Fix spring boot starter failing without logback

instrumentation/spring/spring-boot-autoconfigure/build.gradle.kts

@@ -105,6 +105,27 @@ testing {
       }
     }
   }
+
+  suites {
+    val testLogbackMissing by registering(JvmTestSuite::class) {
+      dependencies {
+        implementation(project())
+        implementation("org.springframework.boot:spring-boot-autoconfigure:$springBootVersion")
+
+        implementation("org.slf4j:slf4j-api") {
+          version {
+            strictly("1.7.32")
+          }
+        }
+      }
+    }
+  }
+}
+
+configurations.configureEach {
+  if (name.contains("testLogbackMissing")) {
+    exclude("ch.qos.logback", "logback-classic")
+  }
 }
 
 tasks {

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/instrumentation/logging/LogbackAppenderApplicationListener.java

@@ -5,15 +5,6 @@
 
 package io.opentelemetry.instrumentation.spring.autoconfigure.instrumentation.logging;
 
-import ch.qos.logback.classic.LoggerContext;
-import ch.qos.logback.classic.spi.ILoggingEvent;
-import ch.qos.logback.core.Appender;
-import io.opentelemetry.instrumentation.logback.appender.v1_0.OpenTelemetryAppender;
-import java.util.Iterator;
-import java.util.Optional;
-import org.slf4j.ILoggerFactory;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
 import org.springframework.boot.context.logging.LoggingApplicationListener;
@@ -27,8 +18,8 @@ public class LogbackAppenderApplicationListener implements GenericApplicationLis
   private static final Class<?>[] SOURCE_TYPES = {
     SpringApplication.class, ApplicationContext.class
   };
-
   private static final Class<?>[] EVENT_TYPES = {ApplicationEnvironmentPreparedEvent.class};
+  private static final boolean LOGBACK_PRESENT = isLogbackPresent();
 
   @Override
   public boolean supportsSourceType(Class<?> sourceType) {
@@ -53,149 +44,29 @@ private static boolean isAssignableFrom(Class<?> type, Class<?>... supportedType
 
