[PM-6153] Dedicated redis connection for rate limiter (#3763)

* rearrange how redis is registered

* separate redis connection string for rate limiter

src/Core/Settings/GlobalSettings.cs

@@ -520,6 +520,7 @@ public class GlobalSettings : IGlobalSettings
 
     public class DistributedIpRateLimitingSettings
     {
+        public string RedisConnectionString { get; set; }
         public bool Enabled { get; set; } = true;
 
         /// <summary>

src/Core/Utilities/CustomRedisProcessingStrategy.cs

@@ -2,6 +2,7 @@
 using AspNetCoreRateLimit.Redis;
 using Bit.Core.Settings;
 using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using StackExchange.Redis;
 
@@ -26,6 +27,7 @@ public class CustomRedisProcessingStrategy : RedisProcessingStrategy
     private const string _redisTimeoutCacheKey = "IpRateLimitRedisTimeout";
 
     public CustomRedisProcessingStrategy(
+        [FromKeyedServices("rate-limiter")]
         IConnectionMultiplexer connectionMultiplexer,
         IRateLimitConfiguration config,
         ILogger<CustomRedisProcessingStrategy> logger,

src/SharedWeb/Utilities/ServiceCollectionExtensions.cs

@@ -49,7 +49,6 @@ using Microsoft.AspNetCore.HttpOverrides;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.AspNetCore.Mvc.Localization;
 using Microsoft.Extensions.Caching.Distributed;
-using Microsoft.Extensions.Caching.StackExchangeRedis;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -667,7 +666,8 @@ public static class ServiceCollectionExtensions
         services.AddHostedService<IpRateLimitSeedStartupService>();
         services.AddSingleton<IRateLimitConfiguration, RateLimitConfiguration>();
 
-        if (!globalSettings.DistributedIpRateLimiting.Enabled || string.IsNullOrEmpty(globalSettings.Redis.ConnectionString))
+        if (!globalSettings.DistributedIpRateLimiting.Enabled ||
+            string.IsNullOrEmpty(globalSettings.DistributedIpRateLimiting.RedisConnectionString))
         {
             services.AddInMemoryRateLimiting();
         }
@@ -679,7 +679,8 @@ public static class ServiceCollectionExtensions
             services.AddSingleton<IClientPolicyStore, MemoryCacheClientPolicyStore>();
 
             // Use a custom Redis processing strategy that skips Ip limiting if Redis is down
-            // Requires a registered IConnectionMultiplexer
+            services.AddKeyedSingleton<IConnectionMultiplexer>("rate-limiter", (_, provider) =>
+                ConnectionMultiplexer.Connect(globalSettings.DistributedIpRateLimiting.RedisConnectionString));
             services.AddSingleton<IProcessingStrategy, CustomRedisProcessingStrategy>();
         }
     }
@@ -698,22 +699,9 @@ public static class ServiceCollectionExtensions
             return;
         }
 
-        // Register the IConnectionMultiplexer explicitly so it can be accessed via DI
+        services.AddStackExchangeRedisCache(options =>
-        // (e.g. for the IP rate limiting store)
-        services.AddSingleton<IConnectionMultiplexer>(
-            _ => ConnectionMultiplexer.Connect(globalSettings.Redis.ConnectionString));
-
-        // Explicitly register IDistributedCache to re-use existing IConnectionMultiplexer
-        // to reduce the number of redundant connections to the Redis instance
-        services.AddSingleton<IDistributedCache>(s =>
         {
-            return new RedisCache(new RedisCacheOptions
+            options.Configuration = globalSettings.Redis.ConnectionString;
-            {
-                // Use "ProjectName:" as an instance name to namespace keys and avoid conflicts between projects
-                InstanceName = $"{globalSettings.ProjectName}:",
-                ConnectionMultiplexerFactory = () =>
-                    Task.FromResult(s.GetRequiredService<IConnectionMultiplexer>())
-            });
         });
     }