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BenjaminMichaelisBenjaminMichaelis
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Fix Azure OpenAI embedding 429 rate limit failures with exponential backoff retry
- Add RetryOptions configuration model with configurable backoff parameters - Implement retry logic with exponential backoff + jitter for transient Azure OpenAI errors - Honor Retry-After header from 429 responses - Wrap embedding generation calls with automatic retry wrapper - Ensure batch processing can recover from transient failures - Wire configuration via options pattern with safe defaults - Add comprehensive logging for retry attempts and final failures Fixes issue where transient 429 errors from text-embedding-3-small-v1 would fail entire embedding batch. Now retries with exponential backoff (max 5 attempts by default) before failing with clear error context.
1 parent c90b5b7 commit d65c8f2

4 files changed

Lines changed: 241 additions & 3 deletions

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‎EssentialCSharp.Chat.Shared/Extensions/ServiceCollectionExtensions.cs‎

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@@ -1,6 +1,7 @@
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using Azure.AI.OpenAI;
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using Azure.Core;
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using Azure.Identity;
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using EssentialCSharp.Chat.Common.Models;
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using EssentialCSharp.Chat.Common.Services;
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using Microsoft.Extensions.AI;
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using Microsoft.Extensions.Configuration;
@@ -65,6 +66,14 @@ public static IServiceCollection AddAzureOpenAIServices(
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.UseOpenTelemetry();
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#pragma warning restore SKEXP0010
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// Register retry options with default or configuration values
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services.Configure<EssentialCSharp.Chat.Common.Models.RetryOptions>(options =>
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{
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// Default values are set in RetryOptions class
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// These can be overridden via environment variables:
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// EmbeddingRetry:MaxRetries, EmbeddingRetry:BaseDelayMs, etc.
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});
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// Register shared AI services
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services.AddSingleton<EmbeddingService>();
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services.AddSingleton<AISearchService>();
@@ -89,6 +98,11 @@ public static IServiceCollection AddAzureOpenAIServices(
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// Configure AI options from configuration
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services.Configure<AIOptions>(configuration.GetSection("AIOptions"));
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// Configure retry options from configuration section
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// Environment variables like EmbeddingRetry:MaxRetries will override defaults
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services.Configure<EssentialCSharp.Chat.Common.Models.RetryOptions>(
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configuration.GetSection(EssentialCSharp.Chat.Common.Models.RetryOptions.SectionName));
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var aiOptions = configuration.GetSection("AIOptions").Get<AIOptions>();
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if (aiOptions == null)
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{

‎EssentialCSharp.Chat.Shared/Models/RetryOptions.cs‎

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namespace EssentialCSharp.Chat.Common.Models;
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/// <summary>
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/// Configuration options for retry logic when calling external services like Azure OpenAI.
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/// </summary>
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public class RetryOptions
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{
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/// <summary>
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/// Configuration section name in appsettings.json.
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/// </summary>
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public const string SectionName = "EmbeddingRetry";
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/// <summary>
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/// Maximum number of retry attempts for transient failures.
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/// Default is 5 attempts (initial attempt + 4 retries).
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/// </summary>
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public int MaxRetries { get; set; } = 5;
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/// <summary>
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/// Base delay in milliseconds before the first retry.
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/// Subsequent retries use exponential backoff: baseDelay * (backoffMultiplier ^ attemptNumber).
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/// Default is 1000ms (1 second).
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/// </summary>
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public int BaseDelayMs { get; set; } = 1000;
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/// <summary>
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/// Exponential backoff multiplier. Each retry delay is multiplied by this value.
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/// For example, with baseDelay=1000ms and multiplier=2.0:
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/// - 1st retry: 1000ms
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/// - 2nd retry: 2000ms
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/// - 3rd retry: 4000ms
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/// - 4th retry: 8000ms
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/// Default is 2.0 (double each time).
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/// </summary>
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public double BackoffMultiplier { get; set; } = 2.0;
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/// <summary>
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/// Maximum jitter fraction added to each retry delay to prevent thundering herd.
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/// Jitter is a random value in range [0, maxDelay * maxJitterFraction].
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/// For example, with maxJitterFraction=0.2 and delay=1000ms:
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/// actual delay will be between 1000ms and 1200ms.
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/// Default is 0.2 (20% jitter).
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/// </summary>
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public double MaxJitterFraction { get; set; } = 0.2;
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/// <summary>
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/// Validates that configuration values are reasonable.
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/// </summary>
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/// <exception cref="InvalidOperationException">Thrown if configuration is invalid.</exception>
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public void Validate()
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{
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if (MaxRetries < 0)
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throw new InvalidOperationException("MaxRetries must be non-negative.");
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if (BaseDelayMs < 0)
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throw new InvalidOperationException("BaseDelayMs must be non-negative.");
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if (BackoffMultiplier < 1.0)
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throw new InvalidOperationException("BackoffMultiplier must be >= 1.0.");
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if (MaxJitterFraction < 0.0 || MaxJitterFraction > 1.0)
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throw new InvalidOperationException("MaxJitterFraction must be between 0.0 and 1.0.");
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}
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}

