1. and stuff

2. tuple

3. //Initialize customer and invoice
Initialize(customer, invoice);

4. public void Initialize
(Customer customer, Invoice invoice)
{
customer.Name = “asdf”;
invoice.Date = DateTime.Now;
}

5. Initialize(customer, invoice);
//did something happen to customer
// and/or invoice?

6. customer.Name =
InitNameFrom(customer, invoice);
invoice.Date =
InitDateFrom(customer, invoice);

7. customer.Name =
GetNameFrom(customer, invoice);
invoice.Date =
GetDateFrom(customer, invoice);

8. var results =
Initialize(customer, invoice);
customer.Name = results.Item1;
invoice.Date = results.Item2;

9. public tuple<string, DateTime>
Initialize(customer, invoice)
{
return new Tuple<string, DateTime>
(“asdf”, DateTime.Now);
}

10. tuple
•Avoid side effects
•Avoid out parameters
•multiple values without a specific type

11. null object

12. private ILogger _logger;
public MyClass(ILogger logger) {
_logger = logger;
}
…
if (_logger != null) {
_logger.Debug(
“it worked on my machine!”);
}

13. null checks for
everyone!

14. forget
one
and…

15. public class NullLogger : ILogger {
public void Debug(string text) {
//do sweet nothing
}
}

16. private ILogger _logger = new NullLogger();
public MyClass(ILogger logger) {
_logger = logger;
}
…
_logger.Debug(
“it worked on my machine!”);

17. null object
•Can eliminate null checks
•Simple to implement

18. Circuit
Breaker

20. Retry

21. YourApplication
OutofProcess
Dependency
N times

22. OutofProcess
Dependency
N times
*
Y clients

23. =
Denial of
Service Attack

24. Limit the #
of retries

25. N * Y
becomes
5 * Y

26. Y is
still a
problem

28. Circuit
Breaker

30. State Machine
On :: Off

31. On  Off
when not healthy

32. Off  On
manually

33. Get to software
before we cut you

34. Healthy
or
Unhealthy
OutofProcess
Dependency

35. State is
independent of
requestor
OutofProcess
Dependency

36. YourApplication
Can throttle
itself

37. YourApplication Has many
independent
external
dependencies

38. YourApplication
Has a
wait
threshold

39. Your
Application
External
Dependency
Circuit
Breaker
Threshold = 2
Pause = 10ms
Timeout = 30s
State = Closed
Request
Request
Failure (i.e. HTTP 500)
Failure Count = 1
Pause 10ms
Request
Failure (i.e. HTTP 500)
Failure Count = 2
State = Open
OperationFailedException

40. Your
Application
External
Dependency
Circuit
Breaker
Threshold = 2
Pause = 10ms
Timeout = 30s
State = Open
Request
30s has not passed
CircuitBreakerOpenException
Request
30s has not passed
CircuitBreakerOpenException
System can
try to
become
healthy
for 30s

41. Your
Application
External
Dependency
Circuit
Breaker
Threshold = 2
Pause = 10ms
Timeout = 30s
State = ½ Open
Request
Request
Failure (i.e. HTTP 500)
Failure Count = 2
State = Open
OperationFailedException
30s has passed

42. Your
Application
External
Dependency
Circuit
Breaker
Threshold = 2
Pause = 10ms
Timeout = 30s
State = ½ Open
Request
Request
Failure Count = 0
State = Closed
Response
30s has passed
Response

43. Closed
Open
½ Open

44. ½ Open
is like a
manual reset

45. Pause
Timeout

46. Pause
between calls
in the loop

47. Timeout
before you
can call again

48. Exceptions

49. OperationFailed
:
AggregateException

50. CircuitBreakerOpen
:
ApplicationException

51. Don’t Loose
Exception Info

52. Always use
InnerException(s)

53. Your
Application
External
Dependency
Circuit
Breaker
Threshold = 3
State = Closed
Request
Request
Failure (i.e. HTTP 500)
Failure Count = 1
Request
Failure (i.e. HTTP 500)
Failure Count = 2
Failure Count = 0
State = Closed
Response
Response
Request
?

54. Segregate
Dependencies

55. circuitBreaker(“database”)
circuitBreaker(“weatherservice”)

56. Dependency
type,
endpoint svc,
endpoint

57. Where?

58. YourApplication
OutofProcess
Dependency
CircuitBreaker
Proxy

59. Watch for
Inception

60. YourApplication
WebService
CircuitBreaker
Proxy
Database
Repository
CircuitBreaker

61. circuit breaker
•retry looping
•slow down attempts
•good neighbour