memcached problems...

[Igor Sysoev]

On Mon, Aug 31, 2009 at 05:34:07PM -0400, JG wrote:

> normally, i whould agree. but in this special case the system has trouble to handle the high io load due to really lots of files (about 8 million.... i know... crazy, not my content).
> 
> to get a workaround for the hd io load, i just wanted to get nginx to load the swf and flv files into memcached which should be possible for my understanding. 
> 
> i think i found one of my problems, the missing fallback server if the content isnt already in memcached. 
> 
> but now i get 502 bad gateway error messages, and such strange error log entries
> 
> 2009/08/31 23:21:17  30612#0: 8192 worker_connections is not enough while accepting new connection on 0.0.0.0:81
> 
> ? no connections yet ... no production
> 
> but anyway, i trimmed down my config to a minimum for testing
> 
> 
>     server {
>         listen       81;
>         server_name  _;
> 
>         #access_log  logs/host.access.log  main;
> 
>         location / {
>             set $memcached_key  $uri;
>             memcached_pass      127.0.0.1:11211;
>             error_page 404 502  = /fallback;
> #           default_type        text/html;
> 
>             root   /usr/share/nginx/html;
>             index  index.html index.htm;
>         }
> 
>         location /fallback {
>             proxy_pass http://127.0.0.1:81;
>         }
> 
>         location ~ \.php$ {
>             set $memcached_key  $uri;
>             memcached_pass      127.0.0.1:11211;
> 
>             root           /home/www/htdocs;
>             fastcgi_pass   127.0.0.1:9000;
>             fastcgi_index  index.php;
>             fastcgi_param  SCRIPT_FILENAME  /home/www/htdocs$fastcgi_script_name;
>             include        fastcgi_params;
>         }
> 
> 
> 
> PHP works well, but it doesnt seem to get stored in memcached, why? and, for example if i try to download a zip file i get this in the error log
> 
> 2009/08/31 23:30:16  30815#0: *12285 recv() failed (104: Connection reset by peer) while reading response header from upstream, client: 127.0.0.1, server: _, request: "GET /koch/_banner/paldauer/paldauer.zip HTTP/1.0", upstream: "http://127.0.0.1:81/yes/_this/doesnt/work.zip", host: "127.0.0.1:81", referrer: "http://ftp.nastyhost.de:81/koch/_banner/paldauer/index.php"
> 
> please igor, anyhow if you got an idea how i can get nginx to use memcached to store content... 

nginx can not store data in memcached, it can ony get data from it.
As to "recv() failed (104: Connection reset by peer)" this is some connection
problem between nginx and 127.0.0.1:81.

However, as I already said, memcached will not resolve your problem.
You just will waste CPU time and memory. Instead you should tune kernel
to allow cache as much as possible. How much is the host physical memory
and how much is whole size of flv/swf content ?

I can not say about Linux, but in FreeBSD this can be done by increasing
"sysctl kern.maxvnodes", which is 100,000 vnodes by default. A kernel
stores file pages binding them to a vnode.


-- 
Igor Sysoev
http://sysoev.ru/en/