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node_modules/mocha/lib/nodejs/parallel-buffered-runner.js

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+/**
+ * A test Runner that uses a {@link module:buffered-worker-pool}.
+ * @module parallel-buffered-runner
+ * @private
+ */
+
+'use strict';
+
+const allSettled = require('@ungap/promise-all-settled').bind(Promise);
+const Runner = require('../runner');
+const {EVENT_RUN_BEGIN, EVENT_RUN_END} = Runner.constants;
+const debug = require('debug')('mocha:parallel:parallel-buffered-runner');
+const {BufferedWorkerPool} = require('./buffered-worker-pool');
+const {setInterval, clearInterval} = global;
+const {createMap, constants} = require('../utils');
+const {MOCHA_ID_PROP_NAME} = constants;
+const {createFatalError} = require('../errors');
+
+const DEFAULT_WORKER_REPORTER = require.resolve(
+  './reporters/parallel-buffered'
+);
+
+/**
+ * List of options to _not_ serialize for transmission to workers
+ */
+const DENY_OPTIONS = [
+  'globalSetup',
+  'globalTeardown',
+  'parallel',
+  'p',
+  'jobs',
+  'j'
+];
+
+/**
+ * Outputs a debug statement with worker stats
+ * @param {BufferedWorkerPool} pool - Worker pool
+ */
+/* istanbul ignore next */
+const debugStats = pool => {
+  const {totalWorkers, busyWorkers, idleWorkers, pendingTasks} = pool.stats();
+  debug(
+    '%d/%d busy workers; %d idle; %d tasks queued',
+    busyWorkers,
+    totalWorkers,
+    idleWorkers,
+    pendingTasks
+  );
+};
+
+/**
+ * The interval at which we will display stats for worker processes in debug mode
+ */
+const DEBUG_STATS_INTERVAL = 5000;
+
+const ABORTED = 'ABORTED';
+const IDLE = 'IDLE';
+const ABORTING = 'ABORTING';
+const RUNNING = 'RUNNING';
+const BAILING = 'BAILING';
+const BAILED = 'BAILED';
+const COMPLETE = 'COMPLETE';
+
+const states = createMap({
+  [IDLE]: new Set([RUNNING, ABORTING]),
+  [RUNNING]: new Set([COMPLETE, BAILING, ABORTING]),
+  [COMPLETE]: new Set(),
+  [ABORTED]: new Set(),
+  [ABORTING]: new Set([ABORTED]),
+  [BAILING]: new Set([BAILED, ABORTING]),
+  [BAILED]: new Set([COMPLETE, ABORTING])
+});
+
+/**
+ * This `Runner` delegates tests runs to worker threads.  Does not execute any
+ * {@link Runnable}s by itself!
+ * @public
+ */
+class ParallelBufferedRunner extends Runner {
+  constructor(...args) {
+    super(...args);
+
+    let state = IDLE;
+    Object.defineProperty(this, '_state', {
+      get() {
+        return state;
+      },
+      set(newState) {
+        if (states[state].has(newState)) {
+          state = newState;
+        } else {
+          throw new Error(`invalid state transition: ${state} => ${newState}`);
+        }
+      }
+    });
+
+    this._workerReporter = DEFAULT_WORKER_REPORTER;
+    this._linkPartialObjects = false;
+    this._linkedObjectMap = new Map();
+
+    this.once(Runner.constants.EVENT_RUN_END, () => {
+      this._state = COMPLETE;
+    });
+  }
+
+  /**
+   * Returns a mapping function to enqueue a file in the worker pool and return results of its execution.
+   * @param {BufferedWorkerPool} pool - Worker pool
+   * @param {Options} options - Mocha options
+   * @returns {FileRunner} Mapping function
+   * @private
+   */
+  _createFileRunner(pool, options) {
+    /**
+     * Emits event and sets `BAILING` state, if necessary.
+     * @param {Object} event - Event having `eventName`, maybe `data` and maybe `error`
+     * @param {number} failureCount - Failure count
+     */
+    const emitEvent = (event, failureCount) => {
+      this.emit(event.eventName, event.data, event.error);
+      if (
+        this._state !== BAILING &&
+        event.data &&
+        event.data._bail &&
+        (failureCount || event.error)
+      ) {
+        debug('run(): nonzero failure count & found bail flag');
+        // we need to let the events complete for this file, as the worker
+        // should run any cleanup hooks
+        this._state = BAILING;
+      }
+    };
+
+    /**
+     * Given an event, recursively find any objects in its data that have ID's, and create object references to already-seen objects.
