[misc] bail out from pdf caching processing after 10s or earlier

...for fast compiles.

services/clsi/app/js/CompileManager.js

@@ -292,6 +292,8 @@ module.exports = CompileManager = {
                   timings['cpu-time'] / stats['latex-runs']
                 )
               }
+              // Emit compile time.
+              timings.compile = ts
 
               return OutputFileFinder.findOutputFiles(
                 resourceList,
@@ -317,8 +319,7 @@ module.exports = CompileManager = {
                         )
                       }
 
-                      // Emit compile time.
-                      timings.compile = ts
+                      // Emit e2e compile time.
                       timings.compileE2E = timerE2E.done()
 
                       if (stats['pdf-size']) {

services/clsi/app/js/ContentCacheManager.js

@@ -10,21 +10,26 @@ const Settings = require('settings-sharelatex')
 const OError = require('@overleaf/o-error')
 const pLimit = require('p-limit')
 const { parseXrefTable } = require('../lib/pdfjs/parseXrefTable')
+const { TimedOutError } = require('./Errors')
 
 /**
  *
  * @param {String} contentDir path to directory where content hash files are cached
  * @param {String} filePath the pdf file to scan for streams
  * @param {number} size the pdf size
+ * @param {number} compileTime
  */
-async function update(contentDir, filePath, size) {
+async function update(contentDir, filePath, size, compileTime) {
+  const checkDeadline = getDeadlineChecker(compileTime)
   const ranges = []
   const newRanges = []
   // keep track of hashes expire old ones when they reach a generation > N.
   const tracker = await HashFileTracker.from(contentDir)
   tracker.updateAge()
 
-  const rawTable = await parseXrefTable(filePath, size)
+  checkDeadline('after init HashFileTracker')
+
+  const rawTable = await parseXrefTable(filePath, size, checkDeadline)
   rawTable.sort((a, b) => {
     return a.offset - b.offset
   })
@@ -32,6 +37,8 @@ async function update(contentDir, filePath, size) {
     obj.idx = idx
   })
 
+  checkDeadline('after parsing')
+
   const uncompressedObjects = []
   for (const object of rawTable) {
     if (!object.uncompressed) {
@@ -50,12 +57,14 @@ async function update(contentDir, filePath, size) {
     if (size < Settings.pdfCachingMinChunkSize) {
       continue
     }
-    uncompressedObjects.push(object)
+    uncompressedObjects.push({ object, idx: uncompressedObjects.length })
   }
 
+  checkDeadline('after finding uncompressed')
+
   const handle = await fs.promises.open(filePath)
   try {
-    for (const object of uncompressedObjects) {
+    for (const { object, idx } of uncompressedObjects) {
       let buffer = Buffer.alloc(object.size, 0)
       const { bytesRead } = await handle.read(
         buffer,
@@ -63,6 +72,7 @@ async function update(contentDir, filePath, size) {
         object.size,
         object.offset
       )
+      checkDeadline('after read ' + idx)
       if (bytesRead !== object.size) {
         throw new OError('could not read full chunk', {
           object,
@@ -80,6 +90,7 @@ async function update(contentDir, filePath, size) {
       buffer = buffer.subarray(objectIdRaw.byteLength)
 
       const hash = pdfStreamHash(buffer)
+      checkDeadline('after hash ' + idx)
       const range = {
         objectId: objectIdRaw.toString(),
         start: object.offset + objectIdRaw.byteLength,
@@ -92,12 +103,15 @@ async function update(contentDir, filePath, size) {
       if (tracker.track(range)) continue
 
       await writePdfStream(contentDir, hash, buffer)
+      checkDeadline('after write ' + idx)
       newRanges.push(range)
     }
   } finally {
     await handle.close()
   }
 
+  // NOTE: Bailing out below does not make sense.
+  //       Let the next compile use the already written ranges.
   const reclaimedSpace = await tracker.deleteStaleHashes(5)
   await tracker.flush()
   return [ranges, newRanges, reclaimedSpace]
@@ -219,6 +233,28 @@ async function writePdfStream(dir, hash, buffer) {
   }
 }
 
