Given a standard Express.js setup
const express = require('express');
const app = express();
const router = express.Router();
router.get('/test/:id', (req, res) => {
return res.status(200).json({ hello: 'world' });
});
app.use('/api', router);
app.listen(3000, () => console.info('Up on port 3000));
I am making 1000 requests agains the endpoint, one after the other:
const fetch = require('node-fetch');
for (let i = 0; i < 1000; i++) {
let id = Math.floor(Math.random() * 12) + 1;
fetch(`http://localhost:3000/api/test/${id}`).then(res => res.json()).then(data => console.log(data)).catch(error => console.error(error));
}
I do see the data returned however, every now and then I see an ECONNRESET
error. The amount of ECONNRESET
error messages also vary: sometimes I get a few, sometimes a lot more. I do understand the message but I can't get my head around solving the issue behind it.
Here's a sample error:
{ FetchError: request to http://localhost:3000/api/test/8 failed, reason: connect ECONNRESET 127.0.0.1:3000
at ClientRequest.<anonymous> (node_modules/node-fetch/lib/index.js:1345:11)
at ClientRequest.emit (events.js:182:13)
at Socket.socketErrorListener (_http_client.js:399:9)
at Socket.emit (events.js:182:13)
at emitErrorNT (internal/streams/destroy.js:82:8)
at emitErrorAndCloseNT (internal/streams/destroy.js:50:3)
at process.internalTickCallback (internal/process/next_tick.js:72:19)
message:
'request to http://localhost:3000/api/departments/8 failed, reason: connect ECONNRESET 127.0.0.1:3000',
type: 'system',
errno: 'ECONNRESET',
code: 'ECONNRESET' }
Note that I have tried to make the request using axios, the built-in HTTP module all to avail. I'm sure the issue is with my Express app handling the request but not sure how to fix it exactly.
Update 1:
As per the suggestion in the ment, here's the async version:
async function f() {
const array = Array.from(Array(1000).keys());
for (const el of array) {
try {
let id = Math.floor(Math.random() * 12) + 1;
const result = await fetch(`http://localhost:3000/api/test/${id}`).then(res => res.json());
console.log(result);
return result;
} catch(e) {
console.log(e);
}
}
}
f();
Now I am receiving occasional ECONNREFUSED
messages.
Update 2:
Based on Mazki516's answer here's the solution that works:
// previous require statements
const cluster = require('cluster');
const os = require('os');
if (cluster.isMaster) {
const cpuCount = os.cpus().length
for (let i = 0; i < cpuCount; i++) {
cluster.fork()
}
} else {
const app = express();
// rest of the route definitions
// also app.listen() etc...
}
cluster.on('exit', worker => {
console.log(`${worker.id} removed`);
cluster.fork();
});
Given a standard Express.js setup
const express = require('express');
const app = express();
const router = express.Router();
router.get('/test/:id', (req, res) => {
return res.status(200).json({ hello: 'world' });
});
app.use('/api', router);
app.listen(3000, () => console.info('Up on port 3000));
I am making 1000 requests agains the endpoint, one after the other:
const fetch = require('node-fetch');
for (let i = 0; i < 1000; i++) {
let id = Math.floor(Math.random() * 12) + 1;
fetch(`http://localhost:3000/api/test/${id}`).then(res => res.json()).then(data => console.log(data)).catch(error => console.error(error));
}
I do see the data returned however, every now and then I see an ECONNRESET
error. The amount of ECONNRESET
error messages also vary: sometimes I get a few, sometimes a lot more. I do understand the message but I can't get my head around solving the issue behind it.
Here's a sample error:
{ FetchError: request to http://localhost:3000/api/test/8 failed, reason: connect ECONNRESET 127.0.0.1:3000
at ClientRequest.<anonymous> (node_modules/node-fetch/lib/index.js:1345:11)
at ClientRequest.emit (events.js:182:13)
at Socket.socketErrorListener (_http_client.js:399:9)
at Socket.emit (events.js:182:13)
at emitErrorNT (internal/streams/destroy.js:82:8)
at emitErrorAndCloseNT (internal/streams/destroy.js:50:3)
at process.internalTickCallback (internal/process/next_tick.js:72:19)
message:
'request to http://localhost:3000/api/departments/8 failed, reason: connect ECONNRESET 127.0.0.1:3000',
type: 'system',
errno: 'ECONNRESET',
code: 'ECONNRESET' }
Note that I have tried to make the request using axios, the built-in HTTP module all to avail. I'm sure the issue is with my Express app handling the request but not sure how to fix it exactly.
Update 1:
As per the suggestion in the ment, here's the async version:
async function f() {
const array = Array.from(Array(1000).keys());
for (const el of array) {
try {
let id = Math.floor(Math.random() * 12) + 1;
const result = await fetch(`http://localhost:3000/api/test/${id}`).then(res => res.json());
console.log(result);
return result;
} catch(e) {
console.log(e);
}
}
}
f();
Now I am receiving occasional ECONNREFUSED
messages.
Update 2:
Based on Mazki516's answer here's the solution that works:
// previous require statements
const cluster = require('cluster');
const os = require('os');
if (cluster.isMaster) {
const cpuCount = os.cpus().length
for (let i = 0; i < cpuCount; i++) {
cluster.fork()
}
} else {
const app = express();
// rest of the route definitions
// also app.listen() etc...
}
cluster.on('exit', worker => {
console.log(`${worker.id} removed`);
cluster.fork();
});
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edited Nov 16, 2018 at 16:33
Tamas
asked Nov 16, 2018 at 15:30
TamasTamas
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2
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1
You are trying to use an
aync
action (fetch) in async
code (for loop). See this, maybe it helps. – lependu Commented Nov 16, 2018 at 15:45 - updated the code, now I get ECONNREFUSED from fetch in some cases. – Tamas Commented Nov 16, 2018 at 15:55
2 Answers
Reset to default 11One of the reasons you see this is because you make the calls in "parallel" . You do start the calls one after the other , but the loops will end probably before the first results returned from the server. The loop continues until the end , making the call stack filled with 1000 async requests to the server .
Your'e are hitting hardware/software limits and nothing is wrong with the code. if you did want to build a server which can handle 1k (and much more) requests concurrently I would take a look into the "cluster" module of node .
Please notice that when doing network job between server , it's acceptable to use a concurrency limit . (for example: up to 4 requests concurrently)
but you can always scale your server beyond one machine and handle much more traffic .
I faced the same issue as you, and I was able to solve with the @lependu ment (can't ment below there due to my reputation).
But basically I mapped my data array inside an await Promise.all
and it worked perfectly.
In my case I switched from:
for (let i = 0; i < dataSet.length; i++) {
const object = dataSet[i];
const objectID = await post(url, object);
ids.push(objectID);
}
To:
await Promise.all(dataSet.map(async (object) => {
const objectID = await post(url, object);
ids.push(objectID);
}));
Credits to @lependu - the answer in Using async/await with a forEach loop and the post How to use async/await inside loops in JavaScript