RedisExtensions.cs

using System;
using System.Threading.Tasks;
using StackExchange.Redis;

namespace Gofer.NET
{
    public static class RedisExtensions
    {
       /// <summary>
        /// Blocks for blockingTimeout amount of time, and tries to take the lock at an interval of tryLockInterval.
        /// If the lock cannot be obtained before the timeout, throws an exception.
        /// </summary>
        /// <exception cref="ApplicationException">
        /// Thrown if the attempt to lock the resource takes longer than blockingTimeout.
        /// </exception>
        public static async Task<RedisLock> LockBlockingAsync(this IConnectionMultiplexer redis, 
            string key, 
            TimeSpan? duration=null,
            TimeSpan? blockingTimeout=null,
            TimeSpan? tryLockInterval=null,
            string token=null)
        {
            duration = duration ?? TimeSpan.FromMinutes(5);
            blockingTimeout = blockingTimeout ?? TimeSpan.FromSeconds(60);
            tryLockInterval = tryLockInterval ?? TimeSpan.FromMilliseconds(200);
            
            RedisValue actualToken = token ?? Guid.NewGuid().ToString();
            var db = redis.GetDatabase();

            var startTime = DateTime.Now;
            while (true)
            {
                if (await db.LockTakeAsync(key, actualToken, duration.Value))
                {
                    return new RedisLock(db, key, actualToken);
                }

                await Task.Delay(tryLockInterval.Value);

                if ((DateTime.Now - startTime) >= blockingTimeout)
                {
                    throw new Exception("Unable to lock resource.");
                }
            }
        }
        
        /// <summary>
        /// Tries to take a lock, then returns null immediately if it's not successful.
        /// </summary>
        /// <param name="redis"></param>
        /// <param name="key"></param>
        /// <param name="duration"></param>
        /// <returns></returns>
        public static async Task<RedisLock> LockNonBlockingAsync(this IConnectionMultiplexer redis, 
            string key, 
            TimeSpan? duration=null,
            string token=null)
        {
            duration = duration ?? TimeSpan.FromMinutes(5);
            
            RedisValue actualToken = token ?? Guid.NewGuid().ToString();
            var db = redis.GetDatabase();

            if (await db.LockTakeAsync(key, actualToken, duration.Value))
            {
                return new RedisLock(db, key, actualToken);
            }

            return null;
        }

    }
}