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Add %P to log_line_prefix for parallel group leader

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This is useful for monitoring purposes with log parsing.  Similarly to
pg_stat_activity, the leader's PID is shown only for active parallel
workers, minimizing the log footprint for the leaders as the equivalent
shared memory field is set as long as a backend is alive.

Author: Justin Pryzby
Reviewed-by: Álvaro Herrera, Michael Paquier, Julien Rouhaud, Tom Lane
Discussion: https://postgr.es/m/20200315111831.GA21492@telsasoft.com
This commit is contained in:
Michael Paquier 2020-08-03 13:38:48 +09:00
parent f44b9b625b
commit b8fdee7d0c
3 changed files with 47 additions and 1 deletions
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9
doc/src/sgml/config.sgml
View File

@ -6694,6 +6694,12 @@ local0.* /var/log/postgresql
<entry>Process ID</entry>
<entry>no</entry>
</row>
<row>
<entry><literal>%P</literal></entry>
<entry>Process ID of the parallel group leader, if this process
is a parallel query worker</entry>
<entry>no</entry>
</row>
<row>
<entry><literal>%t</literal></entry>
<entry>Time stamp without milliseconds</entry>
@ -7026,7 +7032,7 @@ log_line_prefix = '%m [%p] %q%u@%d/%a '
character count of the error position therein,
location of the error in the PostgreSQL source code
(if <varname>log_error_verbosity</varname> is set to <literal>verbose</literal>),
application name, and backend type.
application name, backend type, and process ID of parallel group leader.
Here is a sample table definition for storing CSV-format log output:
<programlisting>
@ -7056,6 +7062,7 @@ CREATE TABLE postgres_log
location text,
application_name text,
backend_type text,
leader_pid integer,
PRIMARY KEY (session_id, session_line_num)
);
</programlisting>

38
src/backend/utils/error/elog.c
View File

@ -2448,6 +2448,29 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
else
appendStringInfo(buf, "%d", MyProcPid);
break;
case 'P':
if (MyProc)
{
PGPROC *leader = MyProc->lockGroupLeader;
/*
* Show the leader only for active parallel workers. This
* leaves out the leader of a parallel group.
*/
if (leader == NULL || leader->pid == MyProcPid)
appendStringInfoSpaces(buf,
padding > 0 ? padding : -padding);
else if (padding != 0)
appendStringInfo(buf, "%*d", padding, leader->pid);
else
appendStringInfo(buf, "%d", leader->pid);
}
else if (padding != 0)
appendStringInfoSpaces(buf,
padding > 0 ? padding : -padding);
break;
case 'l':
if (padding != 0)
appendStringInfo(buf, "%*ld", padding, log_line_number);
@ -2836,6 +2859,21 @@ write_csvlog(ErrorData *edata)
else
appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
appendStringInfoChar(&buf, ',');
/* leader PID */
if (MyProc)
{
PGPROC *leader = MyProc->lockGroupLeader;
/*
* Show the leader only for active parallel workers. This leaves out
* the leader of a parallel group.
*/
if (leader && leader->pid != MyProcPid)
appendStringInfo(&buf, "%d", leader->pid);
}
appendStringInfoChar(&buf, '\n');
/* If in the syslogger process, try to write messages direct to file */

1
src/backend/utils/misc/postgresql.conf.sample
View File

@ -537,6 +537,7 @@
# %h = remote host
# %b = backend type
# %p = process ID
# %P = process ID of parallel group leader
# %t = timestamp without milliseconds
# %m = timestamp with milliseconds
# %n = timestamp with milliseconds (as a Unix epoch)