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warlock.js
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warlock.js
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const UUID = require('uuid');
const { ParityDel, ParityRelock } = require('./scripts');
module.exports = function (redis) {
const warlock = {};
const parityDel = ParityDel(redis);
const parityRelock = ParityRelock(redis);
warlock.makeKey = function (key) {
return `${key}:lock`;
};
/**
* Set a lock key
* @param {string} key Name for the lock key. String please.
* @param {integer} ttl Time in milliseconds for the lock to live.
* @param {Function} cb
*/
warlock.lock = function (key, ttl, cb) {
cb = cb || function () {};
if (typeof key !== 'string') {
return cb(new Error('lock key must be string'));
}
let id;
UUID.v1(null, (id = new Buffer(16)));
id = id.toString('base64');
redis.set(
warlock.makeKey(key), id,
'PX', ttl, 'NX',
(err, lockSet) => {
if (err) return cb(err);
const unlock = lockSet ? warlock.unlock.bind(warlock, key, id) : false;
return cb(err, unlock, id);
},
);
return key;
};
warlock.unlock = async (key, id, cb) => {
cb = cb || function () {};
if (typeof key !== 'string') {
return cb(new Error('lock key must be string'));
}
const numKeys = 1;
const _key = warlock.makeKey(key);
try {
const result = await parityDel(numKeys, _key, id);
cb(null, result);
} catch (e) {
cb(e);
}
};
/**
* Set a lock optimistically (retries until reaching maxAttempts).
*/
warlock.optimistic = function (key, ttl, maxAttempts, wait, cb) {
let attempts = 0;
var tryLock = function () {
attempts += 1;
warlock.lock(key, ttl, (err, unlock) => {
if (err) return cb(err);
if (typeof unlock !== 'function') {
if (attempts >= maxAttempts) {
const e = new Error('unable to obtain lock');
e.maxAttempts = maxAttempts;
e.key = key;
e.ttl = ttl;
e.wait = wait;
return cb(e);
}
return setTimeout(tryLock, wait);
}
return cb(err, unlock);
});
};
tryLock();
};
warlock.touch = async (key, id, ttl, cb) => {
if (typeof key !== 'string') {
const e = new Error('lock key must be string');
e.id = id;
e.key = key;
e.ttl = ttl;
if (!cb) throw e;
return cb(e);
}
try {
const result = await parityRelock(3, warlock.makeKey(key), ttl, id);
return cb ? cb(null, result) : result;
} catch (e) {
if (!cb) throw e;
return cb(e);
}
};
return warlock;
};