Hello,
I've encountered a problem of PostgreSQL startup, and I can think of a
simple solution for that. However, I don't yet have much knowledge about
PostgreSQL implementation, I'd like to ask you about what is the best and
easiest solution. If it is easy for me to work on during my spare time at
home, I'm willing to implement the patch.
[problem]
I can't reliably wait for the completion of PostgreSQL startup. I want
pg_ctl to wait until the server completes startup and accepts connections.
Yes, we have "-w" and "-t wait_second" options of pg_ctl. However, what
value should I specify to -t? I have to specify much time, say 3600 seconds,
in case the startup processing takes long for crash recovery or archive
recovery.
The bad thing is that pg_ctl continues to wait until the specified duration
passes, even if postgres fails to start. For example, it is naturally
desirable for pg_ctl to terminate when postgresql.conf contains a syntax
error.
[solution idea]
Use unnamed pipes for postmaster to notify pg_ctl of the completion of
startup. That is:
pg_ctl's steps:
1. create a pair of unnamed pipes.
2. starts postgres.
3. read the pipe, waiting for a startup completion message from postmaster.
postmaster's steps:
1. inherit a pair of unnamed pipes from pg_ctl.
2. do startup processing.
3. write a startup completion message to the pipe, then closes the pipe.
I'm wondering if this is correct and easy. One concern is whether postmaster
can inherit pipes through system() call.
Please give me your ideas. Of course, I would be very happy if some
experienced community member could address this problem.
And finally, do you think this should be handled as a bug, or an improvement
in 9.2?
Regards
MauMau