key-file-storage

key-file-storage

Simple key-value storage directly on file system, maps each key to a separate file.

No database and database overhead anymore, just plain file-system and simple files containing JSON data! It's great for applications with small and medium data sizes.

• Simple key-value storage model
• Very easy to learn and use
• Both Synchronous and Asynchronous API
• One JSON containing file per each key
• Built-in configurable cache
• Both Promise and Callback support

Just give it a try, you'll like it!

Installation

Installing package on Node.js (Node.js 6.0.0 or higher is required) :

$ npm install key-file-storage

Initialization

Initializing key-file storage :

var keyFileStorage = require("key-file-storage");

// Using an unlimited cache
var kfs = keyFileStorage('/path/to/storage/directory');

// or

// Using a custom cache
var kfs = keyFileStorage('/path/to/storage/directory', cacheConfig);

The value of cacheConfig can be

1. true (By default) : Unlimited cache, anything will be cached on memory, good for small data volumes.
2. false : No cache, read the files from disk every time, good when other applications can modify the files' contents arbitrarily.
3. n (An integer number) : Limited cache, only the n latest referred key-values will be cached, good for large data volumes where only a fraction of data is being used frequently .

Usage

Synchronous API

As simple as native javascript objects :

// Set
kfs['key'] = value;

// Get
kfs['key'];

// Delete
delete kfs['key'];

// Check for existence
'key' in kfs    // true or false

// Clear all database
delete kfs['*'];

• You can use kfs.keyName instead of kfs['keyName'] anywhere if the key name allows.

• undefined is not supported as a savable value, but null is. Saving a key with value undefined is equivalent to remove it. So, you can use kfs['key'] = undefined or even kfs['*'] = undefined to delete data.

• Synchronous API will throw an exception if any errors happens, so you shall handle it your way.

Asynchronous API with Promises

Every one of the following calls returns a promise :

// Set
kfs('key', value);

// Get
kfs('key');

// Delete
new kfs('key');

// Check for existence
('key' in kfs(), kfs())    // resolves to true or false

// Clear all database
new kfs('*');  /* or */  new kfs();

• Once again, undefined is not supported as a savable value, but null is. Saving a key with value undefined is equivalent to remove it. So, you can use kfs('key', undefined) or even kfs('*', undefined) to delete data.

Asynchronous API with Callbacks

The same as asynchronous with promises, but with callback function as the last input value of kfs() :

// Set
kfs('key', value, callback);

// Get
kfs('key', callback);

// Delete
new kfs('key', callback);

// Check for existence
'key' in kfs(callback)             // No promise returns anymore
/* or */
('key' in kfs(), kfs(callback))    // resolves to true or false

// Clear all database
new kfs('*', callback);  /* or */  new kfs(callback);

• These calls still return a promise on their output (except for 'key' in kfs(callback) form of existence check).

• The first input parameter of all callback functions is err, so you shall handle it within the callback. Set, Get and Existence check callbacks provide the return values as their second input parameter.

Notes

• NOTE 1 : Each key will map to a separate file (using the key itself as its relative path) so there is no need to load all the database file for any key access. Also, keys can be relative paths, e.g: data.json, /my/key/01 or any/other/relative/path/to/a/file.

• NOTE 2 : There is a built-in implemented cache, so accessing a certain key more than once won't require file-system level operations (off course with some active cache).

Contribute

The code is very simple and straightforward. It would be nice if you had any suggestions or contribution on it or detected any bug or issue.

• See the code on GitHub.com
• Contact me by my gmail address (Hessam A Shokravi)