From: | "Iwata, Aya" <iwata(dot)aya(at)jp(dot)fujitsu(dot)com> |
---|---|
To: | 'Yugo Nagata' <nagata(at)sraoss(dot)co(dot)jp> |
Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | RE: libpq debug log |
Date: | 2018-09-04 00:29:09 |
Message-ID: | 71E660EB361DF14299875B198D4CE5423DE4A154@g01jpexmbkw25 |
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Lists: | pgsql-hackers |
> > I'm going to propose libpq debug log for analysis of queries on the application
> side.
> > I think that it is useful to determine whether the cause is on the application
> side or the server side when a slow query occurs.
>
> Do you mean you want to monitor the protocol message exchange at the client
> side to analyze performance issues, right? Actually, this might be useful to
> determin where is the problem, for example, the client application, the backend
> PostgreSQL, or somewhere in the network.
>
> Such logging can be implemented in the application, but if libpq provides the
> standard way, it would be helpful to resolve a problem without modifying the
> application code.
Since I'd like to monitor the information the server and the client exchange,
I think monitoring protocol messages is good.
When a slow query is occurs, we check this client side trace log.
The purpose of this log acquisition I thought is to identify where is the problem:
server side, application side or traffic.
And if the problem is in application side, checking the trace log to identify what is the problem.
> > The provided information is "date and time" at which execution of processing
> is started, "query", "application side processing", which is picked up
> information from PQtrace(), and "connection id", which is for uniquely
> identifying the connection.
>
> I couldn't image how this is like. Could you show us a sample of log lines in
> your head?
I am roughly thinking as follows;
...
START : 2018/09/03 18:16:35.357 CONNECTION(1)
STATUS : Connection
SEND MESSAGE : 2018/09/03 18:16:35.358
<information send to backend...>
RECEIVE MESSAGE : 2018/09/03 18:16:35.359
<information receive from backend...>
END : 2018/09/03 18:16:35.360
...
START : 2018/09/03 18:16:35.357 CONNECTION(1)
QUERY : DECLARE myportal CURSOR FOR select * from pg_database
SEND MESSAGE : 2018/09/03 18:16:35.358
<information send to backend...>
RECEIVE MESSAGE : 2018/09/03 18:16:35.359
<information receive from backend...>
END : 2018/09/03 18:16:35.360
...
> > To collect the log, set the connection string or environment variable.
> > - logdir or PGLOGDIR : directory where log file written
> > - logsize or PGLOGSIZE : maximum log size
>
> How we can specify the log file name? What should happen if a file size exceeds
> to PGLOGSIZE?
The log file name is determined as follow.
libpq-%ApplicationName-%Y-%m-%d_%H%M%S.log
When the log file size exceeds to PGLOGSIZE, the log is output to another file.
Regards,
Aya Iwata
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