Upstream too big - nginx + codeigniter

I am getting this error from Nginx, but can't seem to figure it out! I am using codeigniter and am using the database for sessions. So I'm wondering how the header can ever be too big. Is there anyway to check what the header is? or potentially see what I can do to fix this error?

Let me know if you need me to put up any conf files or whatever and I'll update as you request them

2012/12/15 11:51:39 [error] 2007#0: *5778 upstream sent too big header while reading response header from upstream, client: 24.63.77.149, server: jdobres.xxxx.com, request: "POST /main/login HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "jdobres.xxxxx.com", referrer: "http://jdobres.xxxx.com/"

UPDATE

I added the following into conf:

proxy_buffer_size   512k;
proxy_buffers   4 512k;
proxy_busy_buffers_size   512k;

And now I still get the following:

2012/12/16 12:40:27 [error] 31235#0: *929 upstream sent too big header while reading response header from upstream, client: 24.63.77.149, server: jdobres.xxxx.com, request: "POST /main/login HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "jdobres.xxxx.com", referrer: "http://jdobres.xxxx.com/"

Add this to your http {} of the nginx.conf file normally located at /etc/nginx/nginx.conf:

proxy_buffer_size   128k;
proxy_buffers   4 256k;
proxy_busy_buffers_size   256k;

Then add this to your php location block, this will be located in your vhost file look for the block that begins with location ~ .php$ {

fastcgi_buffer_size 128k;
fastcgi_buffers 4 256k;
fastcgi_busy_buffers_size 256k;

Modify your nginx configuration and change/set the following directives:

    proxy_buffer_size   128k;
    proxy_buffers   4 256k;
    proxy_busy_buffers_size   256k;

using nginx + fcgiwrap + request too long

I had the same problem because I use a nginx + fcgiwrap configuration:

location ~ ^.*\.cgi$ {
    fastcgi_pass  unix:/var/run/fcgiwrap.sock;
    fastcgi_index index.cgi;
    fastcgi_param SCRIPT_FILENAME /opt/nginx/bugzilla/$fastcgi_script_name;
    include /etc/nginx/fastcgi_params;
    # attachments can be huge
    client_max_body_size 0;
    client_body_in_file_only clean;
    # this is where requests body are saved
    client_body_temp_path /opt/nginx/bugzilla/data/request_body 1 2;
}

and the client was doing a request with a URL that was about 6000 characters (a bugzilla request).

debugging...

location ~ ^.*\.cgi$ {
    error_log /var/log/nginx/bugzilla.log debug;
    # ...
}

This is what I got in the logs:

2015/03/18 10:24:40 [debug] 4625#0: *2 upstream split a header line in FastCGI records
2015/03/18 10:24:40 [error] 4625#0: *2 upstream sent too big header while reading response header from upstream, client: 10....

can I have "414 request-uri too large" instead of "502 bad gateway"?

Yes you can! I was reading https://stackoverflow.com/questions/1067334/how-to-set-the-allowed-url-length-for-a-nginx-request-error-code-414-uri-too before because I thought "hey the URL's too long" but I was getting 502's rather than 414's.

large_client_header_buffers

Try #1:

# this goes in http or server block... so outside the location block
large_client_header_buffers 4 8k;

This fails, my URL is 6000 characters < 8k. Try #2:

large_client_header_buffers 4 4k;

Now I don't see a 502 Bad Gateway anymore and instead I see a 414 Request-URI Too Large

"upstream split a header line in FastCGI records"

Did some research and found somewhere on the internet:

• http://forum.nginx.org/read.php?2,4704,4704
• https://www.ruby-forum.com/topic/4422529
• http://mailman.nginx.org/pipermail/nginx/2009-August/014709.html
• http://mailman.nginx.org/pipermail/nginx/2009-August/014716.html

This was sufficient for me:

location ~ ^.*\.cgi$ {
    # holds request bigger than 4k but < 8k
    fastcgi_buffer_size 8k;
    # getconf PAGESIZE is 4k for me...
    fastcgi_buffers 16 4k;
    # ...
}

I have proven that this is also sent when an invalid header is transmitted. Invalid characters or formatting of the HTTP headers, cookie expiration set back by more than a month, etc will all cause: upstream sent too big header while reading response header from upstream

I encountered this problem in the past (not using codeigniter but it happens whenever the responses contain a lot of header data) and got used to tweaking the buffers as suggested here, but recently I got bitten by this issue again and the buffers were apparently okay.

Turned out it was spdy's fault which I was using on this particular project and solved by enabling spdy headers compression like this:

spdy_headers_comp 6;

Problem: upstream sent too big header while reading 
response header from upstream Nginx with Magento 2

Solution: Replace given below setting into /nginx.conf.sample File

• fastcgi_buffer_size 4k;

with

• fastcgi_buffer_size 128k;
• fastcgi_buffers 4 256k;
• fastcgi_busy_buffers_size 256k;