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17 messages in ru.sysoev.nginxRe: Is it possible to monitor the fai...| From | Sent On | Attachments |
|---|---|---|
| Robbie Allen | Jun 27, 2008 5:22 pm | |
| Alexander Staubo | Jun 27, 2008 5:39 pm | |
| Robbie Allen | Jun 27, 2008 6:08 pm | |
| Rt Ibmer | Jun 27, 2008 6:54 pm | |
| mike | Jun 27, 2008 11:02 pm | |
| Grzegorz Nosek | Jun 28, 2008 4:50 am | |
| Grzegorz Nosek | Jun 28, 2008 5:31 am | |
| mike | Jun 28, 2008 9:14 am | |
| Alexander Staubo | Jun 28, 2008 12:28 pm | |
| Grzegorz Nosek | Jun 28, 2008 12:53 pm | |
| Almir Karic | Jun 28, 2008 1:30 pm | |
| Brice Figureau | Jun 28, 2008 2:36 pm | |
| Alexander Staubo | Jun 28, 2008 4:02 pm | |
| Rt Ibmer | Jun 28, 2008 9:38 pm | |
| Grzegorz Nosek | Jun 29, 2008 10:57 am |  .patch, .patch, .patch |
| Brice Figureau | Jun 30, 2008 12:23 pm | |
| Grzegorz Nosek | Jun 30, 2008 12:49 pm |
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| Subject: | Re: Is it possible to monitor the fair proxy balancer? | Actions... |
|---|---|---|
| From: | Grzegorz Nosek (grze...@public.gmane.org) | |
| Date: | Jun 28, 2008 12:53:43 pm | |
| List: | ru.sysoev.nginx | |
On sob, cze 28, 2008 at 09:28:45 +0200, Alexander Staubo wrote:
On Sat, Jun 28, 2008 at 2:31 PM, Grzegorz Nosek <grze...@public.gmane.org> wrote:
However, there still remains the issue of communication between the load balancer and the outside world, i.e. *how* would you like to be told that a backend has been deemed up/down
HAProxy -- apologies for having to mention it again, but it's a useful template -- has a simple status page similar to Nginx's stub status. It comes in HTML and CSV formats, and lists all backends (and frontends) and their status (up, down, going down, going up) and a ton of metrics (current number of connections, number of bytes transfered, error count, retry count, and so on). It can also export the same information on a secure domain socket if you don't want to go through HTTP.
The question wasn't really caused by the perceived impossibility of the task :) A status page is certainly simple enough (i.e. fits in the nginx model somewhat), though it has the disadvantage that you have to poll it periodically. I don't think that a dedicated socket for querying backends is a good design for nginx, so I'd like to gather ideas about how to notify the outside world. A log message? Sending a signal somewhere? An SNMP trap? Every way has its advantages and disadvantages, so I'd like to pick the one that sucks the least.
and *how* would you like to tell nginx that backend 1.2.3.4 is currently down?
Pardon me for asking a naive question, but to change the list of backends, would you not simply edit the config file and do a SIGHUP? I would reset whatever internal structures that are kept by the workers, but I can't think of anything that's not okay to lose.
Yes. That's the obvious solution but apparently not always acceptable, especially when you'd want to use an external monitoring system to do this automatically.
- a new option, e.g. max_requests 10 10 20 20 (specifying the number for each backend in the order of server directives)
That's a horrible syntax and one that is going to cause problems as you add or remove backends from the config. A max_requests setting belongs on each backend declaration.
Like I wrote in the snipped part, I cannot easily add options to the server directives (at least without patching nginx or reinventing the square wheel). I don't like the max_requests idea too, for precisely the same reason. I presume that means the overloading of weight=X is at least acceptable.
So, what say you, is such a feature (amounting to returning 502 errors after a certain amount of concurrent requests is reached) generally desired? If so, how would you like to configure it?
You should only return an error if a request cannot be served within a given timeout, not when all backends are full.
Will have to think about it. This has the potential of busy-looping when all the backends are indeed full (or down, but then one can just send a hard error and be done with it). I don't think nginx has a way to be told "everything is unavailable now, come back to me in a second or two" or even better "I'll tell you when to ask me again".
Best regards, Grzegorz Nosek