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overleaf/libraries/redis-wrapper/index.js

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const crypto = require('node:crypto')
const os = require('node:os')
const { promisify } = require('node:util')
const Redis = require('ioredis')
const {
RedisHealthCheckTimedOut,
RedisHealthCheckWriteError,
RedisHealthCheckVerifyError,
} = require('./Errors')
const HEARTBEAT_TIMEOUT = 2000
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// generate unique values for health check
const HOST = os.hostname()
const PID = process.pid
const RND = crypto.randomBytes(4).toString('hex')
let COUNT = 0
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function createClient(opts) {
const standardOpts = Object.assign({}, opts)
delete standardOpts.key_schema
if (standardOpts.retry_max_delay == null) {
standardOpts.retry_max_delay = 5000 // ms
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}
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if (standardOpts.endpoints) {
throw new Error(
'@overleaf/redis-wrapper: redis-sentinel is no longer supported'
)
}
let client
if (standardOpts.cluster) {
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delete standardOpts.cluster
client = new Redis.Cluster(opts.cluster, standardOpts)
} else {
client = new Redis(standardOpts)
}
monkeyPatchIoRedisExec(client)
client.healthCheck = callback => {
if (callback) {
// callback based invocation
healthCheck(client).then(callback).catch(callback)
} else {
// Promise based invocation
return healthCheck(client)
}
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}
return client
}
async function healthCheck(client) {
// check the redis connection by storing and retrieving a unique key/value pair
const uniqueToken = `host=${HOST}:pid=${PID}:random=${RND}:time=${Date.now()}:count=${COUNT++}`
// o-error context
const context = {
uniqueToken,
stage: 'add context for a timeout',
}
await runWithTimeout({
runner: runCheck(client, uniqueToken, context),
timeout: HEARTBEAT_TIMEOUT,
context,
})
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}
async function runCheck(client, uniqueToken, context) {
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const healthCheckKey = `_redis-wrapper:healthCheckKey:{${uniqueToken}}`
const healthCheckValue = `_redis-wrapper:healthCheckValue:{${uniqueToken}}`
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// set the unique key/value pair
context.stage = 'write'
const writeAck = await client
.set(healthCheckKey, healthCheckValue, 'EX', 60)
.catch(err => {
throw new RedisHealthCheckWriteError('write errored', context, err)
})
if (writeAck !== 'OK') {
context.writeAck = writeAck
throw new RedisHealthCheckWriteError('write failed', context)
}
// check that we can retrieve the unique key/value pair
context.stage = 'verify'
const [roundTrippedHealthCheckValue, deleteAck] = await client
.multi()
.get(healthCheckKey)
.del(healthCheckKey)
.exec()
.catch(err => {
throw new RedisHealthCheckVerifyError(
'read/delete errored',
context,
err
)
})
if (roundTrippedHealthCheckValue !== healthCheckValue) {
context.roundTrippedHealthCheckValue = roundTrippedHealthCheckValue
throw new RedisHealthCheckVerifyError('read failed', context)
}
if (deleteAck !== 1) {
context.deleteAck = deleteAck
throw new RedisHealthCheckVerifyError('delete failed', context)
}
}
function unwrapMultiResult(result, callback) {
// ioredis exec returns a results like:
// [ [null, 42], [null, "foo"] ]
// where the first entries in each 2-tuple are
// presumably errors for each individual command,
// and the second entry is the result. We need to transform
// this into the same result as the old redis driver:
// [ 42, "foo" ]
//
// Basically reverse:
// https://github.com/luin/ioredis/blob/v4.17.3/lib/utils/index.ts#L75-L92
const filteredResult = []
for (const [err, value] of result || []) {
if (err) {
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return callback(err)
} else {
filteredResult.push(value)
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}
}
callback(null, filteredResult)
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}
const unwrapMultiResultPromisified = promisify(unwrapMultiResult)
function monkeyPatchIoRedisExec(client) {
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const _multi = client.multi
client.multi = function () {
const multi = _multi.apply(client, arguments)
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const _exec = multi.exec
multi.exec = callback => {
if (callback) {
// callback based invocation
_exec.call(multi, (error, result) => {
// The command can fail all-together due to syntax errors
if (error) return callback(error)
unwrapMultiResult(result, callback)
})
} else {
// Promise based invocation
return _exec.call(multi).then(unwrapMultiResultPromisified)
}
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}
return multi
}
}
async function runWithTimeout({ runner, timeout, context }) {
let healthCheckDeadline
await Promise.race([
new Promise((resolve, reject) => {
healthCheckDeadline = setTimeout(() => {
// attach the timeout when hitting the timeout only
context.timeout = timeout
reject(new RedisHealthCheckTimedOut('timeout', context))
}, timeout)
}),
runner.finally(() => clearTimeout(healthCheckDeadline)),
])
}
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module.exports = {
createClient,
}