Restarting express server in esbuild - express

Question

I am trying to create a simple express server with esbuild. These are my code
import express from "express";
const app = express();
const port = 3000;
const stopServer = {
stop: () => {},
};
export const createServer = async () => {
app.get("/", async (req, res) => {
res.json({
first: "Hello",
});
});
const server = app.listen(port, () => {
console.log(`Listening on port: ${port}`);
});
stopServer.stop = () => {
server.close();
};
};
export const stop = () => {
stopServer.stop();
stopServer.stop = () => {};
};
esbuild.config.js
const esbuild = require("esbuild");
const path = require("path");
const restartPlugin = () => {
return {
name: "restart-express",
setup(build) {
build.onEnd(async (res) => {
const { stop, createServer } = await import("../dist/server.js");
stop();
createServer();
});
},
};
};
const run = async () => {
await esbuild.build({
entryPoints: [path.resolve(__dirname, "../src/server.ts")],
outdir: path.resolve(__dirname, "../dist"),
platform: "node",
sourcemap: true,
format: "cjs",
watch: {
onRebuild: async (err, res) => {
if (err) {
console.error(err);
} else {
console.log("There is some change");
}
},
},
plugins: [restartPlugin()],
});
};
run();
Reference for plugin : https://github.com/evanw/esbuild/issues/1258#issuecomment-834676530
If you were to run this application It i will work initially but when you change the code, the server wont get updated even if you refresh the page.
I am not really sure where I am making mistake, Any help please

Answer 1

The problem is that node cache the import("..dist/server.js"), as a result it will never return new module. To solve this problem we will write a function
const purgeAppRequireCache = (buildPath) => {
for (let key in require.cache) {
if (key.startsWith(buildPath)) {
delete require.cache[key];
}
}
};
Which will remove the cache from the node. We can also use this function in this manner. Which solves my problem
const esbuild = require("esbuild");
const path = require("path");
const startPlugin = () => {
return {
name: "startPlugin",
setup(build) {
build.onEnd((res) => {
const serverPath = path.resolve(__dirname, "../dist/server.js");
const { stop } = require("../dist/server.js");
stop();
purgeAppRequireCache(serverPath);
purgeAppRequireCache(path.resolve(__dirname, "../src"));
const { listen } = require("../dist/server");
listen();
});
},
};
};
const run = async () => {
await esbuild.build({
entryPoints: [path.resolve(__dirname, "../src/server.tsx")],
outdir: path.resolve(__dirname, "../dist"),
platform: "node",
sourcemap: true,
format: "cjs",
watch: true,
bundle: true,
plugins: [startPlugin()],
});
};
run();
const purgeAppRequireCache = (buildPath) => {
for (let key in require.cache) {
if (key.startsWith(buildPath)) {
delete require.cache[key];
}
}
};

Answer 2

If you not reload runtime, the global's object and sub require(xxx) maby have same error.
You can use kill and fork cluster when change you code, it's same fast like require(xxx), there have example codes: https://github.com/ymzuiku/bike/blob/master/lib/index.js
If you need see kill and fork cluster example, here's a same feature package, also use esbuild, but it use fs.watch: https://www.npmjs.com/package/bike
Hope there could help you :)

Answer 3

#es-exec/esbuild-plugin-serve or #es-exec/esbuild-plugin-start are two alternative esbuild plugins that you can try. They run your bundles or any command line script for you after building your project (supports watch mode for rebuilding on file changes).
The documentation can be found at the following:
#es-exec/esbuild-plugin-serve
#es-exec/esbuild-plugin-start
Disclaimer: I am the author of these packages.