Log4j and Logback appenders opt-in to using GlobalOpenTelemetry (open-telemetry#8791)

Author: jack-berg

instrumentation/log4j/log4j-appender-2.17/library/README.md

@@ -56,3 +56,23 @@ The following demonstrates how you might configure the appender in your `log4j.x
 
 In this example Log4j2 log events will be sent to both the console appender and
 the `OpenTelemetryAppender`.
+
+In order to function, `OpenTelemetryAppender` needs access to an `OpenTelemetry` instance. This must
+be set programmatically during application startup as follows:
+
+```java
+import io.opentelemetry.instrumentation.log4j.appender.v2_17.OpenTelemetryAppender;
+import io.opentelemetry.sdk.OpenTelemetrySdk;
+
+public class Application {
+
+  public static void main(String[] args) {
+    OpenTelemetrySdk openTelemetrySdk = // Configure OpenTelemetrySdk
+
+    // Find OpenTelemetryAppender in log4j configuration and install openTelemetrySdk
+    OpenTelemetryAppender.install(openTelemetrySdk);
+
+    // ... proceed with application
+  }
+}
+```

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

@@ -8,7 +8,6 @@
 import static java.util.Collections.emptyList;
 
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
-import io.opentelemetry.api.GlobalOpenTelemetry;
 import io.opentelemetry.api.OpenTelemetry;
 import io.opentelemetry.api.logs.LogRecordBuilder;
 import io.opentelemetry.instrumentation.log4j.appender.v2_17.internal.ContextDataAccessor;
@@ -20,13 +19,16 @@
 import java.util.function.BiConsumer;
 import java.util.stream.Collectors;
 import javax.annotation.Nullable;
+import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.ThreadContext;
 import org.apache.logging.log4j.core.Appender;
 import org.apache.logging.log4j.core.Core;
 import org.apache.logging.log4j.core.Filter;
 import org.apache.logging.log4j.core.Layout;
 import org.apache.logging.log4j.core.LogEvent;
+import org.apache.logging.log4j.core.LoggerContext;
 import org.apache.logging.log4j.core.appender.AbstractAppender;
+import org.apache.logging.log4j.core.config.Configuration;
 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.PluginBuilderAttribute;
@@ -44,7 +46,29 @@ public class OpenTelemetryAppender extends AbstractAppender {
   static final String PLUGIN_NAME = "OpenTelemetry";
 
   private final LogEventMapper<ReadOnlyStringMap> mapper;
-  @Nullable private OpenTelemetry openTelemetry;
+  private OpenTelemetry openTelemetry;
+
+  /**
+   * Installs the {@code openTelemetry} instance on any {@link OpenTelemetryAppender}s identified in
+   * the {@link LoggerContext}.
+   */
+  public static void install(OpenTelemetry openTelemetry) {
+    org.apache.logging.log4j.spi.LoggerContext loggerContextSpi = LogManager.getContext(false);
+    if (!(loggerContextSpi instanceof LoggerContext)) {
+      return;
+    }
+    LoggerContext loggerContext = (LoggerContext) loggerContextSpi;
+    Configuration config = loggerContext.getConfiguration();
+    config
+        .getAppenders()
+        .values()
+        .forEach(
+            appender -> {
+              if (appender instanceof OpenTelemetryAppender) {
+                ((OpenTelemetryAppender) appender).setOpenTelemetry(openTelemetry);
+              }
+            });
+  }
 
   @PluginBuilderFactory
   public static <B extends Builder<B>> B builder() {
@@ -97,6 +121,7 @@ public B setCaptureContextDataAttributes(String captureContextDataAttributes) {
       return asBuilder();
     }
 
+    /** Configures the {@link OpenTelemetry} used to append logs. */
     @CanIgnoreReturnValue
     public B setOpenTelemetry(OpenTelemetry openTelemetry) {
       this.openTelemetry = openTelemetry;
@@ -105,6 +130,10 @@ public B setOpenTelemetry(OpenTelemetry openTelemetry) {
 
     @Override
     public OpenTelemetryAppender build() {
+      OpenTelemetry openTelemetry = this.openTelemetry;
+      if (openTelemetry == null) {
+        openTelemetry = OpenTelemetry.noop();
+      }
       return new OpenTelemetryAppender(
           getName(),
           getLayout(),
@@ -152,14 +181,14 @@ private static List<String> splitAndFilterBlanksAndNulls(String value) {
         .collect(Collectors.toList());
   }
 
+  /**
+   * Configures the {@link OpenTelemetry} used to append logs. This MUST be called for the appender
+   * to function. See {@link #install(OpenTelemetry)} for simple installation option.
+   */
   public void setOpenTelemetry(OpenTelemetry openTelemetry) {
     this.openTelemetry = openTelemetry;
   }
 
-  private OpenTelemetry getOpenTelemetry() {
-    return openTelemetry == null ? GlobalOpenTelemetry.get() : openTelemetry;
-  }
-
   @Override
   public void append(LogEvent event) {
     String instrumentationName = event.getLoggerName();
@@ -168,7 +197,7 @@ public void append(LogEvent event) {
     }
 
