observe.js

'use strict';

const {
  ArrayFrom,
  ArrayIsArray,
  ArrayPrototypeFilter,
  ArrayPrototypeIncludes,
  ArrayPrototypePush,
  ArrayPrototypeSlice,
  ArrayPrototypeSort,
  ObjectDefineProperties,
  ObjectFreeze,
  ObjectKeys,
  SafeMap,
  SafeSet,
  Symbol,
} = primordials;

const {
  constants: {
    NODE_PERFORMANCE_ENTRY_TYPE_GC,
    NODE_PERFORMANCE_ENTRY_TYPE_HTTP2,
    NODE_PERFORMANCE_ENTRY_TYPE_HTTP,
  },
  installGarbageCollectionTracking,
  observerCounts,
  removeGarbageCollectionTracking,
  setupObservers,
} = internalBinding('performance');

const {
  InternalPerformanceEntry,
  isPerformanceEntry,
} = require('internal/perf/performance_entry');

const {
  codes: {
    ERR_INVALID_ARG_VALUE,
    ERR_INVALID_ARG_TYPE,
    ERR_MISSING_ARGS,
  },
} = require('internal/errors');

const {
  validateCallback,
  validateObject,
} = require('internal/validators');

const {
  customInspectSymbol: kInspect,
  deprecate,
} = require('internal/util');

const {
  setImmediate,
} = require('timers');

const { inspect } = require('util');

const kBuffer = Symbol('kBuffer');
const kCallback = Symbol('kCallback');
const kDispatch = Symbol('kDispatch');
const kEntryTypes = Symbol('kEntryTypes');
const kMaybeBuffer = Symbol('kMaybeBuffer');
const kDeprecatedFields = Symbol('kDeprecatedFields');
const kType = Symbol('kType');

const kDeprecationMessage =
  'Custom PerformanceEntry accessors are deprecated. ' +
  'Please use the detail property.';

const kTypeSingle = 0;
const kTypeMultiple = 1;

let gcTrackingInstalled = false;

const kSupportedEntryTypes = ObjectFreeze([
  'function',
  'gc',
  'http',
  'http2',
  'mark',
  'measure',
]);

const kObservers = new SafeSet();
const kPending = new SafeSet();
let isPending = false;

function queuePending() {
  if (isPending) return;
  isPending = true;
  setImmediate(() => {
    isPending = false;
    for (const pending of kPending)
      pending[kDispatch]();
    kPending.clear();
  });
}

function getObserverType(type) {
  switch (type) {
    case 'gc': return NODE_PERFORMANCE_ENTRY_TYPE_GC;
    case 'http2': return NODE_PERFORMANCE_ENTRY_TYPE_HTTP2;
    case 'http': return NODE_PERFORMANCE_ENTRY_TYPE_HTTP;
  }
}

function maybeDecrementObserverCounts(entryTypes) {
  for (const type of entryTypes) {
    const observerType = getObserverType(type);

    if (observerType !== undefined) {
      observerCounts[observerType]--;

      if (observerType === NODE_PERFORMANCE_ENTRY_TYPE_GC &&
          observerCounts[observerType] === 0) {
        removeGarbageCollectionTracking();
      }
    }
  }
}

function maybeIncrementObserverCount(type) {
  const observerType = getObserverType(type);

  if (observerType !== undefined) {
    observerCounts[observerType]++;
    if (!gcTrackingInstalled &&
        observerType === NODE_PERFORMANCE_ENTRY_TYPE_GC) {
      installGarbageCollectionTracking();
      gcTrackingInstalled = true;
    }
  }
}

class PerformanceObserverEntryList {
  constructor(entries) {
    this[kBuffer] = ArrayPrototypeSort(entries, (first, second) => {
      if (first.startTime < second.startTime) return -1;
      if (first.startTime > second.startTime) return 1;
      return 0;
    });
  }

  getEntries() {
    return ArrayPrototypeSlice(this[kBuffer]);
  }

  getEntriesByType(type) {
    type = `${type}`;
    return ArrayPrototypeFilter(
      this[kBuffer],
      (entry) => entry.entryType === type);
  }

  getEntriesByName(name) {
    name = `${name}`;
    return ArrayPrototypeFilter(
      this[kBuffer],
      (entry) => entry.name === name);
  }

