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Web Workers · 28 Task Queues and Measurement
Series contents · Technology map
Stage: Validating Throughput and Responsiveness · Editable example · Storage ID: web-workers-03
Goals and learning outcomes
- Learning outcome: explain the role of Total cost. Input cases: the same task on the main thread, 1 Worker, and 2 Workers.
- Deliverable: a report on correctness, end-to-end latency, input delay, and peak buffers. Explain the rationale for handling Decision-making, linking it to the code.
Prerequisites
Prepare the experiment results for Lifetime management and Repeated execution from Unit 27, “Disposal and Restart”.
Key concepts and explanations
Total cost
More Workers are not always faster. Evaluate transfer, waiting, and memory costs together.
Decision-making
Input responsiveness and total throughput may differ. Base adoption decisions on correctness and measured evidence.
Practice setup
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-28.js in a separate practice project, use the existing web-workers-03 as a reference, integrate a bounded queue, cancellation, and recovery, and prepare a report. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: the same task on the main thread, 1 Worker, and 2 Workers. Baseline: 1 Worker. Run under the baseline conditions, then record observations and errors in notes/day-28.md.
- Variable: Worker count; changed value: 2 Workers. Run again through the same input path. Deliverable to save: a report on correctness, end-to-end latency, input delay, and peak buffers. Hypothesis to check: The tradeoff between throughput and UI responsiveness becomes apparent. Compare it with the actual results, and record whether they agree and why they differ.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| Worker count | 1 Worker | 2 Workers | The tradeoff between throughput and UI responsiveness becomes apparent. |
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: a report on correctness, end-to-end latency, input delay, and peak buffers. 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: Total cost and Decision-making. For unexpected items, at least 1 cause or reason they remain unresolved is recorded.
Self-check
- Which processing stage does Total cost affect in this exercise? Input cases: the same task on the main thread, 1 Worker, and 2 Workers.
- Variable: Worker count. Hypothesis to check: The tradeoff between throughput and UI responsiveness becomes apparent. Did the actual results agree with the hypothesis? Explain the evidence in terms of Decision-making.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
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