kv-cache

A persistent key/value cache.

Install

npm install --save kv-cache

Example

import {createFileCache} from 'kv-cache';

// Specify a path to a directory where the values will be stored
const cacheDir = '/path/to/some/directory';

const cache = createFileCache(cacheDir);

cache.events.on('error' => console.error('Cache error: ' + err));

cache.get('foo').then(data => {
  console.log(data); // null

  cache.set('foo', 'bar');

  cache.get('foo').then(data => {
    console.log(data); // 'bar'

    cache.invalidate('foo');

    cache.get('foo').then(data => {
      console.log(data); // null
    });
  });
});

key should be a string or an array of strings. Keys are hashed with murmur to produce consistent and performant mappings.

value should be a JSON-serializable value.

get calls will resolve when the file has been read either from disk or memory.

set calls will update the memory store immediately, but will only resolve once the value has been persisted to disk.

invalidate calls will update the memory store immediately, but will only resolve once the associated value has been removed from disk.

events is an EventEmitter instance that emits 'error' events. If you dont want to wait for set or invalidate calls to be resolved or rejected, you can use it to handle error conditions.

File cache

import {createFileCache} from 'kv-cache';

const cache = createFileCache('/path/to/directory');

Persists data to a directory where each key is mapped to distinct file. Spreading keys across files avoids IO overhead associated with stale data. To reduce filesystem reads on repeated gets, it maintains an in-memory map from a key to the serialized object.

When get is called, it looks for JSON data in either memory or the filesystem, then parses the stored JSON and provides the object. If no associated data exists, null is provided.

When set is called, the value is immediately serialized to JSON, preserved in memory, then asynchronously written to disk.

When invalidate is called, it removes any related data in memory and then asynchronously remove the related file. Note: invalidating a missing key will not produce an error.

Mock cache

import {createMockCache} from 'kv-cache';

const cache = createMockCache();

Presents a similar API to the file cache, however it will immediately resolve all promises with null.

This is useful as a drop-in replacement, if you want to debug or profile without the serialization or IO overheads.