Add extraRunParams for hooks, commands, and crons

[emanuelefaja]

Problem

extraSwarmParams works great for long-running services (docker service create), but hooks (hook:deploy:start:before, hook:deploy:start:after), disco run commands, cron jobs, and CGI handlers use docker container create instead — and they don't support any extra Docker parameters.

This becomes a problem when containers need to reach services on the Docker host. For example, if you run a database proxy (like ProxySQL or PgBouncer) on the host machine, services can reach it via --host host.docker.internal:host-gateway in extraSwarmParams. But deploy hooks that need to run database migrations can't reach the proxy at all, because hooks don't support extra params.

We ran into this during a database migration: our Prisma migration hook (npx prisma migrate deploy) needed to connect to a database proxy on the host, but the hook container couldn't resolve host.docker.internal. We had to remove the migration hook from disco.json entirely and run migrations manually as a workaround.

Solution

Add a new extraRunParams field to the service definition in disco.json. This is passed as extra arguments to docker container create for:

• hook:deploy:start:before
• hook:deploy:start:after
• disco run commands
• Cron jobs
• CGI handlers

This is separate from extraSwarmParams because docker service create and docker container create accept different flags (e.g. --host vs --add-host).

Example

{
  "services": {
    "web": {
      "port": 8000,
      "extraSwarmParams": "--host host.docker.internal:host-gateway"
    },
    "hook:deploy:start:before": {
      "type": "command",
      "command": "npx prisma migrate deploy",
      "extraRunParams": "--add-host host.docker.internal:host-gateway"
    }
  }
}

Changes

• discofile.py: Add extraRunParams field to Service model
• docker.py: Add extra_params argument to run() function
• deploymentflow.py: Pass extraRunParams to both before/after deploy hooks
• commandruns.py: Pass extraRunParams to disco run commands
• asyncworker.py: Pass extraRunParams to cron jobs
• cgi.py: Pass extraRunParams to CGI handlers

[emanuelefaja]

@gregsadetsky let me know if you've got any feedback on this PR.

[gregsadetsky]

Thank you! We'll take a look and get back to you