Replication re-sync failure

Hi All,

if there is network disruption during initial sync. doe mongodb start syncing from the begining or it will start where it left off.

Regards,
Naseer.

Hi Naseer,

That’s a very good question. The short answer is no.

However, there are two things to consider here. The length of time the node is down and the size of your configured oplog. If your oplog throughput is high and you have a small oplog configured, there is a possibility that the nodes will not be able to find a common point when and will require a resync. You can read more about the initial sync process in our documentation here:

https://docs.mongodb.com/manual/core/replica-set-sync/#initial-sync

Thank you Barryoneill,

if i understand correctly. if there is network disruption(lets say 5 minutes) during initial sync(where replica set scan all documents during initial sync) and still it can start from place where it left off.

if yes, i would like to know how initial sync will know where it left off… because in initial sync it will scan all documents from collection. so how it will track where initial sync was stopped at which point?

Fault Tolerance

To recover from transient network or operation failures, initial sync has built-in retry logic.

Changed in version 3.4: MongoDB 3.4 improves the initial sync retry logic to be more resilient to intermittent failures on the network.

@ naseer561

This does not appear to be a question related to the lectures or labs in this course, and in any case it’s already been answered. If you actually have a question and are not merely looking to repeat the documentation, please post again.