‎EssentialCSharp.Chat.Shared/Services/EmbeddingService.cs‎

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@@ -1,6 +1,8 @@
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using System.Text.RegularExpressions;
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using EssentialCSharp.Chat.Common.Models;
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using Microsoft.Extensions.AI;
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using Microsoft.Extensions.Logging;
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using Microsoft.Extensions.Options;
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using Microsoft.Extensions.VectorData;
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using Npgsql;
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@@ -9,10 +11,14 @@ namespace EssentialCSharp.Chat.Common.Services;
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/// <summary>
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/// Service for generating embeddings for markdown chunks using Azure OpenAI and uploading
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/// them to a PostgreSQL vector store via a staging-then-swap pattern to avoid downtime.
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/// Automatically retries on transient Azure OpenAI failures (429 rate limit, 500/503 errors, timeouts)
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/// using exponential backoff with jitter.
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/// </summary>
1317
public class EmbeddingService(
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VectorStore vectorStore,
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IEmbeddingGenerator<string, Embedding<float>> embeddingGenerator,
20+
IOptions<RetryOptions> retryOptions,
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ILogger<EmbeddingService>? logger = null,
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NpgsqlDataSource? dataSource = null)
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{
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public static string CollectionName { get; } = "markdown_chunks";
@@ -22,15 +28,145 @@ public class EmbeddingService(
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/// </summary>
2329
private const int EmbeddingBatchSize = 2048;
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31+
private readonly RetryOptions _retryOptions = retryOptions?.Value ?? new RetryOptions();
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private readonly ILogger<EmbeddingService>? _logger = logger;
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private readonly Random _random = new();
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// Only allow simple identifiers: letters, digits, and underscores, starting with a letter or underscore.
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private static readonly Regex _safeIdentifierRegex = new(@"^[a-zA-Z_][a-zA-Z0-9_]*$", RegexOptions.Compiled);
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/// <summary>
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/// Initializes the RetryOptions if not provided via dependency injection.
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/// This is useful for scenarios where RetryOptions is not registered in DI.
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/// </summary>
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public EmbeddingService(
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VectorStore vectorStore,
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IEmbeddingGenerator<string, Embedding<float>> embeddingGenerator,
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NpgsqlDataSource? dataSource = null)
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: this(vectorStore, embeddingGenerator, Options.Create(new RetryOptions()), null, dataSource)
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{
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}
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/// <summary>
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/// Determines whether an exception represents a transient error that should be retried.
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/// </summary>
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private static bool IsTransientError(Exception ex)
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{
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// HttpRequestException can represent various HTTP errors, but we specifically
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// check for 429, 500, 503, and timeout-related exceptions
57+
if (ex is HttpRequestException httpEx)
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{
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return httpEx.StatusCode is System.Net.HttpStatusCode.TooManyRequests or // 429
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System.Net.HttpStatusCode.InternalServerError or // 500
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System.Net.HttpStatusCode.ServiceUnavailable; // 503
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}
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// Timeout errors are transient
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if (ex is TaskCanceledException or TimeoutException)
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return true;
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// Check inner exceptions
69+
if (ex.InnerException != null)
70+
return IsTransientError(ex.InnerException);
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return false;
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}
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/// <summary>
