I don't see any thing in the logs telling me why these processes died. I verified that there was no EAC stop command issued. And the Workbench process was still running with a start date from 3 weeks ago, which tells me the instance/server/host has been up the entire time.
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One other thought which you may have had as well, did the dgraph process possibly die with an abnormal end? I would also look in the dgraph's log file for any ERRORs or FATALs and I would also look for a core.*.dmp file that are sometimes generated when the dgraph process fails. I can't remember exactly what the files are called, but you may try grep'ing for "core" or ".dmp"