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Node侧实现内容压缩(gzip/br/deflate)介绍与实践 ​

背景 ​

在查看自己的应用日志时，发现进入日志页面后总是要几秒钟才会加载（接口没做分页），于是打开网络面板查看

图片

图片

这才发现接口返回的数据都没有被压缩，本以为接口用Nginx反向代理了，Nginx会自动帮我做这一层（这块后面探究一下，理论上是可行的）

这里的后端是 Node 服务

本文就分享一下 HTTP数据压缩相关知识以及笔者的在Node侧的实践

前置知识 ​

下面的客户端均指浏览器

accept-encoding ​

accept-encoding

客户端在向服务端发起请求时，会在请求头(request header)中添加accept-encoding字段，其值标明客户端支持的压缩内容编码格式

content-encoding ​

content-encoding

服务端在对返回内容执行压缩后，通过在响应头（response header）中添加content-encoding，来告诉浏览器内容实际压缩使用的编码算法

deflate/gzip/br ​

deflate是同时使用了LZ77算法与哈夫曼编码（Huffman Coding）的一个无损数据压缩算法。

gzip 是基于 DEFLATE 的算法

br指代Brotli，该数据格式旨在进一步提高压缩比，对文本的压缩相对deflate能增加20%的压缩密度，而其压缩与解压缩速度则大致不变

zlib模块 ​

Node.js包含一个zlib 模块，提供了使用 Gzip、Deflate/Inflate、以及 Brotli 实现的压缩功能

这里以gzip为例分场景列举多种使用方式，Deflate/Inflate与Brotli使用方式一样，只是API不一样

基于stream的操作

基于的操作

基于buffer的操作

基于的操作

引入几个所需的模块

js
const zlib = require('zlib')
const fs = require('fs')
const stream = require('stream')
const testFile = 'tests/origin.log'
const targetFile = `${testFile}.gz`
const decodeFile = `${testFile}.un.gz`
const zlib = require('zlib')
const fs = require('fs')
const stream = require('stream')
const testFile = 'tests/origin.log'
const targetFile = `${testFile}.gz`
const decodeFile = `${testFile}.un.gz`

文件的解/压缩 ​

解/压缩结果查看，这里使用du指令直接统计解压缩前后结果

sh
# 执行
du -ah tests

# 结果如下
108K    tests/origin.log.gz
2.2M    tests/origin.log
2.2M    tests/origin.log.un.gz
4.6M    tests
# 执行
du -ah tests

# 结果如下
108K    tests/origin.log.gz
2.2M    tests/origin.log
2.2M    tests/origin.log.un.gz
4.6M    tests

基于流(stream)的操作 ​

使用createGzip与createUnzip

  • 注：所有 zlib API，除了那些显式同步的 API，都使用 Node.js 内部线程池，可以看做是异步的
  • 因此下面的示例中的压缩和解压代码应分开执行，否则会报错

方式1： 直接利用实例上的pipe方法传递流

js
// 压缩
const readStream = fs.createReadStream(testFile)
const writeStream = fs.createWriteStream(targetFile)
readStream.pipe(zlib.createGzip()).pipe(writeStream)

// 解压
const readStream = fs.createReadStream(targetFile)
const writeStream = fs.createWriteStream(decodeFile)
readStream.pipe(zlib.createUnzip()).pipe(writeStream)
// 压缩
const readStream = fs.createReadStream(testFile)
const writeStream = fs.createWriteStream(targetFile)
readStream.pipe(zlib.createGzip()).pipe(writeStream)

// 解压
const readStream = fs.createReadStream(targetFile)
const writeStream = fs.createWriteStream(decodeFile)
readStream.pipe(zlib.createUnzip()).pipe(writeStream)

方式2： 利用stream上的pipeline，可在回掉中单独做其它的处理

js
// 压缩
const readStream = fs.createReadStream(testFile)
const writeStream = fs.createWriteStream(targetFile)
stream.pipeline(readStream, zlib.createGzip(), writeStream, err => {
    if (err) {
        console.error(err);
    }
})

// 解压
const readStream = fs.createReadStream(targetFile)
const writeStream = fs.createWriteStream(decodeFile)
stream.pipeline(readStream, zlib.createUnzip(), writeStream, err => {
    if (err) {
        console.error(err);
    }
})
// 压缩
const readStream = fs.createReadStream(testFile)
const writeStream = fs.createWriteStream(targetFile)
stream.pipeline(readStream, zlib.createGzip(), writeStream, err => {
    if (err) {
        console.error(err);
    }
})

// 解压
const readStream = fs.createReadStream(targetFile)
const writeStream = fs.createWriteStream(decodeFile)
stream.pipeline(readStream, zlib.createUnzip(), writeStream, err => {
    if (err) {
        console.error(err);
    }
})

方式3： Promise化pipeline方法

js
const { promisify } = require('util')
const pipeline = promisify(stream.pipeline)

