Re: Comments on the fastestmirror plugin

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On Fri, 2010-03-12 at 19:20 -0430, Patrick O'Callaghan wrote:
> On Fri, 2010-03-12 at 12:57 -0600, Robert Nichols wrote:
> > On 03/12/2010 08:08 AM, Patrick O'Callaghan wrote:
> > > The yum fastestmirror plugin (yum-plugin-fastestmirror) claims to
> > > evaluate the speed of a bunch of repo mirrors and use the fastest one
> > > relative to the user's location.
> > >
> > > However AFAIK what it *actually* does is make a test connection to the
> > > to the candidate mirrors and order them according to response time,
> > > which in many cases is dominated by network latency, which can distort
> > > the results. For well-connected user machines in first-world countries
> > > it probably doesn't matter much, and may have the beneficial effect of
> > > spreading the load over a wider range of mirrors, but for those of us in
> > > a less privileged position it can matter a lot. Ironically, these are
> > > the cases where such an optimization could do the most good.
> > >
> > > A case in point: I live in Venezuela and on several recent occasions yum
> > > decided that my closest repo was in Puerto Rico, which as the packet
> > > flies is probably true. However the b/w I got as a result was around 2
> > > or 3kbps.
> > 
> > If there are particular hosts or domains you want to avoid, you can edit
> > /etc/yum/pluginconf.d/fastestmirror.conf and add an "exclude" line.
> > There is a commented-out sample exclude line at the bottom of that file:
> > 
> >           #exclude=.gov, facebook
> 
> True. I had seen that line but didn't take sufficient notice of it. Of
> course the fact that the plugin comes with *no documentation whatsoever*
> (not so much as a README file) means that its effect is a matter of
> guesswork. It's fairly obvious what ".gov" means in the above example,
> but what does "facebook" mean? Is this a substring match? Against the
> whole domain or against each component? Is there an #include directive
> as well? Inquiring minds want to know.

Further to the above, I tried the following line in fastestmirror.conf:

        exclude=.upr.edu, .br, .cl
        
and then ran yum update:

        Loaded plugins: changelog, fastestmirror, merge-conf, presto,
        protectbase, refresh-packagekit
        Loading mirror speeds from cached hostfile
        Excluding mirror: fedora.c3sl.ufpr.br
        Excluding mirror: fedora.pop.com.br
        Excluding mirror: mirror.ispbrasil.com.br
        Excluding mirror: mirrors.hpcf.upr.edu
         * fedora: mirror.ispbrasil.com.br
        ...
        
Note the last line. It looks like my earlier remark about it being
"fairly obvious" what excluding a domain does, turns out not to be true.
I no longer have any idea what fastestmirror thinks it's doing, and
since as I said it isn't documented, neither do I know if this is a bug
or a feature.

poc

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