Account for memory and disk usage — Build the smallest useful slice

PART I

Warm-up

Reconnect with a useful idea before starting account for memory and disk usage. In one or two sentences, describe the input, output or host boundary from the previous exercise that this lesson builds on. If you are arriving directly, skim the worked example first; there is no locked prerequisite.

A rough note is enough. You can revise it after the example.

PART II

Instruction & guided example

Build a two-resource admission check

A budget dashboard must state what is counted, when it was measured and which limit applies. Memory and disk are different resources: free disk cannot satisfy an exhausted memory allocation. Separate live usage, reservations and estimated future work so the display does not promise capacity that has already been committed.

Exercise host contract: memory budget is 64 MiB and disk budget 200 MiB. Preview buffers use 24 MiB memory; an active transform reserves 16 MiB memory; report files use 90 MiB disk; a pending export reserves 40 MiB disk. Counts include the stated workload only; runtime overhead, sampling accuracy and atomic reservations require host documentation.

Supplied case: New thumbnail job needs 20 MiB memory and 80 MiB disk in addition to committed 40 memory and 130 disk.

Worked reasoning: Memory would become 60, within 64; disk would become 210, above 200. The job fails the combined admission rule because every required resource must fit. Keep the two reasons visible rather than averaging percentages.

Contrast and diagnosis: Adding free memory to free disk produces a meaningless total for a job that needs distinct resource types.

Worked reasoning and supplied artifact

// Disposable exercise fixture / host-contract notes; not executable API syntax.
// Supplied input: New thumbnail job needs 20 MiB memory and 80 MiB disk in addition to committed 40 memory and 130 disk.
// Worked prediction: Memory would become 60, within 64; disk would become 210, above 200. The job fails the combined admission rule because every required resource must fit. Keep the two reasons visible rather than averaging percentages.
// Rejected alternative: Adding free memory to free disk produces a meaningless total for a job that needs distinct resource types.

Illustrative example from the proposed WillowScript design. The language and WUIX/WMATH/WDB/WAUDIO/WTMP services are not implemented in the supplied source. This site has no interpreter, VM or native host and does not execute or certify the snippet.

Try the guided change

Reconstruct the supplied worked case first: list its inputs, intermediate decisions and final artifact. Compare each row with the explanation and identify exactly where the rejected alternative fails. Then use the changed inputs in Part IV for independent work.

• Write the supplied inputs and initial state before following the example.
• Reconstruct each intermediate calculation or host decision, then compare with the worked artifact.
• Explain why the contrasting alternative fails before attempting the changed inputs in Part IV.

PART III

Take a breather

Step back after the guided example. Look away from the screen, stretch, or reread your prediction. This is an optional learning pause, not a timer or an assessment gate.

When you return, try to name the lesson’s key idea without copying its wording. If that feels difficult, return to Part II and trace one line rather than restarting the entire lesson.

PART IV

Independent practice

Project context: Resource budget dashboard. Build a small, understandable change around account for memory and disk usage.

Evaluate jobs needing memory/disk pairs(10, 50), (30, 20), (20, 80). State the failing resource for each refusal.

What to produce

Evaluate jobs needing memory/disk pairs(10, 50), (30, 20), (20, 80). State the failing resource for each refusal. Include input → intermediate decision/state → predicted outcome, with any required host rule stated explicitly.

• State the intended behavior in a sentence before editing.
• Use only source-backed syntax and the host services whose contract you have been given.
• Record a normal case and a boundary or unavailable-resource case.
• Label hand predictions separately from anything actually measured in a supplied toolchain.

Syntax colors are a reading aid, not a compiler. The line you are editing stays uncolored until you move to a different line; capitalization is never changed. Drafts stay on this browser and code is not executed.

import tmp;
const cache = tmp.create({
    name: "report-cache",
    storage: "ssd",
    maxSize: "2GB",
    lifetime: { duration: "30m", refreshOnAccess: true },
    cleanup: { automatic: true, onCrashRecovery: true }
});

PART V

Self-check

Use this check to notice what to revisit. It does not award a private course grade, block another page or claim to verify compiled code. Every answer has a learning explanation.

You may keep exploring even if you are unsure. Use the hint, compare the trace, and revise your explanation.

PART VI

Recap & small task

Bring the idea back to the mod feature you are building. A useful recap connects the mechanism to a decision you can make in your own code.

• Build a two-resource admission check
• Explain the decision for the supplied case, then independently work the changed fixture.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

In one or two sentences, name the decisive rule in “Build a two-resource admission check” and predict the outcome of one changed input from your independent fixture. State which host behavior still needs real verification.

This marks your personal practice record only. It is not a certification or an official workspace assessment.