Fact-Based Monitoring
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The document discusses the evolution of monitoring in systems management, emphasizing the transition from host-centric approaches to fact-based monitoring using tools like Puppet and MCollective. It highlights the importance of expressive queries and metadata in optimizing monitoring and configuration processes. Key takeaways include that hosts are not central to monitoring, and queries should be focused on using Puppet facts for better efficiency.
![“[SQL brings] immunity of application to change in storage
structure and access strategy”
–C.J. Date (1977)
http://www.cs.berkeley.edu/~brewer/cs262/SystemR.pdf](https://image.slidesharecdn.com/fact-basedmonitoringpuppetconf2014-141023141923-conversion-gate01/85/Fact-Based-Monitoring-10-320.jpg)
![In Datadog (metrics)
• “All provisioned web servers in the production environment,
datacenter ABC must respond to queries within 200ms”
$ puppet module install datadog-datadog_agent
class {
‘datadog_agent’:
api_key => …,
tags => [$environment],
fact_to_tags => [“datacenter”]
}
include datadog_agent::integrations::nginx](https://image.slidesharecdn.com/fact-basedmonitoringpuppetconf2014-141023141923-conversion-gate01/85/Fact-Based-Monitoring-31-320.jpg)
Fact-Based Monitoring
- 1. Fact-based Monitoring puppetconf 2014 Alexis Lê-Quôc @alq
- 2. Alexis Lê-Quôc, @alq CTO at Datadog
- 3. Poll: Monitoring makes me… happy proud cry want to hide
- 4. Puppet brings Automation to Systems Management
- 5. Improve Monitoring the way Puppet has improved Systems Management
- 6. “The good old days” • Your “CMDB” was Excel • SSH in and hack away • Little time for anything else
- 7. Then Puppet came… • Expressive rules that capture expected result • Using facts and classifiers, a.k.a. metadata to figure out where to apply changes • That freed up a lot of our time* * on a per-machine basis
- 8. “Puppet brings immunity of configuration to change in infrastructure” –Me (just now)
- 9. I have seen this before…
- 10. “[SQL brings] immunity of application to change in storage structure and access strategy” –C.J. Date (1977) http://www.cs.berkeley.edu/~brewer/cs262/SystemR.pdf
- 11. SQL • 1974 IBM introduces System R and its Structured Query Language • Expressive rules that capture expected result • Using facts and predicates, a.k.a. metadata to figure out what data to get • That freed up a lot of development time
- 12. SQL • From a time-consuming, imperative mess (“how”) • … to expressive data queries (“what”) SQL query SELECT (desired facts) FROM (existing facts) WHERE (matching criteria)
- 13. Puppet • From a time-consuming, imperative mess (“how”) • … to expressive configuration queries (“what”) puppet apply CHANGE (desired facts) FROM (existing puppet facts) WHERE (matching puppet classes)
- 14. Is there a pattern?
- 15. “Break free from ever more complex naming conventions for hostnames as a means of identity. Use a very rich set of meta data provided by each machine to address them.” –MCollective overview
- 16. MCollective • From a time-consuming, imperative mess (“how”) • … to expressive orchestration queries (“what”) mco rpc service restart service=nginx -F webpool=A EXEC (desired actions) FROM (existing puppet facts) WHERE (matching puppet classes)
- 17. Back to monitoring • Monitoring is to behavior what Puppet is to configuration • Monitoring is to behavior what MCollective is to orchestration
- 18. Monitoring • From a time-consuming, imperative mess (“how”) • … to expressive monitoring queries (“what”) Monitoring query MONITOR (desired behavior) FROM (existing heartbeats/metrics) WHERE (matching puppet facts)
- 19. Examples • “All provisioned web servers in the production environment, datacenter ABC must respond to queries within 200ms” • “All PostgreSQL servers must have a postgres: bgwriter process running” • “At least one ActiveMQ server is up to support mcollective" • Never mention a hostname
- 20. Hosts are not the center of the monitoring universe. Facts are! Hosts are just places where facts occur.
- 21. The proof is in the pudding…
- 22. Hosts at the center of the universe a.k.a. the Wrong Way
- 23. “Its fairly straightforward, so hopefully you find things easy to understand…” –Nagios Core 4 manual on monitoring clusters
- 24. Host-centric: Monitor a DNS cluster check_command check_service_cluster!"DNS Cluster"!0!1! $SERVICESTATEID:host1:DNS Service$,$SERVICESTATEID:host2:DNS Service$,$SERVICESTATEID:host3:DNS Service$ Where do host1, host2, host3 come from?
- 25. Host-centric: can’t use facts directly • “Host groups solve this problem”. No, they don’t. • Combinatorial explosion, e.g. trivially • 4 data centers (us-1, us-2, eu, apac) • 5 classes (web, db, cache, appserver, hadoop) • 3 environments (test, staging, prod) • => up to 119 materialized host groups
- 26. Nagios-bashing? • No! • Same fatal flaw with all host-centric monitoring tools • Host-centric monitoring forces an extra, expensive step: • replicate fact-based conditionals in host-centric templates
- 27. “Please note that this module is not for the faint of heart. Even I (the author) have my head hurt each time I have to make modifications to it…” –puppet-nagios author
- 28. Facts at the center of the universe a.k.a. the Right Way "De Revolutionibus manuscript p9b" by Nicolas Copernicus - www.bj.uj.edu.pl. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:De_Revolutionibus_manuscript_p9b.jpg#mediaviewer/ File:De_Revolutionibus_manuscript_p9b.jpga
- 29. Earlier Examples • “All provisioned web servers in the production environment, datacenter ABC must respond to queries within 200ms” • “All PostgreSQL servers must have a postgres: bgwriter process running” • “At least one ActiveMQ server is up to support mcollective"
- 30. In Sensu (heartbeats) • “All PostgreSQL servers must have a postgres: bgwriter process running” class postgres::monitoring::sensu { sensu::subscription { 'postgres': } } • Monitoring using a fact-based query • Is node of class “postgres” and subscribed to “postgres” or not? • If so, it will execute the postgres check
- 31. In Datadog (metrics) • “All provisioned web servers in the production environment, datacenter ABC must respond to queries within 200ms” $ puppet module install datadog-datadog_agent class { ‘datadog_agent’: api_key => …, tags => [$environment], fact_to_tags => [“datacenter”] } include datadog_agent::integrations::nginx
- 32. In Datadog (metrics) • Monitoring using a fact-based query • Puppet facts directly reused max(nginx.request.latency{production,datacenter:ABC}) < 200
- 33. What to take away
- 34. Fact-based monitoring 1. Hosts are not at the center of the monitoring universe 2. Expressive monitoring uses queries 3. Monitoring queries should use Puppet facts
- 35. Thank you!