@esfx/async-readerwriterlock Package
The @esfx/async-readerwriterlock package provides the AsyncReaderWriterLock class, an async coordination primitive.
Installation
npm i @esfx/async-readerwriterlock
Usage
import { AsyncReaderWriterLock } from "@esfx/async-readerwriterlock";
interface User { id: string, name: string, email: string }
// 'rwlock' protects access to 'userCache' and data stored on disk
const rwlock = new AsyncReaderWriterLock();
const userCache = new Map<string, User>();
async function getUser(id: string) {
// get read access
const lk = await rwlock.read();
try {
let user = userCache.get(id);
if (!user) {
user = await readUserFromDisk(id);
userCache.set(id, user);
}
return user;
}
finally {
// release read access
lk.unlock();
}
}
async function addUser(user: User) {
// get write access
const lk = await rwlock.write();
try {
userCache.set(user.id, user);
await writeUserToDisk(user.id, user);
}
finally {
// release write access
lk.unlock();
}
}
async function updateUser(id: string, oldData: User, newData: User) {
// get upgradeable read access
const lk = await rwlock.upgradeableRead();
try {
// verify that we are ok to make changes...
let user = userCache.get(id);
if (!user || user.name === oldData.name && user.email === oldData.email) {
// looks safe, so upgrade to a write lock
const updlk = await lk.upgrade();
try {
if (!user) {
user = { id } as User;
userCache.set(id, user);
}
user.name = newData.name;
user.email = newData.email;
await writeUserToDisk(user.id, user);
}
finally {
updlk.unlock(); // release the write lock
}
}
}
finally {
lk.unlock(); // release the read lock
}
}
Classes
AsyncReaderWriterLock
Coordinates readers and writers for a resource.