Support older log4j2 versions in the javaagent (#5979)

instrumentation/log4j/log4j-appender-2.17/javaagent/build.gradle.kts

@@ -6,7 +6,7 @@ muzzle {
   pass {
     group.set("org.apache.logging.log4j")
     module.set("log4j-core")
-    versions.set("[2.11.0,)")
+    versions.set("[2.0,)")
     assertInverse.set(true)
   }
 }

instrumentation/log4j/log4j-appender-2.17/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/log4j/appender/v2_17/Log4jHelper.java

@@ -30,7 +30,7 @@ public final class Log4jHelper {
     LogBuilder builder =
         AgentLogEmitterProvider.get().logEmitterBuilder(instrumentationName).build().logBuilder();
     Map<String, String> contextData = ThreadContext.getImmutableContext();
-    mapper.mapLogEvent(builder, message, level, throwable, null, contextData);
+    mapper.mapLogEvent(builder, message, level, throwable, contextData);
     builder.emit();
   }
 

instrumentation/log4j/log4j-appender-2.17/library/src/main/java/io/opentelemetry/instrumentation/log4j/appender/v2_17/OpenTelemetryAppender.java

@@ -13,6 +13,7 @@ import io.opentelemetry.instrumentation.log4j.appender.v2_17.internal.LogEventMa
 import io.opentelemetry.instrumentation.sdk.appender.internal.DelegatingLogEmitterProvider;
 import io.opentelemetry.sdk.logs.SdkLogEmitterProvider;
 import java.io.Serializable;
+import java.util.concurrent.TimeUnit;
 import java.util.function.BiConsumer;
 import javax.annotation.Nullable;
 import org.apache.logging.log4j.core.Appender;
@@ -24,6 +25,7 @@ import org.apache.logging.log4j.core.appender.AbstractAppender;
 import org.apache.logging.log4j.core.config.Property;
 import org.apache.logging.log4j.core.config.plugins.Plugin;
 import org.apache.logging.log4j.core.config.plugins.PluginBuilderFactory;
+import org.apache.logging.log4j.core.time.Instant;
 import org.apache.logging.log4j.util.ReadOnlyStringMap;
 
 @Plugin(
@@ -74,12 +76,15 @@ public class OpenTelemetryAppender extends AbstractAppender {
         logEmitterProviderHolder.get().logEmitterBuilder(instrumentationName).build().logBuilder();
     ReadOnlyStringMap contextData = event.getContextData();
     mapper.mapLogEvent(
-        builder,
+        builder, event.getMessage(), event.getLevel(), event.getThrown(), contextData);
-        event.getMessage(),
+
-        event.getLevel(),
+    Instant timestamp = event.getInstant();
-        event.getThrown(),
+    if (timestamp != null) {
-        event.getInstant(),
+      builder.setEpoch(
-        contextData);
+          TimeUnit.MILLISECONDS.toNanos(timestamp.getEpochMillisecond())
+              + timestamp.getNanoOfMillisecond(),
+          TimeUnit.NANOSECONDS);
+    }
     builder.emit();
   }
 

instrumentation/log4j/log4j-appender-2.17/library/src/main/java/io/opentelemetry/instrumentation/log4j/appender/v2_17/internal/LogEventMapper.java

@@ -19,11 +19,9 @@ import io.opentelemetry.semconv.trace.attributes.SemanticAttributes;
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.util.List;
-import java.util.concurrent.TimeUnit;
 import javax.annotation.Nullable;
 import org.apache.logging.log4j.Level;
 import org.apache.logging.log4j.core.LogEvent;
-import org.apache.logging.log4j.core.time.Instant;
 import org.apache.logging.log4j.message.MapMessage;
 import org.apache.logging.log4j.message.Message;
 
@@ -96,7 +94,6 @@ public final class LogEventMapper<T> {
       Message message,
       Level level,
       @Nullable Throwable throwable,
-      @Nullable Instant timestamp,
       T contextData) {
 
     AttributesBuilder attributes = Attributes.builder();
@@ -123,13 +120,6 @@ public final class LogEventMapper<T> {
     builder.setAttributes(attributes.build());
 
     builder.setContext(Context.current());
-
-    if (timestamp != null) {
-      builder.setEpoch(
-          TimeUnit.MILLISECONDS.toNanos(timestamp.getEpochMillisecond())
-              + timestamp.getNanoOfMillisecond(),
-          TimeUnit.NANOSECONDS);
-    }
   }
 
   // visible for testing
@@ -155,7 +145,10 @@ public final class LogEventMapper<T> {
     }
 
     if (captureMapMessageAttributes) {
-      mapMessage.forEach(
+      // TODO (trask) this could be optimized in 2.9 and later by calling MapMessage.forEach()
+      mapMessage
+          .getData()
+          .forEach(
               (key, value) -> {
                 if (value != null
                     && (!checkSpecialMapMessageAttribute