Configuring the X-Ray SDK for .NET - Amazon X-Ray
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Configuring the X-Ray SDK for .NET

You can configure the X-Ray SDK for .NET with plugins to include information about the service that your application runs on, modify the default sampling behavior, or add sampling rules that apply to requests to specific paths.

For .NET web applications, add keys to the appSettings section of your Web.config file.

Example Web.config
<configuration> <appSettings> <add key="AWSXRayPlugins" value="EC2Plugin"/> <add key="SamplingRuleManifest" value="sampling-rules.json"/> </appSettings> </configuration>

For .NET Core, create a file named appsettings.json with a top-level key named XRay.

Example .NET appsettings.json
{ "XRay": { "AWSXRayPlugins": "EC2Plugin", "SamplingRuleManifest": "sampling-rules.json" } }

Then, in your application code, build a configuration object and use it to initialize the X-Ray recorder. Do this before you initialize the recorder.

Example .NET Core Program.cs – Recorder configuration
using Amazon.XRay.Recorder.Core; ... AWSXRayRecorder.InitializeInstance(configuration);

If you are instrumenting a .NET Core web application, you can also pass the configuration object to the UseXRay method when you configure the message handler. For Lambda functions, use the InitializeInstance method as shown above.

For more information on the .NET Core configuration API, see Configure an ASP.NET Core App on


Use plugins to add data about the service that is hosting your application.

  • Amazon EC2 – EC2Plugin adds the instance ID, Availability Zone, and the CloudWatch Logs Group.

  • Elastic Beanstalk – ElasticBeanstalkPlugin adds the environment name, version label, and deployment ID.

  • Amazon ECS – ECSPlugin adds the container ID.

To use a plugin, configure the X-Ray SDK for .NET client by adding the AWSXRayPlugins setting. If multiple plugins apply to your application, specify all of them in the same setting, separated by commas.

Example Web.config - plugins
<configuration> <appSettings> <add key="AWSXRayPlugins" value="EC2Plugin,ElasticBeanstalkPlugin"/> </appSettings> </configuration>
Example .NET Core appsettings.json – Plugins
{ "XRay": { "AWSXRayPlugins": "EC2Plugin,ElasticBeanstalkPlugin" } }

Sampling rules

The SDK uses the sampling rules you define in the X-Ray console to determine which requests to record. The default rule traces the first request each second, and five percent of any additional requests across all services sending traces to X-Ray. Create additional rules in the X-Ray console to customize the amount of data recorded for each of your applications.

The SDK applies custom rules in the order in which they are defined. If a request matches multiple custom rules, the SDK applies only the first rule.


If the SDK can't reach X-Ray to get sampling rules, it reverts to a default local rule of the first request each second, and five percent of any additional requests per host. This can occur if the host doesn't have permission to call sampling APIs, or can't connect to the X-Ray daemon, which acts as a TCP proxy for API calls made by the SDK.

You can also configure the SDK to load sampling rules from a JSON document. The SDK can use local rules as a backup for cases where X-Ray sampling is unavailable, or use local rules exclusively.

Example sampling-rules.json
{ "version": 2, "rules": [ { "description": "Player moves.", "host": "*", "http_method": "*", "url_path": "/api/move/*", "fixed_target": 0, "rate": 0.05 } ], "default": { "fixed_target": 1, "rate": 0.1 } }

This example defines one custom rule and a default rule. The custom rule applies a five-percent sampling rate with no minimum number of requests to trace for paths under /api/move/. The default rule traces the first request each second and 10 percent of additional requests.

The disadvantage of defining rules locally is that the fixed target is applied by each instance of the recorder independently, instead of being managed by the X-Ray service. As you deploy more hosts, the fixed rate is multiplied, making it harder to control the amount of data recorded.

On Amazon Lambda, you cannot modify the sampling rate. If your function is called by an instrumented service, calls that generated requests that were sampled by that service will be recorded by Lambda. If active tracing is enabled and no tracing header is present, Lambda makes the sampling decision.

To configure backup rules, tell the X-Ray SDK for .NET to load sampling rules from a file with the SamplingRuleManifest setting.

