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Topic Title: 502 bad gateway error when attempting to log in to Columbus
Topic Summary: too many python processes running
Created On: 1/5/2017 5:59 AM
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 1/5/2017 5:59 AM
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Posts: 76
Joined: 5/16/2014

The 502 bad gateway error tends to mean that there has been or is currently a communication issue between the client web interface and an up stream server, in this case it would indicate an issue communicating with the Columbus server.

The last time I encountered the issue we were able to attribute it to too many python processes running which was effectively blocking communication between the clients and the Columbus server.

Typically you might only expect to see 4 or 5 python processes running at any one time, and you should certainly not have any more than 10. If this is the case then it's likely there are some 'stale' or stalled processes that need killing - as was the case for me.

A simple workaround for this is to just restart the Columbus web component:

$ sudo /etc/init.d/columbus restart web

This would bring the server back up but it didn't help with root cause analysis. You might wish to try the following workflow to verify that it's the same issue:

$ sudo /etc/init.d/columbus stop web

# now check if there are any "python" processes still alive

$ ps -fU columbus

# if in this output list there are "python" processes still listed, kill

them manually:

$ sudo kill (pid of python process)

# start columbus web again

$ sudo /etc/init.d/columbus start web

If the error goes away then this suggests that it's the number of python processes that is causing the issue.

The problem with this approach is that it mean that any users currently logged in would potentially lose their work e.g. if building an analysis BB routine.

Alternatively it might be sufficient for you to kill the stale "python" processes from time to time. You can identify these stale processes by looking at the output of:

$ ps -fU columbus

As described here:

Following on from that you might then just need to filter out those older processes using a similar workflow as described here:



Edited: 4/21/2017 at 7:41 AM by RAH
 10/15/2018 12:25 PM
User is offline View Users Profile Print this message


Posts: 76
Joined: 5/16/2014

The following command will give you the number of python processes:

ps -fU columbus | grep [m] | wc -l


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