Node Memcached Set (Detailed Guide w/ Code Examples)

Use Case(s)

• Caching data that's expensive to fetch or compute: The set method in Memcached allows you to store any serialized data against a key, which makes it ideal for storing results of complex queries, computationally heavy data, or frequently accessed information.
• Session storage: In web-based applications, Memcached's set function can be used to store session data, improving the speed and efficiency of your application.

Code Examples

Let's start by assuming that you have already installed memcached and the Node.js client memcached.

    let memcached = require('memcached');
    let client  = new memcached('localhost:11211');

1. Setting a Key:

To set a key with a value, you use the set function. Here's an example:

    client.set('myKey', 'Hello, Memcached!', 10, function(err) {
        if(err) console.error(err);
    });

In this example, we're setting a key 'myKey' with the value 'Hello, Memcached!'. The 10 is the expiration time in seconds. If there's an error, it will be logged to the console.

2. Retrieving a Key:

To verify the key has been set, you can retrieve it using the get function:

    client.get('myKey', function(err, data){
        if(err) console.error(err);
        console.log(data);
    });

The get function takes a key as the first argument, and a callback function as the second argument. This callback function is executed once the data is retrieved.

Best Practices

• Only store serialized data: Non-string data types need to be serialized (converted into a string format) before they are stored in Memcached.
• Keep keys short: Keys in Memcached are limited to 250 bytes. Also, shorter keys will take up less memory and network bandwidth.
• Handle errors: Network issues or other problems can cause operations to fail. Always include error handling code when working with Memcached.

Common Mistakes

• Not checking if the memcached server is running and connected: Before setting or getting values, always ensure that the memcached server is running and the client is connected to it.
• Over-reliance on cache: Remember, Memcached is not a persistent storage system. It's meant for caching data to improve speed, not to act as a primary data store.

FAQs

1. What types of data can I store with Memcached set?
   • You can store any serializable data including strings, numbers, Booleans, JSON objects, and more.
2. What happens when Memcached runs out of memory?
   • When Memcached runs out of memory, it uses an LRU (Least Recently Used) algorithm to evict old data and make room for new data.
3. Is the data stored in Memcached secure?
   • No, Memcached does not provide any built-in security features. Anyone connected to the network can read or write data to the cache. It should be used only within trusted networks.