+     * @param {Object} event - Event having `eventName`, maybe `data` and maybe `error`
+     */
+    const linkEvent = event => {
+      const stack = [{parent: event, prop: 'data'}];
+      while (stack.length) {
+        const {parent, prop} = stack.pop();
+        const obj = parent[prop];
+        let newObj;
+        if (obj && typeof obj === 'object') {
+          if (obj[MOCHA_ID_PROP_NAME]) {
+            const id = obj[MOCHA_ID_PROP_NAME];
+            newObj = this._linkedObjectMap.has(id)
+              ? Object.assign(this._linkedObjectMap.get(id), obj)
+              : obj;
+            this._linkedObjectMap.set(id, newObj);
+            parent[prop] = newObj;
+          } else {
+            throw createFatalError(
+              'Object missing ID received in event data',
+              obj
+            );
+          }
+        }
+        Object.keys(newObj).forEach(key => {
+          const value = obj[key];
+          if (value && typeof value === 'object' && value[MOCHA_ID_PROP_NAME]) {
+            stack.push({obj: value, parent: newObj, prop: key});
+          }
+        });
+      }
+    };
+
+    return async file => {
+      debug('run(): enqueueing test file %s', file);
+      try {
+        const {failureCount, events} = await pool.run(file, options);
+
+        if (this._state === BAILED) {
+          // short-circuit after a graceful bail. if this happens,
+          // some other worker has bailed.
+          // TODO: determine if this is the desired behavior, or if we
+          // should report the events of this run anyway.
+          return;
+        }
+        debug(
+          'run(): completed run of file %s; %d failures / %d events',
+          file,
+          failureCount,
+          events.length
+        );
+        this.failures += failureCount; // can this ever be non-numeric?
+        let event = events.shift();
+
+        if (this._linkPartialObjects) {
+          while (event) {
+            linkEvent(event);
+            emitEvent(event, failureCount);
+            event = events.shift();
+          }
+        } else {
+          while (event) {
+            emitEvent(event, failureCount);
+            event = events.shift();
+          }
+        }
+        if (this._state === BAILING) {
+          debug('run(): terminating pool due to "bail" flag');
+          this._state = BAILED;
+          await pool.terminate();
+        }
+      } catch (err) {
+        if (this._state === BAILED || this._state === ABORTING) {
+          debug(
+            'run(): worker pool terminated with intent; skipping file %s',
+            file
+          );
+        } else {
+          // this is an uncaught exception
+          debug('run(): encountered uncaught exception: %O', err);
+          if (this.allowUncaught) {
+            // still have to clean up
+            this._state = ABORTING;
+            await pool.terminate(true);
+          }
+          throw err;
+        }
+      } finally {
+        debug('run(): done running file %s', file);
+      }
+    };
+  }
+
+  /**
+   * Listen on `Process.SIGINT`; terminate pool if caught.
+   * Returns the listener for later call to `process.removeListener()`.
+   * @param {BufferedWorkerPool} pool - Worker pool
+   * @returns {SigIntListener} Listener
+   * @private
+   */
+  _bindSigIntListener(pool) {
+    const sigIntListener = async () => {
+      debug('run(): caught a SIGINT');
+      this._state = ABORTING;
+
+      try {
+        debug('run(): force-terminating worker pool');
+        await pool.terminate(true);
+      } catch (err) {
+        console.error(
+          `Error while attempting to force-terminate worker pool: ${err}`
+        );
+        process.exitCode = 1;
+      } finally {
+        process.nextTick(() => {
+          debug('run(): imminent death');
+          this._state = ABORTED;
+          process.kill(process.pid, 'SIGINT');
+        });
+      }
+    };
+
+    process.once('SIGINT', sigIntListener);
+
+    return sigIntListener;
+  }
+
+  /**
+   * Runs Mocha tests by creating a thread pool, then delegating work to the
+   * worker threads.
+   *
+   * Each worker receives one file, and as workers become available, they take a
+   * file from the queue and run it. The worker thread execution is treated like
+   * an RPC--it returns a `Promise` containing serialized information about the
+   * run.  The information is processed as it's received, and emitted to a
+   * {@link Reporter}, which is likely listening for these events.
+   *
+   * @param {Function} callback - Called with an exit code corresponding to
+   * number of test failures.
+   * @param {{files: string[], options: Options}} opts - Files to run and
+   * command-line options, respectively.
+   */
+  run(callback, {files, options = {}} = {}) {
+    /**
+     * Listener on `Process.SIGINT` which tries to cleanly terminate the worker pool.
