Did you ever find a solution to this problem. I think we're experiencing the same issue with our 7.0.3 server.
The tabcmd fails occasionally with the 502 proxy error after 30 minutes. I'm curious to know what configuration settings we could change to improve matters.
Did anyone get a resolution to this issue?
We have just (over the sudden) started to experience the same issue with some reports that we have generated and emailed for a long time. There has been no change/modification to the reports.
A quick fix is to increase the gateway timeout time (default is 30 minutes) - refer to tableau server admin guide if more detailas are needed (http://downloads.tableausoftware.com/quickstart/server-guides/en-us/server_admin7.0.pdf)
However, I don't think this is the optimal solution to this issue. Tableau has been notified of that and we are still waiting for a good fix/answer.
Just came across this old thread while trying to track down a "502 Proxy Error" message from tabcmd.
It turns out that the same error message can be triggered by various different underlying issues - it basically indicates that the connection between two of Tableau's server processes has gone away. In my cases this was because one of the server processes had failed with an Out of Memory error. Other cases I've seen on the forums and an article in the knowledgebase indicate that it can be due to exceeding a timeout value. Just pointing out that raising the timeout value isn't necessarily the answer - though if the failure happens after 30 minutes (or whatever your timeouts are set to) that would be the place to start.