All you need to know about Redis
I know, the title is a bit provocative or presumptuous if you prefer, but I think this post could be useful if you wanna approach to Redis as cache server using .NET. For all the people who don't know what Redis is, let me quote that definition:
Redis is an open source, BSD licensed, advanced key-value cache and store.
And why is it so cool? This is probably the best answer you can find on internet (source here):
Redis running on an entry level laptop can scan a 1 million key database in 40 milliseconds.
Installation
Now that is clear why Redis is so cool and why lot of enterprise applications use it, we can see how to use it. First of all we have to download Redis from here, unzip the file and run it locally
> redis-server.exe redis.conf
and the console output should be something like this:
if you want to use Redis on Microsoft Azure, you can do it by creating your instance here:
choose the best plan for you, the location, add your name in the proper field and create it.
creation could take a while and sometime you can get errors. The reason is that the portal is still in beta but don't worry, keep trying till you get the redis cache server up & running
Configuration
Here we go, Redis is up & running on your dev machine and/or on Azure if you choose it. Before to start writing code, it's important to choose the client library to use. The most used libraries are
The first one is free and opensource so, if you want to use it, you can do easily. The other one has a AGPL license (from 149$ to 249$).
if you prefer ServiceStack.Redis you can downgrade to version 3.9.71 which was the last truly free
In this article I'm going to use StackExchange.Redis so, let's start to install it using NuGet
PM> Install-Package StackExchange.Redis
There is also a StrongName (StackExchange.Redis.StrongName) package if you need to use it into a signed library.
Now, it's time to write some good code:
namespace imperugo.blog.redis
{
class Program
{
private static ConnectionMultiplexer connectionMultiplexer;
private static IDatabase database;
static void Main(string[] args)
{
Configure();
}
private static void Configure()
{
//use locally redis installation
var connectionString = string.Format("{0}:{1}", "127.0.0.1", 6379);
//use azure redis installation
var azureConnectionString = string.Format("{0}:{1},ssl=true,password={2}",
"imperugo-test.redis.cache.windows.net",
6380,
"Azure Primary Key");
connectionMultiplexer = ConnectionMultiplexer.Connect(connectionString);
database = connectionMultiplexer.GetDatabase();
}
}
}
For some plans, Redis on azure uses SSL by default. If you prefer a no-secure connection you can enable it via Azure Portal, in this case use 6379 and remove
ssl=truefrom the connection string
Add and Retrieve cache objects
StackExchange stores data into Redis sending/retrieving a byte[] or so, whatever you are storing into Redis must be converted into a byte[] (string is automatically converted by StackExchange.Redis implementation so we don't have to do it).
Let's start with simple object like a string
private static bool StoreData(string key, string value)
{
return database.StringSet(key, value);
}
private static string GetData(string key)
{
return database.StringGet(key);
}
private static void DeleteData(string key)
{
database.KeyDelete(key);
}
and now we can use this methods
static void Main(string[] args)
{
Configure();
bool stored = StoreData("MyKey","my first cache string");
if (stored)
{
var cachedData = GetData("MyKey");
bool isIt = cachedData == "my first cache string";
}
}
That's pretty simple but what about storing complex objects?
As I wrote above, StackExchange.Redis stores only byte[] data so we have to serialize our complex object and convert it into a byte[] (there is an implicit conversion in case of string, for this reason we didn't convert the type string to byte[])
The easiest (and probably the best) way to store complex objects consists to serilize the object into a string before to store the data into Redis.
Choose your favorite serialized (NewtonSoft in my case ) and create some helpers like here
public bool Add<T>(string key, T value, DateTimeOffset expiresAt) where T : class
{
var serializedObject = JsonConvert.SerializeObject(value);
var expiration = expiresAt.Subtract(DateTimeOffset.Now);
return database.StringSet(key, serializedObject, expiration);
}
public T Get<T>(string key) where T : class
{
var serializedObject = database.StringGet(key);
return JsonConvert.DeserializeObject<T>(serializedObject)
}
Now we are able to put and retrieve complex objects into Redis, next step is to remove it and check if the value exists
public bool Remove(string key)
{
return database.KeyDelete(key);
}
public bool Exists(string key)
{
return database.KeyExists(key);
}
if you need async methods, don't worry, StackExchange.Redis has an async overload for almost every method
Resources
Redis Commands absolutety the best reference to understand how Redis works and what StackExchage.Redis does under the table.
StackExchage.Redis documentation is absolutely helpful if you choose this library as your wrapper.
StackExchange.Redis.Extensions is a great library (and I suggest to you it) that wrap the common operation needed with StackExchange.Redis (basically you don't need to serialize objects or create helpers like I explained above):
- Add complex objects to Redis;
- Remove an object from Redis;
- Search Keys into Redis;
- Retrieve multiple objects with a single roundtrip;
- Store multiple objects with a single roundtrip;
- Async methods;
- Retrieve Redis Server status;
- Much more;
It uses Json.Net (NewtonSoft), Jil or Message Pack CLI to serialize objects into a byte[].
Anyway we'll see it with the next blog post.
Investigating Timeout Exceptions in StackExchange.Redis for Azure Redis Cache great article about possible timeout exception problem with Redis and Azure
Dashboard
Azure Dashboard
It offers basic stats but it's free when you use Redis with Microsoft Azure
Probably the most complete dashboard for Redis, offers a set of stats about your Redis servers, supports Azure and has a good prompt allowing you to run Redis command directly on the server without using C# or any other programming language. Unfortunately it is not free, here plans and pricing.
Open Source tool for Windows, Mac and Linux hosted on Github here (right now it the version 0.7.6) offers to run Redis commands into Redis like Redismin, but unfortunately it doesn't support Azure yet (there is an issue about that opened here).
It's a real time dashboard for Redis written using Python.
Conclusions
Redis is absolutely one of the best in memory database available right now. There is a wrapper for every language, it's got a good documentation and it's free. If I were you I'd give it a look!
staytuned!
