Re: hung backends stuck in spinlock heavy endless loop

On Wed, Jan 14, 2015 at 8:41 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Merlin Moncure <mmoncure@gmail.com> writes:
>> There were seven process with that backtrace exact backtrace (except
>> that randomly they are sleeping in the spinloop).   Something else
>> interesting: autovacuum has been running all night as well.  Unlike
>> the other process however, cpu utilization does not register on top.
>> I backtraced them as well.  They are not identical.  One of them looks
>> like this:
>
> What are the autovac processes doing (according to pg_stat_activity)?

pid,running,waiting,query
27885,15:40:46.904039,f,autovacuum: VACUUM ANALYZE onesitepmc.propertyguestcard
7209,00:24:44.162684,f,"SELECT n.nspname as ""Schema"", c.relname as ""Name"", CASE c.relkind WHEN 'r' THEN 'table'
WHEN'v' THEN 'view' WHEN 'm'
 
THEN 'materialized view' WHEN 'i' THEN 'index' WHEN 'S' THEN
'sequence' WHEN 's' THEN 'special' WHEN 'f' THEN 'foreign table' END
as ""Type"", pg_catalog.pg_get_userbyid(c.relowner) as ""Owner""
FROM pg_catalog.pg_class c    LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN ('r','v','m','S','f','')     AND n.nspname <> 'pg_catalog'     AND n.nspname <> 'information_schema'
   AND n.nspname !~ '^pg_toast' AND pg_catalog.pg_table_is_visible(c.oid)
 
ORDER BY 1,2;"
7105,00:28:40.789221,f,autovacuum: VACUUM ANALYZE pg_catalog.pg_class
31282,15:28:29.070942,f,SELECT CDSReconcileRunTable(867)
31792,15:27:09.483365,f,SELECT CDSReconcileRunTable(874)
7135,00:26:08.977953,t,vacuum VERBOSE pg_class;
32725,15:24:46.008341,f,SELECT CDSReconcileRunTable(884)
32367,15:25:44.4206,f,SELECT CDSReconcileRunTable(881)
32492,15:25:31.27934,f,SELECT CDSReconcileRunTable(883)
31899,15:26:57.246415,f,SELECT CDSReconcileRunTable(875)
32368,15:25:44.418445,f,SELECT CDSReconcileRunTable(880)
7270,00:21:42.274104,f,"SELECT n.nspname as ""Schema"",c.relname as ""Name"", CASE c.relkind WHEN 'r' THEN 'table' WHEN
'v'THEN 'view' WHEN 'm'
 
THEN 'materialized view' WHEN 'i' THEN 'index' WHEN 'S' THEN
'sequence' WHEN 's' THEN 'special' WHEN 'f' THEN 'foreign table' END
as ""Type"", pg_catalog.pg_get_userbyid(c.relowner) as ""Owner""
FROM pg_catalog.pg_class c    LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN ('r','v','m','S','f','')     AND n.nspname <> 'pg_catalog'     AND n.nspname <> 'information_schema'
   AND n.nspname !~ '^pg_toast' AND pg_catalog.pg_table_is_visible(c.oid)
 
ORDER BY 1,2;"
7403,00:00:00,f,"COPY  ( select pid, now ( ) - query_start as running,
waiting, query from pg_stat_activity ) TO STDOUT csv header ;"

notes:
*) SELECT CDSReconcileRunTable(xxx) are the replication processes.
they are burning cpu.
*) SELECT n.nspname ... is via psql \d.  they stick when invoked and
do not respond to cancel. they are also burning cpu
*) the autovacum processes do not respond to cancel. however, one of
them did earlier (tracing in from lazy_vacuum_index ()) did respond.
However, now, it doesn't (upon being respawned via AV) with the same
backtrace.  The blocked manual vacuum verbose did cancel

merlin