Re: transaction blocking on COMMIT

On 05/24/21 19:24, Christophe Pettus wrote:
>
>> On May 24, 2021, at 09:22, Bob Jolliffe <bobjolliffe@gmail.com> wrote:
>>
>> It is hard to say as it only happens for 30s couple of times per day.
>> Everything does return to normal after the blocking transaction is
>> committed.  It could be a disk thing or even a network issue (the java
>> app is on a different machine to the db).  But I never saw
>> transactions blocked in commit before so was wondering if there is any
>> rational set of reasons why it might do that.
> One thing you can check is to turn off synchronous_commit (understanding the possibility of "time loss" in the event
ofa system crash).  If that mitigates the problem, the issue is likely the I/O subsystem blocking during the fsync()
operation.
>
>
Just a question. Is there a btrfs(with compression maybe) around? 30 
seconds is a commit(file system) timeout for btrfs. Some processes like 
btrfs cleaner/allocate/worker on top of CPU/io use?