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Merge pull request #4184 from overleaf/jpa-incremental-caching
[perf] serviceWorker: fill the browser cache incrementally GitOrigin-RevId: 3e72838d7521f1adc63661e8e4235aaa104fef79
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1 changed files with 55 additions and 23 deletions
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@ -10,6 +10,7 @@ const PDF_REQUEST_MATCHER = /^\/project\/[0-9a-f]{24}\/.*\/output.pdf$/
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const PDF_JS_CHUNK_SIZE = 128 * 1024
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const MAX_SUBREQUEST_COUNT = 8
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const MAX_SUBREQUEST_BYTES = 4 * PDF_JS_CHUNK_SIZE
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const INCREMENTAL_CACHE_SIZE = 1000
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// Each compile request defines a context (essentially the specific pdf file for
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// that compile), requests for that pdf file can use the hashes in the compile
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@ -23,6 +24,7 @@ const CLIENT_CONTEXT = new Map()
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function getClientContext(clientId) {
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let clientContext = CLIENT_CONTEXT.get(clientId)
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if (!clientContext) {
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const cached = new Set()
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const pdfs = new Map()
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const metrics = {
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version: VERSION,
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@ -39,7 +41,7 @@ function getClientContext(clientId) {
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requestedBytes: 0,
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compileCount: 0,
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}
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clientContext = { pdfs, metrics }
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clientContext = { pdfs, metrics, cached }
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CLIENT_CONTEXT.set(clientId, clientContext)
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// clean up old client maps
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expirePdfContexts()
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@ -54,8 +56,9 @@ function getClientContext(clientId) {
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*/
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function registerPdfContext(clientId, path, pdfContext) {
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const clientContext = getClientContext(clientId)
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const { pdfs, metrics } = clientContext
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const { pdfs, metrics, cached } = clientContext
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pdfContext.metrics = metrics
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pdfContext.cached = cached
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// we only need to keep the last 3 contexts
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for (const key of pdfs.keys()) {
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if (pdfs.size < 3) {
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@ -228,10 +231,11 @@ function handleProbeRequest(request, file) {
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* @param {string} compileGroup
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* @param {Date} pdfCreatedAt
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* @param {Object} metrics
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* @param {Set} cached
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*/
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function processPdfRequest(
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event,
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{ file, clsiServerId, compileGroup, pdfCreatedAt, metrics }
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{ file, clsiServerId, compileGroup, pdfCreatedAt, metrics, cached }
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) {
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const response = handleProbeRequest(event.request, file)
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if (response) {
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@ -249,9 +253,13 @@ function processPdfRequest(
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// Check that handling the range request won't trigger excessive subrequests,
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// (to avoid unwanted latency compared to the original request).
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const chunks = getMatchingChunks(file.ranges, start, end)
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const { chunks, newChunks } = cutRequestAmplification(
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getMatchingChunks(file.ranges, start, end),
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cached,
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metrics
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)
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const dynamicChunks = getInterleavingDynamicChunks(chunks, start, end)
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const chunksSize = countBytes(chunks)
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const chunksSize = countBytes(newChunks)
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const size = end - start
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if (chunks.length === 0 && dynamicChunks.length === 1) {
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@ -265,29 +273,13 @@ function processPdfRequest(
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})
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return
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}
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if (
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chunks.length + (dynamicChunks.length > 0 ? 1 : 0) >
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MAX_SUBREQUEST_COUNT
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) {
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// fall back to the original range request when splitting the range creates
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// too many subrequests.
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metrics.tooManyRequestsCount++
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trackDownloadStats(metrics, {
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size,
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cachedCount: 0,
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cachedBytes: 0,
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fetchedCount: 1,
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fetchedBytes: size,
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})
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return
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}
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if (
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chunksSize > MAX_SUBREQUEST_BYTES &&
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!(dynamicChunks.length === 0 && chunks.length === 1)
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!(dynamicChunks.length === 0 && newChunks.length <= 1)
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) {
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// fall back to the original range request when a very large amount of
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// object data would be requested, unless it is the only object in the
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// request.
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// request or everything is already cached.
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metrics.tooLargeOverheadCount++
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trackDownloadStats(metrics, {
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size,
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@ -370,6 +362,9 @@ function processPdfRequest(
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if (blobFetchDate < pdfCreatedAt) {
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cachedCount++
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cachedBytes += chunkSize
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// Roll the position of the hash in the Map.
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cached.delete(chunk.hash)
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cached.add(chunk.hash)
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} else {
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// Blobs are fetched in bulk.
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fetchedCount++
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@ -636,6 +631,43 @@ function getMatchingChunks(chunks, start, end) {
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return matchingChunks
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}
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/**
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* @param {Array} potentialChunks
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* @param {Set} cached
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* @param {Object} metrics
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*/
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function cutRequestAmplification(potentialChunks, cached, metrics) {
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const chunks = []
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const newChunks = []
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let tooManyRequests = false
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for (const chunk of potentialChunks) {
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if (cached.has(chunk.hash)) {
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chunks.push(chunk)
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continue
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}
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if (newChunks.length < MAX_SUBREQUEST_COUNT) {
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chunks.push(chunk)
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newChunks.push(chunk)
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} else {
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tooManyRequests = true
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}
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}
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if (tooManyRequests) {
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metrics.tooManyRequestsCount++
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}
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if (cached.size > INCREMENTAL_CACHE_SIZE) {
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for (const key of cached) {
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if (cached.size < INCREMENTAL_CACHE_SIZE) {
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break
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}
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// Map keys are stored in insertion order.
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// We re-insert keys on cache hit, 'cached' is a cheap LRU.
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cached.delete(key)
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}
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}
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return { chunks, newChunks }
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}
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/**
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* @param {Array} chunks
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* @param {number} start
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