Java Spring 引导嵌入式 MongoDB 不触发 TTL 移除

Question

I am trying to test MongoDB TTL functionality for short-lived collections. Using @Indexed annotation on field like this:

@Indexed(name = "deleteAt", expireAfterSeconds = 5)
private Date deleteAt;

In constructor I initialise deleteAt to this.deleteAt = new Date() and I expect after inserting my Document to Mongo that after it's TTLManager will run this collection will be removed. But It is not being removed even waiting for a few minutes doesn't help. I ran db.serverStatus().metrics.ttl in mongo shell and it returned:

[
  {
    "deletedDocuments": 0,
    "passes": 8
  }
]

And command db.adminCommand({getParameter:1, ttlMonitorEnabled: 1}) returns:

[
  {
    "ok": 1,
    "ttlMonitorEnabled": true
  }
]

Is something wrong with my code? Or it is because of embedded mongo doesn't support this, is it possible to configure embedded mongo so it would work? I am using https://github.com/flapdoodle-oss/de.flapdoodle.embed.mongo for embedded MongoDB with default settings.

Answer 1

It's only MongoDB server ( mongod ) feature

A background thread in mongod reads the values in the index and removes expired documents from the collection.

https://docs.mongodb.com/manual/core/index-ttl/#delete-operations

Embedded MongoDB framework "simulates" mongod process with MongodProcess class only to deploy a basic embedded server.

https://github.com/flapdoodle-oss/de.flapdoodle.embed.mongo/blob/master/src/main/java/de/flapdoodle/embed/mongo/MongodProcess.java