overleaf/services/document-updater/app/coffee/LockManager.coffee

72 lines
2.3 KiB
CoffeeScript

metrics = require('./Metrics')
Settings = require('settings-sharelatex')
rclient = require("./RedisBackend").createClient()
keys = require('./RedisKeyBuilder')
logger = require "logger-sharelatex"
os = require "os"
crypto = require "crypto"
HOST = os.hostname()
PID = process.pid
RND = crypto.randomBytes(4).toString('hex')
COUNT = 0
module.exports = LockManager =
LOCK_TEST_INTERVAL: 50 # 50ms between each test of the lock
MAX_LOCK_WAIT_TIME: 10000 # 10s maximum time to spend trying to get the lock
LOCK_TTL: 30 # seconds. Time until lock auto expires in redis.
# 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
randomLock : () ->
time = Date.now()
return "locked:host=#{HOST}:pid=#{PID}:random=#{RND}:time=#{time}:count=#{COUNT++}"
unlockScript: 'if redis.call("get", KEYS[1]) == ARGV[1] then return redis.call("del", KEYS[1]) else return 0 end';
tryLock : (doc_id, callback = (err, isFree)->)->
lockValue = LockManager.randomLock()
key = keys.blockingKey(doc_id:doc_id)
rclient.set key, lockValue, "EX", @LOCK_TTL, "NX", (err, gotLock)->
return callback(err) if err?
if gotLock == "OK"
metrics.inc "doc-not-blocking"
callback err, true, lockValue
else
metrics.inc "doc-blocking"
logger.log {doc_id}, "doc is locked"
callback err, false
getLock: (doc_id, callback = (error) ->) ->
startTime = Date.now()
do attempt = () ->
if Date.now() - startTime > LockManager.MAX_LOCK_WAIT_TIME
e = new Error("Timeout")
e.doc_id = doc_id
return callback(e)
LockManager.tryLock doc_id, (error, gotLock, lockValue) ->
return callback(error) if error?
if gotLock
callback(null, lockValue)
else
setTimeout attempt, LockManager.LOCK_TEST_INTERVAL
checkLock: (doc_id, callback = (err, isFree)->)->
key = keys.blockingKey(doc_id:doc_id)
rclient.exists key, (err, exists) ->
return callback(err) if err?
exists = parseInt exists
if exists == 1
metrics.inc "doc-blocking"
callback err, false
else
metrics.inc "doc-not-blocking"
callback err, true
releaseLock: (doc_id, lockValue, callback)->
key = keys.blockingKey(doc_id:doc_id)
rclient.eval LockManager.unlockScript, 1, key, lockValue, callback