upstream sent too big header while reading response header from upstream

Question

I am getting these kind of errors:

2014/05/24 11:49:06 [error] 8376#0: *54031 upstream sent too big header while reading response header from upstream, client: 107.21.193.210, server: aamjanata.com, request: "GET /the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https://aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20https:/aamjanata.com/the-brainwash-chronicles-sponsored-by-gujarat-government/,%20ht

Always it is the same. A url repeated over and over with comma separating. Can't figure out what is causing this. Anyone have an idea?

Update: Another error:

http request count is zero while sending response to client

Here is the config. There are other irrelevant things, but this part was added/edited

fastcgi_cache_path /var/nginx-cache levels=1:2 keys_zone=WORDPRESS:100m inactive=60m;
fastcgi_cache_key "$scheme$request_method$host$request_uri";
fastcgi_cache_use_stale error timeout invalid_header http_500;
fastcgi_ignore_headers Cache-Control Expires Set-Cookie;
proxy_buffer_size   128k;
proxy_buffers   4 256k;
proxy_busy_buffers_size   256k;
    # Upstream to abstract backend connection(s) for PHP.
    upstream php {
            #this should match value of "listen" directive in php-fpm pool
            server unix:/var/run/php5-fpm.sock;
    }

And then in the server block: set $skip_cache 0;

    # POST requests and urls with a query string should always go to PHP
    if ($request_method = POST) {
            set $skip_cache 1;
    }
    if ($query_string != "") {
            set $skip_cache 1;
    }

    # Don't cache uris containing the following segments
    if ($request_uri ~* "/wp-admin/|/xmlrpc.php|wp-.*.php|/feed/|index.php|sitemap(_index)?.xml") {
            set $skip_cache 1;
    }

    # Don't use the cache for logged in users or recent commenters
    if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") {
            set $skip_cache 1;
    }

    location / {
            # This is cool because no php is touched for static content.
            # include the "?$args" part so non-default permalinks doesn't break when using query string
            try_files $uri $uri/ /index.php?$args;
    }


    location ~ \.php$ {
            try_files $uri /index.php;
            include fastcgi_params;
            fastcgi_pass php;
            fastcgi_read_timeout 3000;

            fastcgi_cache_bypass $skip_cache;
            fastcgi_no_cache $skip_cache;

            fastcgi_cache WORDPRESS;
            fastcgi_cache_valid  60m;
    }

    location ~ /purge(/.*) {
        fastcgi_cache_purge WORDPRESS "$scheme$request_method$host$1";
    }`

Answer 1

Add the following to your conf file

fastcgi_buffers 16 16k; 
fastcgi_buffer_size 32k;

Answer 2

If nginx is running as a proxy / reverse proxy

that is, for users of ngx_http_proxy_module

In addition to fastcgi, the proxy module also saves the request header in a temporary buffer.

So you may need also to increase the proxy_buffer_size and the proxy_buffers, or disable it totally (Please read the nginx documentation).

Example of proxy buffering configuration

http {
  proxy_buffer_size   128k;
  proxy_buffers   4 256k;
  proxy_busy_buffers_size   256k;
}

Example of disabling your proxy buffer (recommended for long polling servers)

http {
  proxy_buffering off;
}

For more information: Nginx proxy module documentation

Answer 3

Plesk instructions

I combined the top two answers here

In Plesk 12, I had nginx running as a reverse proxy (which I think is the default). So the current top answer doesn't work as nginx is also being run as a proxy.

I went to Subscriptions | [subscription domain] | Websites & Domains (tab) | [Virtual Host domain] | Web Server Settings.

Then at the bottom of that page you can set the Additional nginx directives which I set to be a combination of the top two answers here:

fastcgi_buffers         16  16k;
fastcgi_buffer_size         32k;
proxy_buffer_size          128k;
proxy_buffers            4 256k;
proxy_busy_buffers_size    256k;

Answer 4

upstream sent too big header while reading response header from upstream is nginx's generic way of saying "I don't like what I'm seeing"

1. Your upstream server thread crashed
2. The upstream server sent an invalid header back
3. The Notice/Warnings sent back from STDERR overflowed their buffer and both it and STDOUT were closed

3: Look at the error logs above the message, is it streaming with logged lines preceding the message? PHP message: PHP Notice: Undefined index: Example snippet from a loop my log file:

2015/11/23 10:30:02 [error] 32451#0: *580927 FastCGI sent in stderr: "PHP message: PHP Notice:  Undefined index: Firstname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Lastname in /srv/www/classes/data_convert.php on line 1090
... // 20 lines of same
PHP message: PHP Notice:  Undefined index: Firstname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Lastname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undef
2015/11/23 10:30:02 [error] 32451#0: *580927 FastCGI sent in stderr: "ta_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Firstname

you can see in the 3rd line from the bottom that the buffer limit was hit, broke, and the next thread wrote in over it. Nginx then closed the connection and returned 502 to the client.

2: log all the headers sent per request, review them and make sure they conform to standards (nginx does not permit anything older than 24 hours to delete/expire a cookie, sending invalid content length because error messages were buffered before the content counted...). getallheaders function call can usually help out in abstracted code situations php get all headers

examples include:

<?php
//expire cookie
setcookie ( 'bookmark', '', strtotime('2012-01-01 00:00:00') );
// nginx will refuse this header response, too far past to accept
....
?>

and this:

<?php
header('Content-type: image/jpg');
?>

<?php   //a space was injected into the output above this line
header('Content-length: ' . filesize('image.jpg') );
echo file_get_contents('image.jpg');
// error! the response is now 1-byte longer than header!!
?>

1: verify, or make a script log, to ensure your thread is reaching the correct end point and not exiting before completion.