>In my opinion, the whole concept of load balancing and mirrors should be 
>outside p2's concern. How to best distribute the material and ensure delivery 
>is 
>far better catered for using other well-known technologies specially designed 
>to handle this and Eclipse.org already exploits this for read-only CVS.
>How do others perceive the use of mirrors in p2?

+1 in tycho builds, p2 mirrors have done more harm than good for the reasons 
you stated.
We have introduced a disableP2Mirrors flag [1] which we have decided to set to 
true on a corporate level.

Also, with the current mirror concept all metadata traffic still goes to 
eclipse.org, 
contributing to HTTP latency problems such as [2].

Regards,
Jan

[1] https://bugs.eclipse.org/bugs/show_bug.cgi?id=353175 
[2] https://bugs.eclipse.org/bugs/show_bug.cgi?id=347403 

From: thomas@xxxxxxx (Thomas Hallgren) 
Posted At: Dienstag, 20. September 2011 09:18
Posted To: p2-dev
Conversation: p2-dev
Subject: [p2-dev] Evaluate the usefulness of using Eclipse mirrors

Hi,

All of our builds that run outside Eclipse are now started with 
-Declipse.p2.mirrors=false. The same is true for my own IDE. Why? Because 
everything works much better that way even though I'm in Europe. Our builds 
fail intermittently without this property and updating my IDE seems to take 
forever.

I'm well aware that the use of this flag will increase the load on eclipse.org 
and I really wish I could avoid that, but with builds frequently failing and 
downloads that frequently hit sites that take forever to never respond, I can't.

I think there are many reasons for why the mirrors concept performs badly. The 
most obvious one is that some update sites have a mirrorsURL that is incorrect. 
I've seen a lot of sites for one version (say 3.7) that appoints an update site 
targeted for another (3.6) and thereby sending p2 on a wild goose chase around 
the world in order to find something that it will never find. I've been guilty 
of that error myself. It's easy enough to forget. I've seen other sites where 
this URL is just plain wrong. Site's that use a URL although they don't have 
mirrors at all, etc.

Perhaps it's time to evaluate the whole concept of using mirrors this way? Does 
it bring any advantages in real life or is it just a feature that works well in 
theory? Could it be that it causes a lot of pain and time consuming problems 
for users of p2 and hence bad will for p2 (this is my own concern) so that we 
could do better without it? If so, what other options are there?

In my opinion, the whole concept of load balancing and mirrors should be 
outside p2's concern. How to best distribute the material and ensure delivery 
is far better catered for using other well-known technologies specially 
designed to handle this and Eclipse.org already exploits this for read-only CVS.
How do others perceive the use of mirrors in p2?

Regards,
Thomas Hallgren

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