title: PostgreSQL Exception: “An I/O error occured while sending to the backend”
body: <p>I run two web app in a machine and one DB in another machine.(They use the same DB)
  One can run very well,But another one always down after about 4 hours.</p>
  
  <p>Here is error information:</p>
  
  <pre><code>Error 2014-11-03 13:31:05,902 [http-bio-8080-exec-7] ERROR spi.SqlExceptionHelper  - An I/O error occured while sending to the backend.
  | Error 2014-11-03 13:31:05,904 [http-bio-8080-exec-7] ERROR spi.SqlExceptionHelper  - This connection has been closed.
  </code></pre>
  
  <p>Postgresql logs:</p>
  
  <pre><code>2014-10-26 23:41:31 CDT WARNING:  pgstat wait timeout
  2014-10-27 01:13:48 CDT WARNING:  pgstat wait timeout
  2014-10-27 03:55:46 CDT LOG:  could not receive data from client: Connection timed out
  2014-10-27 03:55:46 CDT LOG:  unexpected EOF on client connection
  </code></pre>
  
  <p>Who caused this problem, app or database? or net?</p>