Added note about DNS

README.md

@@ -132,3 +132,11 @@ You can instrument class methods, just like instance methods, using the metaprog
 AWS::S3::Base.singleton_class.extend StatsD::Instrument
 AWS::S3::Base.singleton_class.statsd_measure :request, 'S3.request'
 ```
+
+## Reliance on DNS
+Out of the box StatsD is set up to be unidirectional fire-and-forget over UDP. Configuring the StatsD host to be a non-ip will trigger a DNS lookup (ie synchronous round trip network call) for each metric sent. This can be particularly problematic in clouds that have a shared DNS infrastructure such as AWS.
+
+### Common Workarounds
+1. Using an IP avoids the DNS lookup but generally requires an application deploy to change.
+2. Hardcoding the DNS/IP pair in /etc/hosts allows the IP to change without redeploying your application but fails to scale as the number of servers increases.
+3. Installing caching software such as nscd that uses the DNS TTL avoids most DNS lookups but makes the exact moment of change indeterminate.