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Web Workers · 27 Disposal and Restart
Series contents · Technology map
Stage: Validating Throughput and Responsiveness · Editable example · Storage ID: web-workers-step-27
Goals and learning outcomes
- Learning outcome: explain the role of Lifetime management. Input cases: 5 cycles of running, disposing, and restarting.
- Deliverable: completed IDs by generation and remaining resource counts. Explain the rationale for handling Repeated execution, linking it to the code.
Prerequisites
Prepare the experiment results for Peak usage and Limits from Unit 26, “Memory and Pool Limits”.
Key concepts and explanations
Lifetime management
Clean up Workers, timers, and ports when the page feature ends. Remove requests that have already ended from pending as well.
Repeated execution
A new generation ID distinguishes it from earlier responses. Calling dispose twice must be safe.
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-27.js in a separate practice project, call terminate, clearTimeout, and port.close in dispose, then restart. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: 5 cycles of running, disposing, and restarting. Baseline: After completion. Run under the baseline conditions, then record observations and errors in notes/day-27.md.
- Variable: Disposal timing; changed value: During computation. Run again through the same input path. Deliverable to save: completed IDs by generation and remaining resource counts. Hypothesis to check: No interrupted task remains, and new tasks complete normally. Compare it with the actual results, and record whether they agree and why they differ.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| Disposal timing | After completion | During computation | No interrupted task remains, and new tasks complete normally. |
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: completed IDs by generation and remaining resource counts. 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: Lifetime management and Repeated execution. For unexpected items, at least 1 cause or reason they remain unresolved is recorded.
Self-check
- Which processing stage does Lifetime management affect in this exercise? Input cases: 5 cycles of running, disposing, and restarting.
- Variable: Disposal timing. Hypothesis to check: No interrupted task remains, and new tasks complete normally. Did the actual results agree with the hypothesis? Explain the evidence in terms of Repeated execution.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
An interactive Disposal and Restart 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: Memory and Pool Limits · Next: Task Queues and Measurement