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Using LWP: is there a way to get the server response time?

by isync (Hermit)
on May 11, 2007 at 10:42 UTC ( #614869=perlquestion: print w/replies, xml ) Need Help??

isync has asked for the wisdom of the Perl Monks concerning the following question:


Using the LWP set of mudules, especially LWP::UserAgent I am trying to find out how I am able to measure the time between issuing of a request against a server and the start of the server responding.

So far I only managed to measure the time betwen start of the request and finish of the request. But this takes downloading data into account as well. Is there a hidden var or a method to measure just the "performance" of the called server? Maybe by using the :content_cf callback??
  • Comment on Using LWP: is there a way to get the server response time?

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Re: Using LWP: is there a way to get the server response time?
by Tomte (Priest) on May 11, 2007 at 11:26 UTC

    If raw performance (time from "request-came-in" to "about-to-start-sending") is what you want to measure, in my humble opinion you should measure that on the server itself, not the client, otherwise the network will allways interfere with your measurements - in our current projects we send an X-header holding the processing time: X-Time: 0.017s


    An intellectual is someone whose mind watches itself.
    -- Albert Camus

      Mmmh. So is a http response alsways a combination of header+response and I have no handle to get into the data-chunks (and their timing) received by LWP::UserAgent?

      I am not able to get on the server side. So my only chance is to calculate: ((overall-response-time / transferred-bytes) / my-network-throughput-capacity) or something like that to get a hint of the time used to prepare the response on the server side?
Re: Using LWP: is there a way to get the server response time?
by PreferredUserName (Pilgrim) on May 11, 2007 at 15:54 UTC
    Libcurl keeps good information on this kind of thing (see CURLINFO_STARTTRANSFER_TIME). Info:

    There's a Perl module: WWW::Curl at

    You could also just record the time at intervals in LWP::Protocol::http::request().

      I am not so familar with the LWP internals and never came to the "LWP::Protocol" branch... How would I poll LWP::Protocol::http::request()? By getting the private $sel_timeout var? A code hint would be great!

      I don't want to switch over to curl...
        OK, do a:
        locate Protocol/
        or similar to find where your LWP::Protocol::http module lives. Mine is in /usr/share/perl5/LWP/Protocol/ Search for the request() subroutine. Add these lines up at the top of it:
        use Time::HiRes qw(time); my @times;
        Add a line containing "push @times, time();" before the following three lines:
        if ($has_content) { block, ... $response = $self->collect($arg, $response, sub { ... unless ($drop_connection) {
        and then add this at the bottom:
        warn "wrote-request read-headers read-content\n@times\n";
        If this is anything but a quick hack, it might be better to subclass or otherwise hook into LWP::Protocol::http to make it more maintainable. Another approach would be to just do a HEAD and then a GET, with the difference in times being the content-transfer time.

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