symlink目录中的pm2应用会产生502 Bad Gateway

Question

I have a node.js application configured to run via pm2 in a directory structure like this:

/opt/project/v1/web/index.js
/opt/project/current -> /opt/project/v1

That is, current is a symlink to v1 . I need pm2 to start the app in current/web , not in v1/web .

I first did this:

cd /opt/project/current/web
pm2 start index.js

The web site ran fine, but pm2 resolved the symlink to /opt/project/v1/web/index.js . So I found this forum thread about pm2 resolving symlinks , and from there I tried this instead:

cd /opt/project
pm2 start current/web/index.js

The process appeared to start, and pm2 showed it in the list and showed the symbolic path, except visiting the page now yields a 502 (Bad Gateway) error.

The output of pm2 show for that last attempt is:

┌───────────────────┬───────────────────────────────────────┐
│ status            │ online                                │
│ name              │ index                                 │
│ restarts          │ 7                                     │
│ uptime            │ 2s                                    │
│ script path       │ /opt/project/current/web/index.js     │
│ script args       │ N/A                                   │
│ error log path    │ /root/.pm2/logs/index-error-0.log     │
│ out log path      │ /root/.pm2/logs/index-out-0.log       │
│ pid path          │ /root/.pm2/pids/index-0.pid           │
│ interpreter       │ node                                  │
│ interpreter args  │ N/A                                   │
│ script id         │ 0                                     │
│ exec cwd          │ /opt/project                          │
│ exec mode         │ fork_mode                             │
│ node.js version   │ 6.8.1                                 │
│ watch & reload    │ ✘                                     │
│ unstable restarts │ 0                                     │
│ created at        │ 2016-12-03T22:08:58.972Z              │
└───────────────────┴───────────────────────────────────────┘

Thinking that perhaps the different cwd was a problem, I then tried this, also from that thread:

1. Create a file app.json :

    { "apps": [ { "name": "index", "script": "index.js", "args": [], "watch": true, "node_args": "", "merge_logs": true, "cwd": "/opt/project/current/web", "env": { } } ] } 

2. Start with pm2 start app.json

When I did it this way the results were the same as the previous attempt except pm2 showed the correct cwd, but still got a 502.

None of the log files seem to show any errors and pm2 shows the app as online.

I really don't know anything about node.js or pm2 , I was handed an existing system and tasked with reorganizing the file system a bit. I have a very basic working knowledge of pm2 's commands now, but that's about it.

So my question is: How can I get the app to run in the symlink'd path and why does it respond with a 502 when I try?

Answer 1

Well, I figured it out. I solved it by using this configuration file (saved as app.json):

{
    "apps": [
    {
        "name": "index",
        "script": "./index.js",
        "cwd": "/opt/project/current/web",
        "exec_mode": "fork_mode",
        "env": {
        }
    }
    ]
}

And starting it like:

cd /opt/project
pm2 start current/web/app.json

And it worked like a charm, although I'm not sure exactly which difference here solved the problem, I didn't take the time to investigate further.