Simple lib to handle fire and forget operations.
$ npm install fire-and-forgetter --save
In NodeJs applications performing fire and forget operations we need a way to wait until all those operations complete in order to perform a graceful application shutdown.
Also, fire and forget operations must have proper error handling in order to avoid 'unhandledRejection'.
const express = require('express')
const someDb = require('some-db');
const app = express();
(async function main() {
const db = await someDb.connect();
app.post('/', (req, res) => {
res.send('Got request, now I am processing it in fire and forget mode');
process(req.body);
})
async function process(payload) {
// do some stuff that could take several milliseconds
// i.e interact with another service, I/O operations, etc..
// then finally we persist the payload.
await db.insert(payload);
}
const server = app.listen(3000);
process.on('SIGTERM', async () => {
try {
await new Promise(resolve => server.close(resolve));
// above we have closed the web server, now we are closing db connection
// however we have may some fire and forget operation still in progress
// so close the db now won't result in a clear application shutdown
await db.close();
process.exit(0);
} catch (error) {
process.exit(1);
}
});
})().catch(() => {
process.exit(1);
});Note: this example is a simplified version of real code, the someDb is a fake package and I haven't execute this code.
Fire and forgetter is a tiny library to keep the state of fire and forget operations.
It ensures that a catch is always added to these operations (to avoid any Unhandled Promise Rejections that could lead in memory leaks).
Finally it provides a close method that:
- resolves when all pending fire and forget operations have been fulfilled or rejected
- mark the instance as closed so no new fire an forget operations can be executed.
const express = require('express')
const someDb = require('some-db');
const fireAndForgetter = require('fire-and-forgetter').default;
const app = express();
(async function main() {
const fireAndForget = fireAndForgetter();
const db = await someDb.connect();
app.post('/', (req, res) => {
res.send('Got request, now I am processing it in fire and forget mode');
fireAndForget(() => process(req.body));
})
async function process(payload) {
// do some stuff that could take several milliseconds
// i.e interact with another service, I/O operations, etc..
// then finally we persist the payload.
await db.insert(payload);
}
const server = app.listen(3000);
process.on('SIGTERM', async () => {
try {
await new Promise(resolve => server.close(resolve));
// above we have closed the web server, now before closing db connection
// we are going to close fireAndForget so we wait until all fire and forget
// operations have been complete and we can safetly close the database connection
// in order to ensure a good application shutdown
await fireAndForget.close();
await db.close();
process.exit(0);
} catch (error) {
process.exit(1);
}
});
})().catch(() => {
process.exit(1);
});Please check tests in order to get more information about the fire and forgetter API.
MIT