invoker.js

A simple node.js script for managing services. invoker.js allows you to start, stop and tail the logs of services.

Installation

npm install -g invoker.js

Getting Started

In your project root, define an invoker.json file. e.g.:

{
    "redis": {
        "command": "redis-server"
    },

    "elasticsearch": {
        "command": "./elasticsearch/bin/elasticsearch"
    }
}

You can then start a service like so: invoker start redis

Stop a service like so: invoker stop redis

And tail the logs like so: invoker tail redis

You can additionally list the services that are currently running via: invoker list

invoker.json specification

invoker.json specifies the services to manage. The JSON object keys are the service names. The values can specify either command-based or module-based services. The above example specifies a couple of command-based services. These are services that are started simply by executing the specified command. On stop, the services are issued a SIGTERM. The normal log and error log are populated via the process' stdout and stderr, respectively.

With command-based services, you can also specify command-line arguments and options to pass to the call to child_process.spawn. Example:

{
    "redis": {
        "command": "redis-server",
        "args": ["./conf/redis.conf"],
        "options": {
            "cwd": "./data"
        }
    }
}

For more advanced usage, you can define a module-based service, where invoker calls a node.js module to start and stop the service. This is useful for a number of cases, e.g. when you want to shutdown a service by doing something other than sending a SIGTERM. Here's an example module that would manage elasticsearch using its shutdown API:

var child_process = require("child_process");
var http = require("http");

module.exports = {
    // Called on service start
    // cmd - The name of the service to start - always `elasticsearch` here
    // config - The service config from invoker.json
    // options - Command-line options passed in
    // cb - The callback to call with the proc object once it's started
    start: function(cmd, config, options, cb) {
        var proc = child_process.spawn("./etc/elasticsearch/bin/elasticsearch");
        cb(proc);
    },

    // Called on service stop
    // cmd - The name of the service to stop - always `elasticsearch` here
    // config - The service config from invoker.json
    // options - Command-line options passed in
    // pid - The PID of the managing invoker.js instance to stop
    // cb - The callback to call when the service is stopped. Optionally
    //      pass in an error object. If there is an error, invoker.js will
    //      still try to cleanup before throwing the error.
    stop: function(cmd, config, options, pid, cb) {
        var opts = {
            port: 9200,
            method: "POST",
            path: "/_shutdown"
        };

        var req = http.request(opts, function(res) {
            if(res.statusCode != 200) {
                cb(new Error("Unexpected status code: " + res.statusCode));
            } else {
                cb();
            }
        });

        req.on("error", function(e) {
            cb(e);
        });

        req.end();
    }
};

Assuming you saved this to ./elasticsearch-invoker.js, your invoker.json would then have this specification:

{
    "elasticsearch": {
        "module": "./elasticsearch-invoker"
    }
}