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From Joshua Marantz <jmara...@google.com>
Subject Re: aprmemcache question
Date Wed, 26 Sep 2012 23:17:07 GMT
+dev (sorry for the duplicate; my first attempt failed due to not being a

Keeping modules-dev on CC if that's appropriate.

Thanks, Jeff, I was wondering if there was a units issue there.  I'm still
wondering if anyone can describe the meaning of that argument in more
detail.  Is that related to my multiget APR_TIMEUP returns?   The phrase
"time to live of client connection" confuses me.  Would it be inaccurate to
instead say "the maximum number of seconds apr_memcache is willing to wait
for a single operation?  Or does it mean *both*, implying that a fresh
TCP/IP connection is made for every new operation, but will stay alive for
only a certain number of seconds.

I have a practical question about how I release software given this change.
 Our module (mod_pagespeed) is documented to run with Apache 2.2 and Apache
2.4.  It seems like for 2.2 I should probably multiple my desired argument
by a million.  Same with for 2.4.x and earlier, for some value of x.  How
should I work this in my code?  Should I query the version number using an
apr utility or something and multiply by a million in certain cases?

What's the best practice calling this function for module developers?


On Wed, Sep 26, 2012 at 6:20 PM, Jeff Trawick <trawick@gmail.com> wrote:

> On Wed, Sep 26, 2012 at 5:38 PM, Joshua Marantz <jmarantz@google.com>
> wrote:
> > Hi,
> >
> > I've been having some success with the apr_memcache_* functions.  In
> > load-tests, however, I'm finding a lot of timeouts
> > with apr_memcache_multgetp.  Specifically, the status returned with the
> > individual elements is APR_TIMEUP.
> >
> > This leads me to wonder what the significance of the second to last arg
> to
> > this function is:
> >
> > apr_memcache_server_create(
> >           pool_, hosts_[i].c_str(), ports_[i],
> >           kDefaultServerMin, kDefaultServerSmax,
> >           thread_limit_, kDefaultServerTtlUs, &server);
> >
> > I have kDefaultServerSmax initialized to 600, as that's the value I found
> > in mod_socache_memcache.c   But that seems stingy (if it's really in
> > microseconds).  Should I be giving that a few hundred millis instead?
> >
> http://apr.apache.org/docs/apr-util/1.4/group___a_p_r___util___m_c.html#ga18ddd72bc1ab5edb0a08a8f26f193bd3
> > claims
> > that means "time to live of client connection" but I don't understand
> what
> > that phrase means exactly, or if it relates to the APR_TIMEUP returns
> I've
> > been suffering from.
> >
> > My code is here;
> >
> http://code.google.com/p/modpagespeed/source/browse/trunk/src/net/instaweb/apache/apr_mem_cache.cc
> >
> > -Josh
> dev@apr.apache.org is a better place to ask about details of apr
> functions.
> Coincidentally, earlier today I committed someone's fix for the
> confusion about the units of ttl:
> http://svn.apache.org/viewvc?view=revision&revision=1390530
> It is supposed to be in seconds.  Pick up the tiny change to
> apr_memcache.c and see if that helps anything.  You should continue
> this discussion on dev@apr.apache.org.
> --
> Born in Roswell... married an alien...
> http://emptyhammock.com/

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