Thread: Reduce the time to know trigger_file's existence

<p class="MsoNormal" style="LINE-HEIGHT:normal;MARGIN:0cm 0cm 0pt"><span style="FONT-FAMILY:'Courier
New';FONT-SIZE:10pt"><fontface="trebuchet ms,sans-serif">Hi, </font></span><div class="MsoNormal"
style="LINE-HEIGHT:normal;MARGIN:0cm0cm 0pt"><span style="FONT-FAMILY:'Courier New'"><font face="trebuchet
ms,sans-serif"></font></span> </div><divclass="MsoNormal" style="LINE-HEIGHT:normal;MARGIN:0cm 0cm 0pt"><span
style="FONT-FAMILY:'CourierNew'"><font face="trebuchet ms,sans-serif">We are trying to introduce a thread that monitors
thecreation of the trigger_file. As and when the file is created, the process that monitors postgres server needs to be
notifiedthrough the inotify API.</font></span></div><p class="MsoNormal" style="LINE-HEIGHT:normal;MARGIN:0cm 0cm
0pt"><spanstyle="FONT-FAMILY:'Courier New'"><font face="trebuchet ms,sans-serif">This is to reduce the 3-4 seconds
delaythat exists with the current implementation in postgres. As per the current implementation, the thread checks for
theexistence of the file every 5 seconds. If the file got created just 1 second after the sleep, there is a wait time
of4 seconds before we know whether the file is present or not. We intend to avoid this delay by using
inotify().</font></span><pclass="MsoNormal" style="LINE-HEIGHT:normal;MARGIN:0cm 0cm 0pt"><span
style="FONT-FAMILY:'CourierNew'"><font face="trebuchet ms,sans-serif">PostgreSQL version number you are running:
postgres9.1.5</font></span><p class="MsoNormal" style="LINE-HEIGHT:normal;MARGIN:0cm 0cm 0pt"><font face="trebuchet
ms,sans-serif"><spanstyle="FONT-FAMILY:'Courier New'"><font face="trebuchet ms,sans-serif">How you installed
PostgreSQL</font>:</span>Downloaded and compiled the sources</font><div class="MsoNormal"
style="LINE-HEIGHT:normal;MARGIN:0cm0cm 0pt"><font face="trebuchet ms,sans-serif"></font> </div><div class="MsoNormal"
style="LINE-HEIGHT:normal;MARGIN:0cm0cm 0pt"><font face="trebuchet ms,sans-serif">Does anyone have suggestions on the
appropriateplace to add inotify_add_watch to achieve our objective?</font></div><div class="MsoNormal"
style="LINE-HEIGHT:normal;MARGIN:0cm0cm 0pt"><font face="Trebuchet MS">Thanks in advance.</font></div> 

On Mon, Sep 3, 2012 at 2:19 AM, togetinfo mail <togetinfomail@gmail.com> wrote:
> We are trying to introduce a thread that monitors the creation of the
> trigger_file. As and when the file is created, the process that monitors
> postgres server needs to be notified through the inotify API.
>
> This is to reduce the 3-4 seconds delay that exists with the current
> implementation in postgres. As per the current implementation, the thread
> checks for the existence of the file every 5 seconds. If the file got
> created just 1 second after the sleep, there is a wait time of 4 seconds
> before we know whether the file is present or not. We intend to avoid this
> delay by using inotify().
>
> PostgreSQL version number you are running: postgres 9.1.5
>
> How you installed PostgreSQL: Downloaded and compiled the sources
>
> Does anyone have suggestions on the appropriate place to add
> inotify_add_watch to achieve our objective?
> Thanks in advance.

I'm not in favor of this approach, because it will only work on Linux.

Also, can't you bypass this problem altogether by using "pg_ctl promote"?

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company