+function getDeadlineChecker(compileTime) {
+  const maxOverhead = Math.min(
+    // Adding 10s to a 40s compile time is OK.
+    compileTime / 4,
+    // Adding 30s to a 120s compile time is not OK, limit to 10s.
+    Settings.pdfCachingMaxProcessingTime
+  )
+
+  const deadline = Date.now() + maxOverhead
+  let lastStage = { stage: 'start', now: Date.now() }
+  return function (stage) {
+    const now = Date.now()
+    if (now > deadline) {
+      throw new TimedOutError(stage, {
+        lastStage: lastStage.stage,
+        diffToLastStage: now - lastStage.now
+      })
+    }
+    lastStage = { stage, now }
+  }
+}
+
 function promiseMapWithLimit(concurrency, array, fn) {
   const limit = pLimit(concurrency)
   return Promise.all(array.map((x) => limit(() => fn(x))))

services/clsi/app/js/ContentCacheMetrics.js

@@ -19,6 +19,9 @@ function getSystemLoad() {
 const ONE_MB = 1024 * 1024
 
 function emitPdfStats(stats, timings) {
+  if (stats['pdf-caching-timed-out']) {
+    Metrics.inc('pdf-caching-timed-out')
+  }
   if (timings['compute-pdf-caching']) {
     emitPdfCachingStats(stats, timings)
   } else {

services/clsi/app/js/Errors.js

@@ -4,6 +4,8 @@
 */
 // TODO: This file was created by bulk-decaffeinate.
 // Fix any style issues and re-enable lint.
+const OError = require('@overleaf/o-error')
+
 let Errors
 var NotFoundError = function (message) {
   const error = new Error(message)
@@ -29,7 +31,10 @@ var AlreadyCompilingError = function (message) {
 }
 AlreadyCompilingError.prototype.__proto__ = Error.prototype
 
+class TimedOutError extends OError {}
+
 module.exports = Errors = {
+  TimedOutError,
   NotFoundError,
   FilesOutOfSyncError,
   AlreadyCompilingError

services/clsi/app/js/OutputCacheManager.js

@@ -26,6 +26,7 @@ const Metrics = require('./Metrics')
 
 const OutputFileOptimiser = require('./OutputFileOptimiser')
 const ContentCacheManager = require('./ContentCacheManager')
+const { TimedOutError } = require('./Errors')
 
 module.exports = OutputCacheManager = {
   CONTENT_SUBDIR: 'content',
@@ -281,7 +282,16 @@ module.exports = OutputCacheManager = {
           contentDir,
           outputFilePath,
           pdfSize,
+          timings.compile,
           function (err, result) {
+            if (err && err instanceof TimedOutError) {
+              logger.warn(
+                { err, outputDir, stats, timings },
+                'pdf caching timed out'
+              )
+              stats['pdf-caching-timed-out'] = 1
+              return callback(null, outputFiles)
+            }
             if (err) return callback(err, outputFiles)
             const [contentRanges, newContentRanges, reclaimedSpace] = result
 

services/clsi/app/lib/pdfjs/FSPdfManager.js

@@ -4,10 +4,10 @@ const { MissingDataException } = require('pdfjs-dist/lib/core/core_utils')
 const { FSStream } = require('./FSStream')
 
 class FSPdfManager extends LocalPdfManager {
-  constructor(docId, options) {
+  constructor(docId, { fh, size, checkDeadline }) {
     const nonEmptyDummyBuffer = Buffer.alloc(1, 0)
     super(docId, nonEmptyDummyBuffer)
-    this.stream = new FSStream(options.fh, 0, options.size)
+    this.stream = new FSStream(fh, 0, size, null, null, checkDeadline)
     this.pdfDocument = new PDFDocument(this, this.stream)
   }
 

services/clsi/app/lib/pdfjs/FSStream.js

@@ -4,11 +4,12 @@ const { MissingDataException } = require('pdfjs-dist/lib/core/core_utils')
 const BUF_SIZE = 1024 // read from the file in 1024 byte pages
 
 class FSStream extends Stream {
-  constructor(fh, start, length, dict, cachedBytes) {
+  constructor(fh, start, length, dict, cachedBytes, checkDeadline) {
     const nonEmptyDummyBuffer = Buffer.alloc(1, 0)
     super(nonEmptyDummyBuffer, start, length, dict)
     delete this.bytes
     this.fh = fh
+    this.checkDeadline = checkDeadline
     this.cachedBytes = cachedBytes || []
   }
 
