David Mytton is a MongoDB master and the founder of Server Density. In this presentation David delves deeper into what's discussed in our how to monitor MongoDB tutorial (https://blog.serverdensity.com/monitor-mongodb/), with the aim of taking you through: Key MongoDB metrics to monitor. Non-critical MongoDB metrics to monitor. Alerts to set for MongoDB on production. Tools for monitoring MongoDB.

1. How to monitor:
MongoDB
David Mytton
Hangout on Air - Sept 2014
https://blog.serverdensity.com/monitor-mongodb/

2. David Mytton

4. Server Density Architecture

5. Server Density Architecture
● ~100 servers - Ubuntu 12.04

6. Server Density Architecture
● ~100 servers - Ubuntu 12.04
● 50:50 virtual/dedicated

7. Server Density Architecture
● ~100 servers - Ubuntu 12.04
● 50:50 virtual/dedicated
● 200TB/m processed data

8. Server Density Architecture
● ~100 servers - Ubuntu 12.04
● 50:50 virtual/dedicated
● 200TB/m processed data
● Nginx, Python, MongoDB

9. Server Density Architecture
● ~100 servers - Ubuntu 12.04
● 50:50 virtual/dedicated
● 200TB/m processed data
● Nginx, Python, MongoDB
● Softlayer > 1TB RAM, 5TB SSDs

10. Key metrics
● Oplog replication lag
● Replica state
● Lock %
● Disk i/o % utilization

11. Oplog replication lag
● Replica sets: master/slave

12. Oplog replication lag
● Replica sets: master/slave
● Async i.e. eventually consistent

13. Oplog replication lag
● Replica sets: master/slave
● Async i.e. eventually consistent
● Write concern

14. Oplog replication lag

15. Oplog replication lag
https://blog.serverdensity.com/mongodb-benchmarks/

16. Oplog replication lag
● Replica sets: master/slave
● Async i.e. eventually consistent
● Write concern
● Falling behind

17. Reasons for repl falling behind
● Network problems

18. Reasons for repl falling behind
● Network problems
● Hardware problems

19. Reasons for repl falling behind
● Network problems
● Hardware problems
● Shard chunk migrations

20. Reasons for repl falling behind
● Network problems
● Hardware problems
● Shard chunk migrations
● MongoDB bugs

21. Replica state
● Primary / secondary

22. Replica state
● Primary / secondary
● Alert on state change

23. Lock %
● Database locking (2.6)

24. Lock %
● Database locking (2.6)
● Sometimes a problem:

25. Lock %
● Database locking (2.6)
● Sometimes a problem:
● Nearing 100%

26. Lock %
● Database locking (2.6)
● Sometimes a problem:
● Nearing 100%
● Constantly high

27. Lock %
● Database locking (2.6)
● Sometimes a problem:
● Nearing 100%
● Constantly high
● Slows replication

28. Disk i/o % utilization
● Hardware limits

29. Disk i/o % utilization
● Hardware limits
● Nearing 100%

30. Disk i/o % utilization
● Hardware limits
● Nearing 100%
● Constantly high

31. Disk i/o % utilization
● Hardware limits
● Nearing 100%
● Constantly high
● Spinning -> SSD

32. Disk i/o % utilization
https://blog.serverdensity.com/mongodb-performance-ssds-vs-spindle-sas-drives/

33. Disk i/o % utilization
https://blog.serverdensity.com/mongodb-benchmarks/

34. Disk i/o % utilization
● Hardware limits
● Nearing 100%
● Constantly high
● Spinning -> SSD
● Slow queries, hangs, slow repl

35. Non-critical metrics to watch
● Memory usage

36. Non-critical metrics to watch
● Memory usage
● Page faults

37. Non-critical metrics to watch
● Memory usage
● Page faults
● Connections

38. Non-critical metrics to watch
● Memory usage
● Page faults
● Connections
● Shard chunk distribution

39. Non-critical metrics to watch

40. Monitoring tools
● mongostat
● mongotop
● rs.status()
● sh.status()

41. rs.status()

42. sh.status()

43. Server Density

44. MMS

45. Summary
● Critical alerts on key metrics

46. Key metrics
● Oplog replication lag
● Replica state
● Lock %
● Disk i/o % utilization

47. Summary
● Critical alerts on key metrics

48. Summary
● Critical alerts on key metrics
● Watch non-critical

49. Summary
● Critical alerts on key metrics
● Watch non-critical
● Manual tools for real time

50. Summary
● Critical alerts on key metrics
● Watch non-critical
● Manual tools for real time
● Set up a monitoring product

51. Useful resources
● http://docs.mongodb.org/manual/administration/monitoring/
● https://blog.serverdensity.com/monitor-mongodb
● https://blog.serverdensity.com

52. どもありがとうございます
＠davidmytton
david@serverdensity.com
blog.serverdensity.com