overleaf/services/project-history/app/js/LockManager.js

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// TODO: This file was created by bulk-decaffeinate.
// Fix any style issues and re-enable lint.
/*
* decaffeinate suggestions:
* DS101: Remove unnecessary use of Array.from
* DS102: Remove unnecessary code created because of implicit returns
* DS207: Consider shorter variations of null checks
* Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
*/
import async from 'async'
import metrics from '@overleaf/metrics'
import Settings from '@overleaf/settings'
import redis from '@overleaf/redis-wrapper'
import os from 'os'
import crypto from 'crypto'
import logger from '@overleaf/logger'
import OError from '@overleaf/o-error'
const LOCK_TEST_INTERVAL = 50 // 50ms between each test of the lock
const MAX_LOCK_WAIT_TIME = 10000 // 10s maximum time to spend trying to get the lock
export const LOCK_TTL = 360 // seconds
export const MIN_LOCK_EXTENSION_INTERVAL = 1000 // 1s minimum interval when extending a lock
export const UNLOCK_SCRIPT =
'if redis.call("get", KEYS[1]) == ARGV[1] then return redis.call("del", KEYS[1]) else return 0 end'
const EXTEND_SCRIPT =
'if redis.call("get", KEYS[1]) == ARGV[1] then return redis.call("expire", KEYS[1], ARGV[2]) else return 0 end'
const HOST = os.hostname()
const PID = process.pid
const RND = crypto.randomBytes(4).toString('hex')
let COUNT = 0
const rclient = redis.createClient(Settings.redis.lock)
/**
* Container for functions that need to be mocked in tests
*
* TODO: Rewrite tests in terms of exported functions only
*/
export const _mocks = {}
// Use a signed lock value as described in
// http://redis.io/topics/distlock#correct-implementation-with-a-single-instance
// to prevent accidental unlocking by multiple processes
_mocks.randomLock = () => {
const time = Date.now()
return `locked:host=${HOST}:pid=${PID}:random=${RND}:time=${time}:count=${COUNT++}`
}
export function randomLock(...args) {
return _mocks.randomLock(...args)
}
_mocks.tryLock = (key, callback) => {
if (callback == null) {
callback = function () {}
}
const lockValue = randomLock()
return rclient.set(
key,
lockValue,
'EX',
LOCK_TTL,
'NX',
function (err, gotLock) {
if (err != null) {
return callback(
OError.tag(err, 'redis error trying to get lock', { key })
)
}
if (gotLock === 'OK') {
metrics.inc('lock.project.try.success')
return callback(err, true, lockValue)
} else {
metrics.inc('lock.project.try.failed')
return callback(err, false)
}
}
)
}
export function tryLock(...args) {
_mocks.tryLock(...args)
}
_mocks.extendLock = (key, lockValue, callback) => {
if (callback == null) {
callback = function () {}
}
return rclient.eval(
EXTEND_SCRIPT,
1,
key,
lockValue,
LOCK_TTL,
function (err, result) {
if (err != null) {
return callback(
OError.tag(err, 'redis error trying to extend lock', { key })
)
}
if (result != null && result !== 1) {
// successful extension should release exactly one key
metrics.inc('lock.project.extend.failed')
const error = new OError('failed to extend lock', {
key,
lockValue,
result,
})
return callback(error)
}
metrics.inc('lock.project.extend.success')
return callback()
}
)
}
export function extendLock(...args) {
_mocks.extendLock(...args)
}
_mocks.getLock = (key, callback) => {
let attempt
if (callback == null) {
callback = function () {}
}
const startTime = Date.now()
let attempts = 0
return (attempt = function () {
if (Date.now() - startTime > MAX_LOCK_WAIT_TIME) {
metrics.inc('lock.project.get.failed')
return callback(new OError('Timeout', { key }))
}
attempts += 1
return tryLock(key, function (error, gotLock, lockValue) {
if (error != null) {
return callback(OError.tag(error))
}
if (gotLock) {
metrics.gauge('lock.project.get.success.tries', attempts)
return callback(null, lockValue)
} else {
return setTimeout(attempt, LOCK_TEST_INTERVAL)
}
})
})()
}
export function getLock(...args) {
_mocks.getLock(...args)
}
export function checkLock(key, callback) {
if (callback == null) {
callback = function () {}
}
return rclient.exists(key, function (err, exists) {
if (err != null) {
return callback(OError.tag(err))
}
exists = parseInt(exists)
if (exists === 1) {
return callback(err, false)
} else {
return callback(err, true)
}
})
}
_mocks.releaseLock = (key, lockValue, callback) => {
return rclient.eval(UNLOCK_SCRIPT, 1, key, lockValue, function (err, result) {
if (err != null) {
return callback(OError.tag(err))
}
if (result != null && result !== 1) {
// successful unlock should release exactly one key
const error = new OError('tried to release timed out lock', {
key,
lockValue,
redis_result: result,
})
return callback(error)
}
return callback(err, result)
})
}
export function releaseLock(...args) {
_mocks.releaseLock(...args)
}
export function runWithLock(key, runner, callback) {
if (callback == null) {
callback = function () {}
}
return getLock(key, function (error, lockValue) {
if (error != null) {
return callback(OError.tag(error))
}
const lock = new Lock(key, lockValue)
return runner(lock.extend.bind(lock), (error1, ...args) =>
lock.release(function (error2) {
error = error1 || error2
if (error != null) {
return callback(OError.tag(error), ...Array.from(args))
}
return callback(null, ...Array.from(args))
})
)
})
}
export function healthCheck(callback) {
const action = (extendLock, releaseLock) => releaseLock()
return runWithLock(
`HistoryLock:HealthCheck:host=${HOST}:pid=${PID}:random=${RND}`,
action,
callback
)
}
export function close(callback) {
rclient.quit()
return rclient.once('end', callback)
}
class Lock {
constructor(key, value) {
this.key = key
this.value = value
this.slowExecutionError = new OError('slow execution during lock')
this.lockTakenAt = Date.now()
this.timer = new metrics.Timer('lock.project')
}
extend(callback) {
const lockLength = Date.now() - this.lockTakenAt
if (lockLength < MIN_LOCK_EXTENSION_INTERVAL) {
return async.setImmediate(callback)
}
return extendLock(this.key, this.value, error => {
if (error != null) {
return callback(OError.tag(error))
}
this.lockTakenAt = Date.now()
return callback()
})
}
release(callback) {
// The lock can expire in redis but the process carry on. This setTimout call
// is designed to log if this happens.
const lockLength = Date.now() - this.lockTakenAt
if (lockLength > LOCK_TTL * 1000) {
metrics.inc('lock.project.exceeded_lock_timeout')
logger.debug('exceeded lock timeout', {
key: this.key,
slowExecutionError: this.slowExecutionError,
})
}
return releaseLock(this.key, this.value, error => {
this.timer.done()
if (error != null) {
return callback(OError.tag(error))
}
return callback()
})
}
}