Craig Ringer wrote:
On 1/12/2009 11:33 AM, Greg Smith wrote:
1) If you spawn the psql process with bash using "&", you can then find
its pid with "$!", then chain through the process tree with ps and
pg_stat_activity as needed to figure out the backend pid.
I feel like I'm missing something obvious here. How can walking the
process tree starting with the psql pid help you find the backend pid?
The backend and client have no relationship in the process tree. At
some point you have to match the (ip,port) tuple for the client's
connection against pg_stat_activity - what you've listed separately as
(4). Even that won't help if a unix socket is in use, since
client_addr is null and client_port is -1.
It turns out I completely misremembered what I did the last time, so
you're right to call me on this. As I confirmed when I tried to do this
myself again, the two port numbers are completely unrelated via anything
you can see in ps. What I actually did was look at pg_stat_activity,
note what processes were around, spawn the new one, and then look at
pg_stat_activity again to figure out which it is. Not really a great
approach, but a usable one for some situations.
--
Greg Smith 2ndQuadrant Baltimore, MD
PostgreSQL Training, Services and Support
greg@xxxxxxxxxxxxxxx www.2ndQuadrant.com
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