Is there a way to modify the keepAliveTimeout without using a custom server?

[jordie23]

NodeJS defaults keepAliveTimeout to 5 seconds. When NextJS is behind an AWS ELB/ALB, it can cause occasional 502 errors as the ELB's timeout is longer than Next's, which it should be the other way around. Also need to be able to configure headersTimeout for this circumstance.

More info can be found here: https://shuheikagawa.com/blog/2019/04/25/keep-alive-timeout/

[jordie23]

I'm guessing not :( Looks like it needs to be set around here and doesn't seem like there's a way to set it:

next.js/packages/next/server/lib/start-server.ts

Line 17 in 764edc5

srv.on('listening', () => resolve())

Maybe I'll make a feature request. Would rather not lose features to set up a custom server just to get nextjs working properly on AWS.

[tabuchid]

Added a feature request. #28633

[jordie23]

Heya the only solution I was able to find was to modify the IdleTimeout on the AWS ELB to be 4 seconds, i.e 1 second less than node's default 5 seconds.

Which isn't optimal I don't think.

[204Constie]

As the question was not answered and the issue persists i wanted to revive it. Has anyone been able to change the default keep-alive timeout for the server ?

[anuragkalia]

I am also facing the same problem. I can only tweak port and hostname for the server and nothing else. This is the only issue which may potentially force us to move to a custom server, which we really do not want to maintain.

[jordie23]

Has anyone been able to find a solution to this?

[rawpixel-vincent]

We're using patch-package to fix this issue, please make server.keepAliveTimeout a next.js settings 🙏🏻
edit: steps outlined here #19618 (reply in thread)

[rawpixel-vincent]

#22211

[Especially]

@rawpixel-vincent Mind outlining the steps involved?

[rawpixel-vincent]

1. in your project, edit the file node_modules/next/dist/server/lib/start-server.js line 31 add: srv.keepAliveTimeout = 61000; and srv.headersTimeout = 62000; (mind that the timeout must be higher that what you configure as idle_timeout for your alb, default is 60 seconds)
2. add to your dev dependencies patch-package e.g. yarn add -D patch-package
3. run npx patch-package next to create the patch
4. add to your postinstall scripts in the package.json:

 "scripts": {
+  "postinstall": "patch-package"
 }

5. commit the file created in /patches
6. test by deleting your node_modules folder and run yarn install the patch should be applied
   n.b. you need to regenerate the patch every time you upgrade next, but patch-package will show a warning with the steps to do it.

here's an example of the patch generated for next 11.1.2

diff --git a/node_modules/next/dist/server/lib/start-server.js b/node_modules/next/dist/server/lib/start-server.js
index 8edf53d..0ab11a4 100644
--- a/node_modules/next/dist/server/lib/start-server.js
+++ b/node_modules/next/dist/server/lib/start-server.js
@@ -22,6 +22,15 @@ async function start(serverOptions, port, hostname) {
         srv.on('listening', ()=>resolve()
         );
         srv.listen(port, hostname);
+
+        // https://github.com/vercel/next.js/discussions/19618
+        // Ensure all inactive connections are terminated by the ALB,
+        // by setting this a few seconds higher than the ALB idle timeout
+        // https://docs.aws.amazon.com/elasticloadbalancing/latest/application/application-load-balancers.html#connection-idle-timeout
+        // Hint: the alb is pre-opening connections behind the scene
+        srv.keepAliveTimeout = 61000;
+        srv.headersTimeout = 62000;
+
     });
     // It's up to caller to run `app.prepare()`, so it can notify that the server
     // is listening before starting any intensive operations.

[Especially]

That’s excellent cheers for this! For those who Dockerize their NextJS projects and need this to run for your CI, make sure to use

ADD [“patches”, ${WORKDIR}/patches]

Before running npm install

[jordie23]

We are doing something similar to patch, just an awk on the bundle after build. As patch replaces the whole file (IIRC) it’s more likely to break things than a regex search and insert.

