@ehacke/transparent-cache

transparent-cache

Simple transparent caching for Node. Wrap a function and then call it like normal.

Sponsor

asserted.io - Test in Prod

Features

• The cache is periodically updated in the background without blocking the primary call. So it's always fast.
• Just wrap any function and it becomes cached
• Includes both local LRU cache and Redis

Install

This has a peer-dependency on ioredis

npm i -S @ehacke/transparent-cache ioredis

Use

In the most basic case, you can just supply the redis config, and then wrap the function.

The redisConfig option is passed directly to ioredis and has the same properties as its constructor.

import { TransparentCache } from '@ehacke/transparent-cache';

const transparentCache = new TransparentCache({ redisConfig: { host: 'localhost', port: 6379 } });

function someSlowAndExpensiveFunction(someCoolArg) {
  // ... do things you want to cache
}

// By default, the wrapped version will cache results for 30 sec locally and 10 minutes in Redis
const wrappedVersion = transparentCache.wrap(someSlowAndExpensiveFunction);

// No cache yet, call original function. Still slow.
let result = await wrappedVersion('foo');

// Immediately call again...

// Returns value from local cache for arg 'foo'
result = await wrappedVersion('foo'); 

// .... waiting two minutes ....

// Nothing in the local cache, so it goes to Redis
result = await wrappedVersion('foo');

// ... waiting 15 minutes ...

// Nothing in local or Redis, so it calls the original function
result = await wrappedVersion('foo');

// Clear caches locally and remotely for 'foo'
// NOTE: This doesn't clear local caches on other nodes
await wrappedVersion.delete('foo');

// Hits original again because caches were cleared
result = await wrappedVersion('foo');

API

Constructor

During construction, the default values for each wrap call are set.

The local and remote properties are used as the default for each wrap call, but can be overridden.

interface ConstructorInterface {
  redis?: Redis;                // Instead of providing the config below, you can provide a constructed IORedis instance
  redisConfig?: RedisOptions;   // Same as: https://github.com/luin/ioredis/blob/master/API.md#new-redisport-host-options
                                // Defaults to: { keyPrefix: 'trans-cache-', enableOfflineQueue: false }
                                //    This namespaces the keys, and ensures the redis calls fail fast if disconnected
  local?: {
    size?: number;              // Defaults to 1000
    ttlMs?: number;             // Defaults to 30 seconds
  };
  remote?: {
    size?: number;              // Defaults to 10000
    ttlMs?: number;             // Defaults to 10 minutes
    commandTimeoutMs?: number;  // Redis command timeout. Defaults to 50 ms
  };
}

Wrap

import { TransparentCache } from '@ehacke/transparent-cache';

const transparentCache = new TransparentCache({ redisConfig: { host: 'localhost', port: 6379 } });

transparentCache.wrap<TypeOfReturn>(
  functionToWrap,                 // Any function. Promises are awaited
  overrideConfig: {               // Defaults to constructor values 
    local?: {
      size?: number;              // Defaults to 1000
      ttlMs?: number;             // Defaults to 30 seconds
    };
    remote?: {
      size?: number;              // Defaults to 10000
      ttlMs?: number;             // Defaults to 10 minutes
      commandTimeoutMs?: number;  // Redis command timeout. Defaults to 50 ms
    };
    waitForRefresh?: boolean;     // Normally cache refreshes are done in the background. This forces them to block.
  }, 
  functionId,                     // Used as part of the cache key, defaults to the function name if present
  that,                           // Reference to 'this' for the wrapped function, used with .apply()
)

The wrapped version of the function also exposes a .delete() property that can be called to wipe the cache for a specific set of args.

// Clear caches locally and remotely for 'foo'
// NOTE: This doesn't clear local caches on other nodes
await wrappedVersion.delete('foo');