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[local-sync] Optimize snippet extraction

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Summary:
We were seeing JS blocking in snippet extraction of up to 2k ms. This
is because we were walking the entire DOM of a message and extracting
all text, regardless of message size---and using our own homegrown
DOM walker function.

To remedy this, use the standard TreeWalker from the Chrome browser
APIs (which in benchmarks looks 2-4x faster) and also exit out of
the DOM walking process once we've accumulated enough text to create
a snippet. Informal eyeballing of timing metrics for this function suggests
the new implementation is something like 10-100x faster for some messages.

As a bonus, we get to delete some code and end up with a cleaner
implementation!

Test Plan: old unit tests yaay

Reviewers: juan

Reviewed By: juan

Subscribers: evan

Differential Revision: https://phab.nylas.com/D3543
This commit is contained in:
Christine Spang 2016-12-20 15:10:22 -08:00
parent 5015d105b8
commit e924e74c1b
1 changed files with 23 additions and 28 deletions
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51
packages/local-sync/src/shared/message-factory.js
View file

@ -37,48 +37,43 @@ function extractContacts(input) {
}
// Iteratively walk the DOM of this document's <body>, calling the callback on
// each node. Skip any nodes and the skipTags set, including their children.
function _walkBodyDOM(doc, callback, skipTags) {
let nodes = Array.from(doc.body.childNodes);
while (nodes.length) {
const node = nodes.shift();
callback(node);
if (!skipTags.has(node.tagName)) {
if (node.childNodes && node.childNodes.length) {
nodes = Array.from(node.childNodes).concat(nodes);
}
}
}
}
function extractSnippet(plainBody, htmlBody) {
let snippetText = plainBody || '';
let snippetText = plainBody ? plainBody.trim() : '';
if (htmlBody) {
const doc = new DOMParser().parseFromString(htmlBody, 'text/html')
const extractedTextElements = [];
const skipTags = new Set(['TITLE', 'SCRIPT', 'STYLE', 'IMG']);
_walkBodyDOM(doc, (node) => {
const treeWalker = document.createTreeWalker(doc, NodeFilter.SHOW_ELEMENT | NodeFilter.SHOW_TEXT, (node) => {
if (skipTags.has(node.tagName)) {
// skip this node and all its children
return NodeFilter.FILTER_REJECT;
}
if (node.nodeType === Node.TEXT_NODE) {
const nodeValue = node.nodeValue ? node.nodeValue.trim() : null;
if (nodeValue) {
extractedTextElements.push(nodeValue);
return NodeFilter.FILTER_ACCEPT;
}
}
}, new Set(['TITLE', 'SCRIPT', 'STYLE', 'IMG']));
return NodeFilter.FILTER_SKIP;
});
const extractedText = extractedTextElements.join(' ').trim();
if (extractedText) {
snippetText = extractedText;
let extractedText = "";
while (treeWalker.nextNode()) {
// TODO: there may be some elements we don't want to add a space between
if (extractedText) {
extractedText += " ";
}
extractedText += treeWalker.currentNode.nodeValue;
if (extractedText.length > SNIPPET_MAX_SIZE) {
break;
}
}
snippetText = extractedText;
}
// clean up and trim snippet
let trimmed = snippetText.trim().replace(/[\n\r]/g, ' ').replace(/\s\s+/g, ' ').substr(0, SNIPPET_MAX_SIZE);
let trimmed = snippetText.replace(/[\n\r]/g, ' ').replace(/\s\s+/g, ' ').substr(0, SNIPPET_MAX_SIZE);
if (trimmed) {
// TODO: strip quoted text from snippets also
// trim down to approx. SNIPPET_SIZE w/out cutting off words right in the