I've tried to add Datadog to a small Flask app I'm working on without success, it's not as simple as Sentry which I've done in less than a minute. And also as a follow up to this https://news.ycombinator.com/item?id=12682566
I use SumoLogic, but have used Splunk and ES before. Nice thing is they have a free tier that you can ingest 500mb/day of logs, downside is its only 7 days of retention, but for most of my needs I don't really have much usage beyond troubleshooting.