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Refine agent initialization within ElasticApmModule (#2298)
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@stevejgordon
stevejgordon authored Feb 23, 2024
1 parent 45e8b70 commit 2f7d592
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Showing 3 changed files with 115 additions and 150 deletions.
30 changes: 0 additions & 30 deletions src/Elastic.Apm/Helpers/DbgInstanceNameGenerator.cs
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195 changes: 115 additions & 80 deletions src/integrations/Elastic.Apm.AspNetFullFramework/ElasticApmModule.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Data.SqlClient;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Security.Claims;
Expand All @@ -15,7 +16,6 @@
using Elastic.Apm.Api;
using Elastic.Apm.AspNetFullFramework.Extensions;
using Elastic.Apm.Config.Net4FullFramework;
using Elastic.Apm.DiagnosticSource;
using Elastic.Apm.Extensions;
using Elastic.Apm.Helpers;
using Elastic.Apm.Logging;
Expand All @@ -31,47 +31,144 @@ namespace Elastic.Apm.AspNetFullFramework
/// </summary>
public class ElasticApmModule : IHttpModule
{
private static bool _isCaptureHeadersEnabled;
// ReSharper disable once RedundantDefaultMemberInitializer
private static readonly DbgInstanceNameGenerator DbgInstanceNameGenerator = new();
private static volatile bool ApplicationStarted = false;
private static readonly object ApplicationStartedLock = new();
private static bool IsCaptureHeadersEnabled;
private static bool UsingIntegratedPipeline = true;

private static readonly LazyContextualInit InitOnceHelper = new();
private static readonly MethodInfo OnExecuteRequestStepMethodInfo = typeof(HttpApplication).GetMethod("OnExecuteRequestStep");


private readonly string _dbgInstanceName;
private HttpApplication _application;
private IApmLogger _logger;

private readonly Lazy<Type> _httpRouteDataInterfaceType =
new Lazy<Type>(() => Type.GetType("System.Web.Http.Routing.IHttpRouteData,System.Web.Http"));
new(() => Type.GetType("System.Web.Http.Routing.IHttpRouteData,System.Web.Http"));

private Func<object, string> _routeDataTemplateGetter;
private Func<object, decimal> _routePrecedenceGetter;

private static int InstanceCount;

public ElasticApmModule() =>
// ReSharper disable once ImpureMethodCallOnReadonlyValueField
_dbgInstanceName = DbgInstanceNameGenerator.Generate($"{nameof(ElasticApmModule)}.#");

public void Dispose() => _application = null;
public ElasticApmModule()
{
var instanceCounter = Interlocked.Increment(ref InstanceCount);
_dbgInstanceName = $"{nameof(ElasticApmModule)}.#{instanceCounter}";
}

/// <inheritdoc />
public void Init(HttpApplication application)
{
try
{
InitImpl(application);
// If we've already attempted initialisation and determined we are not in integrated mode, we can return quickly here.
// As `UsingIntegratedPipeline` is initialised as `true`, we pass through here at least once.
if (!UsingIntegratedPipeline)
return;

if (!ApplicationStarted)
{
AttemptAgentInitialization();
_logger.Trace()
?.Log($"{nameof(ElasticApmModule)}.{nameof(Init)} was invoked and called {nameof(AttemptAgentInitialization)}.");
}
else
{
_logger ??= CreateScopedLogger();
_logger.Trace()
?.Log($"{nameof(ElasticApmModule)}.{nameof(Init)} was invoked by an instance when the Agent has already been initialized. " +
"No further initialization required.");
}

if (!Agent.Config.Enabled)
return;

