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JamesMGreeneJamesMGreene
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Use node-redis for soft-purging cache on deploy (#18474)
* Use [node-]redis as a direct dependency * Extract Redis client creation to its own module * Attach extensive logging in the Redis client creation module * Allow the rate limiter to pass requests when Redis is disconnected * Update rate-limit-redis * Default error input to empty object for formatRedisError method * Provide a name for the rate limiter's Redis client * Include redis-mock, exclude ioredis/ioredis-mock * Remove unused RedisAccessor#exists method * Switch RedisAccessor to use redis/redis-mock * Provide a name for logging on the Redis page cache * Remove extraneous trailing space from Redis logging prefix Our updated use of console.* will already be adding a space after the prefix * Replace ioredis-mock with redis-mock in tests * Revert removal of ioredis dependency * Bind Redis client to async promisified methods * Extract former RedisAccessor constructor tests to new create-client tests * Update RedisAccessor tests to work with the callback-based redis client * Handle formatting Redis errors (or not) with more resiliency * Remove ioredis as a dependency * Update Redis soft-purging script to use node-redis * Do more promisifying for less ugly code * Add comment explaining TTL of -1 * Make the script executable
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Lines changed: 111 additions & 108 deletions

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‎package-lock.json‎

Lines changed: 6 additions & 50 deletions
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‎package.json‎

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@@ -58,7 +58,6 @@
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"hot-shots": "^8.2.0",
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"html-entities": "^1.2.1",
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"imurmurhash": "^0.1.4",
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"ioredis": "^4.24.4",
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"is-url": "^1.2.4",
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"js-cookie": "^2.2.1",
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"js-yaml": "^3.14.0",

