keeper: improve db start logic #401
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Unfortunately pg_ctl start changed behavior in postgresql 10: pg_ctl for postgres < 10 with -w will returns 0 also if the instance isn't ready to accept connections. Whle in postgres >= 10 it will return a non 0 exit code (1 like when the instance fails to start) making it impossible to distinguish between problems starting an instance (i.e. wrong parameters) or an instance started but not ready to accept connections. To work with all the versions and since we want to distinguish between a failed start and a started but not ready instance we are forced to not use pg_ctl and write part of its logic here (I hate to do this). Now PGManager.start method directly starts the instance using the "postgres" executable and waits 1 minute to see if the process starts (checking its pid file) or exits due to an error. It doesn't check if the instance is ready to accept connections. When needed this is done inside the keeper calling WaitReady.
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Unfortunately pg_ctl start changed behavior in postgresql 10:
pg_ctl for postgres < 10 with -w will returns 0 also if the instance isn't ready
to accept connections.
While in postgres >= 10 it will return a non 0 exit code (1 like when the
instance fails to start) making it impossible to distinguish between problems
starting an instance (i.e. wrong parameters) or an instance started but not
ready to accept connections.
To work with all the versions and since we want to distinguish between a failed
start and a started but not ready instance we are forced to not use pg_ctl and
write part of its logic here (I hate to do this).
Now PGManager.start method directly starts the instance using the "postgres"
executable and waits 1 minute to see if the process starts (checking its pid file)
or exits due to an error. It doesn't check if the instance is ready to accept
connections. When needed this is done inside the keeper calling WaitReady.