On 10/10/07, Henrik Nordstrom <henrik@xxxxxxxxxxxxxxxxxxx> 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
