overleaf/services/clsi/app/coffee/DockerLockManager.coffee

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logger = require "logger-sharelatex"
LockState = {} # locks for docker container operations, by container name
module.exports = LockManager =
MAX_LOCK_HOLD_TIME: 15000 # how long we can keep a lock
MAX_LOCK_WAIT_TIME: 10000 # how long we wait for a lock
LOCK_TEST_INTERVAL: 1000 # retry time
tryLock: (key, callback = (err, gotLock) ->) ->
existingLock = LockState[key]
if existingLock? # the lock is already taken, check how old it is
lockAge = Date.now() - existingLock.created
if lockAge < LockManager.MAX_LOCK_HOLD_TIME
return callback(null, false) # we didn't get the lock, bail out
else
logger.error {key: key, lock: existingLock, age:lockAge}, "taking old lock by force"
# take the lock
LockState[key] = lockValue = {created: Date.now()}
callback(null, true, lockValue)
getLock: (key, callback = (error, lockValue) ->) ->
startTime = Date.now()
do attempt = () ->
LockManager.tryLock key, (error, gotLock, lockValue) ->
return callback(error) if error?
if gotLock
callback(null, lockValue)
else if Date.now() - startTime > LockManager.MAX_LOCK_WAIT_TIME
e = new Error("Lock timeout")
e.key = key
return callback(e)
else
setTimeout attempt, LockManager.LOCK_TEST_INTERVAL
releaseLock: (key, lockValue, callback = (error) ->) ->
existingLock = LockState[key]
if existingLock is lockValue # lockValue is an object, so we can test by reference
delete LockState[key] # our lock, so we can free it
callback()
else if existingLock? # lock exists but doesn't match ours
logger.error {key:key, lock: existingLock}, "tried to release lock taken by force"
callback()
else
logger.error {key:key, lock: existingLock}, "tried to release lock that has gone"
callback()
runWithLock: (key, runner = ( (releaseLock = (error) ->) -> ), callback = ( (error) -> )) ->
LockManager.getLock key, (error, lockValue) ->
return callback(error) if error?
runner (error1, args...) ->
LockManager.releaseLock key, lockValue, (error2) ->
error = error1 or error2
return callback(error) if error?
callback(null, args...)