Internally supporting binding to UNIX domain sockets

Additionally, provide Socket#unicorn_addr which makes it
easy to determine whether a given Socket matches one in
the config.

2 files changed, 35 insertions, 5 deletions

diff --git a/lib/unicorn.rb b/lib/unicorn.rb
index 943ad99..a17ab2d 100644
--- a/lib/unicorn.rb
+++ b/lib/unicorn.rb
@@ -74,7 +74,7 @@ module Unicorn
         instance_variable_set("@#{key.to_s.downcase}", value)
       end
 
-      @socket = Socket.unicorn_tcp_server(@host, @port, 1024)
+      @socket = Socket.unicorn_server_new("#{@host}:#{@port}", 1024)
     end
 
     # Does the majority of the IO processing.  It has been written in Ruby using
diff --git a/lib/unicorn/socket.rb b/lib/unicorn/socket.rb
index 40631d5..717c1a0 100644
--- a/lib/unicorn/socket.rb
+++ b/lib/unicorn/socket.rb
@@ -36,14 +36,44 @@ class Socket
     Socket.unpack_sockaddr_in(getpeername)
   end
 
+  # returns the config-friendly name of the current listener socket, this is
+  # useful for config reloads and even works across execs where the Unicorn
+  # binary is replaced
+  def unicorn_addr
+    @unicorn_addr ||= if respond_to?(:getsockname)
+      port, host = Socket.unpack_sockaddr_in(getsockname)
+      "#{host}:#{port}"
+    elsif respond_to?(:getsockname)
+      addr = Socket.unpack_sockaddr_un(getsockname)
+      # strip the pid from the temp socket path
+      addr.gsub!(/\.\d+$/, '') or
+        raise ArgumentError, "PID not found in path: #{addr}"
+    else
+      raise ArgumentError, "could not determine unicorn_addr for #{self}"
+    end
+  end
+
   class << self
 
-    def unicorn_tcp_server(host, port, backlog = 5)
-      s = new(AF_INET, SOCK_STREAM, 0)
-      s.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC) if defined?(Fcntl::FD_CLOEXEC)
+    # creates a new server, address may be a HOST:PORT or
+    # an absolute path to a UNIX socket.  When creating a UNIX
+    # socket to listen on, we always add a PID suffix to it
+    # when binding and then rename it into its intended name to
+    # atomically replace and start listening for new connections.
+    def unicorn_server_new(address = '0.0.0.0:8080', backlog = 1024)
+      domain, bind_addr = if address[0..0] == "/"
+        [ AF_UNIX, pack_sockaddr_un("#{address}.#{$$}") ]
+      elsif address =~ /^(\d+\.\d+\.\d+\.\d+):(\d+)$/
+        [ AF_INET, pack_sockaddr_in($2.to_i, $1) ]
+      end
+      s = new(domain, SOCK_STREAM, 0)
       s.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1) if defined?(SO_REUSEADDR)
-      s.bind(pack_sockaddr_in(port, host))
+      s.bind(bind_addr)
       s.listen(backlog)
+      s.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC) if defined?(Fcntl::FD_CLOEXEC)
+
+      # atomically replace existing domain socket
+      File.rename("#{address}.#{$$}", address) if domain == AF_UNIX
       s
     end