira.mongodb.org/browse/SERVER-24928)
