Merge pull request #111087 from MS-jgol/sampling-doc

added Java 3.0 info

Author: PRMerger8

articles/azure-monitor/app/sampling.md

@@ -17,7 +17,7 @@ When metric counts are presented in the portal, they are renormalized to take in
 
 * There are three different types of sampling: adaptive sampling, fixed-rate sampling, and ingestion sampling.
 * Adaptive sampling is enabled by default in all the latest versions of the Application Insights ASP.NET and ASP.NET Core Software Development Kits (SDKs). It is also used by [Azure Functions](https://docs.microsoft.com/azure/azure-functions/functions-overview).
-* Fixed-rate sampling is available in recent versions of the Application Insights SDKs for ASP.NET, ASP.NET Core, Java, and Python.
+* Fixed-rate sampling is available in recent versions of the Application Insights SDKs for ASP.NET, ASP.NET Core, Java (both the agent and the SDK), and Python.
 * Ingestion sampling works on the Application Insights service endpoint. It only applies when no other sampling is in effect. If the SDK samples your telemetry, ingestion sampling is disabled.
 * For web applications, if you log custom events and need to ensure that a set of events is retained or discarded together, the events must have the same `OperationId` value.
 * If you write Analytics queries, you should [take account of sampling](../../azure-monitor/log-query/aggregations.md). In particular, instead of simply counting records, you should use `summarize sum(itemCount)`.
@@ -239,7 +239,7 @@ In Metrics Explorer, rates such as request and exception counts are multiplied b
     </TelemetryProcessors>
     ```
 
-	  Alternatively, instead of setting the sampling parameter in the `ApplicationInsights.config` file, you can programmatically set these values:
+      Alternatively, instead of setting the sampling parameter in the `ApplicationInsights.config` file, you can programmatically set these values:
 
     ```csharp
     using Microsoft.ApplicationInsights.Extensibility;
@@ -301,7 +301,29 @@ In Metrics Explorer, rates such as request and exception counts are multiplied b
 
 ### Configuring fixed-rate sampling for Java applications
 
-By default no sampling is enabled in the Java SDK. Currently it only supports fixed rate sampling. Adaptive sampling is not supported in the Java SDK.
+By default no sampling is enabled in the Java agent and SDK. Currently it only supports fixed rate sampling. Adaptive sampling is not supported in Java.
+
+#### Configuring Java Agent
+
+1. Download [applicationinsights-agent-3.0.0-PREVIEW.2.jar](https://github.com/microsoft/ApplicationInsights-Java/releases/download/3.0.0-PREVIEW.2/applicationinsights-agent-3.0.0-PREVIEW.2.jar)
+
+1. To enable sampling add the following to your `ApplicationInsights.json` file:
+
+```json
+{
+  "instrumentationSettings": {
+    "preview": {
+      "sampling": {
+        "fixedRate": {
+          "percentage": 10 //this is just an example that shows you how to enable only only 10% of transaction 
+        }
+      }
+    }
+  }
+}
+```
+
+#### Configuring Java SDK
 
 1. Download and configure your web application with the latest [Application Insights Java SDK](../../azure-monitor/app/java-get-started.md).
 
@@ -530,7 +552,7 @@ The accuracy of the approximation largely depends on the configured sampling per
 
 * Ingestion sampling can occur automatically for any telemetry above a certain volume, if the SDK is not performing sampling. This configuration would work, for example, if you are using an older version of the ASP.NET SDK or Java SDK.
 * If you're using the current ASP.NET or ASP.NET Core SDKs (hosted either in Azure or on your own server), you get adaptive sampling by default, but you can switch to fixed-rate as described above. With fixed-rate sampling, the browser SDK automatically synchronizes to sample related events. 
-* If you're using the current Java SDK, you can configure `ApplicationInsights.xml` to turn on fixed-rate sampling. Sampling is turned off by default. With fixed-rate sampling, the browser SDK and the server automatically synchronize to sample related events.
+* If you're using the current Java agent, you can configure `ApplicationInsights.json` (for Java SDK, configure `ApplicationInsights.xml`) to turn on fixed-rate sampling. Sampling is turned off by default. With fixed-rate sampling, the browser SDK and the server automatically synchronize to sample related events.
 
 *There are certain rare events I always want to see. How can I get them past the sampling module?*