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express-graceful-exit
Advanced tools
Allow graceful exits for express apps, supporting zero downtime deploys
Gracefully decline new requests while shutting down your application. A component that helps support zero downtime deploys for Node.js with Express.
The project was originally developed for Express v3.X, but is used in production with Express v4.X. Please write up an issue or submit a PR if you find bugs using express-graceful-exit with Express v4.X and higher.
$ cd /path/to/your/project
$ npm install express-graceful-exit
v0.X.X versions are backwards API compatible, with these minor behavior changes:
setTimeout
block from v0.2.0 forward, so the timing is slightly different between v0.1.0 to v0.2.x+.The following two components must both be used to enable clean server shutdown, where incoming requests are gracefully declined.
There are multiple exit options for how in-flight requests are handled, ranging from forced exist after a specified deadline to waiting indefinitely for processing to complete.
This middleware should be the very first middleware that gets setup with your Express app.
var express = require('express');
var app = express();
var gracefulExit = require('express-graceful-exit');
var server = app.listen(port)
gracefulExit.init(server) // use init() if configured to exit the process after timeout
app.use(gracefulExit.middleware(app));
This function tells express to accept no new requests and gracefully closes the http server. It can be attached to a signal, or used as a normal function call if another tool is used (such as naught).
// Example for naught
process.on('message', function(message) {
if (message === 'shutdown') {
gracefulExit.gracefulExitHandler(app, server, {
<see options below>
});
}
});
There are no options available currently.
The following options are available:
Option | Description | Default |
---|---|---|
log | Print status messages and errors to the logger | false |
logger | Function that accepts a string to output a log message | console.log |
callback | Optional function that is called with the exit status code once express has shutdown, gracefully or not Use in conjunction with exitProcess: false when the caller handles process shutdown | no-op |
performLastRequest | Process the first request received per connection after exit starts, and include a connection close header in the response for the caller and/or load balancer. The current default is false , but will default to true in the next major release, false is deprecated as of v0.5.0 | false, true is recommended |
errorDuringExit | When requests are refused during graceful exit, respond with an error instead of silently dropping them. The current default is false , but will default to true in the next major release, false is deprecated as of v0.5.0 | false, true is recommended |
getRejectionError | Function returning rejection error for incoming requests during graceful exit | function () { return new Error('Server unavailable, no new requests accepted during shutdown') } |
exitProcess | If true, the module calls process.exit() when express has shutdown, gracefully or not | true |
exitDelay | Wait timer duration in the final internal callback (triggered either by gracefulExitHandler or the hard exit handler) if exitProcess: true | 10ms |
suicideTimeout | How long to wait before giving up on graceful shutdown, then returns exit code of 1 | 2m 10s (130s) |
socketio | An instance of socket.io , used to close all open connections after timeout | none |
force | Instructs the module to forcibly close sockets once the suicide timeout elapses. For this option to work you must call gracefulExit.init(server) when initializing the HTTP server | false |
To gracefully exit this module does the following things:
errorDuringExit
is true, HTTP status code 502 is returned by default, so nginx, ELB, etc will resend to an active servererrorDuringExit
and/or performLastRequest
are set to true, a response is sent with a Connection: close
header0
suicideTimeout
ms, the handler returns 1
process.exit(x)
, this allows the logger time to flush and the app's callback to complete, if anyThis module does not give you zero downtime deploys on its own. It enables the http server to exit gracefully, which when used with a module like naught can provide zero downtime deploys.
This module was originally developed for Frafty (formerly www.frafty.com), a Daily Fantasy Sports site.
FAQs
Allow graceful exits for express apps, supporting zero downtime deploys
The npm package express-graceful-exit receives a total of 5,671 weekly downloads. As such, express-graceful-exit popularity was classified as popular.
We found that express-graceful-exit demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
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