Add debugging logs for lambda API (#2048)

Author: reakaleek

src/api/Elastic.Documentation.Api.Infrastructure/Adapters/AskAi/LlmGatewayAskAiGateway.cs

@@ -25,7 +25,20 @@ public async Task<Stream> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
 		request.Headers.Add("User-Agent", "elastic-docs-proxy/1.0");
 		request.Headers.Add("Accept", "text/event-stream");
 		request.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/json");
+
+		// Use HttpCompletionOption.ResponseHeadersRead to get headers immediately
+		// This allows us to start streaming as soon as headers are received
 		var response = await httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, ctx);
+
+		// Ensure the response is successful before streaming
+		if (!response.IsSuccessStatusCode)
+		{
+			var errorContent = await response.Content.ReadAsStringAsync(ctx);
+			throw new HttpRequestException($"LLM Gateway returned {response.StatusCode}: {errorContent}");
+		}
+
+		// Return the response stream directly - this enables true streaming
+		// The stream will be consumed as data arrives from the LLM Gateway
 		return await response.Content.ReadAsStreamAsync(ctx);
 	}
 }

src/api/Elastic.Documentation.Api.Infrastructure/ServicesExtension.cs

@@ -78,12 +78,23 @@ private static void AddParameterProvider(IServiceCollection services, AppEnv app
 			case AppEnv.Edge:
 				{
 					logger?.LogInformation("Configuring LambdaExtensionParameterProvider for environment {AppEnvironment}", appEnv);
-					_ = services.AddHttpClient(LambdaExtensionParameterProvider.HttpClientName, client =>
+					try
 					{
-						client.BaseAddress = new Uri("http://localhost:2773");
-						client.DefaultRequestHeaders.Add("X-Aws-Parameters-Secrets-Token", Environment.GetEnvironmentVariable("AWS_SESSION_TOKEN"));
-					});
-					_ = services.AddSingleton<IParameterProvider, LambdaExtensionParameterProvider>();
+						_ = services.AddHttpClient(LambdaExtensionParameterProvider.HttpClientName, client =>
+						{
+							client.BaseAddress = new Uri("http://localhost:2773");
+							client.DefaultRequestHeaders.Add("X-Aws-Parameters-Secrets-Token", Environment.GetEnvironmentVariable("AWS_SESSION_TOKEN"));
+						});
+						logger?.LogInformation("Lambda extension HTTP client configured");
+
+						_ = services.AddSingleton<IParameterProvider, LambdaExtensionParameterProvider>();
+						logger?.LogInformation("LambdaExtensionParameterProvider registered successfully");
+					}
+					catch (Exception ex)
+					{
+						logger?.LogError(ex, "Failed to configure LambdaExtensionParameterProvider for environment {AppEnvironment}", appEnv);
+						throw;
+					}
 					break;
 				}
 			case AppEnv.Dev:
@@ -104,10 +115,26 @@ private static void AddAskAiUsecase(IServiceCollection services, AppEnv appEnv)
 	{
 		var logger = GetLogger(services);
 		logger?.LogInformation("Configuring AskAi use case for environment {AppEnvironment}", appEnv);
-		_ = services.AddSingleton<GcpIdTokenProvider>();
-		_ = services.AddScoped<LlmGatewayOptions>();
-		_ = services.AddScoped<AskAiUsecase>();
-		_ = services.AddScoped<IAskAiGateway<Stream>, LlmGatewayAskAiGateway>();
+
+		try
+		{
+			_ = services.AddSingleton<GcpIdTokenProvider>();
+			logger?.LogInformation("GcpIdTokenProvider registered successfully");
+
+			_ = services.AddScoped<LlmGatewayOptions>();
+			logger?.LogInformation("LlmGatewayOptions registered successfully");
+
+			_ = services.AddScoped<AskAiUsecase>();
+			logger?.LogInformation("AskAiUsecase registered successfully");
+
+			_ = services.AddScoped<IAskAiGateway<Stream>, LlmGatewayAskAiGateway>();
+			logger?.LogInformation("LlmGatewayAskAiGateway registered successfully");
+		}
+		catch (Exception ex)
+		{
+			logger?.LogError(ex, "Failed to configure AskAi use case for environment {AppEnvironment}", appEnv);
+			throw;
+		}
 	}
 	private static void AddSearchUsecase(IServiceCollection services, AppEnv appEnv)
 	{

