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Question

我正在运行React应用程序的服务器端渲染。我为此使用express。整个服务器端渲染代码如下：

import * as React from "react"
import * as ReactDOMServer from "react-dom/server"
import * as express from "express"
import { StaticRouter } from "react-router-dom"
import walker = require("react-tree-walker")
import { useStaticRendering } from "mobx-react"

import Helmet from "react-helmet"
import Provider from "../src/Provider"
import { StaticRouterContext } from "react-router"
import version = require("../version")

var _template: string = require(`../dist/${version.v()}/index.html`)

interface IRenderResponse {
    statusCode: number,
    template: string,
    redirect?: string
}

const run = (url: string, locale?: string): Promise<IRenderResponse> => {
    var template: string
    var html: string = ""
    var head: object
    var context: StaticRouterContext = {}

    useStaticRendering(true)

    var routing = (
        <StaticRouter 
            location={url} 
            context={context}
        >
            <Provider defaultLocale={locale} />
        </StaticRouter>
    )

    return new Promise((resolve) => {
        walker(routing, (element, instance) => {
            if (instance && typeof instance._prepare == typeof (() => {}))
                return instance._prepare()
        }).then(() => {
            html = ReactDOMServer.renderToString(routing)
            head = Helmet.renderStatic()
            template = _template.replace(/\${__rh-([a-z]+)}/gi, (match, group) => {
                return head[group].toString()
            })
            template = template.replace(/\${__body}/gi, (match) => {
                return html
            })
            if (context.url)
                context["statusCode"] = 301

            resolve({
                statusCode: context["statusCode"] || 200, 
                template, 
                redirect: context.url
            })
        }).catch((error) => {
            template = _template.replace(/\${__rh-([a-z]+)}/gi, "")
            template = template.replace(/\${__body}/gi, error.stack || error.toString())
            resolve({
                statusCode: 500, 
                template
            })
        })
    })
}

var app = express()

app.get("*", (req, res) => {
    var accepted = req.acceptsLanguages()
    var locale = accepted ? (accepted[0] || "ru").split("-")[0] : "ru"
    run(req.originalUrl, locale).then((data) => {
        if (data.redirect)
            res.redirect(data.redirect)
        else
            res.status(data.statusCode).send(data.template)
    })
})

app.listen(1239)

您可以看到此处使用了react-tree-walker。但是无论我在服务器端渲染中使用什么，都会发生此问题。

问题在于，如果我的node-js服务器在一个线程中运行，那么如果同时执行两个不同的请求，则react-helmet会混合使用字段。例如，如果有两个视图：

class FirstView extends React.Component {
    render() {
        return (
            <Helmet>
                <title>This is first title</title>
                <meta name="description" content="My first view description" />
            </Helmet>
        )
    }
}

和

class SecondView extends React.Component {
    render() {
        return (
            <Helmet>
                <title>This is second title</title>
                <meta name="description" content="My second view description" />
            </Helmet>
        )
    }
}

然后我可以收到这样的东西：

<title>This is first title</title>
<meta name="description" content="My second view description" />

很显然，发生这种情况是因为react-helmet使用静态字段。因此，如果并行处理两个请求，则该字段将混乱地更改。

我怎么打败它？对于高负载项目，通常会出现此问题，这可能会导致SEO崩溃，因为搜寻器可能会收到错误的数据。

webpack.config.js：

var webpack = require("webpack")

var config = {
    mode: "production",
    target: "node",
    entry: __dirname + "/index.tsx",
    output: {
        path: __dirname,
        filename: `index.js`
    },
    module: {
        rules: [
            {
                test: require.resolve("phoenix"),
                use: "imports-loader?window=>global"
            },
            {
                test: /\.tsx?$/,
                loader: "awesome-typescript-loader?configFileName=tsconfig.server.json",
                exclude: /node_modules/
            },
            {
                test: /\.js$/,
                enforce: "pre",
                loader: "source-map-loader"
            },
            {
                test: /\.html$/,
                loader: "html-loader"
            },
            {
                test: /\.(svg|woff|woff2|ttf|otf|png|jpg)$/,
                loader: "url-loader"
            },
            {
                test: /\.(css|sass)$/,
                loader: "ignore-loader"
            }
        ]
    },
    resolve: {
        modules: [
            "node_modules",
            `${__dirname}/../src`
        ],
        extensions: [".js", ".jsx", ".sass", ".json", ".css", ".ts", ".tsx"]
    },
    parallelism: 2,
    plugins: [
        new webpack.DefinePlugin({
            "ENV": JSON.stringify("server"),
            "process.env.ENV": JSON.stringify("server"),
            "process.env.VERSION": JSON.stringify("n/a"),
            "process.env.NODE_ENV": JSON.stringify("production"),
            "global.GENTLY": false
        })
    ]
}

module.exports = config

编辑

根据this issue，似乎react-helmet是线程不安全。是否有可能基于此知识创建一些解决方法？

Answer 1

我觉得require(../dist/${version.v()}/index.html);仅导入模板的一个实例。

通过在所有网络调用中反复要求模板，您可能会一次又一次地更新相同的字符串引用。

所以。您可以执行以下操作：

import(require) template 仅一次在文件顶部。
将其分配给run函数中返回的promise中的字符串类型的新变量，并对其执行替换操作。

基本代码段：

...
import version = require("../version");

import appTemplate = require(`../dist/${version.v()}/index.html`)


interface IRenderResponse {
    statusCode: number,
    template: string,
    redirect?: string
}

const run = (url: string, locale?: string): Promise<IRenderResponse> => {
    var template: string = "";
    var html: string = ""
    var head: object
    var context: StaticRouterContext = {}

    useStaticRendering(true)

    var routing = (
        <StaticRouter 
            location={url} 
            context={context}
        >
            <Provider defaultLocale={locale} />
        </StaticRouter>
    )

    return new Promise((resolve) => {
        walker(routing, (element, instance) => {
            if (instance && typeof instance._prepare == typeof (() => {}))
                return instance._prepare()
        }).then(() => {
            html = ReactDOMServer.renderToString(routing)
            head = Helmet.renderStatic()
            template = appTemplate.replace(/\${__rh-([a-z]+)}/gi, (match, group) => {
                return head[group].toString()
            })
            template = template.replace(/\${__body}/gi, (match) => {
                return html
            })
            if (context.url)
                context["statusCode"] = 301

            resolve({
                statusCode: context["statusCode"] || 200, 
                template, 
                redirect: context.url
            })
        })....

renderStatic期间的反应头盔混合场

编辑

1 个答案: