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Re: [p2-dev] Evaluate the usefulness of using Eclipse mirrors

Maintaining mirrors should be the responsibility of webmaster. The correct mirrors definitely improve the stability.

Our application is using single server(though it's Amazon cloudfront) to deploy products, we're suffering the intermittent timeout to break the entire installation. That's why I contributed the bug 350014.

The latency issue(bug 353175) is caused by a lot of time is wasted on creating the http connection for each network access even though p2 is continuously trying to download a lot of files.

Because ecf doesn't reuse the http connection, which is addressed by bug 297742 and will be fixed soon. However the web server of Eclipse.org doesn't support persistent connection, the ecf improvement can't benefit the downloading experience if we are installing something from eclipse.org.

We deploy much more composite repositories than eclipse.org on Amazon, the performance has significant improvement when using the ecf with the patch attached on bug 297742.

Mengxin Zhu


On 09/20/2011 04:01 PM, Sievers, Jan wrote:
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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