[pwelch]

Agree with this.

If you have money and no time: DataDog

If you don't mind putting in a little time: Sensu

Sensu is straightforward to deploy if you use Chef/Ansible/Puppet. It also supports running Nagios plugins which is pretty useful.

[otterley]

Datadog does WAY more than Sensu does. Sensu doesn't handle metrics with more than 1 dimension, which should be a standard feature of any modern metrics platform.

I also disagree that setting up Sensu takes a "little" time. What is a "little" to an inexperienced Sensu administrator? A day? A week? Several weeks? Quantifying it would be valuable to the reader.