Re: [squid-users] url_rewrite_concurrency singlethreaded redirector performance?

On 10/10/07, Henrik Nordstrom <henrik@henriknordstrom.net> wrote:
> On tis, 2007-10-09 at 11:21 +0200, Sylvain Viart wrote:
>
> > Would than mean we have some performance issue with singlethreaded
> > redirector?
>
> When not using the concurrent mode Squid sends a single request at a
> time to each helper, waiting for it to respond before sending the next
> reques. This works fine for small loads, but when the load increases you
> need very many helpers just to compensate for scheduling delays or Squid
> will get quite upset even if the helper as such is very fast.
>
> In the concurrent mode helper interface Squid batches up to the
> concurrency level number of requests to the same helper, making the
> communication squid<->helper much more efficient. This is actually
> unrelated of if the helper as such is multithreaded or singlethreaded.
>
> The decision on if a concurrent mode helper should be singlethreaded or
> multithreaded depends on the processing done by the helper. If CPU
> processing only then there is generally no benefits of going
> multithreaded. But if the helper often needs to wait on external
> resources such as DNS, databases etc then multithreading the helper may
> be quite beneficial to the operation of the helper, the alternatie is to
> use many helper instances.
>
>
> Most existing helpers can easily be converted to the concurrent mode
> interface to benefit from the batching. The requirements is
> * That the helper uses proper line-oriented reading of requests, making
> sure that the next request is not forgotten if then are received at the
> same time.
> * The format of request/responses is slightly different from the older
> interface, adding a request identifier in front. This needs to be echoed
> back with the answer.
>
> Regards
> Henrik
> Hi,

Regarding the last point, I tried to look up in manual and found that
there is no request identifier mentioned there:
For each requested URL rewriter will receive on line with the format

        URL <SP> client_ip "/" fqdn <SP> user <SP> method <NL>

Can you clarify please?

Thanks in advance
>
>

-- 
M P Keshava