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><A
NAME="MONITORING-PS"
>27.1. Standard Unix Tools</A
></H1
><P
> On most Unix platforms, <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> modifies its
command title as reported by <TT
CLASS="COMMAND"
>ps</TT
>, so that individual server
processes can readily be identified. A sample display is
</P><PRE
CLASS="SCREEN"
>$ ps auxww | grep ^postgres
postgres 15551 0.0 0.1 57536 7132 pts/0 S 18:02 0:00 postgres -i
postgres 15554 0.0 0.0 57536 1184 ? Ss 18:02 0:00 postgres: writer process
postgres 15555 0.0 0.0 57536 916 ? Ss 18:02 0:00 postgres: checkpointer process
postgres 15556 0.0 0.0 57536 916 ? Ss 18:02 0:00 postgres: wal writer process
postgres 15557 0.0 0.0 58504 2244 ? Ss 18:02 0:00 postgres: autovacuum launcher process
postgres 15558 0.0 0.0 17512 1068 ? Ss 18:02 0:00 postgres: stats collector process
postgres 15582 0.0 0.0 58772 3080 ? Ss 18:04 0:00 postgres: joe runbug 127.0.0.1 idle
postgres 15606 0.0 0.0 58772 3052 ? Ss 18:07 0:00 postgres: tgl regression [local] SELECT waiting
postgres 15610 0.0 0.0 58772 3056 ? Ss 18:07 0:00 postgres: tgl regression [local] idle in transaction</PRE
><P>
(The appropriate invocation of <TT
CLASS="COMMAND"
>ps</TT
> varies across different
platforms, as do the details of what is shown. This example is from a
recent Linux system.) The first process listed here is the
master server process. The command arguments
shown for it are the same ones used when it was launched. The next five
processes are background worker processes automatically launched by the
master process. (The <SPAN
CLASS="QUOTE"
>"stats collector"</SPAN
> process will not be present
if you have set the system not to start the statistics collector; likewise
the <SPAN
CLASS="QUOTE"
>"autovacuum launcher"</SPAN
> process can be disabled.)
Each of the remaining
processes is a server process handling one client connection. Each such
process sets its command line display in the form
</P><PRE
CLASS="SCREEN"
>postgres: <TT
CLASS="REPLACEABLE"
><I
>user</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>database</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>host</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>activity</I
></TT
></PRE
><P>
The user, database, and (client) host items remain the same for
the life of the client connection, but the activity indicator changes.
The activity can be <TT
CLASS="LITERAL"
>idle</TT
> (i.e., waiting for a client command),
<TT
CLASS="LITERAL"
>idle in transaction</TT
> (waiting for client inside a <TT
CLASS="COMMAND"
>BEGIN</TT
> block),
or a command type name such as <TT
CLASS="LITERAL"
>SELECT</TT
>. Also,
<TT
CLASS="LITERAL"
>waiting</TT
> is appended if the server process is presently waiting
on a lock held by another session. In the above example we can infer
that process 15606 is waiting for process 15610 to complete its transaction
and thereby release some lock. (Process 15610 must be the blocker, because
there is no other active session. In more complicated cases it would be
necessary to look into the
<A
HREF="view-pg-locks.html"
><TT
CLASS="STRUCTNAME"
>pg_locks</TT
></A
>
system view to determine who is blocking whom.)
</P
><P
> If you have turned off <A
HREF="runtime-config-statistics.html#GUC-UPDATE-PROCESS-TITLE"
>update_process_title</A
> then the
activity indicator is not updated; the process title is set only once
when a new process is launched. On some platforms this saves a measurable
amount of per-command overhead; on others it's insignificant.
</P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
> <SPAN
CLASS="PRODUCTNAME"
>Solaris</SPAN
> requires special handling. You must
use <TT
CLASS="COMMAND"
>/usr/ucb/ps</TT
>, rather than
<TT
CLASS="COMMAND"
>/bin/ps</TT
>. You also must use two <TT
CLASS="OPTION"
>w</TT
>
flags, not just one. In addition, your original invocation of the
<TT
CLASS="COMMAND"
>postgres</TT
> command must have a shorter
<TT
CLASS="COMMAND"
>ps</TT
> status display than that provided by each
server process. If you fail to do all three things, the <TT
CLASS="COMMAND"
>ps</TT
>
output for each server process will be the original <TT
CLASS="COMMAND"
>postgres</TT
>
command line.
</P
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