Orleans and the Azure Redis Cache

Recently, I've been diving into Orleans again, the great open-srouce framework that provides an approach for building large-scale, distributed computing applications. It takes care of concurrency and scaling patterns for you and you can focus on the application itself.

I have been blogging about Orleans before, also explaining about Grains and what they can do for you.

At the moment, I am designing and building a large IoT solution and Orleans is used to keep state of Raspberry Pi 2 devices out in the field. By default, grain state is persisted in Azure Tablestorage but I decided to use Redis instead.

To build your own StorageProvider for Orleans we need to build a class that implements IStorageProvider. See the full implementation below.

 public class RedisStorage : IStorageProvider

    {
        private ConnectionMultiplexer connectionMultiplexer;
        private IDatabase redisDatabase;

        private const string REDIS_CONNECTION_STRING = "RedisConnectionString";
        private const string REDIS_DATABASE_NUMBER = "DatabaseNumber";

        private string serviceId;

        /// <summary> Name of this storage provider instance. </summary>
        /// <see cref="IProvider#Name"/>
        public string Name { get; private set; }

        /// <summary> Logger used by this storage provider instance. </summary>
        /// <see cref="IStorageProvider#Log"/>
        public Logger Log { get; private set; }


        /// <summary> Initialization function for this storage provider. </summary>
        /// <see cref="IProvider#Init"/>
        public async Task Init(string name, IProviderRuntime providerRuntime, IProviderConfiguration config)
        {
            Name = name;
            serviceId = providerRuntime.ServiceId.ToString();

            if (!config.Properties.ContainsKey(REDIS_CONNECTION_STRING) ||
                string.IsNullOrWhiteSpace(config.Properties[REDIS_CONNECTION_STRING]))
            {
                throw new ArgumentException("RedisConnectionString is not set.");
            }
            var connectionString = config.Properties[REDIS_CONNECTION_STRING];

            connectionMultiplexer = await ConnectionMultiplexer.ConnectAsync(connectionString);

            if (!config.Properties.ContainsKey(REDIS_DATABASE_NUMBER) ||
                string.IsNullOrWhiteSpace(config.Properties[REDIS_DATABASE_NUMBER]))
            {
                //do not throw an ArgumentException but use the default database
                redisDatabase = connectionMultiplexer.GetDatabase();
            }
            else
            {
                var databaseNumber = Convert.ToInt16(config.Properties[REDIS_DATABASE_NUMBER]);
                redisDatabase = connectionMultiplexer.GetDatabase(databaseNumber);
            }

            Log = providerRuntime.GetLogger("StorageProvider.RedisStorage." + serviceId);
        }

        // Internal method to initialize for testing
        internal void InitLogger(Logger logger)
        {
            Log = logger;
        }

        /// <summary> Shutdown this storage provider. </summary>
        /// <see cref="IStorageProvider#Close"/>
        public Task Close()
        {
            connectionMultiplexer.Dispose();
            return TaskDone.Done;
        }

        /// <summary> Read state data function for this storage provider. </summary>
        /// <see cref="IStorageProvider#ReadStateAsync"/>
        public async Task ReadStateAsync(string grainType, GrainReference grainReference, IGrainState grainState)
        {
            var primaryKey = grainReference.ToKeyString();

            if (Log.IsVerbose3)
            {
                Log.Verbose3((int)ProviderErrorCode.RedisStorageProvider_ReadingData, "Reading: GrainType={0} Pk={1} Grainid={2} from Database={3}", grainType, primaryKey, grainReference, redisDatabase.Database);
            }

            RedisValue value = await redisDatabase.StringGetAsync(primaryKey);
            var data = new Dictionary<string, object>();
            if (value.HasValue)
            {
                data = JsonConvert.DeserializeObject<Dictionary<string, object>>(value);
            }

            grainState.SetAll(data);

            grainState.Etag = Guid.NewGuid().ToString();
        }

        /// <summary> Write state data function for this storage provider. </summary>
        /// <see cref="IStorageProvider#WriteStateAsync"/>
        public async Task WriteStateAsync(string grainType, GrainReference grainReference, IGrainState grainState)
        {
            var primaryKey = grainReference.ToKeyString();
            if (Log.IsVerbose3)
            {
                Log.Verbose3((int)ProviderErrorCode.RedisStorageProvider_WritingData, "Writing: GrainType={0} PrimaryKey={1} Grainid={2} ETag={3} to Database={4}", grainType, primaryKey, grainReference, grainState.Etag, redisDatabase.Database);
            }
            var data = grainState.AsDictionary();

            var json = JsonConvert.SerializeObject(data);
            await redisDatabase.StringSetAsync(primaryKey, json);
        }

        /// <summary> Clear state data function for this storage provider. </summary>
        /// <remarks>
        /// </remarks>
        /// <see cref="IStorageProvider#ClearStateAsync"/>
        public Task ClearStateAsync(string grainType, GrainReference grainReference, IGrainState grainState)
        {
            var primaryKey = grainReference.ToKeyString();
            if (Log.IsVerbose3)
            {
                Log.Verbose3((int)ProviderErrorCode.RedisStorageProvider_ClearingData, "Clearing: GrainType={0} Pk={1} Grainid={2} ETag={3} DeleteStateOnClear={4} from Table={5}", grainType, primaryKey, grainReference, grainState.Etag, redisDatabase.Database);
            }
            //remove from cache
            redisDatabase.KeyDelete(primaryKey);
            return TaskDone.Done;
        }
    }


The code is pretty straightforward and you can decorate your grain class with the right attribute.

[StorageProvider(ProviderName = "RedisStorage")]

public class HelloGrain : Orleans.Grain<IHelloState>, HelloWorldInterfaces.IHello


The State of HelloGrain will now be persisted inside Redis instead of Azure TableStorage.

See how my cache gets hit all the time!

I will also upload this to the OrleansContrib page on github at https://github.com/OrleansContrib/Orleans.StorageProvider.Redis. I will keep you posted on the progress on my blog....