_routeDataTemplateGetter = CreateWebApiAttributeRouteTemplateGetter();
_routePrecedenceGetter = CreateRoutePrecedenceGetter();

application.BeginRequest += OnBeginRequest;
application.EndRequest += OnEndRequest;
application.Error += OnError;

if (OnExecuteRequestStepMethodInfo != null)
{
// OnExecuteRequestStep is available starting with 4.7.1
try
{
#pragma warning disable IDE0300 // Simplify collection initialization
OnExecuteRequestStepMethodInfo.Invoke(application, new object[] { (Action<HttpContextBase, Action>)OnExecuteRequestStep });
#pragma warning restore IDE0300 // Simplify collection initialization
}
catch (Exception e)
{
_logger.Error()
?.LogException(e, "Failed to invoke OnExecuteRequestStep. .NET runtime: {DotNetRuntimeDescription}; IIS: {IisVersion}",
PlatformDetection.DotNetRuntimeDescription, HttpRuntime.IISVersion);
}
}
}
catch (Exception ex)
{
const string linePrefix = "Elastic APM .NET Agent: ";
System.Diagnostics.Trace.WriteLine($"{linePrefix}[CRITICAL] Exception thrown by {nameof(ElasticApmModule)}.{nameof(InitImpl)}."
Trace.WriteLine($"{linePrefix}[CRITICAL] Exception thrown by {nameof(ElasticApmModule)}.{nameof(Init)}."
+ Environment.NewLine + linePrefix + $"+-> Exception: {ex.GetType().FullName}: {ex.Message}"
+ Environment.NewLine + TextUtils.PrefixEveryLine(ex.StackTrace, linePrefix + " ".Repeat(4))
);
}
}

private void AttemptAgentInitialization()
{
// We use a lock here to ensure that if multiple `HttpApplication` instances are created, each calling the `Init` method
// on registered module, that we initialise the agent only once. The first instance wins and any concurrent calls to `Init`
// should block until this is completed such that they only continue once our initialisation is completed.
lock (ApplicationStartedLock)
{
if (ApplicationStarted)
{
_logger ??= CreateScopedLogger();
_logger.Trace()?.Log("Lock aquired, but Agent singleton has already been initialized. Skipping initialization.");
return;
}

var agentComponents = CreateAgentComponents(_dbgInstanceName);

_logger = agentComponents.Logger.Scoped(_dbgInstanceName);
_logger.Trace()?.Log("Initializing singleton Agent.");

// We store this in a static field as it should be consistent for all invocations. We can then log our error once but
// also short-circuit subsequent `Init` calls when we've already determined the app is hosted on an incompatible pipeline.
UsingIntegratedPipeline = HttpRuntime.UsingIntegratedPipeline;

if (!UsingIntegratedPipeline)
{
_logger.Error()
?.Log("Skipping Agent initialization. Elastic APM Module requires the IIS Application Pool to run under an Integrated Pipeline."
+ " .NET runtime: {DotNetRuntimeDescription}; IIS: {IisVersion}",
PlatformDetection.DotNetRuntimeDescription, HttpRuntime.IISVersion);

return;
}

Agent.Setup(agentComponents);

_logger.Debug()
?.Log("Initialized Agent singleton. .NET runtime: {DotNetRuntimeDescription}; IIS: {IisVersion}",
PlatformDetection.DotNetRuntimeDescription, HttpRuntime.IISVersion);

if (!Agent.Instance.Configuration.Enabled)
return;

IsCaptureHeadersEnabled = Agent.Instance.Configuration.CaptureHeaders;

Agent.Instance.SubscribeIncludingAllDefaults();

ApplicationStarted = true;
}
}

private ScopedLogger CreateScopedLogger() => Agent.Instance.Logger.Scoped(_dbgInstanceName);

/// <summary>
/// Creates a new instance of <see cref="AgentComponents"/> configured
/// to use with ASP.NET Full Framework.
Expand All @@ -96,54 +193,6 @@ internal static AgentComponents CreateAgentComponents(string debugName)
return agentComponents;
}

private void InitImpl(HttpApplication application)
{
var isInitedByThisCall = InitOnceForAllInstancesUnderLock(_dbgInstanceName);

_logger = Agent.Instance.Logger.Scoped(_dbgInstanceName);

if (!Agent.Config.Enabled)
return;

if (!HttpRuntime.UsingIntegratedPipeline)
{
_logger.Error()
?.Log("Skipping Initialization. Elastic APM Module requires the application pool to run under an Integrated Pipeline."
+ " .NET runtime: {DotNetRuntimeDescription}; IIS: {IisVersion}",
PlatformDetection.DotNetRuntimeDescription, HttpRuntime.IISVersion);
return;
}

if (isInitedByThisCall)
{
_logger.Debug()
?.Log("Initialized Agent singleton. .NET runtime: {DotNetRuntimeDescription}; IIS: {IisVersion}",
PlatformDetection.DotNetRuntimeDescription, HttpRuntime.IISVersion);
}

