Re: postgres backend process hang on " D " state

On Mon, May 30, 2022 at 01:19:56AM +0000, James Pang (chaolpan) wrote:
> 1. extensions
> shared_preload_libraries = 'orafce,pgaudit,pg_cron,pg_stat_statements,set_user'
> 2. psql can not login now ,it hang there too, so can not check anything from pg_stats_* views
> 3. one main app user and 2 schemas ,no long running transactions .
> 4. we use /pgdata , it's on xfs , lvm/vg RHEL8.4 ,it's a shared storage, no use root filesystem.
> /dev/mapper/pgdatavg-pgdatalv 500G 230G 271G 46% /pgdata
> /dev/mapper/pgdatavg-pgarchivelv 190G 1.5G 189G 1% /pgarchive
> /dev/mapper/pgdatavg-pgwallv 100G 34G 67G 34% /pgwal

What are the LVM PVs ? Is it a scsi/virt device ? Or iscsi/drbd/???

I didn't hear back if there's any kernel errors.
Is the storage broken/stuck/disconnected ?
Can you run "time find /pgdata /pgarchive /pgwal -ls |wc" ?

Could you run "ps -u postgres -O wchan============================="

Can you strace one of the stuck backends ?

It sounds like you'll have to restart the service or VM (forcibly if necessary)
to resolve the immediate issue and then collect the other info, and leave a
"psql" open to try to (if the problem recurs) check pg_stat_activity and other
DB info.