Logstash, Elasticsearch and Kibana are just fantastic. After being unsatisfied with a whole bunch of Logging As A Service providers (I tried loggly.com, logentries.com and splunkstorm.com) I spent an afternoon setting up Logstash and co and couldn't be happier.

There's a neat demo of Kibana here: http://demo.kibana.org/#/dashboard/elasticsearch/Logstash%20...

The only thing that isn't fully baked in with this stack is alerts (e.g. sending an email if a certain error log message comes in), but you can do that using Logstash filters and outputs, although there's no pretty UI.

There are some excellent Chef cookbooks for setting up Logstash and friends too:

- Logstash: https://github.com/lusis/chef-logstash

- Elasticsearch: https://github.com/elasticsearch/cookbook-elasticsearch

- Kibana: https://github.com/lusis/chef-kibana