feat: log4j2 otel appender configured through env vars

javaagent-log-appender/README.md

@@ -46,6 +46,14 @@ OTEL_LOGS_EXPORTER=otlp
 ../gradlew run
 ```
 
+Allows usage of these env vars or system properties defined in `log4j2.xml`:
+- `LOG_LEVEL` env var or `logLevel` property - controls the log4j2 Root (and inherited) loggers
+level
+- `OTEL_X_LOG_SENDING_DISABLED` env var or `otel.x.log_sending.disabled` property - set to "true" to fully disable the
+`OpenTelemetryAppender`
+- `OTEL_X_LOG_SENDING_LEVEL` env var or `otel.x.log_sending.level` property - defaults to "all", set to relevant log4j2 [Level](https://logging.apache.org/log4j/2.x/manual/customloglevels.html)
+(`off`, `fatal`, `error`, `warn`, `info`, `debug`, `trace`, `all`) to additionally filter what goes to Otel Collector
+
 Watch the collector logs to see exported log records
 
 NOTE: The OpenTelemetry Java Agent uses `http/protobuf` by default, optionally switch to use `grpc` protocol

javaagent-log-appender/build.gradle.kts

@@ -33,7 +33,11 @@ dependencies {
     implementation("io.opentelemetry:opentelemetry-api")
     implementation("io.opentelemetry.semconv:opentelemetry-semconv")
 
-    // OpenTelemetry Java Agent, this brings its own standalone log4j / logback appenders
+    // OpenTelemetry log4j / logback appenders
+    implementation("io.opentelemetry.instrumentation:opentelemetry-log4j-appender-2.17")
+    implementation("io.opentelemetry.instrumentation:opentelemetry-logback-appender-1.0")
+
+    // OpenTelemetry JavaAgent
     agent("io.opentelemetry.javaagent:opentelemetry-javaagent:2.8.0")
 }
 
@@ -45,15 +49,8 @@ application {
 tasks.named<JavaExec>("run") {
     doFirst {
         jvmArgs("-javaagent:${agent.singleFile}")
-        // log4j-appender properties
-        jvmArgs(
-            "-Dotel.instrumentation.log4j-appender.experimental.capture-map-message-attributes=true",
-            "-Dotel.instrumentation.log4j-appender.experimental-log-attributes=true"
-        )
-        // logback-appender properties
-        jvmArgs(
-            "-Dotel.instrumentation.logback-appender.experimental-log-attributes=true",
-            "-Dotel.instrumentation.logback-appender.experimental.capture-key-value-pair-attributes=true"
-        )
+        // disable the OpenTelemetry JavaAgent brought `log4j-appender`
+        // as we bring our own that is configured from `log4j2.xml`
+        jvmArgs("-Dotel.instrumentation.log4j-appender.enabled=false")
     }
 }

javaagent-log-appender/src/main/java/io/opentelemetry/example/logappender/Application.java

@@ -9,6 +9,8 @@
 import java.util.Map;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+
+import io.opentelemetry.instrumentation.log4j.appender.v2_17.OpenTelemetryAppender;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.ThreadContext;
 import org.apache.logging.log4j.message.MapMessage;
@@ -19,17 +21,24 @@ public class Application {
 
   private static final org.apache.logging.log4j.Logger log4jLogger =
       LogManager.getLogger("log4j-logger");
-  private static final org.slf4j.Logger slf4jLogger = LoggerFactory.getLogger("slf4j-logger");
-  private static final java.util.logging.Logger julLogger = Logger.getLogger("jul-logger");
+//  private static final org.slf4j.Logger slf4jLogger = LoggerFactory.getLogger("slf4j-logger");
+//  private static final java.util.logging.Logger julLogger = Logger.getLogger("jul-logger");
 
   public static void main(String[] args) {
-    // Route JUL logs to slf4j
-    SLF4JBridgeHandler.removeHandlersForRootLogger();
-    SLF4JBridgeHandler.install();
+//    // Route JUL logs to slf4j
+//    SLF4JBridgeHandler.removeHandlersForRootLogger();
+//    SLF4JBridgeHandler.install();
+
+    // Must set up the appenders with the current OpenTelemetry instance
+    // from OpenTelemetry JavaAgent
+    // It will do nothing in case no log4j2 appenders are added
+    // or disabled through `OTEL_X_LOG_SENDING_DISABLED=true` / `-Dotel.x.log_sending.disabled=true`
+    OpenTelemetryAppender.install(GlobalOpenTelemetry.get());
 
     // Log using log4j API
     maybeRunWithSpan(() -> log4jLogger.info("A log4j log message without a span"), false);
     maybeRunWithSpan(() -> log4jLogger.info("A log4j log message with a span"), true);
+    maybeRunWithSpan(() -> log4jLogger.error("A log4j log message with a span"), true);
     Map<String, Object> mapMessage = new HashMap<>();
     mapMessage.put("key", "value");
     mapMessage.put("message", "A log4j structured message");
@@ -39,54 +48,54 @@ public static void main(String[] args) {
         () -> log4jLogger.info("A log4j log message with an exception", new Exception("error!")),
         false);
 
-    // Log using slf4j API w/ logback backend
-    maybeRunWithSpan(() -> slf4jLogger.info("A slf4j log message without a span"), false);
-    maybeRunWithSpan(() -> slf4jLogger.info("A slf4j log message with a span"), true);
-    maybeRunWithSpan(
-        () ->
-            slf4jLogger
-                .atInfo()
-                .setMessage("A slf4j structured message")
-                .addKeyValue("key", "value")
-                .log(),
-        false);
-    maybeRunWithSpan(
-        () -> slf4jLogger.info("A slf4j log message with an exception", new Exception("error!")),
-        false);
-
-    // Log using JUL API, bridged to slf4j, w/ logback backend
-    maybeRunWithSpan(() -> julLogger.info("A JUL log message without a span"), false);
-    maybeRunWithSpan(() -> julLogger.info("A JUL log message with a span"), true);
-    maybeRunWithSpan(
-        () ->
-            julLogger.log(
-                Level.INFO, "A JUL log message with an exception", new Exception("error!")),
-        false);
-
-    // Log using OpenTelemetry Log Bridge API
-    // WARNING: This illustrates how to write appenders which bridge logs from
-    // existing frameworks into the OpenTelemetry Log Bridge API. These APIs
-    // SHOULD NOT be used by end users in place of existing log APIs (i.e. Log4j, Slf4, JUL).
