Clarification required on Mirrored read maxTimeMS setting

[venkataraman_r]

Hi Team,

Starting from mongo 4.4, mongo supports mirrored read for good reasons. I understand that. But the document lacking few important information,

1. is it fire and forget request? Is so, what is this maxTimeMS play a role here?
2. If electable secondary doesnt reply within 1000ms will it do retriableRead?
3. does mongo opens additional connections to each electable secondaries for sending this mirrored read? Is so, how many connection and based on what connection setting it created these additional connections?

Thanks,
Venkataraman

[Kobe_W]

Mirrored reads do not affect the primary’s response to the client. The reads that the primary mirrors to secondaries are “fire-and-forget” operations. The primary doesn’t await responses.

from https://www.mongodb.com/docs/manual/replication/#std-label-mirrored-reads

[venkataraman_r]

@Kobe_W Thanks for your reply. Can you please answer the other questions.

1. Then why this maxTimeMS cofig exists for mirrored read
2. how many connections it creates to the secondary for this operation and based on which configuration,

[venkataraman_r]

@venkataraman_r

1. does mongo opens additional connections to each electable secondaries for sending this mirrored read? Is so, how many connection and based on what connection setting it created these additional connections?

Hi Team,

Can you please answer the questions. Due to this mirroredRead we see few extra connections created between primary to secondary which is causing resource usage. We would like to control the number of connections opened between pri and sec. Please reply.