Jim C. Nasby wrote:
Moving to -hackers.
On Fri, May 11, 2007 at 04:37:44PM +0100, Heikki Linnakangas wrote:
If you know when the checkpoint ended, and you know how long each of the
pieces took, you can reconstruct the other times easily. The way you
describe this it is true--that the summary is redundant given the
detail--but if you put yourself in the shoes of a log file parser the
other way around is easier to work with. Piecing together log entries
is a pain, splitting them is easy.
Yeah, if we have the summary line we don't need the other lines and vice
versa. I have sympathy for parsing log files, I've done that a lot in
the past and I can see what you mean. Having the individual lines is
nice when you're monitoring a running system; you don't get the summary
line until the checkpoint is finished. I suppose we can have both the
individual lines and the summary, the extra lines shouldn't hurt anyone,
and you won't get them unless you turn on the new log_checkpoints
If I had to only keep one line out of this, it would be the one with the
summary. It would be nice to have it logged at INFO.
Not to beat a dead horse, but do we really want to force folks to be
parsing logs for performance monitoring? Especially if that log parsing
is just going to result in data being inserted into a table anyway?
I know there's concern about performance of the stats system and maybe
that needs to be addressed, but pushing users to log parsing is a lot of
extra effort, non-standard, likely to be overlooked, and doesn't play
well with other tools. It also conflicts with all the existing
There is two counters for checkpoints in pgstats, the number of timed
(triggered by checkpoint_timeout) and requested (triggered by
Maybe we should improve the stats system so that we can collect events
with timestamps and durations, but in my experience log files actually
are the most reliable and universal way to collect real-time performance
information. Any serious tool has a generic log parser. The other
alternative is SNMP. I welcome the efforts on pgsnmpd..
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