node.js, forever & nginx with 0% downtime upgrades -


the goal here update server via git pull , restart server while using upgraded backup instance avoid missing requests. below nginx config.

nginx backend config

upstream backend {     server localhost:8008 max_fails=1 fail_timeout=3s;     server localhost:9008 backup; }

workflow

  1. fire updated instance of backup server , confirm , responding api requests.
  2. send shutdown command main server calls server.close() , start setting header res.setheader('connection', 'close') requests may still come through due keep-alive connections.
  3. wait till close event fired , confirm server.getconnections returns 0 active connections.
  4. update main server git pull , bring up
  5. confirm , responding api requests.
  6. take down backup server

problem

i'm receiving 502 errors nginx while main server down.


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