net.Server.listen's backlog option is no effect when use pm2

[tangxinfa]

My server's backlog set to 4096 when i call net.Server.listen

When start with pm2, backlog is 511(default value):

# ss -lt | grep 5170
LISTEN     0      511                     *:5170                     *:*       

If use node, backlog is 4096:

# ss -lt | grep 5170
LISTEN     0      4096                    *:5170                     *:*       

My server's node version: v0.12.7, pm2 version: 0.14.3

[tangxinfa]

This problem looks like come from node.js 's cluster module, still don't know how to resolve it.

[Unitech]

What is that backlog?

[tangxinfa]

There is a two example, i set backlog to 64:

Without cluster:

var http       = require('http');

http.createServer(function(req, res) {
    res.writeHead(200);
    res.end("hello world\n");
}).listen(3000, "0.0.0.0", 64);

ss -ltn | grep 3000 output:

LISTEN     0      64           *:3000                     *:*                  

With cluster

var cluster    = require('cluster'),
    http       = require('http');


if (cluster.isMaster) {
    cluster.fork();
} else {
    http.createServer(function(req, res) {
        res.writeHead(200);
        res.end("hello world\n");
    }).listen(3000, "0.0.0.0", 64);
}

ss -ltn | grep 3000 output:

LISTEN     0      511          *:3000                     *:*                  

The backlog take effect is 511 not 64, this means node cluster module NOT take care of the backlog option when we call listen: server.listen(port[, hostname][, backlog][, callback])

[tangxinfa]

Already pulled a request to node: cluster, net: backlog need pass to listen #4056

[eladnava]

Another PR (more recent), which is also now unfortunately closed due to lack of activity: nodejs/node#33827

[eladnava]

This is now fixed in PR nodejs/node#41623 and published in Node 17.6.0!