@@ -23,6 +24,7 @@ class FSStream extends Stream {
   // Manage cached reads from the file
 
   requestRange(begin, end) {
+    this.checkDeadline(`request range ${begin} - ${end}`)
     // expand small ranges to read a larger amount
     if (end - begin < BUF_SIZE) {
       end = begin + BUF_SIZE
@@ -123,6 +125,7 @@ class FSStream extends Stream {
   }
 
   makeSubStream(start, length, dict = null) {
+    this.checkDeadline(`make sub stream start=${start}/length=${length}`)
     // BG: had to add this check for null length, it is being called with only
     // the start value at one point in the xref decoding. The intent is clear
     // enough
@@ -131,7 +134,14 @@ class FSStream extends Stream {
     if (!length) {
       length = this.end - start
     }
-    return new FSStream(this.fh, start, length, dict, this.cachedBytes)
+    return new FSStream(
+      this.fh,
+      start,
+      length,
+      dict,
+      this.cachedBytes,
+      this.checkDeadline
+    )
   }
 }
 

services/clsi/app/lib/pdfjs/parseXrefTable.js

@@ -1,18 +1,21 @@
 const fs = require('fs')
 const { FSPdfManager } = require('./FSPdfManager')
 
-async function parseXrefTable(path, size) {
+async function parseXrefTable(path, size, checkDeadline) {
   if (size === 0) {
     return []
   }
 
   const file = await fs.promises.open(path)
   try {
-    const manager = new FSPdfManager(0, { fh: file, size })
+    const manager = new FSPdfManager(0, { fh: file, size, checkDeadline })
 
     await manager.ensureDoc('checkHeader')
+    checkDeadline('pdfjs: after checkHeader')
     await manager.ensureDoc('parseStartXRef')
+    checkDeadline('pdfjs: after parseStartXRef')
     await manager.ensureDoc('parse')
+    checkDeadline('pdfjs: after parse')
     return manager.pdfDocument.catalog.xref.entries
   } finally {
     file.close()

services/clsi/config/settings.defaults.js

@@ -68,7 +68,9 @@ module.exports = {
   enablePdfCaching: process.env.ENABLE_PDF_CACHING === 'true',
   enablePdfCachingDark: process.env.ENABLE_PDF_CACHING_DARK === 'true',
   pdfCachingMinChunkSize:
-    parseInt(process.env.PDF_CACHING_MIN_CHUNK_SIZE, 10) || 1024
+    parseInt(process.env.PDF_CACHING_MIN_CHUNK_SIZE, 10) || 1024,
+  pdfCachingMaxProcessingTime:
+    parseInt(process.env.PDF_CACHING_MAX_PROCESSING_TIME, 10) || 10 * 1000
 }
 
 if (process.env.ALLOWED_COMPILE_GROUPS) {

services/clsi/test/unit/lib/pdfjsTests.js

@@ -33,7 +33,7 @@ async function loadContext(example) {
 }
 
 async function backFillSnapshot(example, size) {
-  const table = await parseXrefTable(pdfPath(example), size)
+  const table = await parseXrefTable(pdfPath(example), size, () => {})
   await fs.promises.mkdir(Path.dirname(snapshotPath(example)), {
     recursive: true
   })
@@ -53,6 +53,24 @@ describe('pdfjs', function () {
     })
   })
 
+  describe('when the operation times out', function () {
+    it('should bail out', async function () {
+      const path = pdfPath(EXAMPLES[0])
+      const { size } = await loadContext(EXAMPLES[0])
+      const err = new Error()
+      let table
+      try {
+        table = await parseXrefTable(path, size, () => {
+          throw err
+        })
+      } catch (e) {
+        expect(e).to.equal(err)
+        return
+      }
+      expect(table).to.not.exist
+    })
+  })
+
   for (const example of EXAMPLES) {
     describe(example, function () {
       let size, snapshot
@@ -70,7 +88,7 @@ describe('pdfjs', function () {
       })
 
       it('should produce the expected xRef table', async function () {
-        const table = await parseXrefTable(pdfPath(example), size)
+        const table = await parseXrefTable(pdfPath(example), size, () => {})
         expect(table).to.deep.equal(snapshot)
       })
     })