I'm running server-side render of the React application. I'm using express for this purposes. The whole server-side render code looks like this:
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)
You can see that the react-tree-walker is used here. But this problem occurs whatever I'm using for the server-side render.
The problem is that if my node-js server is running in one thread, then if two different requests are being done simultaneously, then react-helmet mixes fields. For example, if there are two views:
class FirstView extends React.Component {
render() {
return (
<Helmet>
<title>This is first title</title>
<meta name="description" content="My first view description" />
</Helmet>
)
}
}
and
class SecondView extends React.Component {
render() {
return (
<Helmet>
<title>This is second title</title>
<meta name="description" content="My second view description" />
</Helmet>
)
}
}
then I can receive the head something like that:
<title>This is first title</title>
<meta name="description" content="My second view description" />
Obviously this happens because of react-helmet uses static fields, I suppose. So, if two requests are being handled in parallel, this fields are being changed chaoticaly.
How can I defeat it? This problem often occurs for high-load projects, and this can crash the SEO, because crawler can receive wrong data.
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
Edit
Seems like, react-helmet is thread-unsafe according to this issue. Is there any possibility to create some workaround based on this knowlenge?
