Deprecate old extensions (#3825)

* Introduce stable property for external extensions

* Update docs to use stable extension property.

Also log a warning if deprecated otel.javaagent.experimental.exporter.jar is used.

* Format

* Format

* Polish

docs/agent-config.md

@@ -58,7 +58,7 @@ You can enable [extensions](../examples/extension/README.md) by setting the corr
 
 | System property                      | Environment variable                 | Description                                                                      |
 |--------------------------------------|--------------------------------------|----------------------------------------------------------------------------------|
-| `otel.javaagent.experimental.extensions` | `OTEL_JAVAAGENT_EXPERIMENTAL_EXTENSIONS` | Path to a an extension jar file or folder, containing jar files. If pointing to a folder, every jar file in that folder will be treated as separate, independent extension|
+| `otel.javaagent.extensions` | `OTEL_JAVAAGENT_EXTENSIONS` | Path to a an extension jar file or folder, containing jar files. If pointing to a folder, every jar file in that folder will be treated as separate, independent extension|
 
 ## Peer service name
 

examples/extension/README.md

@@ -17,12 +17,12 @@ To add the extension to the instrumentation agent:
 
      ```bash
      java -javaagent:path/to/opentelemetry-javaagent-all.jar \
-          -Dotel.javaagent.experimental.extensions=build/libs/opentelemetry-java-instrumentation-extension-demo-1.0-all.jar
+          -Dotel.javaagent.extensions=build/libs/opentelemetry-java-instrumentation-extension-demo-1.0-all.jar
           -jar myapp.jar
      ```
 ## Embed extensions in the OpenTelemetry Agent
 
-To simplify deployment, you can embed extensions into the OpenTelemetry Java Agent to produce a single jar file. With an integrated extension, you no longer need the `-Dotel.javaagent.experimental.extensions` command line option.
+To simplify deployment, you can embed extensions into the OpenTelemetry Java Agent to produce a single jar file. With an integrated extension, you no longer need the `-Dotel.javaagent.extensions` command line option.
 
 For more information, see the `extendedAgent` task in [build.gradle](build.gradle).
 ## Extensions examples

examples/extension/src/test/java/com/example/javaagent/smoketest/IntegrationTest.java

@@ -112,7 +112,7 @@ abstract class IntegrationTest {
       //Asks instrumentation agent to include extensions from given location into its runtime
       result = result.withCopyFileToContainer(
           MountableFile.forHostPath(extensionPath), "/opentelemetry-extensions.jar")
-          .withEnv("OTEL_JAVAAGENT_EXPERIMENTAL_EXTENSIONS", extensionLocation);
+          .withEnv("OTEL_JAVAAGENT_EXTENSIONS", extensionLocation);
     }
     return result;
   }

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/AgentTracerProviderConfigurer.java

@@ -74,8 +74,13 @@ public class AgentTracerProviderConfigurer implements SdkTracerProviderConfigure
     installExportersFromJar(exporterJar, config, sdkTracerProviderBuilder);
   }
 
+  // TODO remove in 1.6
   private static synchronized void installExportersFromJar(
       String exporterJar, Config config, SdkTracerProviderBuilder builder) {
+    logger.warn(
+        "{} is deprecated and will be removed soon! Please use {}",
+        EXPORTER_JAR_CONFIG,
+        ExtensionClassLoader.EXTENSIONS_CONFIG);
     URL url;
     try {
       url = new File(exporterJar).toURI().toURL();

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/ExtensionClassLoader.java

@@ -34,6 +34,8 @@ import net.bytebuddy.dynamic.loading.MultipleParentClassLoader;
 // Used by AgentInitializer
 @SuppressWarnings({"unused", "SystemOut"})
 public class ExtensionClassLoader extends URLClassLoader {
+  public static final String EXTENSIONS_CONFIG = "otel.javaagent.extensions";
+
   // NOTE it's important not to use slf4j in this class, because this class is used before slf4j is
   // configured, and so using slf4j here would initialize slf4j-simple before we have a chance to
   // configure the logging levels
@@ -47,12 +49,11 @@ public class ExtensionClassLoader extends URLClassLoader {
 
     includeEmbeddedExtensionsIfFound(parent, extensions, javaagentFile);
 
-    // TODO add support for old deprecated property otel.javaagent.experimental.exporter.jar
     extensions.addAll(
         parseLocation(
-            System.getProperty(
-                "otel.javaagent.extensions", System.getenv("OTEL_JAVAAGENT_EXTENSIONS")),
+            System.getProperty(EXTENSIONS_CONFIG, System.getenv("OTEL_JAVAAGENT_EXTENSIONS")),
             javaagentFile));
+
     extensions.addAll(
         parseLocation(
             System.getProperty(