Node.js怎麼實現分片上傳？方法介紹
2022-07-29 22:02:50
大檔案上傳會消耗大量的時間，而且中途有可能上傳失敗。這時我們需要前端和後端配合來解決這個問題。
解決步驟：
檔案分片，減少每次請求消耗的時間，如果某次請求失敗可以單獨上傳，而不是從頭開始
通知伺服器端合併檔案分片
控制並行的請求數量，避免瀏覽器記憶體溢位
當因為網路或者其他原因導致某次的請求失敗，我們重新傳送請求
檔案的分片與合併
在JavaScript中，FIle物件是' Blob '物件的子類，該物件包含一個重要的方法slice，通過該方法我們可以這樣分割二進位制檔案:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<script src="https://cdn.bootcdn.net/ajax/libs/axios/0.24.0/axios.min.js"></script>
</head>
<body>
<input type="file" multiple="multiple" id="fileInput" />
<button onclick="SliceUpload()">上傳</button>
<script>
function SliceUpload() {
const file = document.getElementById('fileInput').files[0]
if (!file) return
// 檔案分片
let size = 1024 * 50; //50KB 50KB Section size
let fileChunks = [];
let index = 0; //Section num
for (let cur = 0; cur < file.size; cur += size) {
fileChunks.push({
hash: index++,
chunk: file.slice(cur, cur + size),
});
}
// 上傳分片
const uploadList = fileChunks.map((item, index) => {
let formData = new FormData();
formData.append("filename", file.name);
formData.append("hash", item.hash);
formData.append("chunk", item.chunk);
return axios({
method: "post",
url: "/upload",
data: formData,
});
});
await Promise.all(uploadList);
// 所有分片上傳完成，通知伺服器合併分片
await axios({
method: "get",
url: "/merge",
params: {
filename: file.name,
},
});
console.log("Upload to complete");
}
</script>
</body>
</html>並行控制
如果檔案很大，這樣切分的分片會很多，瀏覽器短時間內就會發起大量的請求，可能會導致記憶體耗盡，所以要進行並行控制。
這裡我們結合Promise.race()方法 控制並行請求的數量，避免瀏覽器記憶體溢位。
// 加入並行控制
async function SliceUpload() {
const file = document.getElementById('fileInput').files[0]
if (!file) return
// 檔案分片
let size = 1024 * 50; //50KB 50KB Section size
let fileChunks = [];
let index = 0; //Section num
for (let cur = 0; cur < file.size; cur += size) {
fileChunks.push({
hash: index++,
chunk: file.slice(cur, cur + size),
});
}
let pool = []; //Concurrent pool
let max = 3; //Maximum concurrency
for (let i = 0; i < fileChunks.length; i++) {
let item = fileChunks[i];
let formData = new FormData();
formData.append("filename", file.name);
formData.append("hash", item.hash);
formData.append("chunk", item.chunk);
// 上傳分片
let task = axios({
method: "post",
url: "/upload",
data: formData,
});
task.then(() => {
// 從並行池中移除已經完成的請求
let index = pool.findIndex((t) => t === task);
pool.splice(index);
});
// 把請求放入並行池中，如果已經達到最大並行量
pool.push(task);
if (pool.length === max) {
//All requests are requested complete
await Promise.race(pool);
}
}
// 所有分片上傳完成，通知伺服器合併分片
await axios({
method: "get",
url: "/merge",
params: {
filename: file.name,
},
});
console.log("Upload to complete");
}使程式碼可複用
function SliceUpload() {
const file = document.getElementById('fileInput').files[0]
if (!file) return
// 檔案分片
let size = 1024 * 50; // 分片大小設定
let fileChunks = [];
let index = 0; // 分片序號
for (let cur = 0; cur < file.size; cur += size) {
fileChunks.push({
hash: index++,
chunk: file.slice(cur, cur + size),
});
}
const uploadFileChunks = async function(list){
if(list.length === 0){
// 所有分片上傳完成，通知如無
await axios({
method: 'get',
url: '/merge',
params: {
filename: file.name
}
});
console.log('Upload to complete')
return
}
let pool = [] // 並行池
let max = 3 // 最大並行數
let finish = 0 // 完成數量
let failList = [] // 失敗列表
for(let i=0;i<list.length;i++){
let item = list[i]
let formData = new FormData()
formData.append('filename', file.name)
formData.append('hash', item.hash)
formData.append('chunk', item.chunk)
let task = axios({
method: 'post',
url: '/upload',
data: formData
})
task.then((data)=>{
// 從並行池中移除已經完成的請求
let index = pool.findIndex(t=> t===task)
pool.splice(index)
}).catch(()=>{
failList.push(item)
}).finally(()=>{
finish++
// 如果有失敗的重新上傳
if(finish===list.length){
uploadFileChunks(failList)
}
})
pool.push(task)
if(pool.length === max){
await Promise.race(pool)
}
}
}
uploadFileChunks(fileChunks)
}伺服器端介面實現
const express = require('express')
const multiparty = require('multiparty')
const fs = require('fs')
const path = require('path')
const { Buffer } = require('buffer')
// file path
const STATIC_FILES = path.join(__dirname, './static/files')
// Temporary path to upload files
const STATIC_TEMPORARY = path.join(__dirname, './static/temporary')
const server = express()
// Static file hosting
server.use(express.static(path.join(__dirname, './dist')))
// Interface for uploading slices
server.post('/upload', (req, res) => {
const form = new multiparty.Form();
form.parse(req, function(err, fields, files) {
let filename = fields.filename[0]
let hash = fields.hash[0]
let chunk = files.chunk[0]
let dir = `${STATIC_TEMPORARY}/${filename}`
// console.log(filename, hash, chunk)
try {
if (!fs.existsSync(dir)) fs.mkdirSync(dir)
const buffer = fs.readFileSync(chunk.path)
const ws = fs.createWriteStream(`${dir}/${hash}`)
ws.write(buffer)
ws.close()
res.send(`${filename}-${hash} Section uploaded successfully`)
} catch (error) {
console.error(error)
res.status(500).send(`${filename}-${hash} Section uploading failed`)
}
})
})
//Merged slice interface
server.get('/merge', async (req, res) => {
const { filename } = req.query
try {
let len = 0
const bufferList = fs.readdirSync(`${STATIC_TEMPORARY}/${filename}`).map((hash,index) => {
const buffer = fs.readFileSync(`${STATIC_TEMPORARY}/${filename}/${index}`)
len += buffer.length
return buffer
});
//Merge files
const buffer = Buffer.concat(bufferList, len);
const ws = fs.createWriteStream(`${STATIC_FILES}/${filename}`)
ws.write(buffer);
ws.close();
res.send(`Section merge completed`);
} catch (error) {
console.error(error);
}
})
server.listen(3000, _ => {
console.log('http://localhost:3000/')
})更多node相關知識，請存取：！
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