Pool and re-use web workers

src/shared/services/WorkPool.js

@@ -0,0 +1,160 @@
+/*
+ * Copyright (c) 2002-2018 "Neo4j, Inc"
+ * Network Engine for Objects in Lund AB [http://neotechnology.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+import { v4 as uuid } from 'uuid'
+
+class WorkPool {
+  static workerStates = {
+    BUSY: 'busy',
+    FREE: 'free'
+  }
+  constructor (createWorker, maxPoolSize = 15) {
+    this.createWorker = createWorker
+    this.maxPoolSize = maxPoolSize
+    this.register = []
+    this.q = []
+  }
+  // Public methods
+  getPoolSize (state) {
+    if (!state) {
+      return this.register.length
+    }
+    return this.register.filter(w => w.state === state).length
+  }
+  getQueueSize () {
+    return this.q.length
+  }
+  getWorkById (id) {
+    for (let i = 0; i < this.q.length; i++) {
+      if (this.q[i].id === id) {
+        return this.q[i]
+      }
+    }
+    return null
+  }
+  doWork ({ id, payload, onmessage }) {
+    const work = this._buildWorkObj({ id: id || uuid(), payload, onmessage })
+    this._addToQ(work)
+    this._next()
+    return work
+  }
+
+  // Implemtation details
+  _getFreeWorker (id) {
+    const len = this.register.length
+    for (let i = len - 1; i >= 0; i--) {
+      if (this.register[i].state === WorkPool.workerStates.FREE) {
+        return this.register[i]
+      }
+    }
+    const poolSize = this.getPoolSize()
+    if (poolSize < this.maxPoolSize) {
+      const workerObj = this._buildWorkerObj(
+        this.createWorker(),
+        WorkPool.workerStates.BUSY
+      )
+      this.register.push(workerObj)
+      return workerObj
+    }
+    return null
+  }
+  _next () {
+    if (!this.getQueueSize()) {
+      return
+    }
+    const workerObj = this._getFreeWorker()
+    if (!workerObj) {
+      return
+    }
+    const work = this.q.shift()
+    workerObj.id = work.id
+    work._assignWorker(workerObj)
+    work._executeInitial()
+  }
+  _addToQ (work) {
+    this.q.push(work)
+  }
+  _removeFromQ (id) {
+    this.q.splice(this.q.findIndex(el => el.id === id), 1)
+  }
+  _unregisterWorker = id => {
+    const worker = this._getWorkerById(id)
+    if (worker === null) {
+      return
+    }
+    worker.state = WorkPool.workerStates.FREE
+    this._next()
+  }
+  _buildWorkObj ({ id, payload, onmessage }) {
+    const obj = {
+      id,
+      _worker: undefined,
+      _executed: false,
+      _finishFn: undefined
+    }
+    obj.execute = payload => {
+      if (payload && obj._workerObj) {
+        obj._workerObj.worker.postMessage(payload)
+      }
+    }
+    obj.onFinish = fn => (obj._finishFn = fn)
+    obj.finish = () => {
+      if (!obj._executed) {
+        this._removeFromQ(id)
+      }
+      obj._workerObj && obj._workerObj.finish(id)
+      obj._finishFn && obj._finishFn({ executed: obj._executed, id })
+    }
+    obj._executeInitial = () => {
+      if (onmessage) {
+        obj._workerObj.worker.onmessage = onmessage
+      }
+      if (payload) {
+        obj._workerObj.worker.postMessage(payload)
+      }
+      obj._executed = true
+    }
+    obj._assignWorker = workerObj => {
+      workerObj.state = WorkPool.workerStates.BUSY
+      obj._workerObj = workerObj
+    }
+
+    return obj
+  }
+  _buildWorkerObj (worker, state) {
+    const obj = {
+      worker,
+      state
+    }
+    obj.finish = id => {
+      this._unregisterWorker(id)
+    }
+    return obj
+  }
+  _getWorkerById (id) {
+    for (let i = 0; i < this.register.length; i++) {
+      if (this.register[i].id === id) {
+        return this.register[i]
+      }
+    }
+    return null
+  }
+}
+
+export default WorkPool