Is there a recommended solution on how to enable mongoDB "change streams" ?

[bodote]

MongoDB has a feature called "change streams". However, this feature is only available if there is a "replica set". The replica set in turn is NOT enabled by default for single instance MongoDBs. You can enable the replica set with de.flapdoodle.embed.mongo. But it seemes a little bit cumbersome though.

Is there any recommendation on how to use this with de.flapdoodle.embed.mongo ?

what we do is this:

 @Override
            public Transition<MongodArguments> mongodArguments() {
                return Start.to(MongodArguments.class)
                        .initializedWith(MongodArguments.defaults()
                                .withReplication(Storage.of("testRepSet", 5000))
                                .withUseNoJournal(false));
            }

plus :

 mongoClient.getDatabase("admin").runCommand(new Document("replSetInitiate", new Document()));

immediately @BeforeEach test.

especially the need for this admin - command above turned out to be somehow problematic and lead to unstable test until we wraped it part of the test code in some await().atMost(10, SECONDS).until(() -> {...}

Is there any better way ?

[michaelmosmann]

@bodote i will have a look at this.. do you have any error message for the "unstable" case?

[bodote]

I think that this is a timeing / race condition problem, e.g. when i try to access the mongoDB immediately after sending the
mongoClient.getDatabase("admin").runCommand(new Document("replSetInitiate", new Document()));
then sometimes i got the error that the database is not in primary or secondary state. When i add a Thread.sleep(500) the problem disapears.

[bodote]

and it would by nicer if the de.flapdoodle.embed.mongo library would itself take care of the
mongoClient.getDatabase("admin").runCommand(new Document("replSetInitiate", new Document()));
command , wouldn't it?

[michaelmosmann]

@bodote I am not sure about that:) as there are unlimited ways to work with a mongodb database and i can not handle all of them.. but maybe it is something very simple.. as some kind of listener which is triggered if mongodb changes its state..

[michaelmosmann]

as @XSpielinbox noticed in the issue.. if you are using the spring integration i did write some code to handle this replicaset stuff: https://github.com/flapdoodle-oss/de.flapdoodle.embed.mongo.spring/blob/041421695626591599798602a39df8a61e3fdb42/src/main/java/de/flapdoodle/embed/mongo/spring/autoconfigure/AbstractServerFactory.java#L84

maybe i should backport it to the mongodb project

[michaelmosmann]

@bodote i will create an issue from that..

[michaelmosmann]

--> #497

[michaelmosmann]

@bodote .. i close this. Reopen if needed..