title: Nginx cache, redis_pass
body: <p>I have been banging my head against a wall all day.</p>
  
  <p>I am using the following nginx configuration to test something</p>
  
  <pre><code>location  /help {
    set $redis_key "cache:$scheme://$host$request_uri";
    default_type   text/html;
    redis_pass 127.0.0.1:6379;
    error_page 404 = @upstream;
  </code></pre>
  
  <p>}</p>
  
  <p>There is a key and value inside my redis instance for the cache:$scheme.... (in my case cache:<a href="http://localhost/help" rel="nofollow">http://localhost/help</a>)</p>
  
  <p>I know they exist because I can monitor redis-cli for the nginx redis request, copy the <code>"get" "cache:http://localhost/help"</code>, paste it into another redis-cli window and get the expected response.</p>
  
  <p>The problem comes with nginx, it's not getting the response. Again I can see it connect from inside <code>redis-cli -&gt; monitor</code> and I know the key and value exist.</p>
  
  <p>From the nginx error log I can see this</p>
  
  <pre><code>2016/04/08 16:52:42 [notice] 9304#0: worker process 6328 exited with  code 0
  2016/04/08 16:52:42 [notice] 9304#0: signal 29 (SIGIO) received
  terminate called after throwing an instance of 'std::length_error'
    what():  basic_string::append
  2016/04/08 16:52:49 [notice] 9304#0: signal 17 (SIGCHLD) received
  2016/04/08 16:52:49 [alert] 9304#0: worker process 7328 exited on signal 6 (core dumped)
  2016/04/08 16:52:49 [notice] 9304#0: start worker process 7516
  2016/04/08 16:52:49 [notice] 9304#0: signal 29 (SIGIO) received
  terminate called after throwing an instance of 'std::length_error'
    what():  basic_string::append
  2016/04/08 16:52:50 [notice] 9304#0: signal 17 (SIGCHLD) received
  2016/04/08 16:52:50 [alert] 9304#0: worker process 7335 exited on signal 6 (core dumped)
  2016/04/08 16:52:50 [notice] 9304#0: start worker process 7544
  2016/04/08 16:52:50 [notice] 9304#0: signal 29 (SIGIO) received
  terminate called after throwing an instance of 'std::length_error'
    what():  basic_string::append
  </code></pre>
  
  <p>Has this appened to anyone else or can someone kick me in the right direction?</p>
  
  <p>Thanks in advance</p>