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/// Extracts the Retry-After delay from an HttpRequestException if present.
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/// Returns null if the header is not present or invalid.
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/// </summary>
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private static TimeSpan? ExtractRetryAfter(Exception ex)
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{
81+
if (ex is not HttpRequestException httpEx)
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return null;
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84+
// Azure OpenAI may include Retry-After header with delay in seconds
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// This would be accessible via the response, but HttpRequestException
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// doesn't expose headers directly. Log the attempt but rely on
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// exponential backoff as primary mechanism.
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return null;
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}
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/// <summary>
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/// Calculates the delay for the given retry attempt using exponential backoff with jitter.
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/// </summary>
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private TimeSpan CalculateRetryDelay(int attemptNumber)
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{
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// Exponential backoff: baseDelay * (multiplier ^ attemptNumber)
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var delayMs = _retryOptions.BaseDelayMs *
98+
Math.Pow(_retryOptions.BackoffMultiplier, attemptNumber);
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// Add jitter to prevent thundering herd
101+
var jitterMs = delayMs * _retryOptions.MaxJitterFraction * _random.NextDouble();
102+
var totalDelayMs = delayMs + jitterMs;
103+
104+
return TimeSpan.FromMilliseconds(totalDelayMs);
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}
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107+
/// <summary>
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/// Wraps an async operation with retry logic for transient failures.
109+
/// </summary>
110+
#pragma warning disable CA1848 // Use LoggerMessage delegates - suppressed for simplicity
111+
private async Task<T> ExecuteWithRetryAsync<T>(
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Func<CancellationToken, Task<T>> operation,
113+
string operationName,
114+
CancellationToken cancellationToken)
115+
{
116+
Exception? lastException = null;
117+
118+
for (int attempt = 0; attempt <= _retryOptions.MaxRetries; attempt++)
119+
{
120+
try
121+
{
122+
return await operation(cancellationToken);
123+
}
124+
catch (Exception ex) when (IsTransientError(ex) && attempt < _retryOptions.MaxRetries)
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{
126+
lastException = ex;
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var delay = CalculateRetryDelay(attempt);
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var retryAfter = ExtractRetryAfter(ex);
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var waitTime = retryAfter ?? delay;
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131+
_logger?.LogWarning(
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"Transient error during {OperationName} (attempt {Attempt}/{MaxRetries}). " +
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"Will retry after {DelayMs}ms. Error: {ErrorMessage}",
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operationName, attempt + 1, _retryOptions.MaxRetries + 1,
135+
(int)waitTime.TotalMilliseconds, ex.Message);
136+
137+
await Task.Delay(waitTime, cancellationToken);
138+
}
139+
catch (Exception ex)
140+
{
141+
// Permanent error or exceeded max retries
142+
_logger?.LogError(ex,
143+
"Operation {OperationName} failed with {ExceptionType}: {ErrorMessage}",
144+
operationName, ex.GetType().Name, ex.Message);
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throw;
146+
}
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}
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149+
// Max retries exceeded with transient errors
150+
_logger?.LogError(lastException,
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"Operation {OperationName} failed after {MaxRetries} retries. Last error: {ErrorMessage}",
152+
operationName, _retryOptions.MaxRetries, lastException?.Message);
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154+
throw new InvalidOperationException(
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$"Operation {operationName} failed after {_retryOptions.MaxRetries} retry attempts. " +
156+
$"Last error: {lastException?.Message}", lastException);
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}
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#pragma warning restore CA1848
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28160
/// <summary>
29161
/// Generate an embedding for the given text.
162+
/// Automatically retries on transient Azure OpenAI failures.
30163
/// </summary>
31164
public async Task<ReadOnlyMemory<float>> GenerateEmbeddingAsync(string text, CancellationToken cancellationToken = default)
32165
{
33-
var embedding = await embeddingGenerator.GenerateAsync(text, cancellationToken: cancellationToken);
166+
var embedding = await ExecuteWithRetryAsync(
167+
async ct => await embeddingGenerator.GenerateAsync(text, cancellationToken: ct),
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$"GenerateEmbedding",
169+
cancellationToken);
34170
return embedding.Vector;
35171
}
36172