// 压缩
const readStream = fs.createReadStream(testFile)
const writeStream = fs.createWriteStream(targetFile)
pipeline(readStream, zlib.createGzip(), writeStream)
    .catch(err => {
        console.error(err);
    })

// 解压
const readStream = fs.createReadStream(targetFile)
const writeStream = fs.createWriteStream(decodeFile)
pipeline(readStream, zlib.createUnzip(), writeStream)
    .catch(err => {
        console.error(err);
    })
const { promisify } = require('util')
const pipeline = promisify(stream.pipeline)

// 压缩
const readStream = fs.createReadStream(testFile)
const writeStream = fs.createWriteStream(targetFile)
pipeline(readStream, zlib.createGzip(), writeStream)
    .catch(err => {
        console.error(err);
    })

// 解压
const readStream = fs.createReadStream(targetFile)
const writeStream = fs.createWriteStream(decodeFile)
pipeline(readStream, zlib.createUnzip(), writeStream)
    .catch(err => {
        console.error(err);
    })

基于Buffer的操作 ​

利用 gzip 与 unzip API，这两个方法包含同步与异步类型

  • 压缩
    • gzip
    • gzipSync
  • 解压
    • unzip
    • unzipSync

方式1： 将readStream转Buffer,然后进行进一步操作

  • gzip：异步
js
// 压缩
const buff = []
readStream.on('data', (chunk) => {
    buff.push(chunk)
})
readStream.on('end', () => {
    zlib.gzip(Buffer.concat(buff), targetFile, (err, resBuff) => {
        if(err){
            console.error(err);
            process.exit()
        }
        fs.writeFileSync(targetFile,resBuff)
    })
})
// 压缩
const buff = []
readStream.on('data', (chunk) => {
    buff.push(chunk)
})
readStream.on('end', () => {
    zlib.gzip(Buffer.concat(buff), targetFile, (err, resBuff) => {
        if(err){
            console.error(err);
            process.exit()
        }
        fs.writeFileSync(targetFile,resBuff)
    })
})
  • gzipSync：同步
js
// 压缩
const buff = []
readStream.on('data', (chunk) => {
    buff.push(chunk)
})
readStream.on('end', () => {
    fs.writeFileSync(targetFile,zlib.gzipSync(Buffer.concat(buff)))
})
// 压缩
const buff = []
readStream.on('data', (chunk) => {
    buff.push(chunk)
})
readStream.on('end', () => {
    fs.writeFileSync(targetFile,zlib.gzipSync(Buffer.concat(buff)))
})

方式2： 直接通过readFileSync读取

js
// 压缩
const readBuffer = fs.readFileSync(testFile)
const decodeBuffer = zlib.gzipSync(readBuffer)
fs.writeFileSync(targetFile,decodeBuffer)

// 解压
const readBuffer = fs.readFileSync(targetFile)
const decodeBuffer = zlib.gzipSync(decodeFile)
fs.writeFileSync(targetFile,decodeBuffer)
// 压缩
const readBuffer = fs.readFileSync(testFile)
const decodeBuffer = zlib.gzipSync(readBuffer)
fs.writeFileSync(targetFile,decodeBuffer)

// 解压
const readBuffer = fs.readFileSync(targetFile)
const decodeBuffer = zlib.gzipSync(decodeFile)
fs.writeFileSync(targetFile,decodeBuffer)

文本内容的解/压缩 ​

除了对文件压缩，有时候也许要对传输的内容进行直接进行解压缩

这里以压缩文本内容为例

js
// 测试数据
const testData = fs.readFileSync(testFile, { encoding: 'utf-8' })
// 测试数据
const testData = fs.readFileSync(testFile, { encoding: 'utf-8' })

基于流(stream)操作 ​

这块就考虑 string => buffer => stream的转换就行

string => buffer

js
const buffer = Buffer.from(testData)
const buffer = Buffer.from(testData)

buffer => stream

js
const transformStream = new stream.PassThrough()
transformStream.write(buffer)

// or
const transformStream = new stream.Duplex()
transformStream.push(Buffer.from(testData))
transformStream.push(null)
const transformStream = new stream.PassThrough()
transformStream.write(buffer)

// or
const transformStream = new stream.Duplex()
transformStream.push(Buffer.from(testData))
transformStream.push(null)

这里以写入到文件示例，当然也可以写到其它的流里，如HTTP的Response（后面会单独介绍）

js
transformStream
    .pipe(zlib.createGzip())
    .pipe(fs.createWriteStream(targetFile))
transformStream
    .pipe(zlib.createGzip())
    .pipe(fs.createWriteStream(targetFile))

基于Buffer操作 ​

同样利用Buffer.from将字符串转buffer

js
const buffer = Buffer.from(testData)
const buffer = Buffer.from(testData)

然后直接使用同步API进行转换，这里result就是压缩后的内容

js
const result = zlib.gzipSync(buffer)
const result = zlib.gzipSync(buffer)

可以写入文件，在HTTP Server中也可直接对压缩后的内容进行返回

js
fs.writeFileSync(targetFile, result)
fs.writeFileSync(targetFile, result)