[rawpixel-vincent]

thanks for the advice - first look at the codebase, it's not straightforward for a noob to PR a new config option for this - but we're looking into that. On future version I'll look into awk or implement a custom server 😢

[danroestorf]

@jordie23 do you have a code example for how you implemented this?

[tabuchid]

Added a feature request here: #28633

[danroestorf]

I tested out an extremely hacky solution for this that resolved our 502s. I ran a load test before and after adding this to our Docker build, and the results are definitive: no more 502s.

sed -i "/^srv.on('error',reject)/i srv.keepAliveTimeout = 61000; srv.headersTimeout = 62000;" node_modules/next/dist/server/lib/start-server.js

Disclaimer: You probably want to work this example a bit before using it in production.

[tabuchid]

@jordie23 @eretica and anyone else interested. @timneutkens has re-evaluated and is open to a PR that fixes this. #28642 (reply in thread)
I'm not sure when I'll have the capacity to take a look so dropping this here if anyone is interested.

[dardanos]

I'm running next@12.3.1 and building the standalone project with docker. I took an approach similar to @danroestorf. Sharing it in case someone needs a hand:

...
RUN npm run build
RUN echo "server.keepAliveTimeout = 65000; server.headersTimeout = 66000;" >> ./.next/standalone/server.js
...

[ziggy6792]

Hey guys.

Using next 12 it seem like there is a keepAliveTimeout option to configure this.
Am I right?
Does this mean I don't have to do this hack?
Does anyone know how I can use this option

node_modules/next/dist/server/lib/start-server.js

"use strict";
Object.defineProperty(exports, "__esModule", {
    value: true
});
exports.startServer = startServer;
var _log = require("../../build/output/log");
var _http = _interopRequireDefault(require("http"));
var _next = _interopRequireDefault(require("../next"));
function _interopRequireDefault(obj) {
    return obj && obj.__esModule ? obj : {
        default: obj
    };
}
function startServer(opts) {
    let requestHandler;
    const server = _http.default.createServer((req, res)=>{
        return requestHandler(req, res);
    });
    if (opts.keepAliveTimeout) {
        server.keepAliveTimeout = opts.keepAliveTimeout;
    }
    return new Promise((resolve, reject)=>{
        let port = opts.port;
        let retryCount = 0;
        server.on("error", (err)=>{
            if (port && opts.allowRetry && err.code === "EADDRINUSE" && retryCount < 10) {
                (0, _log).warn(`Port ${port} is in use, trying ${port + 1} instead.`);
                port += 1;
                retryCount += 1;
                server.listen(port, opts.hostname);
            } else {
                reject(err);
            }
        });
        let upgradeHandler;
        if (!opts.dev) {
            server.on("upgrade", (req, socket, upgrade)=>{
                upgradeHandler(req, socket, upgrade);
            });
        }
        server.on("listening", ()=>{
            const addr = server.address();
            const hostname = !opts.hostname || opts.hostname === "0.0.0.0" ? "localhost" : opts.hostname;
            const app = (0, _next).default({
                ...opts,
                hostname,
                customServer: false,
                httpServer: server,
                port: addr && typeof addr === "object" ? addr.port : port
            });
            requestHandler = app.getRequestHandler();
            upgradeHandler = app.getUpgradeHandler();
            resolve(app);
        });
        server.listen(port, opts.hostname);
    });
}

//# sourceMappingURL=start-server.js.map

[ziggy6792]

Oh I think I found it here https://github.com/vercel/next.js/pull/35827/files

so just need next start --keepAliveTimeout 61000

Can anyone confirm if this will do?

[sladg]

This seems to be outdated on latest version.

[bmoyroud]

@sladg does setting process.env.KEEP_ALIVE_TIMEOUT to 61000 work for you?

Running npm run build generates the below in .next/standalone/server.js

Tested on Next v14.0.3.