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<== Date ==> <== Thread ==>

Subject: log message filter in Asyn
From: <matthew.pearson@diamond.ac.uk>
To: <tech-talk@aps.anl.gov>
Date: Tue, 17 Apr 2012 12:05:37 +0000
Hi,

Is there any interest in having a log message filter down in the Asyn layer?

We would like to be able to reduce the amount of Asyn error messages (ASYN_TRACE_ERROR) without having to implement crude filters in the drivers. Asyn error messages are commonly used for comms errors, or other warnings and errors. However, these can be printed to the IOC shell either at the record scan rate or a driver polling rate. So having the ability to reduce these down to, say, once a minute or every 10 minutes, would be useful.

It could be done using a hash of the message string and building an ordered hash table with a few fields in it (hash, counter, time). To reduce memory impact, and avoid resizing, the table could be kept at a fixed size (say a 100 or 1000 entries), with old entries removed if new ones need to be entered.

The existing print API would have to be kept the same, and by default rate limiting could be turned off. If it's turned on then it defaults to a certain rate limiting behaviour. But the algorithm could be tweaked at runtime.

Any thoughts on this? I've kept the above ideas fairly simple and focused on log message rate limiting only. As I guess we don't want anything too complicated done in Asyn that could affect the memory footprint or speed too much.

I tried to search tech talk in case people have discussed this before, and I couldn't find anything. Although how best to reduce Asyn error message noise has been discussed.

As an aside to this, how many sites use centralised logging systems?

Cheers,
Matthew

DLS Controls





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Replies:
Re: log message filter in Asyn Andrew Johnson
Re: log message filter in Asyn Eric Norum

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