   @Override
   public void onApplicationEvent(ApplicationEvent event) {
-    if (event instanceof ApplicationEnvironmentPreparedEvent // Event for which
-    // org.springframework.boot.context.logging.LoggingApplicationListener
-    // initializes logging
-    ) {
-      Optional<OpenTelemetryAppender> existingOpenTelemetryAppender = findOpenTelemetryAppender();
-      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent =
-          (ApplicationEnvironmentPreparedEvent) event;
-      if (existingOpenTelemetryAppender.isPresent()) {
-        reInitializeOpenTelemetryAppender(
-            existingOpenTelemetryAppender, applicationEnvironmentPreparedEvent);
-      } else if (isLogbackAppenderAddable(applicationEnvironmentPreparedEvent)) {
-        addOpenTelemetryAppender(applicationEnvironmentPreparedEvent);
-      }
-    }
-  }
-
-  private static boolean isLogbackAppenderAddable(
-      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
-    Boolean otelSdkDisableProperty =
-        evaluateBooleanProperty(applicationEnvironmentPreparedEvent, "otel.sdk.disabled");
-    Boolean logbackInstrumentationEnabledProperty =
-        evaluateBooleanProperty(
-            applicationEnvironmentPreparedEvent, "otel.instrumentation.logback-appender.enabled");
-    return otelSdkDisableProperty == null
-        || !otelSdkDisableProperty.booleanValue()
-        || logbackInstrumentationEnabledProperty == null
-        || logbackInstrumentationEnabledProperty.booleanValue();
-  }
-
-  private static void reInitializeOpenTelemetryAppender(
-      Optional<OpenTelemetryAppender> existingOpenTelemetryAppender,
-      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
-    OpenTelemetryAppender openTelemetryAppender = existingOpenTelemetryAppender.get();
-    // The OpenTelemetry appender is stopped and restarted from the
-    // org.springframework.boot.context.logging.LoggingApplicationListener.initialize
-    // method.
-    // The OpenTelemetryAppender initializes the LoggingEventMapper in the start() method. So, here
-    // we stop the OpenTelemetry appender before its re-initialization and its restart.
-    openTelemetryAppender.stop();
-    initializeOpenTelemetryAppenderFromProperties(
-        applicationEnvironmentPreparedEvent, openTelemetryAppender);
-    openTelemetryAppender.start();
-  }
-
-  private static void addOpenTelemetryAppender(
-      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
-    ch.qos.logback.classic.Logger logger =
-        (ch.qos.logback.classic.Logger)
-            LoggerFactory.getILoggerFactory().getLogger(Logger.ROOT_LOGGER_NAME);
-    OpenTelemetryAppender openTelemetryAppender = new OpenTelemetryAppender();
-    initializeOpenTelemetryAppenderFromProperties(
-        applicationEnvironmentPreparedEvent, openTelemetryAppender);
-    openTelemetryAppender.start();
-    logger.addAppender(openTelemetryAppender);
-  }
-
-  private static void initializeOpenTelemetryAppenderFromProperties(
-      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent,
-      OpenTelemetryAppender openTelemetryAppender) {
-
-    // Implemented in the same way as the
-    // org.springframework.boot.context.logging.LoggingApplicationListener, config properties not
-    // available
-    Boolean codeAttribute =
-        evaluateBooleanProperty(
-            applicationEnvironmentPreparedEvent,
-            "otel.instrumentation.logback-appender.experimental.capture-code-attributes");
-    if (codeAttribute != null) {
-      openTelemetryAppender.setCaptureCodeAttributes(codeAttribute.booleanValue());
-    }
-
-    Boolean markerAttribute =
-        evaluateBooleanProperty(
-            applicationEnvironmentPreparedEvent,
-            "otel.instrumentation.logback-appender.experimental.capture-marker-attribute");
-    if (markerAttribute != null) {
-      openTelemetryAppender.setCaptureMarkerAttribute(markerAttribute.booleanValue());
-    }
-
-    Boolean keyValuePairAttributes =
-        evaluateBooleanProperty(
-            applicationEnvironmentPreparedEvent,
-            "otel.instrumentation.logback-appender.experimental.capture-key-value-pair-attributes");
-    if (keyValuePairAttributes != null) {
-      openTelemetryAppender.setCaptureKeyValuePairAttributes(keyValuePairAttributes.booleanValue());
-    }
-
-    Boolean logAttributes =
-        evaluateBooleanProperty(
-            applicationEnvironmentPreparedEvent,
-            "otel.instrumentation.logback-appender.experimental-log-attributes");
-    if (logAttributes != null) {
-      openTelemetryAppender.setCaptureExperimentalAttributes(logAttributes.booleanValue());
-    }
-
-    Boolean loggerContextAttributes =
-        evaluateBooleanProperty(
-            applicationEnvironmentPreparedEvent,
-            "otel.instrumentation.logback-appender.experimental.capture-logger-context-attributes");
-    if (loggerContextAttributes != null) {
-      openTelemetryAppender.setCaptureLoggerContext(loggerContextAttributes.booleanValue());
+    if (!LOGBACK_PRESENT) {
+      return;
     }
 
