Monday, October 29, 2012

yum and fastestmirror plugin...

Few hours ago I lost my nerves because when I started yum to update my system, download was painfully slow, somewhere around 20kB/s. It is outrageous because I was using 100 Mbps link and that is probably the slowest link in the chain that ends up somewhere in GEANT. Thus, things have to be much faster than that! The best speed that can be achieved is somewhere around 50Mbps and what I was getting wasn't even remotely close to it! This wasn't something I was prepared to accept as is, so I decided to see what's happening.

Yum has a plugin, fastestmirror. The purpose of that plugin is to determine the fastest available mirror and makes yum download from it, not some random one. Usually, this plugin works very well, but this time it didn't. I tried to reset everything with
yum clean all
and than again
yum update
But it didn't help. Googling around I quickly determined that the first command didn't remove fastestmirror's data. What is necessary is to remove cache file stored in /var/cache/yum/x86_64/17/timedhosts.txt (this is location on 64-bit Fedora 17). Well, guess what, this didn't help either. Namely, fastestmirror plugin determines which mirror is the best one based on measuring how much time is necessary to establish connection with a mirror, and then it immediately disconnects. This is all OK, until mirror starts to apply some throttling effectively capping maximum speed. And this was exactly what happened to me.

It used to be possible to send SIGINT signal to yum (pressing Ctrl+C) on which yum would switch to another mirror. But this doesn't work any more. When you press Ctrl+C yum exits. Now, this is expected behavior, but the previous one was actually useful! So, there should be some way to tell yum to switch to next mirror.

In the end I solved this by looking which mirror(s) yum was using. This is printed when yum starts, e.g.:

Loading mirror speeds from cached hostfile
 * fedora:
 * fedora-debuginfo:
 * rpmfusion-free:
 * rpmfusion-free-debuginfo:
 * rpmfusion-free-updates:
 * rpmfusion-free-updates-debuginfo:
 * rpmfusion-nonfree:
 * rpmfusion-nonfree-debuginfo:
 * rpmfusion-nonfree-updates:
 * rpmfusion-nonfree-updates-debuginfo:
 * rpmfusion-nonfree-updates-testing:
 * rpmfusion-nonfree-updates-testing-debuginfo:
 * updates:
 * updates-debuginfo:
The problem was Fedora's main repository, which was downloaded from So, I edited fastestmirror's configuration file /etc/yum/pluginconf.d/fastestmirror.conf and added the following line:
That excluded a bit more mirrors than I intended, but it definitely solved my problem.


Paul said...

big thumb up! same problem here..
installed centos ( via tuwien link ) but its kinda slow!

excluded the .at domain and everything works :)

L said...

As much as I can releate, but blocking all austrian mirrors might be some overkill. Why not be a bit more specific and exclude (has the same effect, but doesn't seem as drastic)

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