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fix(trace viewer): fix memory leak (#32379)

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In the `visit` method, we currently cache the rendered HTML for every
walked node. This re-use works well for traces that consist mostly of
references to earlier snapshots.
But for traces that don't share much, this is a large memory overhead
and leads to the memory crash documented in
https://github.com/microsoft/playwright/issues/32336. For the algocracks
amongst you, the current memory usage for an html tree $h$ is
$\mathcal{O}(|h| * \text{height}(h))$.

This PR removes that cache from the nodes and replaces it with a
snapshot-level cache, fixing the memory crash.
Traces *without* reference should not see a performance impact from
this.
Traces *with* references will have slower initial rendering, but
re-rendering maintains speed because of the snapshot-level cache.

Closes https://github.com/microsoft/playwright/issues/32336

---------

Signed-off-by: Simon Knott <info@simonknott.de>
Co-authored-by: Max Schmitt <max@schmitt.mx>
This commit is contained in:
Simon Knott 2024-09-04 09:57:15 +02:00 committed by GitHub
parent 2fabd15fef
commit b3d767fa14
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GPG key ID: B5690EEEBB952194
1 changed files with 98 additions and 70 deletions
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168
packages/trace-viewer/src/snapshotRenderer.ts
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@ -25,6 +25,34 @@ function isSubtreeReferenceSnapshot(n: NodeSnapshot): n is SubtreeReferenceSnaps
return Array.isArray(n) && Array.isArray(n[0]);
}
let cacheSize = 0;
const cache = new Map<SnapshotRenderer, string>();
const CACHE_SIZE = 300_000_000; // 300mb
function lruCache(key: SnapshotRenderer, compute: () => string): string {
if (cache.has(key)) {
const value = cache.get(key)!;
// reinserting makes this the least recently used entry
cache.delete(key);
cache.set(key, value);
return value;
}
const result = compute();
while (cache.size && cacheSize + result.length > CACHE_SIZE) {
const [firstKey, firstValue] = cache.entries().next().value;
cacheSize -= firstValue.length;
cache.delete(firstKey);
}
cache.set(key, result);
cacheSize += result.length;
return result;
}
export class SnapshotRenderer {
private _snapshots: FrameSnapshot[];
private _index: number;
@ -51,89 +79,89 @@ export class SnapshotRenderer {
}
render(): RenderedFrameSnapshot {
const visit = (n: NodeSnapshot, snapshotIndex: number, parentTag: string | undefined, parentAttrs: [string, string][] | undefined): string => {
const result: string[] = [];
const visit = (n: NodeSnapshot, snapshotIndex: number, parentTag: string | undefined, parentAttrs: [string, string][] | undefined) => {
// Text node.
if (typeof n === 'string') {
// Best-effort Electron support: rewrite custom protocol in url() links in stylesheets.
// Old snapshotter was sending lower-case.
if (parentTag === 'STYLE' || parentTag === 'style')
return rewriteURLsInStyleSheetForCustomProtocol(n);
return escapeHTML(n);
result.push(rewriteURLsInStyleSheetForCustomProtocol(n));
else
result.push(escapeHTML(n));
return;
}
if (!(n as any)._string) {
if (isSubtreeReferenceSnapshot(n)) {
// Node reference.
const referenceIndex = snapshotIndex - n[0][0];
if (referenceIndex >= 0 && referenceIndex <= snapshotIndex) {
const nodes = snapshotNodes(this._snapshots[referenceIndex]);
const nodeIndex = n[0][1];
if (nodeIndex >= 0 && nodeIndex < nodes.length)
(n as any)._string = visit(nodes[nodeIndex], referenceIndex, parentTag, parentAttrs);
}
} else if (isNodeNameAttributesChildNodesSnapshot(n)) {
const [name, nodeAttrs, ...children] = n;
// Element node.
// Note that <noscript> will not be rendered by default in the trace viewer, because
// JS is enabled. So rename it to <x-noscript>.
const nodeName = name === 'NOSCRIPT' ? 'X-NOSCRIPT' : name;
const attrs = Object.entries(nodeAttrs || {});
const builder: string[] = [];
builder.push('<', nodeName);
const kCurrentSrcAttribute = '__playwright_current_src__';
const isFrame = nodeName === 'IFRAME' || nodeName === 'FRAME';
const isAnchor = nodeName === 'A';
const isImg = nodeName === 'IMG';
const isImgWithCurrentSrc = isImg && attrs.some(a => a[0] === kCurrentSrcAttribute);
const isSourceInsidePictureWithCurrentSrc = nodeName === 'SOURCE' && parentTag === 'PICTURE' && parentAttrs?.some(a => a[0] === kCurrentSrcAttribute);
for (const [attr, value] of attrs) {
let attrName = attr;
if (isFrame && attr.toLowerCase() === 'src') {
// Never set relative URLs as <iframe src> - they start fetching frames immediately.
attrName = '__playwright_src__';
