Hi all, We are using Hippo 6 with a Cocoon frontend. A few days ago our frontend went down because it ran out of memory. Analysis pointed in the direction of the following:
1. There is a page based on quite a big document (thus memory intensive) that is updated every couple of minutes or so. 2. The page gets a timeout of 30 seconds, so browsers request an update with that frequency. The problem occurred when we had a lot of visitors. At some point the source document was updated and flushed from the cache. Many requests were coming in and as long as the page wasn't cached each request resulted in an attempt to regenerate the page. The result was a load of threads, each of them trying to build the page from the big document and thus together eating up all memory. In a way it surprised us that neither Apache httpd's mod_cache or Cocoon's caching seems to have some mechanism to prevent these redundant parallel activities. Question is whether anyone can point us to a solution? Our own thoughts: First of all we need to assure that at most one thread renders the page. For the other threads two possibilities seem to be reasonable: 1. Serve the "outdated" page as long as the updated is not ready 2. Wait until the updated is available. The first solution seems preferable since it prevents the possibility of having a load of "dangling" requests. However one of the solutions we are thinking of, is to create our own Cocoon cache class, that only allows the first thread to build a specific page and, using semaphores or so, has the others waiting for the first to finish. Obviously it is a solution type 2 but it is attractive because it seems relatively easy to implement. We are basically hesitant to mess more than necessary with Cocoon's caching mechanism. Any advice/ideas on this? Thanks, Reinier ******************************************** Hippocms-dev: Hippo CMS development public mailinglist Searchable archives can be found at: MarkMail: http://hippocms-dev.markmail.org Nabble: http://www.nabble.com/Hippo-CMS-f26633.html