  [kInspect](depth, options) {
    if (depth < 0) return this;

    const opts = {
      ...options,
      depth: options.depth == null ? null : options.depth - 1
    };

    return `PerformanceObserverEntryList ${inspect(this[kBuffer], opts)}`;
  }
}

class PerformanceObserver {
  constructor(callback) {
    // TODO(joyeecheung): V8 snapshot does not support instance member
    // initializers for now:
    // https://bugs.chromium.org/p/v8/issues/detail?id=10704
    this[kBuffer] = [];
    this[kEntryTypes] = new SafeSet();
    this[kType] = undefined;
    validateCallback(callback);
    this[kCallback] = callback;
  }

  observe(options = {}) {
    validateObject(options, 'options');
    const {
      entryTypes,
      type,
    } = { ...options };
    if (entryTypes === undefined && type === undefined)
      throw new ERR_MISSING_ARGS('options.entryTypes', 'options.type');

    switch (this[kType]) {
      case undefined:
        if (entryTypes !== undefined) this[kType] = kTypeMultiple;
        if (type !== undefined) this[kType] = kTypeSingle;
        break;
      case kTypeSingle:
        if (entryTypes !== undefined)
          throw new ERR_INVALID_ARG_VALUE('options.entryTypes', entryTypes);
        break;
      case kTypeMultiple:
        if (type !== undefined)
          throw new ERR_INVALID_ARG_VALUE('options.type', type);
        break;
    }

    if (this[kType] === kTypeMultiple) {
      if (!ArrayIsArray(entryTypes)) {
        throw new ERR_INVALID_ARG_TYPE(
          'options.entryTypes',
          'string[]',
          entryTypes);
      }
      maybeDecrementObserverCounts(this[kEntryTypes]);
      this[kEntryTypes].clear();
      for (let n = 0; n < entryTypes.length; n++) {
        if (ArrayPrototypeIncludes(kSupportedEntryTypes, entryTypes[n])) {
          this[kEntryTypes].add(entryTypes[n]);
          maybeIncrementObserverCount(entryTypes[n]);
        }
      }
    } else {
      if (!ArrayPrototypeIncludes(kSupportedEntryTypes, type))
        return;
      this[kEntryTypes].add(type);
      maybeIncrementObserverCount(type);
    }

    if (this[kEntryTypes].size)
      kObservers.add(this);
    else
      this.disconnect();
  }

  disconnect() {
    maybeDecrementObserverCounts(this[kEntryTypes]);
    kObservers.delete(this);
    kPending.delete(this);
    this[kBuffer] = [];
    this[kEntryTypes].clear();
    this[kType] = undefined;
  }

  takeRecords() {
    const list = this[kBuffer];
    this[kBuffer] = [];
    return new PerformanceObserverEntryList(list);
  }

  static get supportedEntryTypes() {
    return kSupportedEntryTypes;
  }

  [kMaybeBuffer](entry) {
    if (!this[kEntryTypes].has(entry.entryType))
      return;
    ArrayPrototypePush(this[kBuffer], entry);
    kPending.add(this);
    if (kPending.size)
      queuePending();
  }

  [kDispatch]() { this[kCallback](this.takeRecords(), this); }

  [kInspect](depth, options) {
    if (depth < 0) return this;

    const opts = {
      ...options,
      depth: options.depth == null ? null : options.depth - 1
    };

    return `PerformanceObserver ${inspect({
      connected: kObservers.has(this),
      pending: kPending.has(this),
      entryTypes: ArrayFrom(this[kEntryTypes]),
      buffer: this[kBuffer],
    }, opts)}`;
  }
}

function enqueue(entry) {
  if (!isPerformanceEntry(entry))
    throw new ERR_INVALID_ARG_TYPE('entry', 'PerformanceEntry', entry);

  for (const obs of kObservers) {
    obs[kMaybeBuffer](entry);
  }
}

function observerCallback(name, type, startTime, duration, details) {
  const entry =
    new InternalPerformanceEntry(
      name,
      type,
      startTime,
      duration,
      details);

  if (details !== undefined) {
    // GC, HTTP2, and HTTP PerformanceEntry used additional
    // properties directly off the entry. Those have been
    // moved into the details property. The existing accessors
    // are still included but are deprecated.
    entry[kDeprecatedFields] = new SafeMap();

    const detailKeys = ObjectKeys(details);
    const props = {};
    for (let n = 0; n < detailKeys.length; n++) {
      const key = detailKeys[n];
      entry[kDeprecatedFields].set(key, details[key]);
      props[key] = {
        configurable: true,
        enumerable: true,
        get: deprecate(() => {
          return entry[kDeprecatedFields].get(key);
        }, kDeprecationMessage, 'DEP0152'),
        set: deprecate((value) => {
          entry[kDeprecatedFields].set(key, value);
        }, kDeprecationMessage, 'DEP0152'),
      };
    }
    ObjectDefineProperties(entry, props);
  }

  enqueue(entry);
}

setupObservers(observerCallback);

function hasObserver(type) {
  const observerType = getObserverType(type);
  return observerCounts[observerType] > 0;
}

module.exports = {
  PerformanceObserver,
  enqueue,
  hasObserver,
};