}
if (isImg && attr === kCurrentSrcAttribute) {
// Render currentSrc for images, so that trace viewer does not accidentally
// resolve srcset to a different source.
attrName = 'src';
}
if (['src', 'srcset'].includes(attr.toLowerCase()) && (isImgWithCurrentSrc || isSourceInsidePictureWithCurrentSrc)) {
// Disable actual <img src>, <img srcset>, <source src> and <source srcset> if
// we will be using the currentSrc instead.
attrName = '_' + attrName;
}
let attrValue = value;
if (isAnchor && attr.toLowerCase() === 'href')
attrValue = 'link://' + value;
else if (attr.toLowerCase() === 'href' || attr.toLowerCase() === 'src' || attr === kCurrentSrcAttribute)
attrValue = rewriteURLForCustomProtocol(value);
builder.push(' ', attrName, '="', escapeHTMLAttribute(attrValue), '"');
}
builder.push('>');
for (const child of children)
builder.push(visit(child, snapshotIndex, nodeName, attrs));
if (!autoClosing.has(nodeName))
builder.push('</', nodeName, '>');
(n as any)._string = builder.join('');
} else {
// Why are we here? Let's not throw, just in case.
(n as any)._string = '';
if (isSubtreeReferenceSnapshot(n)) {
// Node reference.
const referenceIndex = snapshotIndex - n[0][0];
if (referenceIndex >= 0 && referenceIndex <= snapshotIndex) {
const nodes = snapshotNodes(this._snapshots[referenceIndex]);
const nodeIndex = n[0][1];
if (nodeIndex >= 0 && nodeIndex < nodes.length)
return visit(nodes[nodeIndex], referenceIndex, parentTag, parentAttrs);
}
} else if (isNodeNameAttributesChildNodesSnapshot(n)) {
const [name, nodeAttrs, ...children] = n;
// Element node.
// Note that <noscript> will not be rendered by default in the trace viewer, because
// JS is enabled. So rename it to <x-noscript>.
const nodeName = name === 'NOSCRIPT' ? 'X-NOSCRIPT' : name;
const attrs = Object.entries(nodeAttrs || {});
result.push('<', nodeName);
const kCurrentSrcAttribute = '__playwright_current_src__';
const isFrame = nodeName === 'IFRAME' || nodeName === 'FRAME';
const isAnchor = nodeName === 'A';
const isImg = nodeName === 'IMG';
const isImgWithCurrentSrc = isImg && attrs.some(a => a[0] === kCurrentSrcAttribute);
const isSourceInsidePictureWithCurrentSrc = nodeName === 'SOURCE' && parentTag === 'PICTURE' && parentAttrs?.some(a => a[0] === kCurrentSrcAttribute);
for (const [attr, value] of attrs) {
let attrName = attr;
if (isFrame && attr.toLowerCase() === 'src') {
// Never set relative URLs as <iframe src> - they start fetching frames immediately.
attrName = '__playwright_src__';
}
if (isImg && attr === kCurrentSrcAttribute) {
// Render currentSrc for images, so that trace viewer does not accidentally
// resolve srcset to a different source.
attrName = 'src';
}
if (['src', 'srcset'].includes(attr.toLowerCase()) && (isImgWithCurrentSrc || isSourceInsidePictureWithCurrentSrc)) {
// Disable actual <img src>, <img srcset>, <source src> and <source srcset> if
// we will be using the currentSrc instead.
attrName = '_' + attrName;
}
let attrValue = value;
if (isAnchor && attr.toLowerCase() === 'href')
attrValue = 'link://' + value;
else if (attr.toLowerCase() === 'href' || attr.toLowerCase() === 'src' || attr === kCurrentSrcAttribute)
attrValue = rewriteURLForCustomProtocol(value);
result.push(' ', attrName, '="', escapeHTMLAttribute(attrValue), '"');
}
result.push('>');
for (const child of children)
visit(child, snapshotIndex, nodeName, attrs);
if (!autoClosing.has(nodeName))
result.push('</', nodeName, '>');
return;
} else {
// Why are we here? Let's not throw, just in case.
return;
}
return (n as any)._string;
};
const snapshot = this._snapshot;
let html = visit(snapshot.html, this._index, undefined, undefined);
if (!html)
return { html: '', pageId: snapshot.pageId, frameId: snapshot.frameId, index: this._index };
const html = lruCache(this, () => {
visit(snapshot.html, this._index, undefined, undefined);
// Hide the document in order to prevent flickering. We will unhide once script has processed shadow.
const prefix = snapshot.doctype ? `<!DOCTYPE ${snapshot.doctype}>` : '';
html = prefix + [
'<style>*,*::before,*::after { visibility: hidden }</style>',
`<script>${snapshotScript(this._callId, this.snapshotName)}</script>`
].join('') + html;
const html = result.join('');
// Hide the document in order to prevent flickering. We will unhide once script has processed shadow.
const prefix = snapshot.doctype ? `<!DOCTYPE ${snapshot.doctype}>` : '';
return prefix + [
'<style>*,*::before,*::after { visibility: hidden }</style>',
`<script>${snapshotScript(this._callId, this.snapshotName)}</script>`
].join('') + html;
});
return { html, pageId: snapshot.pageId, frameId: snapshot.frameId, index: this._index };
}