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Re: Cache manager occasionally stops deleting cached files

February 25, 2016 05:46AM
vedranf Wrote:
-------------------------------------------------------
> Hello,
>
> I'm having an issue where nginx (1.8) cache manager suddenly just
> stops deleting content thus the disk soon ends up being full until I
> restart it by hand. After it is restarted, it works normally for a
> couple of days, but then it happens again. Cache has some 30-40k
> files, nothing huge. Relevant config lines are:
>
> proxy_cache_path /home/cache/ levels=2:2 keys_zone=cache:25m
> inactive=7d max_size=2705g use_temp_path=on;
> proxy_temp_path /dev/shm/temp; # reduces parallel writes on
> the disk
> proxy_cache_lock on;
> proxy_cache_lock_age 10s;
> proxy_cache_lock_timeout 30s;
> proxy_ignore_client_abort on;
>
> Server gets roughly 100 rps and normally cache manager deletes a
> couple of files every few seconds, however when it gets stuck this is
> all it does for 20-30 minutes or more, i.e. there are 0 unlinks (until
> I restart it and it rereads the on-disk cache):
>
> ...
> epoll_wait(14, {}, 512, 1000) = 0
> epoll_wait(14, {}, 512, 1000) = 0
> epoll_wait(14, {}, 512, 1000) = 0
> epoll_wait(14, {}, 512, 1000) = 0
> gettid() = 11303
> write(24, "2016/02/18 08:22:02 [alert] 11303#11303: ignore long locked
> inactive cache entry 380d3f178017bcd92877ee322b006bbb, count:1\n",
> 123) = 123
> gettid() = 11303
> write(24, "2016/02/18 08:22:02 [alert] 11303#11303: ignore long locked
> inactive cache entry 7b9239693906e791375a214c7e36af8e, count:24\n",
> 124) = 124
> epoll_wait(14, {}, 512, 1000) = 0
> ...
>
> I assume the mentioned error is due to relatively often nginx restarts
> and is benign. There's nothing else in the error log (except for
> occasional upstream timeouts). I'm aware this likely isn't enough info
> to debug the issue, but do you at least have some ideas on what might
> be causing this issue, where to look? I'm wild guessing cache manager
> waits for some lock to be released, but it never gets released so it
> just waits indefinitely.
>
> Thanks,
> Vedran


We have the same problem, but i'm not sure, that this is caused by often nginx restarts.

As far as i know problem exist since version 1.6 (maybe even earlier, 1.4.6 from ubuntu repo is not affected) till now (1.9.9)

I've collected related forum posts (should help analyze the problem):
https://forum.nginx.org/read.php?21,258292,258292#msg-258292
https://forum.nginx.org/read.php?21,260990,260990#msg-260990
https://forum.nginx.org/read.php?2,263625,263625#msg-263625

Also, i think it's somehow related to write connection leak. (see image link)

https://s3.eu-central-1.amazonaws.com/drive-public-eu/nginx/betelgeuse_nginx_connections.PNG

Here we have our standard nginx configuration (before january, 28) with 7 days inactive time:

proxy_cache_path /mnt/cache1/nginx levels=2:2 keys_zone=a.d-1_cache:2143M inactive=7d max_size=643G loader_sleep=1ms;

Every ~8 days (when writing connections reaches ~10k mark) cache starts growing and fills the disk. Write connections falls on graph are nginx restarts.

On january, 28 i changed inactive time to 8h. After write connections hits ~10k mark, nginx starts filling logs with "ignore long locked inactive cache entry" message (1-2 messages per minute on average).

As you see write connections continuously grows. (When we had to power off the machine it's reached ~60k).

For counting nginx connections we use standard http_stub_status_module.

I think that nginx "reference counter" could be broken, because total established TCP connection remains the same all the time.
Subject Author Posted

Cache manager occasionally stops deleting cached files

vedranf February 18, 2016 11:20AM

Re: Cache manager occasionally stops deleting cached files

Maxim Dounin February 18, 2016 12:12PM

Re: Cache manager occasionally stops deleting cached files

vedranf February 19, 2016 08:00AM

Re: Cache manager occasionally stops deleting cached files

Maxim Dounin February 19, 2016 08:30AM

Re: Cache manager occasionally stops deleting cached files

vergil February 25, 2016 05:46AM

Re: Cache manager occasionally stops deleting cached files

Maxim Dounin February 25, 2016 09:22AM

Re: Cache manager occasionally stops deleting cached files

vergil April 13, 2016 05:08AM



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