     LogRecordBuilder builder =
-        getOpenTelemetry()
+        this.openTelemetry
             .getLogsBridge()
             .loggerBuilder(instrumentationName)
             .build()

instrumentation/log4j/log4j-appender-2.17/library/src/test/java/io/opentelemetry/instrumentation/log4j/appender/v2_17/OpenTelemetryAppenderConfigTest.java

@@ -17,8 +17,11 @@
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.api.trace.SpanContext;
 import io.opentelemetry.context.Scope;
+import io.opentelemetry.sdk.OpenTelemetrySdk;
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
+import io.opentelemetry.sdk.logs.SdkLoggerProvider;
 import io.opentelemetry.sdk.logs.data.LogRecordData;
+import io.opentelemetry.sdk.logs.export.SimpleLogRecordProcessor;
 import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.testing.exporter.InMemoryLogRecordExporter;
 import io.opentelemetry.sdk.trace.SdkTracerProvider;
@@ -30,26 +33,71 @@
 import org.apache.logging.log4j.Marker;
 import org.apache.logging.log4j.MarkerManager;
 import org.apache.logging.log4j.ThreadContext;
+import org.apache.logging.log4j.core.impl.Log4jLogEvent;
+import org.apache.logging.log4j.message.FormattedMessage;
 import org.apache.logging.log4j.message.StringMapMessage;
 import org.apache.logging.log4j.message.StructuredDataMessage;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-abstract class OpenTelemetryAppenderConfigTestBase {
+class OpenTelemetryAppenderTest {
 
-  static final Logger logger = LogManager.getLogger("TestLogger");
+  private static final Logger logger = LogManager.getLogger("TestLogger");
 
-  static InMemoryLogRecordExporter logRecordExporter;
-  static Resource resource;
-  static InstrumentationScopeInfo instrumentationScopeInfo;
-  static OpenTelemetry openTelemetry;
+  private static InMemoryLogRecordExporter logRecordExporter;
+  private static Resource resource;
+  private static InstrumentationScopeInfo instrumentationScopeInfo;
+  private static OpenTelemetry openTelemetry;
+
+  @BeforeAll
+  static void setupAll() {
+    logRecordExporter = InMemoryLogRecordExporter.create();
+    resource = Resource.getDefault();
+    instrumentationScopeInfo = InstrumentationScopeInfo.create("TestLogger");
+
+    SdkLoggerProvider loggerProvider =
+        SdkLoggerProvider.builder()
+            .setResource(resource)
+            .addLogRecordProcessor(SimpleLogRecordProcessor.create(logRecordExporter))
+            .build();
+
+    openTelemetry = OpenTelemetrySdk.builder().setLoggerProvider(loggerProvider).build();
+    OpenTelemetryAppender.install(openTelemetry);
+  }
 
   @BeforeEach
   void setup() {
     logRecordExporter.reset();
     ThreadContext.clearAll();
   }
 
+  @AfterAll
+  static void cleanupAll() {
+    // This is to make sure that other test classes don't have issues with the logger provider set
+    OpenTelemetryAppender.install(null);
+  }
+
+  @Test
+  void initializeWithBuilder() {
+    OpenTelemetryAppender appender =
+        OpenTelemetryAppender.builder()
+            .setName("OpenTelemetryAppender")
+            .setOpenTelemetry(openTelemetry)
+            .build();
+    appender.start();
+
+    appender.append(
+        Log4jLogEvent.newBuilder()
+            .setMessage(new FormattedMessage("log message 1", (Object) null))
+            .build());
+
+    List<LogRecordData> logDataList = logRecordExporter.getFinishedLogRecordItems();
+    assertThat(logDataList)
+        .satisfiesExactly(logRecordData -> assertThat(logDataList.get(0)).hasBody("log message 1"));
+  }
+
   @Test
   void logNoSpan() {
     logger.info("log message 1");

instrumentation/log4j/log4j-appender-2.17/library/src/test/java/io/opentelemetry/instrumentation/log4j/appender/v2_17/OpenTelemetryAppenderConfigWithOpenTelemetryTest.java

@@ -60,3 +60,23 @@ The following demonstrates how you might configure the appender in your `logback
 
 In this example Logback log events will be sent to both the console appender and
 the `OpenTelemetryAppender`.
+
+In order to function, `OpenTelemetryAppender` needs access to an `OpenTelemetry` instance. This must
+be set programmatically during application startup as follows:
+
+```java
+import io.opentelemetry.instrumentation.logback.OpenTelemetryAppender;
+import io.opentelemetry.sdk.OpenTelemetrySdk;
+
+public class Application {
+
+  public static void main(String[] args) {
+    OpenTelemetrySdk openTelemetrySdk = // Configure OpenTelemetrySdk
+
+    // Find OpenTelemetryAppender in logback configuration and install openTelemetrySdk
+    OpenTelemetryAppender.install(openTelemetrySdk);
+
+    // ... proceed with application
+  }
+}
+```