io: retry and reconnect on write errors

Fixes #66

lib/statsd.rb

@@ -477,14 +477,14 @@ def send_to_socket(message)
       # in an inconsistent state if a partial message is written. If that case
       # occurs, the socket is closed down and we retry on a new socket.
       message = @protocol == :tcp ? message + "\n" : message
-      n = socket.write(message)
+      n = socket.write(message) rescue (err = $!; 0)
       if n == message.length
         break
       end
 
       connect
       retries += 1
-      raise "statsd: Failed to send after #{retries} attempts" if retries >= 5
+      raise (err || "statsd: Failed to send after #{retries} attempts") if retries >= 5
     end
     n
   rescue => boom

spec/statsd_spec.rb

@@ -341,7 +341,8 @@ class Statsd::SomeOtherClass; end
     before do
       require 'stringio'
       Statsd.logger = Logger.new(@log = StringIO.new)
-      @socket.instance_eval { def write(*) raise SocketError end }
+      @socket.instance_variable_set(:@err_count, 0)
+      @socket.instance_eval { def write(*) @err_count+=1; raise SocketError end }
     end
 
     it "should ignore socket errors" do
@@ -352,6 +353,13 @@ class Statsd::SomeOtherClass; end
       @statsd.increment('foobar')
       _(@log.string).must_match 'Statsd: SocketError'
     end
+
+    it "should retry and reconnect on socket errors" do
+      $connect_count = 0
+      @statsd.increment('foobar')
+      _(@socket.instance_variable_get(:@err_count)).must_equal 5
+      _($connect_count).must_equal 5
+    end
   end
 
   describe "batching" do