resolve symlinks to Unix domain sockets

Raindrops currently fails when provided a symlink to a socket.
As this is a common practice for many deployment tools (Vlad,
etc.) this patch adds support for finding the realpath prior to
looking the socket up in /proc/net/unix

[ew: commit message subject]

[ew: fixed test to pass under 1.9.3 and 1.8.7:
* Tempfile#unlink is unsafe to call if we want to reuse the
  path, use File.unlink(tmp.path) instead

* The return value of File.symlink is zero (or it raises),
  so it's unusable.

* File.symlink will not call #to_path under 1.8.7, so it's
  necessary to pass pathnames to it, not Tempfile objects.
]

Signed-off-by: Eric Wong <normalperson@yhbt.net>

2 files changed, 29 insertions, 0 deletions

diff --git a/lib/raindrops/linux.rb b/lib/raindrops/linux.rb
index fe2af09..a198253 100644
--- a/lib/raindrops/linux.rb
+++ b/lib/raindrops/linux.rb
@@ -8,6 +8,8 @@
 # Instead of snapshotting, Raindrops::Aggregate::LastDataRecv may be used
 # to aggregate statistics from +all+ accepted sockets as they arrive
 # based on the +last_data_recv+ field in Raindrops::TCP_Info
+require 'pathname'
+
 module Raindrops::Linux
 
   # The standard proc path for active UNIX domain sockets, feel free to call
@@ -41,6 +43,7 @@ module Raindrops::Linux
     else
       paths = paths.map do |path|
         path = path.dup
+        path = Pathname.new(path).realpath.to_s
         path.force_encoding(Encoding::BINARY) if defined?(Encoding)
         rv[path]
         Regexp.escape(path)
diff --git a/test/test_linux.rb b/test/test_linux.rb
index 65f25e0..81463c9 100644
--- a/test/test_linux.rb
+++ b/test/test_linux.rb
@@ -67,6 +67,32 @@ class TestLinux < Test::Unit::TestCase
     assert_equal 1, stats[tmp.path].queued
   end
 
+  def test_unix_resolves_symlinks
+    tmp = Tempfile.new("\xde\xad\xbe\xef") # valid path, really :)
+    File.unlink(tmp.path)
+    us = UNIXServer.new(tmp.path)
+
+    # Create a symlink
+    destination = Tempfile.new("somethingelse")
+    destination.unlink # We need an available name, not an actual file
+    link = File.symlink(tmp, destination)
+
+    @to_close << UNIXSocket.new(tmp.path)
+    stats = unix_listener_stats
+    assert_equal 0, stats[link.path].active
+    assert_equal 1, stats[link.path].queued
+
+    @to_close << UNIXSocket.new(tmp.path)
+    stats = unix_listener_stats
+    assert_equal 0, stats[link.path].active
+    assert_equal 2, stats[link.path].queued
+
+    @to_close << us.accept
+    stats = unix_listener_stats
+    assert_equal 1, stats[link.path].active
+    assert_equal 1, stats[link.path].queued
+  end
+
   def test_tcp
     s = TCPServer.new(TEST_ADDR, 0)
     port = s.addr[1]