mirror of
https://github.com/ChromeDevTools/chrome-devtools-mcp.git
synced 2026-09-14 19:45:30 +08:00
Jack Franklin
d05cbc0511
## Rationale DevTools' `TraceEngine.TraceModel.Model` permanently retains parsed traces in an internal recordings array (`#traces`). Calling `engine.resetProcessor()` between runs only resets the underlying processor and does not clear `#traces`. Because `engine` was previously instantiated as a module-scoped singleton, every performance trace recorded or parsed in a session remained permanently held in heap memory for the lifetime of the process. ## Changes - In `src/processors/PerformanceTrace.ts`, instantiate `DevTools.TraceEngine.TraceModel.Model.createWithAllHandlers()` per invocation of `parseRawTraceBuffer()`. - Remove the module-scoped `engine` singleton and the obsolete `engine.resetProcessor()` call. - Add a unit test in `tests/trace-processing/parse.test.ts` verifying that consecutive trace parses construct isolated `Model` instances and keep internal trace retention bounded at 1. - Add a profiling regression scenario in `scripts/profile/scenarios/performance_trace.ts` to guard against memory retention across consecutive traces during `npm run test:memory`.
82 lines
2.5 KiB
TypeScript
82 lines
2.5 KiB
TypeScript
/**
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* @license
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* Copyright 2025 Google LLC
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* SPDX-License-Identifier: Apache-2.0
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*/
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import assert from 'node:assert';
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import {afterEach, describe, it} from 'node:test';
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import sinon from 'sinon';
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import {
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getTraceSummary,
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parseRawTraceBuffer,
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} from '../../src/processors/PerformanceTrace.js';
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import {DevTools} from '../../src/third_party/index.js';
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import {loadTraceAsBuffer} from './fixtures/load.js';
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describe('Trace parsing', () => {
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afterEach(() => {
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sinon.restore();
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});
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it('creates an isolated model instance for each parsed trace', async () => {
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const createModelSpy = sinon.spy(
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DevTools.TraceEngine.TraceModel.Model,
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'createWithAllHandlers',
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);
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const rawData = loadTraceAsBuffer('basic-trace.json.gz');
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const result1 = await parseRawTraceBuffer(rawData);
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const result2 = await parseRawTraceBuffer(rawData);
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if ('error' in result1) {
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assert.fail(`Unexpected parse failure on first trace: ${result1.error}`);
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}
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if ('error' in result2) {
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assert.fail(`Unexpected parse failure on second trace: ${result2.error}`);
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}
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sinon.assert.calledTwice(createModelSpy);
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const firstModel = createModelSpy.firstCall.returnValue;
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const secondModel = createModelSpy.secondCall.returnValue;
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assert.notStrictEqual(firstModel, secondModel);
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// Verify that each model instance retains only its own trace. If the model
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// were shared, subsequent parses would accumulate in `#traces` and increase size.
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assert.strictEqual(firstModel.size(), 1);
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assert.strictEqual(secondModel.size(), 1);
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});
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it('can parse a Uint8Array from Tracing.stop()', async () => {
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const rawData = loadTraceAsBuffer('basic-trace.json.gz');
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const result = await parseRawTraceBuffer(rawData);
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if ('error' in result) {
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assert.fail(`Unexpected parse failure: ${result.error}`);
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}
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assert.ok(result.parsedTrace);
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assert.ok(result.insights);
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});
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it('can format results of a trace', async t => {
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const rawData = loadTraceAsBuffer('web-dev-with-commit.json.gz');
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const result = await parseRawTraceBuffer(rawData);
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if ('error' in result) {
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assert.fail(`Unexpected parse failure: ${result.error}`);
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}
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assert.ok(result.parsedTrace);
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assert.ok(result.insights);
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const output = getTraceSummary(result);
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t.assert.snapshot(output);
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});
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it('will return a message if there is an error', async () => {
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const result = await parseRawTraceBuffer(undefined);
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assert.deepEqual(result, {
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error: 'No buffer was provided.',
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});
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});
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});
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