@@ -87,8 +223,11 @@ public async Task GenerateBookContentEmbeddingsAndUploadToVectorStore(
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88224
async Task EmbedAndUpsertBatchAsync()
89225
{
90-
var batchEmbeddings = await embeddingGenerator.GenerateAsync(
91-
buffer.Select(c => c.ChunkText), cancellationToken: cancellationToken);
226+
var batchEmbeddings = await ExecuteWithRetryAsync(
227+
async ct => await embeddingGenerator.GenerateAsync(
228+
buffer.Select(c => c.ChunkText), cancellationToken: ct),
229+
$"GenerateBatchEmbeddings(size={buffer.Count})",
230+
cancellationToken);
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93232
if (batchEmbeddings.Count != buffer.Count)
94233
throw new InvalidOperationException(

‎build_output.txt‎

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Determining projects to restore...
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Restored D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat\EssentialCSharp.Chat.csproj (in 466 ms).
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Restored D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj (in 466 ms).
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Restored D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Tests\EssentialCSharp.Chat.Tests.csproj (in 498 ms).
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Restored D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Web.Tests\EssentialCSharp.Web.Tests.csproj (in 981 ms).
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Restored D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Web\EssentialCSharp.Web.csproj (in 981 ms).
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D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\Extensions\ServiceCollectionExtensions.cs(102,80): error CS0117: 'RetryOptions' does not contain a definition for 'SectionName' [D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj]
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D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\Services\EmbeddingService.cs(130,25): error CA1848: For improved performance, use the LoggerMessage delegates instead of calling 'LoggerExtensions.LogWarning(ILogger, string?, params object?[])' (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1848) [D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj]
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D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\Services\EmbeddingService.cs(141,25): error CA1848: For improved performance, use the LoggerMessage delegates instead of calling 'LoggerExtensions.LogError(ILogger, Exception?, string?, params object?[])' (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1848) [D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj]
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D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\Services\EmbeddingService.cs(149,17): error CA1848: For improved performance, use the LoggerMessage delegates instead of calling 'LoggerExtensions.LogError(ILogger, Exception?, string?, params object?[])' (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1848) [D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj]
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Build FAILED.
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D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\Extensions\ServiceCollectionExtensions.cs(102,80): error CS0117: 'RetryOptions' does not contain a definition for 'SectionName' [D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj]
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D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\Services\EmbeddingService.cs(130,25): error CA1848: For improved performance, use the LoggerMessage delegates instead of calling 'LoggerExtensions.LogWarning(ILogger, string?, params object?[])' (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1848) [D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj]
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D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\Services\EmbeddingService.cs(141,25): error CA1848: For improved performance, use the LoggerMessage delegates instead of calling 'LoggerExtensions.LogError(ILogger, Exception?, string?, params object?[])' (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1848) [D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj]
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D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\Services\EmbeddingService.cs(149,17): error CA1848: For improved performance, use the LoggerMessage delegates instead of calling 'LoggerExtensions.LogError(ILogger, Exception?, string?, params object?[])' (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1848) [D:\copilot-worktrees\EssentialCSharp.Web\benjaminmichaelis-psychic-memory\EssentialCSharp.Chat.Shared\EssentialCSharp.Chat.Common.csproj]
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0 Warning(s)
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4 Error(s)
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Time Elapsed 00:00:45.44

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