Fix bug around handling of failures in `spawnWorker` calls (#87)

Fixes #86

If a worker process fails to spawn, we will now complete the work attempt that caused the process to spawn with that failure, instead of never completing the attempt at all, causing a hang, and also leaking the async exception as an unhandled exception.

We could add retry logic in the future if we want, but it is probably unlikely that trying again will work. This way the actual failure should be reliably surfaced though.
4 files changed
tree: e26bc0f3853c032c01acafda20c46b87b0e85a80
  1. .github/
  2. benchmark/
  3. e2e_test/
  4. example/
  5. lib/
  6. test/
  7. tool/
  8. .gitignore
  9. analysis_options.yaml
  14. pubspec.yaml

Tools for creating a persistent worker loop for bazel.


There are two abstract classes provided by this package, AsyncWorkerLoop and SyncWorkerLoop. These each have a performRequest method which you must implement.

Lets look at a simple example of a SyncWorkerLoop implementation:

import 'dart:io';
import 'package:bazel_worker/bazel_worker.dart';

void main() {
  // Blocks until it gets an EOF from stdin.

class SyncSimpleWorker extends SyncWorkerLoop {
  /// Must synchronously return a [WorkResponse], since this is a
  /// [SyncWorkerLoop].
  WorkResponse performRequest(WorkRequest request) {
    File('hello.txt').writeAsStringSync('hello world!');
    return WorkResponse()..exitCode = EXIT_CODE_OK;

And now the same thing, implemented as an AsyncWorkerLoop:

import 'dart:io';
import 'package:bazel_worker/bazel_worker.dart';

void main() {
  // Doesn't block, runs tasks async as they are received on stdin.

class AsyncSimpleWorker extends AsyncWorkerLoop {
  /// Must return a [Future<WorkResponse>], since this is an
  /// [AsyncWorkerLoop].
  Future<WorkResponse> performRequest(WorkRequest request) async {
    await File('hello.txt').writeAsString('hello world!');
    return WorkResponse()..exitCode = EXIT_CODE_OK;

As you can see, these are nearly identical, it mostly comes down to the constraints on your package and personal preference which one you choose to implement.


A package:bazel_worker/testing.dart file is also provided, which can greatly assist with writing unit tests for your worker. See the test/worker_loop_test.dart test included in this package for an example of how the helpers can be used.

Features and bugs

Please file feature requests and bugs at the issue tracker.