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| 1 | +# Command Idempotency Store Improvements |
| 2 | + |
| 3 | +## Overview |
| 4 | + |
| 5 | +The `ICommandIdempotencyStore` interface and its implementations have been significantly improved to address concurrency issues, performance bottlenecks, and memory management concerns. |
| 6 | + |
| 7 | +## Problems Solved |
| 8 | + |
| 9 | +### ✅ 1. Race Conditions Fixed |
| 10 | + |
| 11 | +**Problem**: Race conditions between checking status and setting status |
| 12 | +**Solution**: Added atomic operations |
| 13 | + |
| 14 | +```csharp |
| 15 | +// NEW: Atomic compare-and-swap operations |
| 16 | +Task<bool> TrySetCommandStatusAsync(string commandId, CommandExecutionStatus expectedStatus, CommandExecutionStatus newStatus); |
| 17 | +Task<(CommandExecutionStatus currentStatus, bool wasSet)> GetAndSetStatusAsync(string commandId, CommandExecutionStatus newStatus); |
| 18 | +``` |
| 19 | + |
| 20 | +**Usage in Extensions**: |
| 21 | +```csharp |
| 22 | +// OLD: Race condition prone |
| 23 | +var status = await store.GetCommandStatusAsync(commandId); |
| 24 | +await store.SetCommandStatusAsync(commandId, CommandExecutionStatus.InProgress); |
| 25 | + |
| 26 | +// NEW: Atomic operation |
| 27 | +var (currentStatus, wasSet) = await store.GetAndSetStatusAsync(commandId, CommandExecutionStatus.InProgress); |
| 28 | +``` |
| 29 | + |
| 30 | +### ✅ 2. Batch Operations Added |
| 31 | + |
| 32 | +**Problem**: No batching support - each command processed separately |
| 33 | +**Solution**: Batch operations for better performance |
| 34 | + |
| 35 | +```csharp |
| 36 | +// NEW: Batch operations |
| 37 | +Task<Dictionary<string, CommandExecutionStatus>> GetMultipleStatusAsync(IEnumerable<string> commandIds); |
| 38 | +Task<Dictionary<string, T?>> GetMultipleResultsAsync<T>(IEnumerable<string> commandIds); |
| 39 | + |
| 40 | +// NEW: Batch execution extension |
| 41 | +Task<Dictionary<string, T>> ExecuteBatchIdempotentAsync<T>( |
| 42 | + IEnumerable<(string commandId, Func<Task<T>> operation)> operations); |
| 43 | +``` |
| 44 | + |
| 45 | +**Usage Example**: |
| 46 | +```csharp |
| 47 | +var operations = new[] |
| 48 | +{ |
| 49 | + ("cmd1", () => ProcessOrder1()), |
| 50 | + ("cmd2", () => ProcessOrder2()), |
| 51 | + ("cmd3", () => ProcessOrder3()) |
| 52 | +}; |
| 53 | + |
| 54 | +var results = await store.ExecuteBatchIdempotentAsync(operations); |
| 55 | +``` |
| 56 | + |
| 57 | +### ✅ 3. Memory Leak Prevention |
| 58 | + |
| 59 | +**Problem**: No automatic cleanup of old commands |
| 60 | +**Solution**: Comprehensive cleanup system |
| 61 | + |
| 62 | +```csharp |
| 63 | +// NEW: Cleanup operations |
| 64 | +Task<int> CleanupExpiredCommandsAsync(TimeSpan maxAge); |
| 65 | +Task<int> CleanupCommandsByStatusAsync(CommandExecutionStatus status, TimeSpan maxAge); |
| 66 | +Task<Dictionary<CommandExecutionStatus, int>> GetCommandCountByStatusAsync(); |
| 67 | +``` |
| 68 | + |
| 69 | +**Automatic Cleanup Service**: |
| 70 | +```csharp |
| 71 | +// NEW: Background cleanup service |
| 72 | +services.AddCommandIdempotency<InMemoryCommandIdempotencyStore>(options => |
| 73 | +{ |
| 74 | + options.CleanupInterval = TimeSpan.FromMinutes(10); |
| 75 | + options.CompletedCommandMaxAge = TimeSpan.FromHours(24); |
| 76 | + options.FailedCommandMaxAge = TimeSpan.FromHours(1); |
| 77 | + options.InProgressCommandMaxAge = TimeSpan.FromMinutes(30); |
| 78 | +}); |
| 79 | +``` |
| 80 | + |
| 81 | +### ✅ 4. Simplified Implementation |
| 82 | + |
| 83 | +**Problem**: Complex retry logic and polling |
| 84 | +**Solution**: Simplified with better defaults |
| 85 | + |
| 86 | +```csharp |
| 87 | +// NEW: Improved retry with jitter |
| 88 | +public static async Task<T> ExecuteIdempotentWithRetryAsync<T>( |
| 89 | + this ICommandIdempotencyStore store, |
| 90 | + string commandId, |
| 91 | + Func<Task<T>> operation, |
| 92 | + int maxRetries = 3, |
| 93 | + TimeSpan? baseDelay = null) |
| 94 | +{ |
| 95 | + // Exponential backoff with jitter to prevent thundering herd |
| 96 | + var delay = TimeSpan.FromMilliseconds( |
| 97 | + baseDelay.Value.TotalMilliseconds * Math.Pow(2, retryCount - 1) * |
| 98 | + (0.8 + Random.Shared.NextDouble() * 0.4)); // Jitter: 80%-120% |
| 99 | +} |
| 100 | +``` |
| 101 | + |
| 102 | +**Adaptive Polling**: |
| 103 | +```csharp |
| 104 | +// NEW: Adaptive polling - starts fast, slows down |
| 105 | +private static async Task<T> WaitForCompletionAsync<T>(...) |
| 106 | +{ |
| 107 | + var pollInterval = TimeSpan.FromMilliseconds(10); // Start fast |
| 108 | + const int maxInterval = 1000; // Max 1 second |
