Yum, Proxy Cache Safety, Storage Backend

[Les Mikesell]

Tim Lauridsen wrote:
> 
> This has nothing to do with yum, it is the disto there decides how to
> give access to mirrors, yum just does what the distro repo contig tell 
> it to do.

Yes, as I said, the CentOS 3.x setup was just great where they used 
RRDNS or a geo-ip enabled dns server to keep the URL's consistent. 
However I don't think it is realistic to expect all mirrors to be able 
to work that way - and if you don't have dynamic checking on the DNS 
side (like an F5 Global Load Balancer) or clients that know to retry 
multiple IPs in the returned list, you can end up stuck trying to access 
a dead site.

> "Don't blame the postman for the bad news" :)

Even a postman is going to have trouble when you randomize the addresses...

>> Maybe yum needs to do some tricks with cache control headers or 
>> appending random arguments to ensure the repo data is fresh, but there 
>> has to be some way to make it re-use packages already downloaded in a 
>> local proxy cache without any local changes.   We have several 
>> locations where everyone in a large building has to use the same proxy 
>> to get out, but the people who would be installing/updating their own 
>> linux boxes would not know what anyone else is doing or be likely to 
>> coordinate the choice of a URL if they had to change anything - and 
>> I'd guess that's a common situation.
> 
> This thread is upside down IMHO.
> The proxy don't do the right thing, so let us redesign yum, to fix the 
> problems with the proxy. I seems to be the wrong approach IMHO.

Yum is the piece you can fix, so making it do something reasonable in 
the presence of proxies sounds like not only the right approach but the 
only one possible.  Unless, of course, you'd like to re-invent caching 
proxies to work the way you like and replace all of the existing ones.

> Tim "Proxies is nothing but trouble" :)

Note that if yum acted intelligently with proxies, the whole concept of 
mirror management could be replaced by appropriately placed squid (or 
similar) proxies with no configuration/maintenance other than setting 
them to cache large files and restricting public ones to certain 
targets.  Then if yum noticed that no local proxy was being used, it 
could use some mirrorlist-like mechanism to find one nearby and use it 
explicitly, eliminating any need for a reverse-proxy setup on the proxy 
server side.

-- 
   Les Mikesell
    lesmikesell at gmail.com