Moleculer: Service `dependencies` option

[tinchoz49]

Hi @icebob, as we talk, here is the repository:

https://github.com/tinchoz49/example-moleculer-wait-for-services

[icebob]

Thank you!

[icebob]

@tinchoz49 I checked it. If you return with the waitForServices in started, it will cause a dead lock, because transporter wait for all local services started, but the service wait for receive other services via transporter. Workaround is to remove the return in started. But I will think out something to solve it.

[tinchoz49]

maybe we can define a hook method started or like an option waitForServices in the moleculer.config.js to hook up in the broker.start() promise.

Something like this:

// moleculer.config.js
module.exports = {
  namespace: 'dev',
  nodeID: 'node-' + process.pid,

  waitForServices: ['greeter-two'],
  ...
};

[WoLfulus]

@tinchoz49 I'd sugest something like dependencies or depends_on instead of waitForServices in this case

[icebob]

I vote to dependencies but it would be better to place it into the service schema because every service has different dependencies.
Example:

// posts.service.js
module.exports = {
  name: "posts",
  dependencies: ["users", "comments"]
  ....
}

In this case the broker will call the "posts" service started handler if all dependent services are available.
What do you think?

[tinchoz49]

I like the suggestion! my vote for dependencies at the service schema level.

[WoLfulus]

It doesn't make sense to fire started if dependencies are still pending, so yeah, that works. :)

I'm just wondering if theres interdependent services, for example A <-> B. This scenario will be blocked (if publishing to the network depends on started callback), yet, you can't accept calls if started wasn't called, because some initialization might be pending.

[icebob]

After #112 it should support versioned services too. And need an internal settings for timeout:

// posts.service.js
module.exports = {
  name: "posts",
  settings: {
      $dependencyTimeout: 30000
  },
  dependencies: [
      "likes", // shorthand w/o version
      { name: "users", version: 2 }, // with numeric version
      { name: "comments", version: "staging" } // with string version
  ]
  ....
}

Default value of $dependencyTimeout is 0 - no timeout

[icebob]

Done. Will be released in v0.11.2 (this week)

[tinchoz49]

thanks for making each day this library more awesome!

[icebob]

Released in v0.11.2