| 109 | + |
| 110 | + // Exponential backoff for polling |
| 111 | + pollInterval = TimeSpan.FromMilliseconds( |
| 112 | + Math.Min(pollInterval.TotalMilliseconds * 1.5, maxInterval)); |
| 113 | +} |
| 114 | +``` |
| 115 | + |
| 116 | +## New Features |
| 117 | + |
| 118 | +### 🎯 Health Monitoring |
| 119 | + |
| 120 | +```csharp |
| 121 | +var metrics = await store.GetHealthMetricsAsync(); |
| 122 | +Console.WriteLine($"Total: {metrics.TotalCommands}, Failed: {metrics.FailureRate:F1}%"); |
| 123 | +``` |
| 124 | + |
| 125 | +### 🎯 Easy Service Registration |
| 126 | + |
| 127 | +```csharp |
| 128 | +// Simple registration with automatic cleanup |
| 129 | +services.AddCommandIdempotency<InMemoryCommandIdempotencyStore>(); |
| 130 | + |
| 131 | +// Custom cleanup configuration |
| 132 | +services.AddCommandIdempotency<RedisCommandIdempotencyStore>(options => |
| 133 | +{ |
| 134 | + options.CompletedCommandMaxAge = TimeSpan.FromHours(48); |
| 135 | + options.LogHealthMetrics = true; |
| 136 | +}); |
| 137 | +``` |
| 138 | + |
| 139 | +### 🎯 Orleans Integration Enhancements |
| 140 | + |
| 141 | +The Orleans implementation now supports all new operations: |
| 142 | +- Atomic operations leveraging Orleans grain concurrency model |
| 143 | +- Batch operations using Task.WhenAll for parallel grain calls |
| 144 | +- Automatic cleanup (no-op since Orleans handles grain lifecycle) |
| 145 | + |
| 146 | +## Performance Improvements |
| 147 | + |
| 148 | +### Before: |
| 149 | +- Race conditions causing duplicate executions |
| 150 | +- Individual calls for each command check |
| 151 | +- No cleanup - memory grows indefinitely |
| 152 | +- 5-minute polling timeout (too long) |
| 153 | +- Fixed retry intervals causing thundering herd |
| 154 | + |
| 155 | +### After: |
| 156 | +- ✅ Atomic operations prevent race conditions |
| 157 | +- ✅ Batch operations reduce round trips |
| 158 | +- ✅ Automatic cleanup prevents memory leaks |
| 159 | +- ✅ 30-second polling timeout (more reasonable) |
| 160 | +- ✅ Exponential backoff with jitter prevents thundering herd |
| 161 | +- ✅ Adaptive polling (starts fast, slows down) |
| 162 | + |
| 163 | +## Breaking Changes |
| 164 | + |
| 165 | +### ❌ None - Fully Backward Compatible |
| 166 | + |
| 167 | +All existing code continues to work without changes. New features are additive. |
| 168 | + |
| 169 | +## Usage Examples |
| 170 | + |
| 171 | +### Basic Usage (Unchanged) |
| 172 | +```csharp |
| 173 | +var result = await store.ExecuteIdempotentAsync("cmd-123", async () => |
| 174 | +{ |
| 175 | + return await ProcessPayment(); |
| 176 | +}); |
| 177 | +``` |
| 178 | + |
| 179 | +### New Batch Processing |
| 180 | +```csharp |
| 181 | +var batchOperations = orders.Select(order => |
| 182 | + (order.Id, () => ProcessOrder(order))); |
| 183 | + |
| 184 | +var results = await store.ExecuteBatchIdempotentAsync(batchOperations); |
| 185 | +``` |
| 186 | + |
| 187 | +### Health Monitoring |
| 188 | +```csharp |
| 189 | +var metrics = await store.GetHealthMetricsAsync(); |
| 190 | +if (metrics.StuckCommandsPercentage > 10) |
| 191 | +{ |
| 192 | + logger.LogWarning("High percentage of stuck commands: {Percentage}%", |
| 193 | + metrics.StuckCommandsPercentage); |
| 194 | +} |
| 195 | +``` |
| 196 | + |
| 197 | +### Manual Cleanup |
| 198 | +```csharp |
| 199 | +// Clean up commands older than 1 hour |
| 200 | +var cleanedCount = await store.AutoCleanupAsync( |
| 201 | + completedCommandMaxAge: TimeSpan.FromHours(1), |
| 202 | + failedCommandMaxAge: TimeSpan.FromMinutes(30)); |
| 203 | +``` |
| 204 | + |
| 205 | +## Recommendations |
| 206 | + |
| 207 | +1. **Use automatic cleanup** for production deployments |
| 208 | +2. **Monitor health metrics** to detect issues early |
| 209 | +3. **Use batch operations** when processing multiple commands |
| 210 | +4. **Configure appropriate timeout values** based on your operations |
| 211 | +5. **Consider Orleans implementation** for distributed scenarios |
| 212 | + |
| 213 | +## Migration Path |
| 214 | + |
| 215 | +1. ✅ **No immediate action required** - everything works as before |
| 216 | +2. ✅ **Add cleanup service** when convenient: |
| 217 | + ```csharp |
| 218 | + services.AddCommandIdempotency<YourStore>(); |
| 219 | + ``` |
| 220 | +3. ✅ **Use batch operations** for new high-volume scenarios |
| 221 | +4. ✅ **Monitor health metrics** for operational insights |
| 222 | + |
| 223 | +The improvements provide a production-ready, scalable command idempotency solution while maintaining full backward compatibility. |
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