README

rabbit-lru-cache

A lib to invalidate lru cache keys in distributed systems powered by rabbitmq.

Installation

npm install --save rabbit-lru-cache

Getting Started

This library is powered by lru-cache and amqplib (both peer dependencies).

const createRabbitLRUCache = require("rabbit-lru-cache").default;

const cache = await createRabbitLRUCache({
    name: "example",
    LRUCacheOptions: {
        maxAge: 120000
    },
    amqpConnectOptions: {
        hostname: "localhost",
        username: "guest",
        password: "guest"
    }
});
cache.addInvalidationMessageReceivedListener((content, publisherCacheId) => {
    console.log("Cache Message", "publisherCacheId", publisherCacheId, "content", content);
});
cache.addReconnectingListener((error, attempt, retryInterval) => {
    console.log("Reconnecting", error.message, "attempt", attempt, "retryInterval", retryInterval);
});
cache.addReconnectedListener((error, attempt, retryInterval) => {
    console.log("Reconnected", error.message, "attempt", attempt, "retryInterval", retryInterval);
});
    
await cache.getOrLoad("key", () => Promise.resolve(5));
cache.del("key");

await cache.close(); // gracefully shutdown RabbitMq connection

Every time the lru-cache del or reset function is called a message is published in a fan out exchange and each cache subscribers consume the message to invalidate the corresponding key or the entire cache.

The getOrLoad function forces you to set item in cache only after loading it, avoiding a wrong usage of the library as, for instance, set in cache an item after modifying it. Finally, this function comes with concurrency mechanism to avoid stale data and Thundering herd problem by use the same promise for concurrent requests of the same cache key while the corresponding item is not loaded in cache yet.

The lib handles RabbitMq connection errors and it reconnects automatically if the connection with the broker got lost. During reconnection the local cache get resetted and cache is disabled to ensure it does not store stale data.

Examples

Examples of the usage of this lib can be found in test folder or examples folder.

Test

Run test suite with the following command:

npm test

Test suite requires a RabbitMq server listening at port 5672.

License

MIT

Usage no npm install needed!