On Tue, Jun 14, 2011 at 08:41:59AM -0400, Bill Erickson wrote: > > Hi Dan, > > I'd like to suggest we not make this change or at least make the > default significantly lower. With a 30-second timeout and a slow or > crippled added content provider, it would not take long for the > Apache processes to be gobbled up, leaving EG unusable.
Hmm. I guess as you say below that depends on load and the added content provider; we've been running with timeout set to 45 seconds and using the new OpenLibrary Read API where some requests do take a long time to resolve (30 seconds for an ISBN with many editions is not unusual, at least in this early stage before they've optimized their own service). I thought that with caching integrated into added content, the idea was that the initial request would be costly but subsequent requests would be cached - therefore spreading out the pain. > My preference would be to keep it at 1 w/ the understanding that > users can raise the value if they want to take that risk. If that's > too aggressive for a default, I could maybe see using 2 or 3 > seconds. Anything higher is unsafe, IMO. Of course, it depends on > the environment. Keeping it at 1 would be the status quo, and status quo was that I was seeing plenty of timeouts at that setting both when we had Syndetics as our AC provider and when we switched to OpenLibrary. 2 or 3 would definitely be better. When I raised the default timeout value on IRC a week or two back, the general reaction was that 1 seemed low. If you see AC caching presenting a possible denial of service issue, then maybe we should just eliminate the caching entirely, or overhaul it so that it draws from a different pool of Apache processes than the main Evergreen processes? From what you've described, it sounds like as it currently is architected on a single-server system, a sufficient number of concurrent AC requests would exhaust the available Apache processes no matter what the timeout value is set to; it's less likely to happen at 1, but still a denial of service waiting to happen.