src/api/Elastic.Documentation.Api.Lambda/Program.cs

@@ -10,20 +10,52 @@
 using Elastic.Documentation.Api.Infrastructure;
 using Elastic.Documentation.ServiceDefaults;
 
-var builder = WebApplication.CreateSlimBuilder(args);
+try
+{
+	var process = System.Diagnostics.Process.GetCurrentProcess();
+	Console.WriteLine($"Starting Lambda application... Memory: {process.WorkingSet64 / 1024 / 1024} MB");
 
-builder.AddDocumentationServiceDefaults(ref args);
+	var builder = WebApplication.CreateSlimBuilder(args);
+	process.Refresh();
+	Console.WriteLine($"WebApplication builder created. Memory: {process.WorkingSet64 / 1024 / 1024} MB");
 
-builder.Services.AddAWSLambdaHosting(LambdaEventSource.RestApi, new SourceGeneratorLambdaJsonSerializer<LambdaJsonSerializerContext>());
-builder.Services.AddElasticDocsApiUsecases(Environment.GetEnvironmentVariable("ENVIRONMENT"));
-builder.WebHost.UseKestrelHttpsConfiguration();
+	_ = builder.AddDocumentationServiceDefaults(ref args);
+	process.Refresh();
+	Console.WriteLine($"Documentation service defaults added. Memory: {process.WorkingSet64 / 1024 / 1024} MB");
 
-var app = builder.Build();
+	_ = builder.Services.AddAWSLambdaHosting(LambdaEventSource.RestApi, new SourceGeneratorLambdaJsonSerializer<LambdaJsonSerializerContext>());
+	process.Refresh();
+	Console.WriteLine($"AWS Lambda hosting configured. Memory: {process.WorkingSet64 / 1024 / 1024} MB");
 
-var v1 = app.MapGroup("/docs/_api/v1");
-v1.MapElasticDocsApiEndpoints();
+	var environment = Environment.GetEnvironmentVariable("ENVIRONMENT");
+	Console.WriteLine($"Environment: {environment}");
 
-app.Run();
+	builder.Services.AddElasticDocsApiUsecases(environment);
+	process.Refresh();
+	Console.WriteLine($"Elastic docs API use cases added. Memory: {process.WorkingSet64 / 1024 / 1024} MB");
+
+	_ = builder.WebHost.UseKestrelHttpsConfiguration();
+	process.Refresh();
+	Console.WriteLine($"Kestrel HTTPS configuration applied. Memory: {process.WorkingSet64 / 1024 / 1024} MB");
+
+	var app = builder.Build();
+	process.Refresh();
+	Console.WriteLine($"Application built successfully. Memory: {process.WorkingSet64 / 1024 / 1024} MB");
+
+	var v1 = app.MapGroup("/docs/_api/v1");
+	v1.MapElasticDocsApiEndpoints();
+	Console.WriteLine("API endpoints mapped");
+
+	Console.WriteLine("Application startup completed successfully");
+	app.Run();
+}
+catch (Exception ex)
+{
+	Console.WriteLine($"FATAL ERROR during startup: {ex}");
+	Console.WriteLine($"Exception type: {ex.GetType().Name}");
+	Console.WriteLine($"Stack trace: {ex.StackTrace}");
+	throw;
+}
 
 [JsonSerializable(typeof(APIGatewayProxyRequest))]
 [JsonSerializable(typeof(APIGatewayProxyResponse))]