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>Chapter 26. Monitoring Database Activity</TD
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><A
NAME="MONITORING-PS"
>26.1. Standard Unix Tools</A
></H1
><A
NAME="AEN31526"
></A
><P
> On most 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 960 0.0 1.1 6104 1480 pts/1 SN 13:17 0:00 postgres -i
postgres 963 0.0 1.1 7084 1472 pts/1 SN 13:17 0:00 postgres: writer process
postgres 965 0.0 1.1 6152 1512 pts/1 SN 13:17 0:00 postgres: stats collector process
postgres 998 0.0 2.3 6532 2992 pts/1 SN 13:18 0:00 postgres: tgl runbug 127.0.0.1 idle
postgres 1003 0.0 2.4 6532 3128 pts/1 SN 13:19 0:00 postgres: tgl regression [local] SELECT waiting
postgres 1016 0.1 2.4 6532 3080 pts/1 SN 13:19 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 given when it was launched. The next two
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.) 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 connection source 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 attached if the server process is presently waiting
on a lock held by another server process. In the above example we can infer
that process 1003 is waiting for process 1016 to complete its transaction and
thereby release some lock or other.
</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 useful
amount of per-command overhead, on others it's insignificant.
</P
><DIV
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><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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