[announce] yum: parallel downloading

elison.niven at gmail.com elison.niven at gmail.com
Thu May 17 17:09:59 UTC 2012

On Wed, May 16, 2012 at 9:37 PM, Zdenek Pavlas <zpavlas at redhat.com> wrote:
> Hi,
> A new yum and urlgrabber packages have just hit Rawhide.  These releases
> include some new features, including parallel downloading of packages and
> metadata, and a new mirror selection code.  As we plan to include these
> features in RHEL7, I welcome any feedback or bug reports!
> python-urlgrabber-3.9.1-12.fc18 supports a new API to urlgab() files in
> parallel, and yum-3.4.3-26.fc18 can use this.  Both packages are compatible
> with older versions.
> Feature list:
> - parallel downloading of packages and metadata
> If possible, multiple files are downloaded in parallel.  (see below for the
> limitations that apply)
> - configurable 'max_connections' limit in yum.conf
> This is the maximum number of simultaneous connections Yum makes.  Purpose of
> this is to limit local resources (number of processes forked).  The default is
> to use urlgrabber's default value of 5.
> - mirror limits are honored, too.
> Making many connections to the same mirror usually does not help much, it just
> consumes more resources.  That's why Yum also uses mirror limits from
> metalink.xml.  If no such limit is available, at most 3 simultaneous
> connections are made to any single mirror.
> - new mirror selection algorithm
> The real downloading speed is calculated after each download, and the mirror's
> statistics get updated.  These are in turn used when selecting mirrors for
> further downloads.  This should be more accurate than measuring latencies in
> fastestmirror plugin, but slow mirrors now have to be tried from time to time,
> and the statistics need some time to build up.
> - ctrl-c handling
> This is a long-standing problem in Yum.  Due to various shortcomings in rpm and
> curl it's impossible to react immediately to SIGINT.  But now the downloader
> runs in a different process, so we can exit even if curl is still stuck.
> The "skip to next mirror" feature is gone (we don't want to restart all
> currently running downloads).
> Known limitations:
> - metalink.xml and repomd.xml downloads are not parallelized yet.
> --
> Zdeněk Pavlas
> --
> devel mailing list
> devel at lists.fedoraproject.org
> https://admin.fedoraproject.org/mailman/listinfo/devel

Waiting to get this in Fedora 17. Great work!


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