Resolving 502 Bad Gateway on bbb server

Well there can be multiple reasons for this error. But in my node.js development with mongoDB, this always occurs when mongoDB could not be started. The solution was always to cleanup old mongod.lock files. This is what I use for that

(i) First ensure all your services using mongoDB are shutdown
(2) Run this :

$> sudo find ~/ -name mongod.lock | xargs sudo rm