Browser Error - Failed to load resource: the server responded with a status of 502 (Proxy Error)

Problem

When a user tries to open the Join dialog the display opens and remains empty. Additionally, in the menu, the FlipSheet button is not rendered.

In the Developer Tools section of the browser, the following error message is displayed: 

https://myinstance.datameer.com/columnDefinition/workbook/1234?_=142369295387 Failed to load resource: the server responded with a status of 502 (Proxy Error)

In the log files, the following error message is captured in the conductor.log file: 

[admin] INFO [2015-01-01 00:00:00.000] [1128671313@qtp-569616903-4] (?:?) - Client hung up before request finished. Path: /columnDefinition/workbook/1234

Lastly, in the <INSTALLDIR>/logs/<DATE>.request.log file, the columnDefinitions request returns successfully with an exit status of 200. This confirms that the server is responding correctly.

Cause

This is caused by the client (the web-browser) timing out when waiting to receive data from the server. The duration of this timeout is configurable in the Datameer environment.

Solution

To resolve this issue, increase the "session-timeout" value on the Datameer server by following these steps.

  1. Locate the <INSTALLDIR>/webapps/ROOT/WEB-INF/web.xml file.
  2. Save a copy of this file as a backup.
  3. Edit this file and locate the line that looks like this: <session-timeout>30</session-timeout>
  4. Increase the timeout value (in seconds). As a suggestion, try to double this value. In an extreme example, try setting this value to 3600 (1 hour).
  5. Save the file.
  6. Restart Datameer to activate this new value.