Considering whether adding logging to an application changes it too much.

1. Logging -
Considered Harmful?
David Dancy
Programmation Pty Limited
@4dexpert

3. Race Conditions

4. Racing C#

5. Racing C#
initial = 100

6. Racing C#
initial = 100
-0
100

7. Racing C#
initial = 100
+1
101
-0
100

8. Racing C#
initial = 100
+1
101
-2
99
-0
100

9. Racing C#
initial = 100
+1
101
-2
99
+3
102
-0
100

10. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
-0
100

11. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-0
100

12. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
-0
100

13. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
+7
104
-0
100

14. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
+7
104
-8
96
-0
100

15. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
+7
104
-8
96
+9
105
-0
100

16. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
+7
104
-8
96
+9
105
-10
95
-0
100

17. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
+7
104
-8
96
+9
105
-10
95
+11
106
-0
100

18. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
+7
104
-8
96
+9
105
-10
95
+11
106
-12
94
-0
100

19. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
+7
104
-8
96
+9
105
-10
95
+11
106
-12
94
+13
107
-0
100

20. Racing C#
initial = 100
+1
101
-2
99
+3
102
-4
98
+5
103
-6
97
+7
104
-8
96
+9
105
-10
95
+11
106
-12
94
+13
107
-14
93
-0
100

21. Racing C#
[44006:6972073][2015-08-10T22:14:23.5812750Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 0
[44006:6972073][2015-08-10T22:14:23.5812830Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 1
[44006:6972073][2015-08-10T22:14:23.5812890Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 2
[44006:6972073][2015-08-10T22:14:23.5812940Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 3
[44006:6972073][2015-08-10T22:14:23.5812990Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 4
[44006:6972073][2015-08-10T22:14:23.5813050Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 5
[44006:6972073][2015-08-10T22:14:23.5813110Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 6
[44006:6972073][2015-08-10T22:14:23.5813160Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 7
[44006:6972073][2015-08-10T22:14:23.5813200Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 8
[44006:6972073][2015-08-10T22:14:23.5813260Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 9
[44006:6972073][2015-08-10T22:14:23.5813310Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 10
[44006:6972073][2015-08-10T22:14:23.5813360Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 11
[44006:6972073][2015-08-10T22:14:23.5813400Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 12
[44006:6972073][2015-08-10T22:14:23.5813450Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 13
[44006:6972073][2015-08-10T22:14:23.5813500Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 14
[44006:6972073][2015-08-10T22:14:23.5813610Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L146]: ->
93

22. Racing C#
initial = 100

23. Racing C#
initial = 100
-0
100

24. Racing C#
initial = 100
-0
100
+1
101

25. Racing C#
initial = 100
-0
100
+1
101
+3
104

26. Racing C#
initial = 100
-2
102
-0
100
+1
101
+3
104

27. Racing C#
initial = 100
-2
102
-0
100
+1
101
+3
104
-4
98

28. Racing C#
initial = 100
-2
102
+5
103
-0
100
+1
101
+3
104
-4
98

29. Racing C#
initial = 100
-2
102
+5
103
-6
97
-0
100
+1
101
+3
104
-4
98

30. Racing C#
initial = 100
-2
102
+7
104
+5
103
-6
97
-0
100
+1
101
+3
104
-4
98

31. Racing C#
initial = 100
-2
102
+7
104
+5
103
-6
97
-0
100
+1
101
+3
104
+9
113
-4
98

32. Racing C#
initial = 100
-2
102
+7
104
+5
103
-6
97
-0
100
+1
101
-10
93
+3
104
+9
113
-4
98

33. Racing C#
initial = 100
-2
102
+7
104
+5
103
-6
97
-0
100
+11
104
+1
101
-10
93
+3
104
+9
113
-4
98

34. Racing C#
initial = 100
-2
102
+7
104
+5
103
-6
97
-0
100
+11
104
-8
96
+1
101
-10
93
+3
104
+9
113
-4
98

35. Racing C#
initial = 100
-2
102
+7
104
+5
103
-6
97
-0
100
+11
104
-8
96
+1
101
-10
93
+3
104
-12
84
+9
113
-4
98

36. Racing C#
initial = 100
-2
102
+7
104
+5
103
-6
97
-0
100
+11
104
-8
96
+1
101
-10
93
+3
104
+13
97
-12
84
+9
113
-4
98

37. Racing C#
initial = 100
-2
102
+7
104
+5
103
-6
97
-0
100
+11
104
-8
96
+1
101
-10
93
+3
104
+13
97
-12
84
+9
113
-14
83
-4
98

38. Racing C#
[44006:6972073][2015-08-10T22:14:23.5816070Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 0
[44006:6972073][2015-08-10T22:14:23.5816250Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 1
[44006:6972073][2015-08-10T22:14:23.5816310Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 3
[44006:6972073][2015-08-10T22:14:23.5816310Z][DBUG00009][ViewModels.RaceLoggingViewModel.Run L138]: 2
[44006:6972073][2015-08-10T22:14:23.5816360Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 4
[44006:6972073][2015-08-10T22:14:23.5816410Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 5
[44006:6972073][2015-08-10T22:14:23.5816460Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 6
[44006:6972073][2015-08-10T22:14:23.5816500Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 7
[44006:6972073][2015-08-10T22:14:23.5816550Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 9
[44006:6972073][2015-08-10T22:14:23.5816600Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 10
[44006:6972073][2015-08-10T22:14:23.5816640Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 11
[44006:6972073][2015-08-10T22:14:23.5816680Z][DBUG00009][ViewModels.RaceLoggingViewModel.Run L138]: 8
[44006:6972073][2015-08-10T22:14:23.5816690Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 12
[44006:6972073][2015-08-10T22:14:23.5816740Z][DBUG00010][ViewModels.RaceLoggingViewModel.Run L138]: 13
[44006:6972073][2015-08-10T22:14:23.5816910Z][DBUG00009][ViewModels.RaceLoggingViewModel.Run L138]: 14
[44006:6972073][2015-08-10T22:14:23.5817100Z][DBUG00009][ViewModels.RaceLoggingViewModel.Run L146]: ->
92

39. Racing C#

40. Racing C#

41. Racing C#
Fixed!

42. ????

