在公司内介绍下 netflix hystrix

1. Hystrix 介绍
晓丹 2015/05/29

2. What ?
• https://github.com/Netflix/Hystrix
• Hystrix is a latency and fault tolerance library
designed to isolate points of access to remote
systems, services and 3rd party libraries, stop
cascading failure and enable resilience in
complex distributed systems where failure is
inevitable.

4. Why ?
• 故障是常态
• 远程服务和第三⽅方类库不可靠
• 故障蔓延，恢复延⻓长

6. How ?
• Command
• Thread Pool/Semaphore
• Fallback
• Timeout
• Circuit Breaker
• ……

7. Flow
https://raw.githubusercontent.com/wiki/Netflix/Hystrix/images/hystrix-command-flow-
chart.png

8. Basic
• Hystrix-clj
• (defcommand hello [name] (str “hello,” name))
• defcommand vs. defn

9. Basic
• Synchronous: (hello “dennis”) => hello,dennis
• Asynchronous: (queue #’hello “dennis”)
• RxJava: (observe #’hello “dennis”) =>
rx.Observable

10. Configuration
(defcommand hello
{:hystrix/group-key “CloudCode”
:hystrix/command-key “beforeAction”
:hystrix/thread-pool-key “CloudCode”}
[name]
(str “hello,” name))

11. Command Group
• Group together commands such as for
reporting, alerting, dashboards, or team/library
ownership.
• By default Hystrix group key to define the
command thread-pool unless a separate one is
defined.

12. execution.isolation.strategy
• Thread vs. Semaphore
• coreSize/maxQueueSize vs.
maxConcurrentRequests

13. Fallback
(defcommand hello
{:hystrix/fallback-fn (fn [name] (str “hello from fallback,” name))}
[name]
(throw (ex-info “test” {})

14. Fallback:
Primary + Secondary

15. Request Cache

16. Request Cache
(defcommand hello
{:hystrix/cache-fn (fn [name] name)}
[name]
(println name)
(str “hello,” name))

17. Request Collapsing

18. Request Collapsing
(defcollapser search
"Collapsing single-term search command"
(collapse [arg-lists]
; Create a multi-search command, passing individual terms as a seq of args
(instantiate multi-search (map first arg-lists)))
(map [arg-lists batch-result]
; Map from input args to results. Here we assume order is preserve by
; multi-search so we can return the result list directly
batch-result))
(search “Something1”)
(search “Something2")

19. Circuit Breaker
• Tripping a circuit-breaker to stop all requests to
a particular service for a period of time, either
manually or automatically if the error percentage
for the service passes a threshold.

20. Circuit Breaker

21. Configuration
• Global default from code
• Dynamic global default property
• Instance default from code
• Dynamic instance property
• https://github.com/Netflix/archaius

22. Dashboard
• https://github.com/Netflix/Hystrix/wiki/Metrics-and-Monitoring
• https://github.com/Netflix/Hystrix/wiki/Dashboard

23. Patterns
• Fail Fast
• Fail Silent
• Fallback
• static
• stubbed
• cache vs. network
• Primary + secondary
• https://github.com/Netflix/Hystrix/wiki/How-To-Use#Common-Patterns

24. The End