ChangeStreamTasks incorrectly converts resumeAt Instants into BsonTimestamp [DATAMONGO-2113]

[spring-projects-issues]

Mateusz Stefek opened DATAMONGO-2113 and commented

startAt = changeStreamOptions.getResumeTimestamp().map(Instant::toEpochMilli).map(BsonTimestamp::new)
              .orElse(null);

This is not how an Instant should be converted into a BsonTimestamp, as Bson timestamps are 64 bit values with a special encoding: https://docs.mongodb.com/manual/reference/bson-types/#timestamps

As a result of this bug the following request is not able to read changes from the past hour:

ChangeStreamRequest<MyDocument> request = ChangeStreamRequest.builder(messageListener)
                .collection("myDocuments")
                .resumeAt(Instant.now().minus(1, HOURS))

, but when I pass a fabricated Instant to resumeAt, mongo sends all the changes:

ChangeStreamRequest<MyDocument> request = ChangeStreamRequest.builder(messageListener)
                .collection("myDocuments")
                .resumeAt(Instant.ofEpochMilli((System.currentTimeMillis() / 1000 - 3600) << 32))

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Affects: 2.1.1 (Lovelace SR1)

Issue Links:

• DATAMONGO-2115 Ability to resume ChangeStream at a given cluster timestamp given as BsonTimestamp

Referenced from: pull request #615

Backported to: 2.1.2 (Lovelace SR2)