Part 6: Durable Execution with Temporal | Garage Education

Part 6: Durable Execution with Temporal

Sat, 10 Oct 2026 00:00:00 +0000

Every watcher run is a Temporal workflow. Temporal stores each step, the approval wait, and the result. A worker crash resumes the run where it stopped.

Figure 6.0. The run lives in Temporal, not in the worker. Chapter 23 turns this into an exercise.

Chapter 23: Run state and messages

Sat, 10 Oct 2026 00:00:00 +0000

Temporal workflow history holds the run state. It holds the step count, the state, the approval, and the result. Spring AI Session holds the messages and tool calls. Use the workflow id as the session id. Do not store run state in a separate table. Two stores for one run drift apart.

Figure 23.1. Each fact about a run has exactly one home. A third store, struck out here, would have to agree with the other two and eventually would not.

Exercise. Start a run. Kill the worker after step 2. Restart it. Confirm the run completes without repeating step 1.

Figure 23.2. What you should see in the exercise. Recorded results are replayed from history, not run again.

Chapter 24: Temporal basics for the watcher

Sat, 10 Oct 2026 00:00:00 +0000

Concept	Use in the watcher
Workflow	One watcher run
Activity	One model call, one tool call, one alert post
Signal	Human approval
Timer	Approval deadline
Retry policy	Retry a failed model or tool call
Query	Read the current state

Determinism rule. Workflow code must give the same result on replay. Model calls, tool calls, database writes, and REST calls go in activities. Use Workflow.await, Workflow.sleep, and Workflow.currentTimeMillis() in the workflow. Do not use Thread.sleep or Instant.now() there.

Figure 24.1. The determinism rule as two questions. Thread.sleep and Instant.now() never appear in workflow code.

@WorkflowInterface
public interface WatcherWorkflow {
 @WorkflowMethod RunResult run(WatchRequest request);
 @SignalMethod void decideApproval(boolean approved);
 @QueryMethod String state();
}

Figure 24.2. Every concept in the table, in one run. The figure leaves out how the person's approval reaches the signal; in the exercise below, a REST call sends it.

Verify: Confirm the annotation packages and the starter configuration keys for SDK 1.35.0. Temporal’s Spring Boot starter starts the worker automatically when the app starts.

Exercise. Start a run through a REST endpoint. Read its state with a query. Approve a critical run. Confirm one alert posts.