Add metrics for DNS resolve failure. (#337)

* add dd metrics for dns resolve failure

* bump the version to 0.18.9

Author: bjzhang1101

lib/synapse/service_watcher/dns/dns.rb

@@ -44,7 +44,7 @@ def watch
 
           sleep_until_next_check(start)
         rescue => e
-          log.warn "Error in watcher thread: #{e.inspect}"
+          log.warn "synapse: dns error in watcher thread: #{e.inspect}"
           log.warn e.backtrace
         end
       end
@@ -75,7 +75,8 @@ def resolve_servers
         return resolution
       end
     rescue => e
-      log.warn "Error while resolving host names: #{e.inspect}"
+      statsd_increment('synapse.watcher.dns.resolve_failed', ["service_name:#{@name}"])
+      log.warn "synapse: dns resolve error while resolving host names: #{e.inspect}"
       []
     end
 

lib/synapse/version.rb

@@ -1,3 +1,3 @@
 module Synapse
-  VERSION = "0.18.8"
+  VERSION = "0.18.9"
 end