Node Server中的实践 ​

这里直接使用Node中 http 模块创建一个简单的 Server 进行演示

在其他的 Node Web 框架中，处理思路类似，当然一般也有现成的插件，一键接入

运行结果

js
const http = require('http')
const { PassThrough, pipeline } = require('stream')
const zlib = require('zlib')

// 测试数据
const testTxt = '测试数据123'.repeat(1000)

const app = http.createServer((req, res) => {
    const { url } = req
    // 读取支持的压缩算法
    const acceptEncoding = req.headers['accept-encoding'].match(/(br|deflate|gzip)/g)

    // 默认响应的数据类型
    res.setHeader('Content-Type', 'application/json; charset=utf-8')

    // 几个示例的路由
    const routes = [
        ['/gzip', () => {
            if (acceptEncoding.includes('gzip')) {
                res.setHeader('content-encoding', 'gzip')
                // 使用同步API直接压缩文本内容
                res.end(zlib.gzipSync(Buffer.from(testTxt)))
                return
            }
            res.end(testTxt)
        }],
        ['/deflate', () => {
            if (acceptEncoding.includes('deflate')) {
                res.setHeader('content-encoding', 'deflate')
                // 基于流的单次操作
                const originStream = new PassThrough()
                originStream.write(Buffer.from(testTxt))
                originStream.pipe(zlib.createDeflate()).pipe(res)
                originStream.end()
                return
            }
            res.end(testTxt)
        }],
        ['/br', () => {
            if (acceptEncoding.includes('br')) {
                res.setHeader('content-encoding', 'br')
                res.setHeader('Content-Type', 'text/html; charset=utf-8')
                // 基于流的多次写操作
                const originStream = new PassThrough()
                pipeline(originStream, zlib.createBrotliCompress(), res, (err) => {
                    if (err) {
                        console.error(err);
                    }
                })
                originStream.write(Buffer.from('<h1>BrotliCompress</h1>'))
                originStream.write(Buffer.from('<h2>测试数据</h2>'))
                originStream.write(Buffer.from(testTxt))
                originStream.end()
                return
            }
            res.end(testTxt)
        }]
    ]
    const route = routes.find(v => url.startsWith(v[0]))
    if (route) {
        route[1]()
        return
    }

    // 兜底
    res.setHeader('Content-Type', 'text/html; charset=utf-8')
    res.end(`<h1>404: ${url}</h1>
    <h2>已注册路由</h2>
    <ul>
        ${routes.map(r => `<li><a href="${r[0]}">${r[0]}</a></li>`).join('')}
    </ul>
    `)
    res.end()
})

app.listen(3000)
const http = require('http')
const { PassThrough, pipeline } = require('stream')
const zlib = require('zlib')

// 测试数据
const testTxt = '测试数据123'.repeat(1000)

const app = http.createServer((req, res) => {
    const { url } = req
    // 读取支持的压缩算法
    const acceptEncoding = req.headers['accept-encoding'].match(/(br|deflate|gzip)/g)

    // 默认响应的数据类型
    res.setHeader('Content-Type', 'application/json; charset=utf-8')

    // 几个示例的路由
    const routes = [
        ['/gzip', () => {
            if (acceptEncoding.includes('gzip')) {
                res.setHeader('content-encoding', 'gzip')
                // 使用同步API直接压缩文本内容
                res.end(zlib.gzipSync(Buffer.from(testTxt)))
                return
            }
            res.end(testTxt)
        }],
        ['/deflate', () => {
            if (acceptEncoding.includes('deflate')) {
                res.setHeader('content-encoding', 'deflate')
                // 基于流的单次操作
                const originStream = new PassThrough()
                originStream.write(Buffer.from(testTxt))
                originStream.pipe(zlib.createDeflate()).pipe(res)
                originStream.end()
                return
            }
            res.end(testTxt)
        }],
        ['/br', () => {
            if (acceptEncoding.includes('br')) {
                res.setHeader('content-encoding', 'br')
                res.setHeader('Content-Type', 'text/html; charset=utf-8')
                // 基于流的多次写操作
                const originStream = new PassThrough()
                pipeline(originStream, zlib.createBrotliCompress(), res, (err) => {
                    if (err) {
                        console.error(err);
                    }
                })
                originStream.write(Buffer.from('<h1>BrotliCompress</h1>'))
                originStream.write(Buffer.from('<h2>测试数据</h2>'))
                originStream.write(Buffer.from(testTxt))
                originStream.end()
                return
            }
            res.end(testTxt)
        }]
    ]
    const route = routes.find(v => url.startsWith(v[0]))
    if (route) {
        route[1]()
        return
    }

    // 兜底
    res.setHeader('Content-Type', 'text/html; charset=utf-8')
    res.end(`<h1>404: ${url}</h1>
    <h2>已注册路由</h2>
    <ul>
        ${routes.map(r => `<li><a href="${r[0]}">${r[0]}</a></li>`).join('')}
    </ul>
    `)
    res.end()
})

app.listen(3000)

参考 ​

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