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![“Cynicism is merely the art of seeing things as
they are instead of as they ought to be” [1.]
A cynical software
No intimacy
Internal barriers
Lack of trust
Bad things happen
Resilience to impulse and stress
Sunday 17 November 13
Explain the main attributes of cynical software](https://image.slidesharecdn.com/cynycal-software-131117045329-phpapp01/85/Cynycal-software-9-320.jpg)
![Focus on failures
TESTING
Simulate bad things
Chaos monkey [2]
Sunday 17 November 13
-
we do test but on "sligthly" different topology. It makes hard to reveal some kind of bugs
we mostly test optimistic cases
HTTP mock server (bad responses, slow responses, protocol violation...)
Longevity tests](https://image.slidesharecdn.com/cynycal-software-131117045329-phpapp01/85/Cynycal-software-15-320.jpg)
![Adaptable design
[3]
ARCHITECTURE
Conway’s law
Sunday 17 November 13
ROC
[4]
[5]
- early decisions are hard to revert later (costs)
- Big Up Front Design doesn’t work prefer Adaptable design - Framework, Platform
- restartability (No restart the world), diagnostics (health checks), recovery mechanism circuit breaker, isolation/redundancy ()](https://image.slidesharecdn.com/cynycal-software-131117045329-phpapp01/85/Cynycal-software-16-320.jpg)
Cynycal software
- 1. CYNICAL SOFTWARE Tips forwriting software that do not wake you up at 2am dagi@goodata.com https://twitter.com/_dagi Sunday 17 November 13
- 2. HOW TO BECOMECYNICAL • Eat your own dog food • Strong • Pager feedback duty (Engineer on duty) • DevOps Sunday 17 November 13 No throw over the wall syndrom
- 3.
- 4. http://pragprog.com/book/mnee/release-it Sunday 17 November13 Read an excelent book about Cynical software - stability patterns&anti-patterns - architecture, testing and design
- 5. INTEGRATION POINTS &FAILURE MODES Integration points Backend service Frontend service LB DB LB Frontend service Backend service DB DB Backend service Failure modes LB 3rd party service Sunday 17 November 13 - shift toward SOA, interconnected services, remote communication, 3rd party services how a crack may appear - failure mode integration point cracks are tightly coupled to integration points the way cracks appear and propagated across multiple layers and services Integration points may accelerate (chained reaction) or stop cracks Failure in one component increase the probability of failure in another component service Slow responses, endpoint unreachability High levels of complexity provide more directions for the cracks to propagate in.
- 6.
- 7. User user; Projectsprojects; 1 try { projects = dao.getProjects(user, OFFSET, LIMIT).await(250, MS); } catch (FutureTimeoutException e) { throw new AccountInfoUnavailableException(); } 2 for (Project project : projects) { Set<String> userPermissions = dao.getPermissions(project, user); if (userPermissions.contains(CAN_INIT_DATA)) { Hanging SQL return new AccountInfo(Boolean.TRUE); connection } (90 s timeout) } Client Frontend server Hanging HTTP worker thread (120s) Backend server Hanging HTTP connection (60s C3 timeout) Datacenter AWS Frontend server Datacenter Rackspace Sunday 17 November 13 Backend server C3 MySQL MySQL MySQL MySQL MySQL MySQL
- 8.
- 9. “Cynicism is merelythe art of seeing things as they are instead of as they ought to be” [1.] A cynical software No intimacy Internal barriers Lack of trust Bad things happen Resilience to impulse and stress Sunday 17 November 13 Explain the main attributes of cynical software
- 10. Steady state Circuit breaker Bulkheads Testharness Handshaking Fail fast Timeouts Decoupling middleware STABILITY PATTERNS & ANTIPATTERNS Slow responses SLA inversion Attacks of self denial Unbalanced capacities Unbounded result set Blocked threads Scaling effects Sunday 17 November 13 - the antipatterns will create, accelerate or multiply cracks in the system - the patterns provide architecture and design guidance to reduce, eliminate, or mitigate the effects of cracks in the system
- 11. CIRCUIT BREAKER Frontend service Half-Open Timeout Closed Open Open Failure counter:2 1 0 Sunday 17 November 13 - mediator (decoupling, isolation), integration point wrapper - fail fast, recovery Failure Backend service
- 12. BULKHEADS Hiccup HTTP client Bulkheads Frontend service Connections pool Backend serviceA Backend service B Backend service C Sunday 17 November 13 fat tails - sizing/capacity isolation, degrading functionality
- 13. Latency and FaultTolerance for Distributed Systems https://github.com/Netflix/Hystrix Sunday 17 November 13 - do not reinvent the wheel - OSS, Java - most of the patterns are implemented there (circuit breaker, bulkheads, fail fast)
- 14. public class CommandHelloWorldextends HystrixCommand<String> { private final String name; public CommandHelloWorld(String name) { super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup")); this.name = name; } @Override protected String run() { // a real example would do work like a network call here return "Hello " + name + "!"; } } String s = new CommandHelloWorld("World").execute(); Future<String> fs = new CommandHelloWorld("World").queue(); Sunday 17 November 13 HystrixCommand = circuit breaker + bulkheads Synchronous/Asynchronous usage Async usage Future -> timeout
- 15. Focus on failures TESTING Simulatebad things Chaos monkey [2] Sunday 17 November 13 - we do test but on "sligthly" different topology. It makes hard to reveal some kind of bugs we mostly test optimistic cases HTTP mock server (bad responses, slow responses, protocol violation...) Longevity tests
- 16. Adaptable design [3] ARCHITECTURE Conway’s law Sunday17 November 13 ROC [4] [5] - early decisions are hard to revert later (costs) - Big Up Front Design doesn’t work prefer Adaptable design - Framework, Platform - restartability (No restart the world), diagnostics (health checks), recovery mechanism circuit breaker, isolation/redundancy ()
- 17.