The document discusses the challenges of scaling deep systems in software architecture, focusing on observability and controllability as critical elements for managing complex, multi-layered services. It highlights the significance of effective service level objectives (SLOs) and the role of tracing in reducing cognitive load to improve system management. Furthermore, it emphasizes that deep systems require a different approach to observability, moving beyond traditional methods like metrics and logs by integrating traces for better context and understanding.

1. Ben Sigelman (@el_bhs, bhs@lightstep.com)
Co-founder & CEO: LightStep
Co-creator: OpenTracing, OpenTelemetry, Google Dapper, Google Monarch
Architectures that Scale Deep:
Regaining Control in Deep Systems
QCon SF, November 2019

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properties-deep-systems/

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4. Part I
Scaling, and Deep Systems

5. What is scale, anyway?

6. Scaling wide

7. Scaling wide

8. Scaling wide

9. Scaling wide

10. Scaling wide

11. Scaling deep

12. Scaling deep

13. Scaling deep

14. Scaling deep

15. Scaling deep

16. How does this look
for software?

17. Software: Scaling wide

18. Software: Scaling deep

19. How do real-world
systems look?

20. Microservices at scale aren’t
just wide systems, they’re
deep systems

21. Deep Systems
Architectures with ≥ 4 layers of
independently operated services
(including external/cloud dependencies)
Deep Systems
Architectures with ≥ 4 layers of
independently operated services
(including external/cloud dependencies)

22. What do deep systems sound like?

23. “Don’t deploy on Fridays”
What do deep systems sound like?

24. “Where’s Chris?! I’m dealing with
a P0 and they’re the only one
who knows how to debug this.”
What do deep systems sound like?

25. “It can’t be our fault, our
dashboard says we’re healthy”
What do deep systems sound like?

26. “Kafka is on fire”
What do deep systems sound like?

27. “I need 100% availability
from your team.
One hundred percent.”
What do deep systems sound like?

28. “I didn’t know I depended on
that region”
What do deep systems sound like?

29. “That was on a dashboard but I
can’t find it”
What do deep systems sound like?

30. Lots of challenges:
- People-management
- Security
- Multi-tenancy
- “Big-customer” success
- Performance
- Observability
What do deep systems sound like?

31. Part II
Control Theory: TL;DR Edition

32. Why do we care so much
about observability, anyway?

34. A System
Inputs Outputs
… and its state vector,

35. Inputs
A System
Outputs
… and its state vector,
Observability
How well can you infer
internal state using only
the outputs?

36. Outputs
A System
Inputs
… and its state vector,
Controllability
How well can you
control internal state
using only the inputs?

37. Controllability
is the dual of
Observability

38. Controllability
is the dual of
Observability

39. Part III
What Deep Systems
Mean for Observability

40. # of services
developersperservice
Architectural
evolution
Deep
Systems
Pure Monoliths

41. Stress (n): responsibility without controlStress
what you can control
what you are
responsible for

43. Observability:
Shrink This Gap

44. Mental models
A System

45. Managing Deep Systems
Services must have SLOs
(“Service Level Objectives”: latency, errors, etc)
For effective service management, only
three things matter:
0. Releasing service functionality
1. Gradually improving SLOs
2. Rapidly restoring SLOs
In a deep system, we must control the
entire “triangle” to maintain our SLOs

46. Controllability == ObservabilityControllability == Observability
There’s that word again…

47. Observability: “The Conventional Wisdom”
Observing microservices is hard
Google and Facebook solved this (right???)
They used Metrics, Logging, and Distributed Tracing…
… So we should, too.

48. 3 Pillars, 3 Experiences
Metrics
Logs
Traces

50. Three Pillars?Three Pillars? Two giant pipes…
Logs
Metrics
Without Traces:
Cognitive Load ≈ O(depth2
)

51. Three Pillars?Three Pillars? Two giant pipes…
Logs
Metrics

53. Two giant pipes…
Logs
Metrics
Without Traces:
Cognitive Load ≈ O(depth2
)

55. Traces

56. Traces provide Context

57. Traces provide Context
And context rules out
invalid hypotheses

58. Two giant pipes and a filter
Logs
Metrics
Context
(from traces)

59. Context
(from traces)
Context reduces cognitive load
With Traces:
Cognitive Load ≈ O(depth)
Relevant Metrics
Relevant Logs

60. Observability:
Shrink This Gap

62. Let’s Review

63. Microservices don’t just scale wide,
they scale deep
Recognize deep systems

64. Stress (n): responsibility without controlStress
what you can control
what you are
responsible for

65. “Controllability” (of SLOs)
depends on observability

66. … and traces are not sprinkles
“The Three Pillars of Observability”
is a lousy metaphor

67. Tracing can reduce
cognitive load from
O(depth2
) to O(depth)

68. Tracing is the backbone of
simple observability
in deep systems

69. Thank You
Feedback always
welcome:
twitter → @el_bhs
the emails → bhs@lightstep.com
Play with LightStep,
for free, anytime:
(no email address required!)
lightstep.com/play

70. Watch the video with slide
synchronization on InfoQ.com!
https://www.infoq.com/presentations/
properties-deep-systems/