Thoughts on systems safety, software operations, and sociotechnical systems.
Just listened to Artur railing against squid and preaching the virtues of varnish. He quoted what most people quoted, which is how varnish performs serving out of *memory*. It must be nice to have a working set that small. Until someone can show me numbers of disk-intensive (meaning, full caches, LRU eviction churning all the […]
Thanks to Mark, squid’s got a patch I’ve been wanting for a gazillion years: time-to-serve statistics that don’t include the client’s location http://www.squid-cache.org/bugs/show_bug.cgi?id=2345 Normally, squid’s kept statistics that included the “time” to serve an object, whether it be a HIT, MISS, NEAR HIT, etc. The clock starts for this time when the first headers are […]
Read more Squid patch for making “time” stats more meaningful.
Awhile back, I said I’d love to have a tool that would allow me to peek inside filesystem cache and tell me what files (or pages of files) are inside. Well Peter Zaitsev points to the fincore tool, which comes pretty damn close: you give it a file, and it will tell you which pages […]
This was a fun talk. I saw a lot of nods in the audience when I mentioned things pertaining to social applications (unpredictable usage, etc.). A lot of folks ask questions about how we use ganglia at Flickr. A PDF of my slides are here. If anyone can tell me how to get Keynote2 slides […]
Read more Slides from ‘Capacity Planning for LAMP’ talk at MySQL Conf 2007
Caching systems are finite in size. So what happens when your cache is filled with objects ? No more objects ? Game over ? Hopefully, no. Most modern caches have some form of replacement or eviction policy. What means that based on some criteria, it’ll figure out what objects to throw out the window so […]
So there’s lots of excitement around Varnish, which is a caching proxy that is built to be first and foremost a reverse-proxy, as opposed to squid, which does both forward and reverse. Acceleration (reverse-proxying) is obviously important to us at Flickr, as we use squid extensively.
Taking a look here, it seems like linking squid against TCmalloc could be pretty damn beneficial. UPDATE: done, and tested. not in production yet, we’ll see if I can get to it soon.
Read more memory fragmentation in squid and some solutions….