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From Dave Ingram <>
Subject Re: MySQL Virtual Host and Traffic Module
Date Thu, 19 Mar 2009 06:01:39 GMT
Hi Vaughan,
> Thanks for the response. I haven't thought of doing the SQL query the way
> you suggested, however I agree that it will cause unnecessary load on busy
> servers and I would like to keep this as efficient as possible.
> The second option sounds more reasonable. I have already used threading to
> make a function which ticks on a configurable interval so I suppose each
> child process would dump data for each of its vhosts at this interval, using
> a query similar to what you have suggested.
I think that's probably the most sensible approach. It does mean that 
you won't have up-to-the-moment statistics, and I would guess that you'd 
have to play about with different intervals as the number of hosts grows 
in order for it to scale. You may also want to consider somehow 
staggering the updates, so they don't all happen at once. It may also be 
advisable to perform an UPDATE rather than an INSERT... ON DUPLICATE 
UPDATE once your module knows that there is a value that can be updated 
(i.e. after the query has run once in the simple case, or once this 
day/hour/etc in the complex case).

> I think I might go with the second option for the time being and see how it
> goes but I am still interested to know if there is a way to store per vhost
> data across children?
I would be interested to know how things turn out, and I'd be interested 
to see the final module. I've been thinking about writing a custom 
bandwidth monitoring/limiting module myself, but if I don't need to 
reinvent the wheel...

I'm afraid I can't answer this question in a definite way, though. One 
module that should store per-vhost data like this is mod_cband 
<>, so that might be worth looking 

As a side note, I'd be interested to know how you create/template the 
virtual hosts. I myself have written a database-backed templating module 
that could be used for virtual hosting 
( and I'm curious to 
see other approaches.



> Thanks,
> Vaughan
> -----Original Message-----
> From: Dave Ingram [] 
> Sent: Thursday, 19 March 2009 12:28 AM
> To:
> Subject: Re: MySQL Virtual Host and Traffic Module
> Vaughan,
>> What I have so far are 2 filters which gather the inbound traffic and
>> outbound traffic for each transaction. These work ok and when logging
>> transactions to file all of the in/out byte amounts appear to be correct.
>> The first problem however, is that each child has its own set of memory
> and
>> therefore keeps its own totals per virtual host. This also means that
>> multiple logging events occur for each transaction. I could just log this
>> all to database but it would 1) be inefficient and 2) cause the size of
> the
>> database to grow quite quickly.
> It sounds to me like you could go two ways with this. I don't know the
> format of your database table, but it should be possible to update it
> atomically using something like:
> INSERT INTO bandwidth (vhost_id, bw_in, bw_out) VALUES (42, 1124,
> 5023409) ON DUPLICATE KEY UPDATE bw_in = bw_in + 1124, bw_out = bw_out +
> 5023409
> but that could lead to a lot of load. Another way might be for each
> child to collect statistics and only flush to the database periodically,
> say every 30 seconds (perhaps configurable on a per-vhost basis, so that
> load-heavy sites could have larger update intervals). It would still be
> possible to use the query above though.
> This query could probably even be updated to split statistics on a
> date/time basis, if you require more granular reporting.
> Or have I missed/misunderstood something?
> Dave

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