ReplicaSet - emulate replication lag

[konstantinzelinsky]

Versions

• NodeJS: 18.19.1
• mongodb-memory-server-*: 9.1.1
• mongodb(the binary version): 5.0.3
• mongodb(the js package): -
• mongoose: 6.12.7
• system: MacOS 14.3.1

package: mongo-memory-server

What is your question?

We are using this library for the e2e-testing on our project and want to detect potential problems with replication lag. Is there any way we can emulate a large replication delay? Have already tried to use secondaryDelaySecs as a configuration option for the replica instance. But it's supported and works only with hidden instances.
Maybe there is some other solution to use this library and configure replication lag?

[hasezoey]

i am personally not aware of any other way than those secondaryDelaySecs option

[konstantinzelinsky]

We found solution with using fsyncLock functionality.
We are locking all replicas instances during test, and this emulates replication lag for us