Hi,
On 12/16/20 2:36 PM, Victor Yegorov wrote:
CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. |
After doing this procedure, you can see the startup process and backend
wait for the table lock each other, i.e., deadlock. But this deadlock remains
even after deadlock_timeout passes.
This seems a bug to me.
+1
> * Deadlocks involving the Startup process and an ordinary backend process
> * will be detected by the deadlock detector within the ordinary backend.
The cause of this issue seems that ResolveRecoveryConflictWithLock() that
the startup process calls when recovery conflict on lock happens doesn't
take care of deadlock case at all. You can see this fact by reading the above
source code comment for ResolveRecoveryConflictWithLock().
To fix this issue, I think that we should enable STANDBY_DEADLOCK_TIMEOUT
timer in ResolveRecoveryConflictWithLock() so that the startup process can
send PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK signal to the backend.
Then if PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK signal arrives,
the backend should check whether the deadlock actually happens or not.
Attached is the POC patch implimenting this.
good catch!
I don't see any obvious reasons why the STANDBY_DEADLOCK_TIMEOUT shouldn't be set in ResolveRecoveryConflictWithLock() too (it is already set in ResolveRecoveryConflictWithBufferPin()).
So + 1 to consider this as a bug and for the way the patch proposes to fix it. Bertrand