Set

Basic case

After you've created a client (which will automatically establish a connection), you can start issuing commands! The most basic is to set a value:

client
    .set('firstName', 'Victor')
    .then(function() {
        console.log('Successfully set the key firstName');
    });

Arguments

set() requires 2 arguments and could have up to 4.

The first is always the key and must be a string.
The second is always the value and must be a string.
The third is optional and could be either: (1) a ttl for this key (2) an options object or (3) a callback
The fourth is only present if there is a third argument for ttl or options and a callback is provided.

Key must be a string

Non-string keys are not allowed and Memcache Plus will throw an error if you try to provide a non-string key.

client
    .set({ foo: 'bar' }, myVal)
    .then(function() {
        // This will never happen because an error will be thrown
    })
    .catch(function(err) {
        // This will get hit!
        console.error('Oops we have an error', err);
    });

Value can be of any type

The value can be of any type (numeric, string, object, array, null, etc.)

Memcache Plus will handle converting the value (if necessary) before sending to the Memcached server and converting it back upon retrieval.

For instance, with Memcache Plus you can go ahead and set an object

var myVal = {
    firstName: 'Victor',
    lastName: 'Quinn'
};

client
    .set('user', myVal)
    .then(function() {
        console.log('Successfully set the object');
    });

Then when you get it out it'll be an object:

client
    .get('user')
    .then(function(user) {
        // The user is a JS object:
        // { firstName: 'Victor', lastName: 'Quinn' }
        console.log('Successfully got the object', user);
    });

Same goes for numbers, arrays, etc. Memcache Plus will always return the exact type you put into it.

TTL

A key/value pair can be specified with an optional ttl which will specify how long (in seconds) that object persists before it is automatically purged from the cache.

For example, to set a value that will stay around in the cache for only 10 seconds:

client.set('firstName', 'Victor', 10);

If you perform a get() within 10 seconds for firstName, you'll get back "Victor" but after 10 seconds, you will get null.

Callbacks

Memcache Plus will always return a Promise, but it can also take a traditional callback for any of its methods so it can work just like most of the other Memcache modules out there. For example:

client.set('firstName', 'Victor', function(err) {
    console.log('Successfully set the key firstName');
});

Compression

Optionally you can request that compression be enabled for a given item:

client.set('firstName', 'Victor', { compressed: true })
    .then(function() {
        console.log('Successfully set the key firstName as compressed data');
    });

By enabling this option, every key will be compressed with Node's zlib library prior to being stored.

This is helpful in the event that you are attempting to store data (such as a stringified object) which is too large for the standard Memcache value limit size. It is also helpful in situations where the memory allocated to your Memcache instance is limited, such as on a Raspberry Pi or some other embedded hardware.

For example, if your Memcache server is set with a limit of 1MB for a value and you attempt to store a 1.2MB object, the set will fail. However, enabling compression will cause the value to be compressed with zlib before it is stored so the size may be reduced significantly and save successfully.

Notes:

  1. If you store a value compressed with set() you have to get() it and specify that it was compressed. There is no automatic inspection of values to determine whether they were set with compression and decompress automatically (as this would incur significant performance penalty)
  2. Enabling compression will reduce the size of the objects stored but it will also add a non-negligent performance hit to each set() and get() so use it judiciously!
  3. The maximum key size is 250 bytes. This is a Memcache limitation and this library will throw an error if a key larger than that is provided.

Errors

Memcache Plus will throw errors for any unexpected or broken behavior so you know quickly if something is wrong with your application. These could be things like: trying to set() an item without a key, trying to set() an item that is too large, trying to set() with a key that is too long, and many more.