Good day,

I have a case with a customer that involved Chained Replication.  As I looked through the various documentation articles, I found a paragraph that seemed to conflict with itself:

NOTE

If chained replication is disabled, you still can use replSetSyncFrom to specify that a secondary replicates from another secondary. But that configuration will last only until the secondary recalculates which member to sync from.

It seems that disabled chained replication would prevent moving to another secondary node since the Primary is its target.

There's also no indication of what node a given secondary will use when Chained Replication is disabled.

I confirmed with the expert team that disabling chained replication results in all nodes replicating from the Primary node, and that you can still move it via replSetSyncFrom though if THAT node becomes unavailable, the secondary in question will move to the primary for synch sourcing:

Veera  

Hi @michael.struening ..If you  disable the chaining,  the primary will become the sync source. If the primary is unavailable or unreachable, log an error and periodically check for primary availability. (edited) 

Veera 

If sync source is changed temporarily overrides the default sync target for the current member . If the chaining is disabled already the source ID becomes unavailable, and then it would move to the primary

Can we update the linked documentation pages (and anything connected that I may have missed) to indicate: # Disabling Chained Replication will result in nodes synching from the Primary (and the resulting load on that Primary)

1. You CAN override this sync source via replSetSyncFrom
2. However, if chained replication is disabled and that modified source node is unavailable, then that secondary will move its source ID to the Primary
   If you have any questions or need any clarification, please let me know!
   Thanks!!