Child-service NPM

child-service

Start services as child-process, wait until they are ready and stop them.

Installation

npm install child-service

Usage

Let's assume, we have a service that does not detach, but it is not ready immediately after start. We want to start this service call some endpoints and stop it again (for example in tests). Assume that our service is implemented in service.js (for portability, we use a Node.js program in this example, but I actually wrote this tool for use with chisel.

We can now do the following.

const { ChildService } = require("child-service");
const got = require("got");

// We call nodejs in this example, but in reality, it
// is probably some binary executable.
const childService = new ChildService({
  command: process.execPath, // you can also use a promise here
  args: ["service.js"], // you can also use a promise here
  readyRegex: /Listening on port 3000/,
  spawnOptions: {
    cwd: __dirname
  }
});

(async function () {
  await childService.start();
  console.log("Started!");

  const response = await got("http://127.0.0.1:3000");
  console.log(response.body);

  await childService.stop();
  console.log("Stopped!");
})();

This will start the service, wait until the stdout matches pattern, then call an endpoint and stop it again. The output of this program is:

Started!
hello

Stopped!

The package also makes sure that processes are stopped when the parent-process dies unexpectedly. It takes into account quitting by process.exit() as well as SIGTERM, SIGINT and SIGKILL.

API reference

ChildService

The class for starting and stopping services.

Kind: global class
Access: public

ChildService
- new ChildService(userOptions)
- .start() ⇒ Promise.<void>
- .stop() ⇒ Promise.<void>

new ChildService(userOptions)

Create a new child-service

Param	Type	Description
userOptions	object	parameters
userOptions.command	string \| Promise.<string>	the command to execute
userOptions.args	Array.<string> \| Promise.<Array.<string>>	arguments to the command
userOptions.readyRegex	RegExp	process is assumed to be ready, when this regex matches the output.
userOptions.outputLimit	number	only look for readyRegex in the first "outputLimit" number of bytes of the output.
userOptions.spawnOptions	object	options to pass to child_process.spawn
userOptions.timeoutAfterSignal	number	(default: 1000) how long (in milliseconds) to wait after stopping the child with SIGTERM, before using SIGKILL and after that before giving up.
userOptions.listenOnStderr	boolean	(default: false) whether to wait for "readyRegex" on stderr of the child-process instead of stdout