[SVLS-9784] Forward loaded java runtime version to Compat metadata

README.md

@@ -2,6 +2,14 @@
 
 Datadog library for Java to enable tracing and custom metric submission from [Azure Functions](https://azure.microsoft.com/en-us/products/functions) and [Google Cloud Run Functions (1st gen)](https://cloud.google.com/functions/1stgendocs/concepts/overview).
 
+## Inventory version metadata
+
+With `DD_SERVERLESS_COMPAT_METADATA_ENABLED=true`, inventory reports the wrapper package as
+`serverless_compat_runtime_version`, the embedded binary release as
+`serverless_compat_binary_version`, and the language engine in `runtime`.
+`DD_SERVERLESS_COMPAT_PATH` selects a custom binary but does not change the wrapper package version.
+The binary must supply its own embedded version; an unversioned binary must not inherit the wrapper version.
+
 # Getting Started
 
 - [Install Serverless Monitoring for Azure Functions](https://docs.datadoghq.com/serverless/azure_functions/?code-lang=java)

src/main/java/com/datadog/ServerlessCompatAgent.java

@@ -169,12 +169,22 @@ public static void premain(String agentArgs, Instrumentation instrumentation) {
             String packageVersion = getPackageVersion();
             log.debug("Found package version {}", packageVersion);
 
-            ProcessBuilder processBuilder = new ProcessBuilder(executableFile.getAbsolutePath());
-            processBuilder.environment().put("DD_SERVERLESS_COMPAT_VERSION", packageVersion);
+            ProcessBuilder processBuilder = createProcessBuilder(executableFile, packageVersion, environment);
             processBuilder.inheritIO();
             processBuilder.start();
         } catch (Exception e) {
             log.error("Exception when starting {}", fileName, e);
         }
     }
+
+    static ProcessBuilder createProcessBuilder(File executable, String packageVersion, CloudEnvironment environment) {
+        ProcessBuilder processBuilder = new ProcessBuilder(executable.getAbsolutePath());
+        Map<String, String> childEnvironment = processBuilder.environment();
+        childEnvironment.put("DD_SERVERLESS_COMPAT_VERSION", packageVersion);
+        childEnvironment.put("JAVA_VERSION", System.getProperty("java.version"));
+        if (environment == CloudEnvironment.AZURE_FUNCTION) {
+            childEnvironment.put("FUNCTIONS_WORKER_RUNTIME_VERSION", System.getProperty("java.version"));
+        }
+        return processBuilder;
+    }
 }

src/test/java/com/datadog/ServerlessCompatAgentTest.java

@@ -1,6 +1,7 @@
 package com.datadog;
 
 import java.lang.reflect.Method;
+import java.io.File;
 import java.util.HashMap;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
@@ -13,6 +14,18 @@
 
 class ServerlessCompatAgentTest {
 
+    @Test
+    void childReceivesWrapperAndEngineVersionsForCustomBinary() {
+        File executable = new File("/custom/compat");
+        ProcessBuilder child = ServerlessCompatAgent.createProcessBuilder(
+                executable, "0.25.0", CloudEnvironment.AZURE_FUNCTION);
+        assertEquals(executable.getAbsolutePath(), child.command().get(0));
+        assertEquals("0.25.0", child.environment().get("DD_SERVERLESS_COMPAT_VERSION"));
+        assertEquals(System.getProperty("java.version"), child.environment().get("JAVA_VERSION"));
+        assertEquals(System.getProperty("java.version"), child.environment().get("FUNCTIONS_WORKER_RUNTIME_VERSION"));
+        assertEquals(System.getenv("DD_SERVICE"), child.environment().get("DD_SERVICE"));
+    }
+
     @ParameterizedTest
     @CsvSource({
             "TRACE, TRACE",