I/O Intensive Task Development (TaskPool)
I/O intensive tasks are tasks that require frequent I/O operations such as disk read/write and network communication. While asynchronous concurrency can address the thread blocking issue for single I/O tasks, it falls short in the case of I/O intensive tasks. This is where multithread concurrency comes into play.
The performance focus of I/O intensive tasks is not the CPU processing capability, but the speed and efficiency of I/O operations, since such a task usually requires frequent operations such as disk read/write and network communication. The following uses frequent read/write operations on a system file to simulate concurrency processing of I/O intensive tasks.
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Define a concurrency function that internally calls I/O capabilities intensively.
// a.ts import fs from '@ohos.file.fs'; // Define a concurrency function that internally calls I/O capabilities intensively. // Write data to the file. export async function write(data: string, filePath: string): Promise<void> { let file: fs.File = await fs.open(filePath, fs.OpenMode.READ_WRITE); await fs.write(file.fd, data); fs.close(file); }
import { write } from './a' import { BusinessError } from '@ohos.base'; @Concurrent async function concurrentTest(fileList: string[]): Promise<boolean> { // Write data to the file cyclically. for (let i: number = 0; i < fileList.length; i++) { write('Hello World!', fileList[i]).then(() => { console.info(`Succeeded in writing the file. FileList: ${fileList[i]}`); }).catch((err: BusinessError) => { console.error(`Failed to write the file. Code is ${err.code}, message is ${err.message}`) return false; }) } return true; }
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Use TaskPool to execute the concurrency function that contains the intensive I/O operations. Specifically, call execute() to execute the tasks and process the scheduling result in a callback. For details about how to obtain filePath1 and filePath2 in the example, see Obtaining Application File Paths.
import taskpool from '@ohos.taskpool'; let filePath1: string = "path1"; // Application file path. let filePath2: string = "path2"; // Use TaskPool to execute the concurrency function that contains the intensive I/O operations. // In the case of a large array, the distribution of I/O intensive tasks also preempts the main thread. Therefore, multiple threads are required. taskpool.execute(concurrentTest, [filePath1, filePath2]).then(() => { // Process the scheduling result. })