-    String mdcAttributeProperty =
-        applicationEnvironmentPreparedEvent
-            .getEnvironment()
-            .getProperty(
-                "otel.instrumentation.logback-appender.experimental.capture-mdc-attributes",
-                String.class);
-    if (mdcAttributeProperty != null) {
-      openTelemetryAppender.setCaptureMdcAttributes(mdcAttributeProperty);
-    }
-  }
-
-  private static Boolean evaluateBooleanProperty(
-      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent, String property) {
-    return applicationEnvironmentPreparedEvent
-        .getEnvironment()
-        .getProperty(property, Boolean.class);
-  }
-
-  private static Optional<OpenTelemetryAppender> findOpenTelemetryAppender() {
-    ILoggerFactory loggerFactorySpi = LoggerFactory.getILoggerFactory();
-    if (!(loggerFactorySpi instanceof LoggerContext)) {
-      return Optional.empty();
-    }
-    LoggerContext loggerContext = (LoggerContext) loggerFactorySpi;
-    for (ch.qos.logback.classic.Logger logger : loggerContext.getLoggerList()) {
-      Iterator<Appender<ILoggingEvent>> appenderIterator = logger.iteratorForAppenders();
-      while (appenderIterator.hasNext()) {
-        Appender<ILoggingEvent> appender = appenderIterator.next();
-        if (appender instanceof OpenTelemetryAppender) {
-          OpenTelemetryAppender openTelemetryAppender = (OpenTelemetryAppender) appender;
-          return Optional.of(openTelemetryAppender);
-        }
-      }
+    // Event for which org.springframework.boot.context.logging.LoggingApplicationListener
+    // initializes logging
+    if (event instanceof ApplicationEnvironmentPreparedEvent) {
+      LogbackAppenderInstaller.install((ApplicationEnvironmentPreparedEvent) event);
     }
-    return Optional.empty();
   }
 
   @Override
   public int getOrder() {
     return LoggingApplicationListener.DEFAULT_ORDER + 1; // To execute this listener just after
     // org.springframework.boot.context.logging.LoggingApplicationListener
   }
+
+  private static boolean isLogbackPresent() {
+    try {
+      Class.forName("ch.qos.logback.core.Appender");
+      return true;
+    } catch (ClassNotFoundException exception) {
+      return false;
+    }
+  }
 }

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/instrumentation/logging/LogbackAppenderInstaller.java

