Overview of the Sensu monitoring framework

1. Monitoring with

2. First of all...

3. First of all...

4. Why we (me) don’t like Nagios?
• No active-active cluster

5. Why we (me) don’t like Nagios?
• No active-active cluster (nor easy active-passive one)

6. Why we (me) don’t like Nagios?
• No active-active cluster (nor easy active-passive one)

7. Why we (me) don’t like Nagios?
• No active-active cluster (nor easy active-passive one)
• Restart after adding a host (auto-scaling
anyone??)

8. Why we (me) don’t like Nagios?
• No active-active cluster (nor easy active-passive one)
• Restart after adding a host (auto-scaling
anyone??)
• (Really) difficult to hack on

9. Why we (me) don’t like Nagios?
• The master executes the checks (all of them!)

10. Why we (me) don’t like Nagios?
• The master executes the checks (all of them!)
• Painful config reloads if using slaves

11. Why we (me) don’t like Nagios?
• The master executes the checks (all of them!)
• Painful config reloads if using slaves
• (Quite) hard to configure

12. Why we (me) don’t like Nagios?
• First release: March 14, 1999

13. Why we (me) don’t like Nagios?
• First release: March 14, 1999

15. What’s Sensu?
• A monitoring framework
• They say “monitoring router”
• It takes results of checks and passes them to
handlers

16. Sensu facts
• Active-active cluster

17. Sensu facts
• Active-active cluster
• Hosts automagically registered when agent
starts

18. Sensu facts
• Active-active cluster
• Hosts automagically registered when agent
starts
• Written in Ruby

19. Sensu facts
• Clients execute all the checks (all of them!)

20. Sensu facts
• Clients execute all the checks (all of them!)
• No need to have slaves (but you can if you
want to)

21. Sensu facts
• Clients execute all the checks (all of them!)
• No need to have slaves (but you can if you
want to)
• Configured with small JSON files

22. Sensu facts
• Clients execute all the checks (all of them!)
• No need to have slaves (but you can if you
want to)
• Configured with small JSON files
• Compatible with Nagios plugins!

23. Sensu facts
• IT’S 2014

24. Sensu facts
• IT’S 2014

25. What does Sensu provide?
• Agent (client) to gather check results
• Server to take actions (or not) on these results
• REST API to query the state
• Optional dashboard to query the API

26. What does Sensu NOT provide?
• Storage for the results history
• Notifications
• Graphing

27. Architecture overview

28. Two modes of operation

29. Subscription
subscription messages

30. Subscription
check request

31. Subscription
check results

32. Standalone

33. Standalone
check results

34. • Modes can be mixed
• The client also listens for results in a socket
– Throw JSON to it from your application

36. Handlers
• Each check can have its own handler
• Sensu considers only results flagged as
“metrics” and not-ok’s

37. Handler types
• Pipe: the server executes a script and throws
the event as JSON to the standard input
• TPC and UDP: the server connects to a host
and port and delivers the event
• AMQP: the event can be reinjected in the
broker for further routing

39. Handling events selectively
• What if you don’t want to handle some
events?
• REST API to the rescue

40. Stashes
• A stash is associated with an ID (a “path”)
• You can store here as much shit as you want
• Put a “silence” in the stash, and make your
handlers check for it.

41. Mutators
• A filter to modify event data before passing it
to a handler.
• Example: manipulate events to make them
suitable for graphite before passing them to a
TCP handler

42. Extensions
• Mutators and Handlers running in the same
process than Sensu
• They must be written also in Ruby
• Run in the same event loop

44. Things missing / rant
• You can’t monitor something if you can’t
install an agent on it.
– There’s a ticket open since more than one year
ago...
– Some patches, but still not a solution
• As with nagios, the state is decided by the
plugins.

45. Further research
• http://sensuapp.org/docs/0.12
• https://github.com/sensu
• http://sensuapp.org/support/
• https://metacpan.org/pod/Sensu::API::Client