Did you check the timeout on your apache proxy config? Once apache has detected the backend is not available it won't retry again until a certain number of seconds (timeout) has passed. I pretty sure mod_proxy defaults to 60 seconds, which I usually reduce to get a quicker recovery when Tomcat is back up. Ryan Murray elementn^n -----Original Message----- From: Jenny Brown [mailto:skywind@xxxxxxxxx] Sent: Wednesday, June 10, 2009 12:43 AM To: users@xxxxxxxxxxxxxxxx Subject: Re: 503 status seems to get cached - how do I disable caching? Ok, I tried testing for the hung ajp sockets concept, and got some other useful info too. Problem still remains. Procedure: I stopped all services that make requests to this dev web server (so I am the only user on). I stopped both tomcat and apache, and make sure all processes had exited. (Goal- eliminate open sockets.) I started apache and then tomcat. I logged in to tomcat's manager app via both urls (one through apache, one direct on port 8080), and authenticated. Page came up. I shut down tomcat, refreshed both browser windows, confirmed accurate service-not-available message. This is also the step that would get the error message into apache httpd's cache. Results: I started tomcat, waited several seconds, and refreshed both browser windows. Tomcat-8080 came up fine. Apache still showed the error message. I bounced on shift-control-r (refresh without browser cache) about once per second, in the apache window, for a while. About 40 seconds later (by the clock) apache finally figured out that tomcat was back up. Issue: Is it possible that apache is caching because the same request is coming over and over within a small time frame? Or that there's a header it's setting in the response that affects results? I'm still puzzled. Thanks. Jenny Brown On Tue, Jun 9, 2009 at 3:37 PM, Jenny Brown<skywind@xxxxxxxxx> wrote: > Regarding the possibility of hung AJP sockets: > > That's an interesting question. I have a dev environment where I > could test it out, though it'll be a while before I get an opportunity > to do so. If I can confirm that the absence of pending requests makes > the response time faster, I'll let you know. Likewise if that's not > the issue, I'm back to the drawing board on it. > > Thanks for the ideas. > > Jenny Brown > > > On Mon, Jun 8, 2009 at 1:13 PM, André Warnier<aw@xxxxxxxxxx> wrote: >> Jenny Brown wrote: >>> >>> On Mon, Jun 8, 2009 at 12:50 PM, Jenny Brown<skywind@xxxxxxxxx> wrote: >>>>> >>>>> What you should really try, is to use the browser to access that same >>>>> URL >>>>> directly on Tomcat, without going through Apache, and see how long you >>>>> have >>>>> to wait there to get an answer after you start Tomcat. >>>> >>>> Hitting tomcat directly on port 8080 is very fast. That difference in >>>> speed is what led me to believe that apache seemed to be caching. >>> >>> To clarify this a bit: >>> >>> In a single web browser, I can load >>> http://www.myserver.com:8080/manager/html/ in tomcat and see results, >>> and load http://www.myserver.com/manager/html/ in another window >>> (routes through apache, then ajp to tomcat) and see 503 -- at the same >>> time. >>> >>> That is, tomcat is up, the manager web app is answering requests, and >>> I can interact with it normally, for a significant amount of time, >>> while apache continues to say it can't get to it. >>> >>> >> Allright, so you have done your testing properly. I just wanted to make >> sure you were looking at the right issue (I've had webapps that took 10 >> minutes to get ready to process requests). >> >> And you are using mod_proxy_ajp as a connector, with which I am not >> familiar, so I'll just dream up a scenario for the issue, and maybe a >> specialist can tell us if I'm wrong. >> >> Let's imagine that there is a limited pool of mod_proxy_ajp threads or >> processes that can potentially forward requests to Tomcat. Say there are 15 >> of them, no more. >> Now 15 requests are issued to Apache at the same time, which should get >> proxied to Tomcat. Each request is processed by one of the mod_proxy_ajp >> threads, they all set up a connection to Tomcat, and send their request. >> Next, Tomcat goes down. The ajp threads are still waiting for a response. >> They will keep waiting until some timeout occurs. >> Now more requests arrive in httpd, really for Tomcat. >> But because the 15 ajp threads are busy waiting, these requests have to wait >> (for a free ajp thread). >> Now Tomcat comes back up, but of course that does not help the apache ajp >> threads, who are still waiting on the wrong sockets. >> A direct request to Tomcat goes through quickly. >> A request through Apache however, has to wait for one of the stuck ajp >> threads to realise that there is a problem, and build a new connection to >> Tomcat. >> AJP specialists, what's wrong with the above ? >> >> To Jenny : if you were using mod_jk instead of mod_proxy_ajp, then I think >> something like the cping/cpong feature may help you shorten the response >> time. But I don't know if mod_proxy_ajp has something similar. >> >> I would also in the meantime check if you have the latest version of >> mod_proxy_ajp. It is a (relatively) recent module, in which a lot of >> changes have happened over the last few months. Maybe what you are seeing >> is related to something since corrected. >> >> >> --------------------------------------------------------------------- >> The official User-To-User support forum of the Apache HTTP Server Project. >> See <URL:http://httpd.apache.org/userslist.html> for more info. >> To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx >> " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx >> For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx >> >> > --------------------------------------------------------------------- The official User-To-User support forum of the Apache HTTP Server Project. See <URL:http://httpd.apache.org/userslist.html> for more info. To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx --------------------------------------------------------------------- The official User-To-User support forum of the Apache HTTP Server Project. See <URL:http://httpd.apache.org/userslist.html> for more info. To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx
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