Your Durable Function runs many times

Understand it one step at a time

The short runs these in order in about 22 seconds. Here they are written out — pick any step to jump the short straight to it.

1. 1

   It did not run once

   Your orchestrator function executes again and again. You only ever see the final result.

   Orchestrator idle

2. 2

   It looks like normal code

   Three awaits, top to bottom. Nothing here hints that it gets re-executed.

   Loading orchestrator

3. 3

   It stops at the first await

   The runtime schedules the activity, then the function exits completely. No thread waits around.

   Scheduling activity

4. 4

   The result lands in history

   When the activity finishes, its output is appended to an event history in storage.

   Writing event history

5. 5

   Then it runs again

   From line one. This time the first await returns instantly from history instead of calling anything.

   Replaying from history

6. 6

   One step deeper each time

   Every completed activity extends the history, so each replay gets further before it stops.

   Replaying from history

7. 7

   This is why DateTime breaks

   Anything non-deterministic returns a new value on every replay, so your code stops matching history.

   Replay mismatch

8. 8

   Keep the replay invisible

   Use the context APIs for time and GUIDs, and the whole re-execution stays hidden from you.

   Orchestration complete