Re: Switching XLog source from archive to streaming when primary available

The following review has been posted through the commitfest application:
make installcheck-world: tested, passed
Implements feature: tested, passed
Spec compliant: not tested
Documentation: not tested

Hello

I tested this patch in a setup where the standby is in the middle of replicating and REDOing primary's WAL files during a very large data insertion. During this time, I keep killing the walreceiver process to cause a stream failure and force standby to read from archive. The system will restore from archive for "wal_retrieve_retry_interval" seconds before it attempts to steam again. Without this patch, once the streaming is interrupted, it keeps reading from archive until standby reaches the same consistent state of primary and then it will switch back to streaming again. So it seems that the patch does the job as described and does bring some benefit during a very large REDO job where it will try to re-stream after restoring some WALs from archive to speed up this "catch up" process. But if the recovery job is not a large one, PG is already switching back to streaming once it hits consistent state.

thank you

Cary Huang
HighGo Software Canada