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Web Workers · 13 Termination and Recreation
Series contents · Technology map
Stage: Ownership and Cancellation · Editable example · Storage ID: web-workers-step-13
Goals and learning outcomes
- Learning outcome: explain the role of Terminate. Input cases: stopping a long task and then submitting a new request.
- Deliverable: pending entries before and after termination, and the new result. Explain the rationale for handling Recovery, linking it to the code.
Prerequisites
Prepare the experiment results for Event loop and Cancellation points from Unit 12, “Cooperative Cancellation”.
Key concepts and explanations
Terminate
terminate ends Worker execution immediately. A completion message may never arrive.
Recovery
The main side must explicitly fail pending requests. Start the next task with a new Worker.
Practice setup
First check the execution scope guidance on the example screen. The following describes the environment needed to extend the assignment in a separate project. The existing web-workers-01·02·03 are starting examples. Implement the new assignments in main.js and worker.js in a separate local HTTP project. Preserve CSP and iframe isolation. For SharedArrayBuffer, check COOP and COEP requirements on an external server you control; use the transfer path if they are not met. Measure performance yourself.
The linked example is a starting point. It does not implement every task below. Complete work beyond its supported scope in a separate project.
Practice tasks
- In src/day-13.js in a separate practice project, implement a stop-button path that calls terminate, cleans up pending requests, and recreates the Worker. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: stopping a long task and then submitting a new request. Baseline: Ignore responses. Run under the baseline conditions, then record observations and errors in notes/day-13.md.
- Variable: Stopping method; changed value: terminate. Run again through the same input path. Deliverable to save: pending entries before and after termination, and the new result. Hypothesis to check: The old computation ends and a new Worker handles the next request. Compare it with the actual results, and record whether they agree and why they differ.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| Stopping method | Ignore responses | terminate | The old computation ends and a new Worker handles the next request. |
Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.
Completion criteria
- Required deliverable: pending entries before and after termination, and the new result. Results are available for both the baseline and changed conditions, allowing comparison of 2 conditions; input values and the execution environment are recorded together.
- The explanation of differences between the two conditions connects both concepts: Terminate and Recovery. For unexpected items, at least 1 cause or reason they remain unresolved is recorded.
Self-check
- Which processing stage does Terminate affect in this exercise? Input cases: stopping a long task and then submitting a new request.
- Variable: Stopping method. Hypothesis to check: The old computation ends and a new Worker handles the next request. Did the actual results agree with the hypothesis? Explain the evidence in terms of Recovery.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
An interactive Termination and Recreation experiment with cleanup of the resources it uses.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.
Next learning
Previous: Cooperative Cancellation · Next: Transfer and Cancellation