when keepAlive parameter is set, the TCP keep-alive is enabled but the specified timeout is not applied

[ArnoldZokas]

ioredis version: 4.26.0
Node.js version: 14.16.1
OS: Ubuntu 18.04.3 LTS

Setting the keepAlive option enables the TCP keep-alive mechanism but does not apply the specified timeout.

This can be reproduced with:

const Redis = require("ioredis");

const redis = new Redis({
  host: 'localhost',
  keepAlive: 30000, // should set socket option TCP_KEEPIDLE=30
});

redis.on('connect', () => {
  console.log('Connected!');
});

Running knetstat to inspect socket options shows the socket was created with TCP_KEEPIDLE=60 (which is the Node.js default):

$ cat /proc/net/tcpstat
Recv-Q Send-Q Local Address   Foreign Address  Stat Diag Options
     0      0 127.0.0.1:40792 127.0.0.1:6379   ESTB      SO_REUSEADDR=0,SO_REUSEPORT=0,SO_KEEPALIVE=1,TCP_KEEPIDLE=60,TCP_KEEPCNT=10,TCP_KEEPINTVL=1,TCP_NODELAY=1,TCP_DEFER_ACCEPT=0

---

This is likely due to socket.setKeepAlive() being called after the connection has been established.
To test this I have created a socket and tried calling socket.setKeepAlive() before and after calling socket.connect().

When socket.setKeepAlive() is called before socket.connect():

const net = require('net');

const socket = new net.Socket();

socket.setKeepAlive(true, 10000);

socket.connect({
  host: 'localhost',
  port: 6379,
});

socket.on('connect', () => {
  console.log('Connected!');
});

knetstat reports TCP_KEEPIDLE=10 - keep-alive is enabled and the correct timeout is applied

---

When socket.setKeepAlive() is called after socket.connect():

const net = require('net');

const socket = new net.Socket();

socket.connect({
  host: 'localhost',
  port: 6379,
});

socket.setKeepAlive(true, 10000);

socket.on('connect', () => {
  console.log('Connected!');
});

knetstat reports TCP_KEEPIDLE=60 - keep-alive is enabled but the Node.js default timeout is applied

[marcbachmann]

Thanks for the investigation. I think the cause of that issue is nodejs/node#31663

[github-actions]

🎉 This issue has been resolved in version 5.0.3 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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