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News & Views

September has turned out to have been a very difficult and traumatic month for CPAN Testers. Our server problems have now been resolved, but it has meant more time than was intended has been devoted to rebuilding the website eco-system. It's still not complete, but we are getting there.

The first sites to be reinstated were the CPAN and BACKPAN mirrors. Soon after the Statistics site and Development sites were back online. The database rebuilds took considerably longer than expected, partly because the archive of the original NNTP reports had become corrupted at some point. The checks to ensure all interconnected parts of the databases were correctly referenced also took time. A full backup was then taken so we could start from a known point once all the moving parts were restarted. Just in case anything went wrong again!

The uploads and metabase feed parsers were turned back on, and although both were not the same code that was running on the old server when it died, they both highlighted problems with the server. At first I thought one of the disk was not performing as well as it should have done, but on investigation from the guys at Bytemark, we discovered the kernel that had been installed came with an IO blocking fault. Once upgraded we started to see a much better response time.

Following the reintroduction of the performance tuning code, the metabase feed parser is now processing 4 days worth of reports in a single day. We're currently less than 15 days behind, so hopefully by next week we should be almost realtime.

The builder for the Reports site was switched on to get through the several million requests we had stacked up from the rebuild processes, but with only just over 30,000 unique requests to process it only took a short while to catch up. As of right now I'm turning the builder on only for short periods, to give the metabase feed parser as much processing resources and disk access as possible. There are currently less than 5,000 unique requests for the builder to process, which once we're fully operational, the builder should be able to process in less than a day.

As we are getting much closer to being back to full speed, you might have noticed that the Reports site is back online as of this morning. Both the dynamic and static sites are now available, however the dynamic site no longer accepts requests from robots and spiders. As some don't follow the robots.txt file, this is being done within the Apache config files. For the time being the static site will accept requests from bots, but if there is any abuse, they will also be denied access.

Once upon a time I had hoped the requests from bots would help to build the site, but they have ended up being more of a hindrance than a help. Also the idea that the search engines would help the ranking for Perl within some dubious lists, hasn't really materialised. As such the loss of bots is likely to have more of a benefit than keeping them on side. Interestingly, I have noted that Microsoft have stayed true to their word and removed us from the bot lists. It was just sad that it took such high profile posts to get them to take stock.

The reports emails and the release database are still to do, as are some other small corners of the eco-system. I hope to get to all of these as soon as possible over the next month, and will keep you posted as these come back online.

Many thanks to the support and understanding of everyone. It's been a traumatic exercise, but the encourangement and help we have received has been very much appreciated. If you spot any problems in the next month, it is probably something we are already aware of. If it isn't resolved by the end of the month, please let me know or post to the CPAN Testers Discussion list.

A final bit of news that has vindicated my prophecy during YAPC::Europe, is that we did indeed break the 1 million reports barrier, for reports posted in a single month. Looking at the figures so far, I'm not expecting this to be repeated for September, as I suspect some have not been so active due to the downtime for CPAN Testers last month. However, it now highlights that we can indeed cope with such a high volume of reports. It will be interesting to see whether October picks up the pace again :)

Posted by Barbie
on 3rd October 2011

With the problems we have been having for the last year with the old CPAN Testers server, we started planning to upgrade to a new server some time ago. With the events at the end of August, our timeline was brought forward several weeks. Having already made some preliminary enquiries, with the possibility of another sponsorship deal, we applied for a new server with Bytemark. Birmingham Perl Mongers have previously had dealings with Bytemark, and their support staff have always provided an excellent service. With our Open Source status the guys at Bytemark not only provided us with a server, but also offered us very welcome discount.

Having started to build the server from scratch, rebuilding all the databases and files, it became evident that we had some problems. As mentioned in the last update, the guys at Bytemark stepped up and helped us to identify the problem and fix it very quickly. This is nothing like the help and support we have previously received, and I am rather glad we have made this particular move. Hopefully we won't have to upgrade again for quite some time.

For those that might be interested the current spec is as follows:

CPU: AMD Phenom II X6 1055T (2.8GHz)
DSK: 2 × 500GB (RAID1)

This is a 6 core machine, and the performance improvement is already noticable. I was recently asked whether our code was written to cope with parallel processing, but with so many processes all running at once, we wouldn't see the benefit. The extra capacity does mean that database lookups and statistical analysis now perform much better, and even bzip isn't causing us too many problems now. However, to avoid the slashdot effect, all bots, spiders and crawlers will be blocked from accessing the main dynamic Reports site. This may be lifted at some point in the future, but the benefit both to help building pages, and to promote Perl via dubious lists, hasn't materialised. They will be able to access the static site, so they won't be blocked entirely.

If you or your company would be interested in sponsoring CPAN Testers, please get in touch. We have already been offered some private donations and backup services, and thanks to the support of Birmingham Perl Mongers we are able to fund the new server for another year, but we are always happy to talk to anyone who can help continue CPAN Testers for many years to come.

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