Cluster listen doesn't resolve UNIX domain socket paths relative to worker CWD

[laino]

• Version: v8.6.0
• Subsystem: net, cluster

When calling server.listen('./socket.sock') in a worker, the relative path is passed as-is to the master,
causing the path to be relative to the master's CWD, instead of the child process' CWD.

This behavior is inconsistent with listen(...) outside of a worker.

Here's a short example illustrating the issue:

const cluster = require('cluster');
const http = require('http');

if (cluster.isMaster) {
    cluster.fork();
} else {
    const server = http.createServer();
    process.chdir('/tmp');
    server.listen("./test.sock");
}

Expected outcome: test.sock is created in /tmp.
Actual outcome: test.sock is created in the previous directory.

Solution:

UNIX domain socket paths should immediately be resolved to absolute paths using path.resolve(...)
before anything else is done with them (such as passing them to the master process).

[addaleax]

Yes, this sounds like a bug, thanks for reporting.

One thing that makes this tricky: There is a pretty short path limit (~100 bytes) on what can be passed to .listen(), so we’ve been forced to migrate to using relative paths in Node’s own test suite to keep them short enough.

[laino]

We could call path.relative(process.cwd(), socketPath) in the master right before the actual call to listen, then take whichever is shorter: the absolute path or the relative path.