43. Accidental Locks

44. Accidental Locks
I/O operations using [System.Console] are
synchronized, which means multiple threads
can read from, or write to, the streams.

45. Accidental Locks
I/O operations using [System.Console] are
synchronized, which means multiple threads
can read from, or write to, the streams.
https://github.com/dotnet/corefx/blob/master/src/System.Console/src/System/IO/
SyncTextWriter.cs

46. Introducing…

47. TPL Dataflow

48. TPL Dataflow
ActionBlock<T>
TransformBlock<T, U>
TransformManyBlock<T, U>

49. TPL Dataflow
ActionBlock<T>
TransformBlock<T, U>
TransformManyBlock<T, U>
BatchBlock<T>
JoinBlock<T, U, …>
BatchedJoinBlock<T, U, …>

50. TPL Dataflow
ActionBlock<T>
TransformBlock<T, U>
TransformManyBlock<T, U>
BufferBlock<T>
WriteOnceBlock<T>
BroadcastBlock<T>
BatchBlock<T>
JoinBlock<T, U, …>
BatchedJoinBlock<T, U, …>

51. Execution
TPL Dataflow
ActionBlock<T>
TransformBlock<T, U>
TransformManyBlock<T, U>
BufferBlock<T>
WriteOnceBlock<T>
BroadcastBlock<T>
BatchBlock<T>
JoinBlock<T, U, …>
BatchedJoinBlock<T, U, …>

52. Grouping
Execution
TPL Dataflow
ActionBlock<T>
TransformBlock<T, U>
TransformManyBlock<T, U>
BufferBlock<T>
WriteOnceBlock<T>
BroadcastBlock<T>
BatchBlock<T>
JoinBlock<T, U, …>
BatchedJoinBlock<T, U, …>

53. Buffer
Grouping
Execution
TPL Dataflow
ActionBlock<T>
TransformBlock<T, U>
TransformManyBlock<T, U>
BufferBlock<T>
WriteOnceBlock<T>
BroadcastBlock<T>
BatchBlock<T>
JoinBlock<T, U, …>
BatchedJoinBlock<T, U, …>

54. TPL Dataflow

55. TPL Dataflow

56. TPL Dataflow
BufferBlock<T>

57. TPL Dataflow
BufferBlock<T>

58. TPL Dataflow
BatchBlock<T>
BufferBlock<T>

59. TPL Dataflow
BatchBlock<T>
BufferBlock<T>

60. TPL Dataflow
BatchBlock<T>
BufferBlock<T>
TransformManyBlock<T, U>

61. TPL Dataflow
BatchBlock<T>
BufferBlock<T>
TransformManyBlock<T, U>

62. TPL Dataflow
BatchBlock<T>
BufferBlock<T>
TransformManyBlock<T, U>
JoinBlock<T, U, …>

63. TPL Dataflow
BatchBlock<T>
BufferBlock<T>
TransformManyBlock<T, U>
JoinBlock<T, U, …>

64. TPL Dataflow
BatchBlock<T>
BufferBlock<T>
TransformManyBlock<T, U>
JoinBlock<T, U, …>
ActionBlock<T>

65. Safe Logger

66. Safe Logger
• Create interface ILogger

67. Safe Logger
• Create interface ILogger
• Debug

68. Safe Logger
• Create interface ILogger
• Debug
• Info

69. Safe Logger
• Create interface ILogger
• Debug
• Info
• Include / Exclude

70. Safe Logger

71. Safe Logger
2015-07-29 18:00:12.565 SimpleLog.iOS
[57400:1766661]
[2015-07-29T08:00:12.5657180Z]
[DBUG00001]
[SimpleLog.StartPage.OnSizeAllocated L24]: Size: [568, 288]

72. Safe Logger

73. Safe Logger

74. Safe Logger
• Create LogData class implementing ILogData

75. Safe Logger
• Create LogData class implementing ILogData
• Use ActionBlock<ILogData>

76. Safe Logger
• Create LogData class implementing ILogData
• Use ActionBlock<ILogData>
• Profit!

77. Safe Logger

78. Safe Logger

79. Safe Logger
• Test harness for different
logging strategies
• Use Scale to increase time
spent working vs logging

80. Safe Logger
iOS Native Console
Blocking
√ Scale
Queue
√ √
Dataflow
√ √

81. Safe Logger
• Android (emulator) very
reluctant to race

82. Safe Logger
Android Native Console
Blocking ? ?
Queue ? ?
Dataflow ? ?

83. Safe Logger
• Hardware behaves differently
• Test on real hardware
• Beware memory limitations

84. DEMO

85. Safe Logging

86. Safe Logging
• There is no completely safe logging

87. Safe Logging
• There is no completely safe logging
• There's only less dangerous logging

88. Safe Logging
• There is no completely safe logging
• There's only less dangerous logging
• Measuring something changes the way it
behaves

89. Safe Logging
• There is no completely safe logging
• There's only less dangerous logging
• Measuring something changes the way it
behaves
• Change as little as possible

90. Safe Logging
• There is no completely safe logging
• There's only less dangerous logging
• Measuring something changes the way it
behaves
• Change as little as possible
• Especially threads

91. CAVEAT LOGITOR