A simple caching module that provides an ability to cache and invalidate your data. Unlike other modules, Mahsan supports the following features:

• Data is stored only in memory (without serialization/deserialization) - this why it's so fast.
• It has a strict invalidation policy which allows clients to invalidate cached entities easily.
• We optimize data transfer to the distributed storage in order to remain performant even on slow connections.

  npm install mahsan --save

// Init
const Cache = require('mahsan');
const cache = new Cache();

// ... do something ...
await cache.set('myKey', {foo: 'bar'});
// ... do something ...
const data = await cache.get('myKey');
console.log(data); // {foo: 'bar'}

const Cache = require('mahsan');
const cache = new Cache();

async getCourses() {
    // Try get data from cache.
    const data = await cache.get(['courses', 'lecturers']);

    if (data) return data;

    const dbResult = await sql(`SELECT c.name AS name, l.name AS lecturer
                                FROM courses AS c
                                LEFT JOIN lecturers AS l ON l.id = c.lecturer_id;`);

    // Save all courses names and related lecturers names in cache (in current NodeJs instance).
    await cache.set(['courses', 'lecturers'], dbResult);
    return dbResult;
}

async getLecturers() {
    // Try get data from cache.
    const data = await cache.get(['lecturers']);

    if (data) return data;

    const dbResult = await sql(`SELECT * FROM lecturers;`);

    // Save all lecturers in cache (in current NodeJs instance).
    await cache.set(['lecturers'], dbResult);
    return dbResult;
}

async deleteCourse(id) {
    await sql(`DELETE FROM courses WHERE id = ?;`, [id]);
    // Invalidate cache for "getCourses()" function.
    await cache.invalidate('courses');
}

async deleteLecturer(id) {
    await sql(`DELETE FROM lecturers WHERE id = ?;`, [id]);
    // Invalidate cache for both "getCourses()" and "getLecturers()" function.
    await cache.invalidate('lecturers');
}

• options (Object)
  • ttl (Number) is a default time to live for all .set() calls in milliseconds. Infinity by default.
  • checkPeriod (Number) is a period in milliseconds, used for deleting expired data. 5 min (5 * 60 * 1000) by default.
  • manager (String|ValidityManager) is a ValidityManager instance or one predefined "InMemory" or "Redis". InMemory by default.
  • managerOptions (Object) is currently necessary only for "Redis" manager.
    • redisClient (redis client).
    • prefix (String) is a prefix for all keys in Redis.
    • ttl (Number) is a default time to live for all Redis keys in milliseconds. 7 days (7 * 24 * 60 * 60 * 1000) by default. This option is necessary in order not to clog up Redis.

Put the value to the cache.

• keyParts (String|Array) is a list of keys used to save the value.
• value (Any) is a user data.
• ttl (Number) is a time to live in milliseconds. This argument affects only local instance cache.

Get the value from the cache.

• keyParts (String|Array) is a list of keys used to retrieve a value previously saved with cache.set() on this NodeJS instance.

Check a value availability.

• keyParts (String|Array) is a list of keys used to retrieve a value previously saved with cache.set() on this NodeJS instance.

Delete a value from the cache (on this NodeJS instance).

• keyParts (String|Array) is a list of keys used to retrieve a value previously saved with cache.set() on this NodeJS instance.

Clear cache on this NodeJS instance.

Invalidate keys locally (in case of Node.JS instance) or globally (in case of Redis).

• keyParts (String|Array) is a list of keys used to retrieve a value.

ValidityManager is an interface which has two methods async sign(keyParts) and async update(keyParts). ValidityManager may be override (for example, with an own implementation of a custom shared storage).

• value argument always stored by reference. Don't modify it after setting/getting from cache.
• mahsan (מחסן) is a storage in Hebrew.