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smacker

Don't smack your developers when a process misbehaves. It's hard to know everything a Node.js process does.

Did you know?

  • Packages you use can emit warnings on process.emitWarning for deprecation notices and unexpected usage, without affecting functionality.
  • Both SIGINT and SIGTERM will by default try to kill your process, without notifying you. This can be confusing when running your Node.js process in foreign environments.
  • Node.js v10.12.0 introduced a new event called multipleResolves - which they recommend should terminate your process, even though it doesn't default to that behaviour.

smacker gracefully handles all these nitty gritties, and fits perfectly into a microservice environment.

Usage

const smacker = require('smacker');
const Service = require('lib/Service');
const service = new Service();
smacker.start(service);

Check out the demo in test/demo.js.

smacker.start(service, {[config][, log] })

  • service <Object> must have a start and stop function, both returning a Promise
  • config <Object> configuration object, contains config for smacker - see below
  • log <Object> logging object for smacker to use, defaults to console. Should have info, warn, and fatal.

smacker will call service.start on smacker.start, and expect the resulting promise to resolve. It installs handlers for SIGINT, SIGTERM and SIGUSR2 and calls service.stop when it receives one of these signals.

Unhandled exceptions and unhandled promise rejections are caught, logged, and your process will be terminated with exit code 1.

It also ensures warnings from process.emitWarning are logged through your logging object.

config

  • logJson <Boolean> determines whether smacker will try to serialize the object before giving it to your logging object. Can be set via the LOGJSON environment variable. Defaults to false.
  • terminateOnMultipleResolves <Boolean> smacker can terminate on the multipleResolves event. This is not always desireable. It defaults to true, since that is recommended behaviour.
  • gracefulShutdownTimeout <Number> smacker will terminate after configured milliseconds (triggered by signals or natually), with exit code 1, if configured. Defaults to undefined.
  • gracefulStartupTimeout <Number> smacker will terminate after configured milliseconds, with exit code 1, if configured and the start-function isn't resolved. Defaults to undefined.
  • signalHandlers[signal] custom signal handlers can be installed after the start-function has been resolved. This will overwrite the native behaviour of the signals. Valid signals are SIGHUP, SIGPIPE, SIGUSR2.

Planned features

  • detecting if service.stop actually leaves the event loop empty