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| /*! | ||
| * Copyright 2018 Google Inc. All Rights Reserved. | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
|
|
||
| 'use strict'; | ||
|
|
||
| import assert from 'assert'; | ||
|
|
||
| /** | ||
| * An auto-resizing pool that distributes concurrent operations over multiple | ||
| * clients of type `T`. | ||
| * | ||
| * ClientPool is used within Firestore to manage a pool of GAPIC clients and | ||
| * automatically initializes multiple clients if we issue more than 100 | ||
| * concurrent operations. | ||
| */ | ||
| export class ClientPool<T> { | ||
| /** Stores each active clients and how many operations it has outstanding. */ | ||
| private activeClients: Map<T, number> = new Map(); | ||
|
|
||
| /** | ||
| * @param {number} concurrentOperationLimit - The number of operations that | ||
| * each client can handle. | ||
| * @param {() => T} clientFactory - A factory function called as needed when | ||
| * new clients are required. | ||
| */ | ||
| constructor( | ||
| private readonly concurrentOperationLimit: number, | ||
| private readonly clientFactory: () => T) {} | ||
|
|
||
| /** | ||
| * Returns an already existing client if it has less than the maximum number | ||
| * of concurrent operations or initializes and returns a new client. | ||
| */ | ||
| private acquire(): T { | ||
| let selectedClient: T|null = null; | ||
| let selectedRequestCount = 0; | ||
|
|
||
| this.activeClients.forEach((requestCount, client) => { | ||
| if (!selectedClient && requestCount < this.concurrentOperationLimit) { | ||
| selectedClient = client; | ||
| selectedRequestCount = requestCount; | ||
| } | ||
| }); | ||
|
|
||
| if (!selectedClient) { | ||
| selectedClient = this.clientFactory(); | ||
| assert( | ||
| !this.activeClients.has(selectedClient), | ||
| 'The provided client factory returned an existing instance'); | ||
| } | ||
|
|
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| this.activeClients.set(selectedClient, selectedRequestCount + 1); | ||
|
|
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| return selectedClient!; | ||
| } | ||
|
|
||
| /** | ||
| * Reduces the number of operations for the provided client, potentially | ||
| * removing it from the pool of active clients. | ||
| */ | ||
| private release(client: T): void { | ||
| let requestCount = this.activeClients.get(client) || 0; | ||
| assert(requestCount > 0, 'No active request'); | ||
|
|
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| requestCount = requestCount! - 1; | ||
| this.activeClients.set(client, requestCount); | ||
|
|
||
| if (requestCount === 0) { | ||
| this.garbageCollect(); | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * The number of currently registered clients. | ||
| * | ||
| * @return {number} Number of currently registered clients. | ||
| */ | ||
| // Visible for testing. | ||
| get size(): number { | ||
| return this.activeClients.size; | ||
| } | ||
|
|
||
| /** | ||
| * Runs the provided operation in this pool. This function may create an | ||
| * additional client if all existing clients already operate at the concurrent | ||
| * operation limit. | ||
| * | ||
| * @param {(client: T) => Promise<V>} op - A callback function that returns a | ||
| * Promise. The client T will be returned to the pool when callback finishes. | ||
| * @return {Promise<V>} A Promise that resolves with the result of `op`. | ||
| */ | ||
| run<V>(op: (client: T) => Promise<V>): Promise<V> { | ||
| const client = this.acquire(); | ||
|
|
||
| return op(client) | ||
| .catch(err => { | ||
| this.release(client); | ||
| return Promise.reject(err); | ||
| }) | ||
| .then(res => { | ||
| this.release(client); | ||
| return res; | ||
| }); | ||
| } | ||
|
|
||
| /** | ||
| * Deletes clients that are no longer executing operations. Keeps up to one | ||
| * idle client to reduce future initialization costs. | ||
| */ | ||
| private garbageCollect(): void { | ||
| let idleClients = 0; | ||
| this.activeClients.forEach((requestCount, client) => { | ||
| if (requestCount === 0) { | ||
| ++idleClients; | ||
|
|
||
| if (idleClients > 1) { | ||
| this.activeClients.delete(client); | ||
| } | ||
| } | ||
| }); | ||
| } | ||
| } |
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