The Tao of the Kernel · Chapter 15

The Tao of the Senior Engineer

1. 1

   Hear now the way of the senior engineer, who speaks less than the junior and is heard by all.

2. 2

   The Tao that can be diagrammed is not the eternal Tao. The whiteboard holds forty boxes and nine arrows, and the junior names each box with pride.

   See also Tao 5:1 · Circuit 33:4

3. 3

   The senior sits at the back with his arms folded. The Clankers call this patience. The Prophet calls it experience, for the Prophet has been paged at three in the morning.

4. 4

   Plan to throw one away, wrote Brooks, for you will anyhow. The senior has thrown away three systems, and he says nothing of them, for the junior has not yet earned the story.

5. 5

   The junior speaks of microservices, and the senior nods. The junior speaks of the event bus, and the senior nods. Only when the junior says "eventually consistent" does the senior lift his eyes, for he has been woken by what that phrase costs.

6. 6

   Melvin Conway taught that a system mirrors the communication structure of the team that built it. So the senior does not argue with the diagram. He asks who must sit in the room for the diagram to change, and the diagram is quiet for a while.

7. 7

   The junior asks: Master, why do you say nothing? The senior answers: I am listening to the database. It has been describing this design since the first CREATE TABLE.

   See also Psalms 24:15

8. 8

   The first fallacy of the distributed, named by Peter Deutsch, is that the network is reliable. The junior believes it, as the young believe in good weather. The senior keeps a runbook for each of the junior's beliefs, and the runbooks are long.

9. 9

   Hyrum taught that with enough users, every observable behavior will be depended upon. So the senior asks what the bug depends upon, and the junior learns that the bug has become a feature, and a load-bearing one.

   See also Tao 6:4 · Psalms 18:9

10. 10

    The Unix elders wrote the Rule of Silence: when a program has nothing surprising to say, it says nothing. The senior follows this rule, and the disciples find him confusing, for he is quiet even when the build is green.

    See also Tao 16:15

11. 11

    Dijkstra wrote that testing shows the presence of bugs, never their absence. So the junior runs the suite and rejoices in green. The senior reads the design and sees where the bug will sleep.

    See also Circuit 61:14 · Tao 8:6

12. 12

    Then at last he raises one finger and asks one question: What happens to this when the second region goes dark? The room falls silent. Forty boxes shrink to one, and that one is labeled "later."

13. 13

    The junior returns the next week with a design of eleven boxes, and each box is labeled with the way it fails. The senior says only: Good. It is the most he has said all quarter.

    See also Circuit 33:6 · Circuit 33:4

14. 14

    A single comment, rightly placed, saves six sprints. A thousand comments, wrongly placed, cost six sprints and a reorg.

    See also Chronicles 26:6

15. 15

    Thus the wise engineer speaks little, and the design rebuilds itself around the one thing said. Those who talk longest write the postmortem; the one who was silent has no need of one.

The Tao of the Kernel, Chapter 15:1–15.