‎script/purge-redis-pages.js‎

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@@ -8,7 +8,10 @@
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//
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// [end-readme]
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const Redis = require('ioredis')
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require('dotenv').config()
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const { promisify } = require('util')
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const createClient = require('../lib/redis/create-client')
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const { REDIS_URL, HEROKU_RELEASE_VERSION, HEROKU_PRODUCTION_APP } = process.env
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const isHerokuProd = HEROKU_PRODUCTION_APP === 'true'
@@ -42,68 +45,109 @@ console.log({
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purgeRenderedPageCache()
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function purgeRenderedPageCache () {
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const redisClient = new Redis(REDIS_URL, {
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db: pageCacheDatabaseNumber,
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// Only add this configuration for TLS-enabled REDIS_URL values.
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// Otherwise, it breaks for local Redis instances without TLS enabled.
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...REDIS_URL.startsWith('rediss://') && {
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tls: {
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// Required for production Heroku Redis
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rejectUnauthorized: false
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}
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}
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const redisClient = createClient({
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url: REDIS_URL,
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db: pageCacheDatabaseNumber
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})
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let totalKeyCount = 0
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let iteration = 0
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let potentialKeyCount = 0
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let totalKeyCount = 0
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// Create a readable stream (object mode) for the SCAN cursor
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const scanStream = redisClient.scanStream({
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match: keyScanningPattern,
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count: scanSetSize
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})
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// Promise wrappers
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const scanAsync = promisify(redisClient.scan).bind(redisClient)
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const quitAsync = promisify(redisClient.quit).bind(redisClient)
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scanStream.on('end', function () {
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console.log(`Done purging keys; affected total: ${totalKeyCount}`)
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console.log(`Time elapsed: ${Date.now() - startTime} ms`)
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// Run it!
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return scan()
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// This seems to be unexpectedly necessary
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process.exit(0)
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})
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//
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// Define other subroutines
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//
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scanStream.on('error', function (error) {
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console.error('An unexpected error occurred!\n' + error.stack)
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console.error('\nAborting...')
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process.exit(1)
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})
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async function scan (cursor = '0') {
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try {
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// [0]: Update the cursor position for the next scan
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// [1]: Get the SCAN result for this iteration
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const [nextCursor, keys] = await scanAsync(
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cursor,
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'MATCH', keyScanningPattern,
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'COUNT', scanSetSize.toString()
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)
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scanStream.on('data', async function (keys) {
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console.log(`[Iteration ${iteration++}] Received ${keys.length} keys...`)
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console.log(`\n[Iteration ${iteration++}] Received ${keys.length} keys...`)
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// NOTE: It is possible for a SCAN cursor iteration to return 0 keys when
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// using a MATCH because it is applied after the elements are retrieved
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if (keys.length === 0) return
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if (dryRun) {
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console.log(`DRY RUN! This iteration might have set TTL for up to ${keys.length} keys:\n - ${keys.join('\n - ')}`)
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}
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87-
if (dryRun) {
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console.log(`DRY RUN! This iteration might have set TTL for up to ${keys.length} keys:\n - ${keys.join('\n - ')}`)
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return
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}
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// NOTE: It is possible for a SCAN cursor iteration to return 0 keys when
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// using a MATCH because it is applied after the elements are retrieved
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//
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// Remember: more or less than COUNT or no keys may be returned
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// See http://redis.io/commands/scan#the-count-option
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// Also, SCAN may return the same key multiple times
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// See http://redis.io/commands/scan#scan-guarantees
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// Additionally, you should always have the code that uses the keys
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// before the code checking the cursor.
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if (keys.length > 0) {
94+
if (dryRun) {
95+
potentialKeyCount += keys.length
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} else {
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totalKeyCount += await updateTtls(keys)
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}
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}
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// Pause the SCAN stream while we set a TTL on these keys
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scanStream.pause()
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// From <http://redis.io/commands/scan>:
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// 'An iteration starts when the cursor is set to 0,
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// and terminates when the cursor returned by the server is 0.'
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if (nextCursor === '0') {
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const dryRunTrailer = dryRun ? ` (potentially up to ${potentialKeyCount})` : ''
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console.log(`\nDone purging keys; affected total: ${totalKeyCount}${dryRunTrailer}`)
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console.log(`Time elapsed: ${Date.now() - startTime} ms`)
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// Close the connection
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await quitAsync()
111+
return
112+
}
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// Find existing TTLs to ensure we aren't extending the TTL if it's already set
96-
// PTTL mykey // only operate on -1 result values or those greater than ONE_HOUR_FROM_NOW
97-
const pttlPipeline = redisClient.pipeline()
114+
// Tail recursion
115+
return scan(nextCursor)
116+
} catch (error) {
117+
console.error('An unexpected error occurred!\n' + error.stack)
118+
console.error('\nAborting...')
119+
process.exit(1)
120+
}
121+
}
122+
123+
// Find existing TTLs to ensure we aren't extending the TTL if it's already set
124+
async function getTtls (keys) {
125+
const pttlPipeline = redisClient.batch()
98126
keys.forEach(key => pttlPipeline.pttl(key))
99-
const pttlResults = await pttlPipeline.exec()
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101-
// Update pertinent keys to have TTLs set
128+
const pttlPipelineExecAsync = promisify(pttlPipeline.exec).bind(pttlPipeline)
129+
const pttlResults = await pttlPipelineExecAsync()
130+
131+
if (pttlResults == null || pttlResults.length === 0) {
132+
throw new Error('PTTL results were empty')
133+
}
134+
135+
return pttlResults
136+
}
137+
138+
async function updateTtls (keys) {
139+
const pttlResults = await getTtls(keys)
140+
141+
// Find pertinent keys to have TTLs set
102142
let updatingKeyCount = 0
103-
const pexpireAtPipeline = redisClient.pipeline()
143+
const pexpireAtPipeline = redisClient.batch()
144+
104145
keys.forEach((key, i) => {
105-
const [error, pttl] = pttlResults[i]
106-
const needsShortenedTtl = error == null && (pttl === -1 || pttl > expirationDuration)
146+
// Only operate on -1 result values or those greater than ONE_HOUR_FROM_NOW
147+
const pttl = pttlResults[i]
148+
// A TTL of -1 means the entry was not configured with any TTL (expiration)
149+
// currently and will remain as a permanent entry unless a TTL is added
150+
const needsShortenedTtl = pttl === -1 || pttl > expirationDuration
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const isOldKey = !HEROKU_RELEASE_VERSION || !key.startsWith(`${HEROKU_RELEASE_VERSION}:`)
108152

109153
if (needsShortenedTtl && isOldKey) {
@@ -112,17 +156,21 @@ function purgeRenderedPageCache () {
112156
}
113157
})
114158

159+
console.log(`Purging ${updatingKeyCount} keys...`)
160+
115161
// Only update TTLs if there are records worth updating
116-
if (updatingKeyCount > 0) {
117-
// Set all the TTLs
118-
const pexpireAtResults = await pexpireAtPipeline.exec()
119-
const updatedResults = pexpireAtResults.filter(([error, result]) => error == null && result === 1)
162+
if (updatingKeyCount === 0) return
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121-
// Count only the entries whose TTLs were successfully updated
122-
totalKeyCount += updatedResults.length
164+
// Set all the TTLs
165+
const pexpireAtPipelineExecAsync = promisify(pexpireAtPipeline.exec).bind(pexpireAtPipeline)
166+
const pexpireAtResults = await pexpireAtPipelineExecAsync()
167+
168+
if (pttlResults == null || pttlResults.length === 0) {
169+
throw new Error('PEXPIREAT results were empty')
123170
}
124171

125-
// Resume the SCAN stream
126-
scanStream.resume()
127-
})
172+
// Count only the entries whose TTLs were successfully updated
173+
const updatedResults = pexpireAtResults.filter((result) => result === 1)
174+
return updatedResults.length
175+
}
128176
}

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