cluster: resolve relative unix socket paths

Relative unix sockets paths were previously interpreted relative
to the master's CWD, which was inconsistent with non-cluster behavior.
A test case has been added as well.

PR-URL: https://github.com/nodejs/node/pull/16749
Fixes: https://github.com/nodejs/node/issues/16387
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

2 files changed, 25 insertions, 2 deletions

diff --git a/lib/internal/cluster/child.js b/lib/internal/cluster/child.js
index 98c5e7b5597..40c1a123275 100644
--- a/lib/internal/cluster/child.js
+++ b/lib/internal/cluster/child.js
@@ -1,6 +1,7 @@
 'use strict';
 const assert = require('assert');
 const util = require('util');
+const path = require('path');
 const EventEmitter = require('events');
 const Worker = require('internal/cluster/worker');
 const { internal, sendHelper } = require('internal/cluster/utils');
@@ -48,7 +49,14 @@ cluster._setupWorker = function() {
 
 // obj is a net#Server or a dgram#Socket object.
 cluster._getServer = function(obj, options, cb) {
-  const indexesKey = [options.address,
+  let address = options.address;
+
+  // Resolve unix socket paths to absolute paths
+  if (options.port < 0 && typeof address === 'string' &&
+      process.platform !== 'win32')
+    address = path.resolve(address);
+
+  const indexesKey = [address,
                       options.port,
                       options.addressType,
                       options.fd ].join(':');
@@ -64,6 +72,8 @@ cluster._getServer = function(obj, options, cb) {
     data: null
   }, options);
 
+  message.address = address;
+
   // Set custom data on handle (i.e. tls tickets key)
   if (obj._getServerData)
     message.data = obj._getServerData();
diff --git a/lib/internal/cluster/master.js b/lib/internal/cluster/master.js
index 408b31c2b77..280955549ad 100644
--- a/lib/internal/cluster/master.js
+++ b/lib/internal/cluster/master.js
@@ -2,6 +2,7 @@
 const assert = require('assert');
 const { fork } = require('child_process');
 const util = require('util');
+const path = require('path');
 const EventEmitter = require('events');
 const RoundRobinHandle = require('internal/cluster/round_robin_handle');
 const SharedHandle = require('internal/cluster/shared_handle');
@@ -276,6 +277,18 @@ function queryServer(worker, message) {
   var handle = handles[key];
 
   if (handle === undefined) {
+    let address = message.address;
+
+    // Find shortest path for unix sockets because of the ~100 byte limit
+    if (message.port < 0 && typeof address === 'string' &&
+        process.platform !== 'win32') {
+
+      address = path.relative(process.cwd(), address);
+
+      if (message.address.length < address.length)
+        address = message.address;
+    }
+
     var constructor = RoundRobinHandle;
     // UDP is exempt from round-robin connection balancing for what should
     // be obvious reasons: it's connectionless. There is nothing to send to
@@ -287,7 +300,7 @@ function queryServer(worker, message) {
     }
 
     handles[key] = handle = new constructor(key,
-                                            message.address,
+                                            address,
                                             message.port,
                                             message.addressType,
                                             message.fd,