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<p class=MsoPlainText>The following is a patch I’ve made to varnish that
I hope improves the random director: which anyone’s welcome to use (even
varnish trunk?). My motivation was to reduce the number of vcl_error
calls when a director is mostly good. You can get the entire patch at
this link.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><a
href="http://github.com/cep21/Varnish/commit/6f5e98143ac2636504d9febf574b14c3c1a072fc">http://github.com/cep21/Varnish/commit/6f5e98143ac2636504d9febf574b14c3c1a072fc</a><o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Here’s the commit message:<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Random director tries all backends before giving up<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Summary:<o:p></o:p></p>
<p class=MsoPlainText>The current random director gives up when it can't get a
FD to the backend it wants retries times in a row. Rather than give up
and return NULL, which is guaranteed to cause a vcl_error, as a last ditch
effort we try all other healthy backends until we get one that works.
This is mostly useful in the between time after a backend server dies and
before the health check fails enough to mark a backend unhealthy.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Backwards Compatibility = Not strictly backwards
compatible. In cases when the old code would of fallen through to
vcl_error this will give a shot at getting a good result.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Performance = In the worse case, this will add extra
calls for getting a FD, but only for situations that vcl_error<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Test Plan: New varnish unittest. It fails in the
old code and works in this new code.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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