[FEATURE REQUEST] List of available plugins

[SerafimArts]

When starting a worker, it makes sense to pass a list of available plugins to env variables, like:

RR_PLUGINS=temporal,jobs,http,grpc

This information is required to determine the presence and/or availability of some external service. A simple example that implements a polyfill for queues (jobs) when they are absent (or when they are disabled) in the RR:

class Factory
{

    // ....
    
    public function create(): QueueInterface
    {
        if ($this->env->isAvailable('jobs')) {
            return new Queue($this->rpc);
        }

        return new SyncQueue();
    }
}

[rustatian]

It's not possible to do that via the env variable. Because the server which starts a PHP process can be in the middle of the topological sorted graph. The second reason is that the config does not represent the actual set of the running plugins (some of them might be disabled) (as for the solution to read the .rr.yaml to determine the plugins set).

The possible solution that I see here is to ask endure after the Serve stage about the actual plugins set. And provide the list via some RPC call. But this is my first thought about the problem. Expected to be in the SPRINT 2021-05-04 (not sure).

[rustatian]

The second solution is to use Status plugin for that purpose (which is used to provide different statuses about the runtime). Create an additional RPC call and add IsActive method to the interface. IsActive method (go) will grab all plugins which fit the interface and provide the list to the PHP.