Merge pull request #24102 from overleaf/bg-backup-stats-script

add backup sampling script

GitOrigin-RevId: cfd546d421cdcfb9f8ad2111703a437a7272bd54

services/history-v1/storage/scripts/backup_sample.mjs

@@ -0,0 +1,169 @@
+// @ts-check
+import { ObjectId } from 'mongodb'
+import { READ_PREFERENCE_SECONDARY } from '@overleaf/mongo-utils/batchedUpdate.js'
+import { db, client } from '../lib/mongodb.js'
+
+const projectsCollection = db.collection('projects')
+
+// Enable caching for ObjectId.toString()
+ObjectId.cacheHexString = true
+
+// Configuration
+const SAMPLE_SIZE_PER_ITERATION = process.argv[2]
+  ? parseInt(process.argv[2], 10)
+  : 10000
+const TARGET_ERROR_PERCENTAGE = process.argv[3]
+  ? parseFloat(process.argv[3])
+  : 5.0
+
+let gracefulShutdownInitiated = false
+
+process.on('SIGINT', handleSignal)
+process.on('SIGTERM', handleSignal)
+
+function handleSignal() {
+  gracefulShutdownInitiated = true
+  console.warn('graceful shutdown initiated')
+}
+
+async function takeSample(sampleSize) {
+  const results = await projectsCollection
+    .aggregate(
+      [
+        { $sample: { size: sampleSize } },
+        {
+          $project: {
+            _id: 0,
+            hasBackup: {
+              $ifNull: ['$overleaf.backup.lastBackedUpVersion', false],
+            },
+          },
+        },
+        {
+          $group: {
+            _id: null,
+            totalSampled: { $sum: 1 },
+            backedUp: {
+              $sum: {
+                $cond: ['$hasBackup', 1, 0],
+              },
+            },
+          },
+        },
+      ],
+      { readPreference: READ_PREFERENCE_SECONDARY }
+    )
+    .toArray()
+
+  if (results.length === 0) {
+    return { totalSampled: 0, backedUp: 0 }
+  }
+
+  return results[0]
+}
+
+function calculateStatistics(
+  cumulativeSampled,
+  cumulativeBackedUp,
+  totalPopulation
+) {
+  const proportion = cumulativeBackedUp / cumulativeSampled
+
+  // Standard error with finite population correction
+  const fpc = Math.sqrt(
+    (totalPopulation - cumulativeSampled) / (totalPopulation - 1)
+  )
+  const stdError =
+    Math.sqrt((proportion * (1 - proportion)) / cumulativeSampled) * fpc
+
+  // 95% confidence interval is approximately ±1.96 standard errors
+  const marginOfError = 1.96 * stdError
+
+  return {
+    proportion,
+    percentage: (proportion * 100).toFixed(2),
+    marginOfError,
+    errorPercentage: (marginOfError * 100).toFixed(2),
+    lowerBound: ((proportion - marginOfError) * 100).toFixed(2),
+    upperBound: ((proportion + marginOfError) * 100).toFixed(2),
+    sampleSize: cumulativeSampled,
+    populationSize: totalPopulation,
+  }
+}
+
+async function main() {
+  console.log('Date:', new Date().toISOString())
+  const totalCount = await projectsCollection.estimatedDocumentCount({
+    readPreference: READ_PREFERENCE_SECONDARY,
+  })
+  console.log(
+    `Total projects in collection (estimated): ${totalCount.toLocaleString()}`
+  )
+  console.log(`Target margin of error: ${TARGET_ERROR_PERCENTAGE}%`)
+
+  let cumulativeSampled = 0
+  let cumulativeBackedUp = 0
+  let currentError = Infinity
+  let iteration = 0
+
+  console.log('Iteration | Total Sampled | % Backed Up | Margin of Error')
+  console.log('----------|---------------|-------------|----------------')
+
+  while (currentError > TARGET_ERROR_PERCENTAGE) {
+    if (gracefulShutdownInitiated) {
+      console.log('Graceful shutdown initiated. Exiting sampling loop.')
+      break
+    }
+
+    iteration++
+    const { totalSampled, backedUp } = await takeSample(
+      SAMPLE_SIZE_PER_ITERATION
+    )
+    cumulativeSampled += totalSampled
+    cumulativeBackedUp += backedUp
+
+    const stats = calculateStatistics(
+      cumulativeSampled,
+      cumulativeBackedUp,
+      totalCount
+    )
+    currentError = parseFloat(stats.errorPercentage)
+
+    console.log(
+      `${iteration.toString().padStart(9)} | ` +
+        `${cumulativeSampled.toString().padStart(13)} | ` +
+        `${stats.percentage.padStart(10)}% | ` +
+        `\u00B1${stats.errorPercentage}%`
+    )
+
+    // Small delay between iterations
+    await new Promise(resolve => setTimeout(resolve, 100))
+  }
+
+  const finalStats = calculateStatistics(
+    cumulativeSampled,
+    cumulativeBackedUp,
+    totalCount
+  )
+
+  console.log(
+    `Projects sampled: ${cumulativeSampled.toLocaleString()} out of ${totalCount.toLocaleString()}`
+  )
+  console.log(
+    `Estimated percentage with lastBackedUpVersion: ${finalStats.percentage}%`
+  )
+  console.log(
+    `95% Confidence Interval: ${finalStats.lowerBound}% - ${finalStats.upperBound}%`
+  )
+  console.log(`Final Margin of Error: \u00B1${finalStats.errorPercentage}%`)
+}
+
+main()
+  .then(() => console.log('Done.'))
+  .catch(err => {
+    console.error('Error:', err)
+    process.exitCode = 1
+  })
+  .finally(() => {
+    client.close().catch(err => console.error('Error closing MongoDB:', err))
+  })