-    io.opentelemetry.api.logs.Logger customAppenderLogger =
-        GlobalOpenTelemetry.get().getLogsBridge().get("custom-log-appender");
-    maybeRunWithSpan(
-        () ->
-            customAppenderLogger
-                .logRecordBuilder()
-                .setSeverity(Severity.INFO)
-                .setBody("A log message from a custom appender without a span")
-                .setAttribute(AttributeKey.stringKey("key"), "value")
-                .emit(),
-        false);
-    maybeRunWithSpan(
-        () ->
-            customAppenderLogger
-                .logRecordBuilder()
-                .setSeverity(Severity.INFO)
-                .setBody("A log message from a custom appender with a span")
-                .setAttribute(AttributeKey.stringKey("key"), "value")
-                .emit(),
-        true);
+//    // Log using slf4j API w/ logback backend
+//    maybeRunWithSpan(() -> slf4jLogger.info("A slf4j log message without a span"), false);
+//    maybeRunWithSpan(() -> slf4jLogger.info("A slf4j log message with a span"), true);
+//    maybeRunWithSpan(
+//        () ->
+//            slf4jLogger
+//                .atInfo()
+//                .setMessage("A slf4j structured message")
+//                .addKeyValue("key", "value")
+//                .log(),
+//        false);
+//    maybeRunWithSpan(
+//        () -> slf4jLogger.info("A slf4j log message with an exception", new Exception("error!")),
+//        false);
+//
+//    // Log using JUL API, bridged to slf4j, w/ logback backend
+//    maybeRunWithSpan(() -> julLogger.info("A JUL log message without a span"), false);
+//    maybeRunWithSpan(() -> julLogger.info("A JUL log message with a span"), true);
+//    maybeRunWithSpan(
+//        () ->
+//            julLogger.log(
+//                Level.INFO, "A JUL log message with an exception", new Exception("error!")),
+//        false);
+//
+//    // Log using OpenTelemetry Log Bridge API
+//    // WARNING: This illustrates how to write appenders which bridge logs from
+//    // existing frameworks into the OpenTelemetry Log Bridge API. These APIs
+//    // SHOULD NOT be used by end users in place of existing log APIs (i.e. Log4j, Slf4, JUL).
+//    io.opentelemetry.api.logs.Logger customAppenderLogger =
+//        GlobalOpenTelemetry.get().getLogsBridge().get("custom-log-appender");
+//    maybeRunWithSpan(
+//        () ->
+//            customAppenderLogger
+//                .logRecordBuilder()
+//                .setSeverity(Severity.INFO)
+//                .setBody("A log message from a custom appender without a span")
+//                .setAttribute(AttributeKey.stringKey("key"), "value")
+//                .emit(),
+//        false);
+//    maybeRunWithSpan(
+//        () ->
+//            customAppenderLogger
+//                .logRecordBuilder()
+//                .setSeverity(Severity.INFO)
+//                .setBody("A log message from a custom appender with a span")
+//                .setAttribute(AttributeKey.stringKey("key"), "value")
+//                .emit(),
+//        true);
   }
 
   private static void maybeRunWithSpan(Runnable runnable, boolean withSpan) {

javaagent-log-appender/src/main/resources/log4j2.xml

@@ -1,13 +1,34 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Configuration status="WARN">
+    <Properties>
+        <Property name="logLevel" value="${env:LOG_LEVEL:-info}"/>
+        <Property name="otel.x.log_sending.disabled" value="${env:OTEL_X_LOG_SENDING_DISABLED}"/>
+        <Property name="otel.x.log_sending.level" value="${env:OTEL_X_LOG_SENDING_LEVEL:-all}"/>
+    </Properties>
     <Appenders>
         <Console name="ConsoleAppender" target="SYSTEM_OUT" follow="true">
             <PatternLayout pattern="log4j2: %d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
         </Console>
+        <Select>
+            <SystemPropertyArbiter propertyName="otel.x.log_sending.disabled" propertyValue="true">
+                <!-- noop -->
+            </SystemPropertyArbiter>
+            <DefaultArbiter>
+                <OpenTelemetry name="OpenTelemetryAppender" captureMapMessageAttributes="true" captureExperimentalAttributes="true"/>
+            </DefaultArbiter>
+        </Select>
     </Appenders>
     <Loggers>
-        <Root level="info">
+        <Root level="${logLevel}">
             <AppenderRef ref="ConsoleAppender" />
+            <Select>
+                <SystemPropertyArbiter propertyName="otel.x.log_sending.disabled" propertyValue="true">
+                    <!-- noop -->
+                </SystemPropertyArbiter>
+                <DefaultArbiter>
+                    <AppenderRef ref="OpenTelemetryAppender" level="${otel.x.log_sending.level}" />
+                </DefaultArbiter>
+            </Select>
         </Root>
     </Loggers>
 </Configuration>