Logging

[Anders Berg]

On Jul 10, 2006, at 10:29, Anders Nordby wrote:

> Hi,
>
> Will it be possible to log cache misses? And would it be possible  
> to log
> them separately?

Hi Anders,

while I might not be the right one to answer I'll give it a shot.
Right now Varnish is logging alot of data involved in the request  
handling to shared memory on each of the Varnish servers. It's a  
shared memory buffer at a fixed size (default 8M right now I think),  
and Varnish writes to it in a FIFO manner.
Logging is about attaching itself to the SHM log and "tailing" it. We  
have a client for tailing the SHM log on one machine, but in the end  
product we are aiming for central log managment. One machine connects  
itself through the logging API (secured) to all the servers and  
gathers data to a central place. There you would write a filter that  
can read and present whatever data you'd like to view. From what I  
understand, even if a pure cachemiss logger is not present at launch  
we will have at least some common loggers and writing a cachemiss  
logger is what DES and PHK refer to as a SMOP :) Logging to SHM is  
extremely cheap and we will not bog the servers down with logparsing  
and such. We will have to wait and see what this is like networkwise,  
but I guess there is always a way around that that's easier. I am  
uncertain if we are gonnna implement a way to tell the Varnish daemon  
itself what we want it to logg in V 1.0.

Here is some info about the logging:

http://projects.linpro.no/pipermail/varnish-dev/2006-March/000096.html

Please correct me if I am wrong :)

Anders Berg



>
> Cache misses are of particular interest to us here in Aftenposten &  
> Finn.
> We control what will be cached and how long using the Cache-Control  
> header.
> Sometimes people forget to add that in some page/code/whatever, and we
> want to see it when it happens.
>
> PS: Performance counters? :-)
>
> Cheers,
>
> -- 
> Anders.
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