Example .NET Web.config - sampling rules
<configuration> <appSettings> <add key="SamplingRuleManifest" value="sampling-rules.json"/> </appSettings> </configuration>
Example .NET Core appsettings.json – Sampling rules
{ "XRay": { "SamplingRuleManifest": "sampling-rules.json" } }

To use only local rules, build the recorder with a LocalizedSamplingStrategy. If you have backup rules configured, remove that configuration.

Example .NET global.asax – Local sampling rules
var recorder = new AWSXRayRecorderBuilder().WithSamplingStrategy(new LocalizedSamplingStrategy("samplingrules.json")).Build(); AWSXRayRecorder.InitializeInstance(recorder: recorder);
Example .NET Core Program.cs – Local sampling rules
var recorder = new AWSXRayRecorderBuilder().WithSamplingStrategy(new LocalizedSamplingStrategy("sampling-rules.json")).Build(); AWSXRayRecorder.InitializeInstance(configuration,recorder);

Logging (.NET)

The X-Ray SDK for .NET uses the same logging mechanism as the Amazon SDK for .NET. If you already configured your application to log Amazon SDK for .NET output, the same configuration applies to output from the X-Ray SDK for .NET.

To configure logging, add a configuration section named aws to your App.config file or Web.config file.

Example Web.config - logging
... <configuration> <configSections> <section name="aws" type="Amazon.AWSSection, AWSSDK.Core"/> </configSections> <aws> <logging logTo="Log4Net"/> </aws> </configuration>

For more information, see Configuring Your Amazon SDK for .NET Application in the Amazon SDK for .NET Developer Guide.

Logging (.NET Core)

The X-Ray SDK for .NET uses the same logging options as the Amazon SDK for .NET. To configure logging for .NET Core applications, pass the logging option to the AWSXRayRecorder.RegisterLogger method.

For example, to use log4net, create a configuration file that defines the logger, the output format, and the file location.

Example .NET Core log4net.config
<?xml version="1.0" encoding="utf-8" ?> <log4net> <appender name="FileAppender" type="log4net.Appender.FileAppender,log4net"> <file value="c:\logs\sdk-log.txt" /> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%date [%thread] %level %logger - %message%newline" /> </layout> </appender> <logger name="Amazon"> <level value="DEBUG" /> <appender-ref ref="FileAppender" /> </logger> </log4net>

Then, create the logger and apply the configuration in your program code.

Example .NET Core Program.cs – Logging
using log4net; using Amazon.XRay.Recorder.Core; class Program { private static ILog log; static Program() { var logRepository = LogManager.GetRepository(Assembly.GetEntryAssembly()); XmlConfigurator.Configure(logRepository, new FileInfo("log4net.config")); log = LogManager.GetLogger(typeof(Program)); AWSXRayRecorder.RegisterLogger(LoggingOptions.Log4Net); } static void Main(string[] args) { ... } }

For more information on configuring log4net, see Configuration on

Environment variables

You can use environment variables to configure the X-Ray SDK for .NET. The SDK supports the following variables.

  • AWS_XRAY_TRACING_NAME – Set a service name that the SDK uses for segments. Overrides the service name that you set on the servlet filter's segment naming strategy.

  • AWS_XRAY_DAEMON_ADDRESS – Set the host and port of the X-Ray daemon listener. By default, the SDK uses for both trace data (UDP) and sampling (TCP). Use this variable if you have configured the daemon to listen on a different port or if it is running on a different host.

    • Same portaddress:port

    • Different portstcp:address:port udp:address:port

  • AWS_XRAY_CONTEXT_MISSING – Set to RUNTIME_ERROR to throw exceptions when your instrumented code attempts to record data when no segment is open.

    Valid Values
    • RUNTIME_ERROR – Throw a runtime exception.

    • LOG_ERROR – Log an error and continue (default).

    • IGNORE_ERROR – Ignore error and continue.

    Errors related to missing segments or subsegments can occur when you attempt to use an instrumented client in startup code that runs when no request is open, or in code that spawns a new thread.