Re: Log levels for checkpoint/bgwriter monitoring

On Mar 5, 2007, at 8:34 PM, Greg Smith wrote:
> On Thu, 22 Feb 2007, Jim C. Nasby wrote:
>
>> It would also be extremely useful to make checkpoint stats visible  
>> somewhere in the database (presumably via the existing stats  
>> mechanism)... I'm thinking just tracking how many pages had to be  
>> flushed during a checkpoint would be a good start.
>
> I'm in the middle of testing an updated version of the patch, once  
> I nail down exactly what needs to be logged I'd planned to open a  
> discussion on which of those things would be best served by  
> pg_stats instead of a log.
>
> I decided specifically to aim for the logs instead for the  
> checkpoint data because if you're in a situation where are  
> inserting fast enough that the checkpoints are spaced closely  
> together, you'd end up having to poll pg_stats all the time for  
> make sure you catch them all, which becomes even less efficient  
> than just logging the data.

It's always good to be able to log stuff for detailed  
troubleshooting, so that's a good place to start. The flipside is  
that it's much easier to machine-parse a table rather than trying to  
scrape the logs. And I don't think we'll generally care about each  
individual checkpoint; rather we'll want to look at things like  
'checkpoints/hour' and 'checkpoint written pages/hour'.
--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)