+     */
+    let sigIntListener;
+
+    // assign the reporter the worker will use, which will be different than the
+    // main process' reporter
+    options = {...options, reporter: this._workerReporter};
+
+    // This function should _not_ return a `Promise`; its parent (`Runner#run`)
+    // returns this instance, so this should do the same. However, we want to make
+    // use of `async`/`await`, so we use this IIFE.
+    (async () => {
+      /**
+       * This is an interval that outputs stats about the worker pool every so often
+       */
+      let debugInterval;
+
+      /**
+       * @type {BufferedWorkerPool}
+       */
+      let pool;
+
+      try {
+        pool = BufferedWorkerPool.create({maxWorkers: options.jobs});
+
+        sigIntListener = this._bindSigIntListener(pool);
+
+        /* istanbul ignore next */
+        debugInterval = setInterval(
+          () => debugStats(pool),
+          DEBUG_STATS_INTERVAL
+        ).unref();
+
+        // this is set for uncaught exception handling in `Runner#uncaught`
+        // TODO: `Runner` should be using a state machine instead.
+        this.started = true;
+        this._state = RUNNING;
+
+        this.emit(EVENT_RUN_BEGIN);
+
+        options = {...options};
+        DENY_OPTIONS.forEach(opt => {
+          delete options[opt];
+        });
+
+        const results = await allSettled(
+          files.map(this._createFileRunner(pool, options))
+        );
+
+        // note that pool may already be terminated due to --bail
+        await pool.terminate();
+
+        results
+          .filter(({status}) => status === 'rejected')
+          .forEach(({reason}) => {
+            if (this.allowUncaught) {
+              // yep, just the first one.
+              throw reason;
+            }
+            // "rejected" will correspond to uncaught exceptions.
+            // unlike the serial runner, the parallel runner can always recover.
+            this.uncaught(reason);
+          });
+
+        if (this._state === ABORTING) {
+          return;
+        }
+
+        this.emit(EVENT_RUN_END);
+        debug('run(): completing with failure count %d', this.failures);
+        callback(this.failures);
+      } catch (err) {
+        // this `nextTick` takes us out of the `Promise` scope, so the
+        // exception will not be caught and returned as a rejected `Promise`,
+        // which would lead to an `unhandledRejection` event.
+        process.nextTick(() => {
+          debug('run(): re-throwing uncaught exception');
+          throw err;
+        });
+      } finally {
+        clearInterval(debugInterval);
+        process.removeListener('SIGINT', sigIntListener);
+      }
+    })();
+    return this;
+  }
+
+  /**
+   * Toggle partial object linking behavior; used for building object references from
+   * unique ID's.
+   * @param {boolean} [value] - If `true`, enable partial object linking, otherwise disable
+   * @returns {Runner}
+   * @chainable
+   * @public
+   * @example
+   * // this reporter needs proper object references when run in parallel mode
+   * class MyReporter() {
+   *   constructor(runner) {
+   *     this.runner.linkPartialObjects(true)
+   *       .on(EVENT_SUITE_BEGIN, suite => {
+             // this Suite may be the same object...
+  *       })
+  *       .on(EVENT_TEST_BEGIN, test => {
+  *         // ...as the `test.parent` property
+  *       });
+  *   }
+  * }
+  */
+  linkPartialObjects(value) {
+    this._linkPartialObjects = Boolean(value);
+    return super.linkPartialObjects(value);
+  }
+
+  /**
+   * If this class is the `Runner` in use, then this is going to return `true`.
+   *
+   * For use by reporters.
+   * @returns {true}
+   * @public
+   */
+  isParallelMode() {
+    return true;
+  }
+
+  /**
+   * Configures an alternate reporter for worker processes to use. Subclasses
+   * using worker processes should implement this.
+   * @public
+   * @param {string} path - Absolute path to alternate reporter for worker processes to use
+   * @returns {Runner}
+   * @throws When in serial mode
+   * @chainable
+   */
+  workerReporter(reporter) {
+    this._workerReporter = reporter;
+    return this;
+  }
+}
+
+module.exports = ParallelBufferedRunner;
+
+/**
+ * Listener function intended to be bound to `Process.SIGINT` event
+ * @private
+ * @callback SigIntListener
+ * @returns {Promise<void>}
+ */
+
+/**
+ * A function accepting a test file path and returning the results of a test run
+ * @private
+ * @callback FileRunner
+ * @param {string} filename - File to run
+ * @returns {Promise<SerializedWorkerResult>}
+ */