NGINX Unit + Flask = not found among the available application modules

this is happens when i upload config.json:

sudo curl -X PUT --data-binary @config.json --unix-socket /var/run/control.unit.sock http://localhost/config
{
        "error": "Invalid configuration.",
        "detail": "The module to run \"python 3.6\" is not found among the available application modules."
}

i tried: Python, Python 3.7

my config.json that i trying to upload:

    {
  "listeners": {
    "*:1234": {
      "pass": "applications/flask"
    }
  },
  "applications": {
    "flask": {
      "type": "python 3.6",
      "processes": 5,
      "path": "/home/123/123/",
      "home": "/home/123/123/venv/",
      "module": "wsgi",
      "user": "root",
      "group": "root"
    }
  }
}

This is all happens when i trying to make simple flask-demo with nginx unit

Solution

First, you should check if the python module is properly installed. In order to discover where they are located, you can use the unitd --help as it shows the default options.

$ unitd --help
...

  --modules DIRECTORY  set modules directory name
                       default: "/usr/lib/unit/modules"

If you use a custom systemd unit or script, you should check the option --modules

Simply list the files in the modules directory:

$ ls /usr/lib/unit/modules
python3.6.unit.so  python3.7.unit.so

If they are there, check in the beginning of the unit.log if they were correctly loaded:

$ sudo more /var/log/unit.log 
2020/04/29 22:24:47 [info] 13025#13025 discovery started
2020/04/29 22:24:47 [notice] 13025#13025 module: python 3.6.9 "/usr/lib/unit/modules/python3.6.unit.so"
2020/04/29 22:24:47 [notice] 13025#13025 module: python 3.7.5 "/usr/lib/unit/modules/python3.7.unit.so"
2020/04/29 22:24:47 [notice] 13024#13024 process 13025 exited with code 0
2020/04/29 22:24:47 [info] 13027#13027 router started
2020/04/29 22:24:47 [info] 13026#13026 controller started
2020/04/29 22:24:47 [info] 13027#13027 OpenSSL 1.1.1  11 Sep 2018, 1010100f

If they were not loaded, the log will say the reason. Unit module versions must match the Unit version installed. If you installed a newer version in a system running the old version, you should reinstall the unit modules as well (apt install unit-dev unit-python3.6 unit-python3.7).