_routeDataTemplateGetter = CreateWebApiAttributeRouteTemplateGetter();
_routePrecedenceGetter = CreateRoutePrecedenceGetter();
_application = application;
_application.BeginRequest += OnBeginRequest;
_application.EndRequest += OnEndRequest;
_application.Error += OnError;

if (OnExecuteRequestStepMethodInfo != null)
{
// OnExecuteRequestStep is available starting with 4.7.1
try
{
OnExecuteRequestStepMethodInfo.Invoke(application, new object[] { (Action<HttpContextBase, Action>)OnExecuteRequestStep });
}
catch (Exception e)
{
_logger.Error()
?.LogException(e, "Failed to invoke OnExecuteRequestStep. .NET runtime: {DotNetRuntimeDescription}; IIS: {IisVersion}",
PlatformDetection.DotNetRuntimeDescription, HttpRuntime.IISVersion);
}
}
}

private void RestoreContextIfNeeded(HttpContextBase context)
{
string EventName() => Enum.GetName(typeof(RequestNotification), context.CurrentNotification);
Expand All @@ -153,7 +202,6 @@ private void RestoreContextIfNeeded(HttpContextBase context)
if (urlPath != null && ignoreUrls != null && WildcardMatcher.IsAnyMatch(ignoreUrls, urlPath))
return;


if (Agent.Instance == null)
{
_logger.Trace()?
Expand Down Expand Up @@ -227,7 +275,6 @@ private string TryGetUrlPath(HttpContextBase context)

private void OnExecuteRequestStep(HttpContextBase context, Action step)
{

RestoreContextIfNeeded(context);
step();
}
Expand Down Expand Up @@ -380,7 +427,7 @@ private static void FillSampledTransactionContextRequest(HttpRequest request, IT
{
Socket = new Socket { RemoteAddress = request.UserHostAddress },
HttpVersion = GetHttpVersion(request.ServerVariables["SERVER_PROTOCOL"]),
Headers = _isCaptureHeadersEnabled ? ConvertHeaders(request.Unvalidated.Headers) : null
Headers = IsCaptureHeadersEnabled ? ConvertHeaders(request.Unvalidated.Headers) : null
};
}

Expand Down Expand Up @@ -561,7 +608,7 @@ private static void FillSampledTransactionContextResponse(HttpResponse response,
{
Finished = true,
StatusCode = response.StatusCode,
Headers = _isCaptureHeadersEnabled ? ConvertHeaders(response.Headers) : null
Headers = IsCaptureHeadersEnabled ? ConvertHeaders(response.Headers) : null
};

private void FillSampledTransactionContextUser(HttpContext context, ITransaction transaction)
Expand Down Expand Up @@ -599,20 +646,6 @@ static string GetClaimWithFallbackValue(ClaimsPrincipal principal, string claimT
_logger.Debug()?.Log("Captured user - {CapturedUser}", transaction.Context.User);
}

private static bool InitOnceForAllInstancesUnderLock(string dbgInstanceName) =>
InitOnceHelper.IfNotInited?.Init(() =>
{
var agentComponents = CreateAgentComponents(dbgInstanceName);
Agent.Setup(agentComponents);

if (!Agent.Instance.Configuration.Enabled)
return;

_isCaptureHeadersEnabled = Agent.Instance.Configuration.CaptureHeaders;

Agent.Instance.SubscribeIncludingAllDefaults();
}) ?? false;

/// <summary>
/// Compiles a delegate from a lambda expression to get a route's DataTokens property,
/// which holds the precedence value.
Expand Down Expand Up @@ -680,5 +713,7 @@ private Func<object, string> CreateWebApiAttributeRouteTemplateGetter()

return null;
}

public void Dispose() { }
}
}
40 changes: 0 additions & 40 deletions test/Elastic.Apm.Tests/HelpersTests/DbgInstanceNameGeneratorTests.cs
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