@@ -0,0 +1,156 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.spring.autoconfigure.instrumentation.logging;
+
+import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.Appender;
+import io.opentelemetry.instrumentation.logback.appender.v1_0.OpenTelemetryAppender;
+import java.util.Iterator;
+import java.util.Optional;
+import org.slf4j.ILoggerFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
+
+class LogbackAppenderInstaller {
+
+  static void install(ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
+    Optional<OpenTelemetryAppender> existingOpenTelemetryAppender = findOpenTelemetryAppender();
+    if (existingOpenTelemetryAppender.isPresent()) {
+      reInitializeOpenTelemetryAppender(
+          existingOpenTelemetryAppender, applicationEnvironmentPreparedEvent);
+    } else if (isLogbackAppenderAddable(applicationEnvironmentPreparedEvent)) {
+      addOpenTelemetryAppender(applicationEnvironmentPreparedEvent);
+    }
+  }
+
+  private static boolean isLogbackAppenderAddable(
+      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
+    Boolean otelSdkDisableProperty =
+        evaluateBooleanProperty(applicationEnvironmentPreparedEvent, "otel.sdk.disabled");
+    Boolean logbackInstrumentationEnabledProperty =
+        evaluateBooleanProperty(
+            applicationEnvironmentPreparedEvent, "otel.instrumentation.logback-appender.enabled");
+    return otelSdkDisableProperty == null
+        || !otelSdkDisableProperty.booleanValue()
+        || logbackInstrumentationEnabledProperty == null
+        || logbackInstrumentationEnabledProperty.booleanValue();
+  }
+
+  private static void reInitializeOpenTelemetryAppender(
+      Optional<OpenTelemetryAppender> existingOpenTelemetryAppender,
+      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
+    OpenTelemetryAppender openTelemetryAppender = existingOpenTelemetryAppender.get();
+    // The OpenTelemetry appender is stopped and restarted from the
+    // org.springframework.boot.context.logging.LoggingApplicationListener.initialize
+    // method.
+    // The OpenTelemetryAppender initializes the LoggingEventMapper in the start() method. So, here
+    // we stop the OpenTelemetry appender before its re-initialization and its restart.
+    openTelemetryAppender.stop();
+    initializeOpenTelemetryAppenderFromProperties(
+        applicationEnvironmentPreparedEvent, openTelemetryAppender);
+    openTelemetryAppender.start();
+  }
+
+  private static void addOpenTelemetryAppender(
+      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
+    ch.qos.logback.classic.Logger logger =
+        (ch.qos.logback.classic.Logger)
+            LoggerFactory.getILoggerFactory().getLogger(Logger.ROOT_LOGGER_NAME);
+    OpenTelemetryAppender openTelemetryAppender = new OpenTelemetryAppender();
+    initializeOpenTelemetryAppenderFromProperties(
+        applicationEnvironmentPreparedEvent, openTelemetryAppender);
+    openTelemetryAppender.start();
+    logger.addAppender(openTelemetryAppender);
+  }
+
+  private static void initializeOpenTelemetryAppenderFromProperties(
+      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent,
+      OpenTelemetryAppender openTelemetryAppender) {
+
+    // Implemented in the same way as the
+    // org.springframework.boot.context.logging.LoggingApplicationListener, config properties not
+    // available
+    Boolean codeAttribute =
+        evaluateBooleanProperty(
+            applicationEnvironmentPreparedEvent,
+            "otel.instrumentation.logback-appender.experimental.capture-code-attributes");
+    if (codeAttribute != null) {
+      openTelemetryAppender.setCaptureCodeAttributes(codeAttribute.booleanValue());
+    }
+
+    Boolean markerAttribute =
+        evaluateBooleanProperty(
+            applicationEnvironmentPreparedEvent,
+            "otel.instrumentation.logback-appender.experimental.capture-marker-attribute");
+    if (markerAttribute != null) {
+      openTelemetryAppender.setCaptureMarkerAttribute(markerAttribute.booleanValue());
+    }
+
+    Boolean keyValuePairAttributes =
+        evaluateBooleanProperty(
+            applicationEnvironmentPreparedEvent,
+            "otel.instrumentation.logback-appender.experimental.capture-key-value-pair-attributes");
+    if (keyValuePairAttributes != null) {
+      openTelemetryAppender.setCaptureKeyValuePairAttributes(keyValuePairAttributes.booleanValue());
+    }
+
+    Boolean logAttributes =
+        evaluateBooleanProperty(
+            applicationEnvironmentPreparedEvent,
+            "otel.instrumentation.logback-appender.experimental-log-attributes");
+    if (logAttributes != null) {
+      openTelemetryAppender.setCaptureExperimentalAttributes(logAttributes.booleanValue());
+    }
+
+    Boolean loggerContextAttributes =
+        evaluateBooleanProperty(
+            applicationEnvironmentPreparedEvent,
+            "otel.instrumentation.logback-appender.experimental.capture-logger-context-attributes");
+    if (loggerContextAttributes != null) {
+      openTelemetryAppender.setCaptureLoggerContext(loggerContextAttributes.booleanValue());
+    }
+
+    String mdcAttributeProperty =
+        applicationEnvironmentPreparedEvent
+            .getEnvironment()
+            .getProperty(
+                "otel.instrumentation.logback-appender.experimental.capture-mdc-attributes",
+                String.class);
+    if (mdcAttributeProperty != null) {
+      openTelemetryAppender.setCaptureMdcAttributes(mdcAttributeProperty);
+    }
+  }
+
+  private static Boolean evaluateBooleanProperty(
+      ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent, String property) {
+    return applicationEnvironmentPreparedEvent
+        .getEnvironment()
+        .getProperty(property, Boolean.class);
+  }
+
+  private static Optional<OpenTelemetryAppender> findOpenTelemetryAppender() {
+    ILoggerFactory loggerFactorySpi = LoggerFactory.getILoggerFactory();
+    if (!(loggerFactorySpi instanceof LoggerContext)) {
+      return Optional.empty();
+    }
+    LoggerContext loggerContext = (LoggerContext) loggerFactorySpi;
+    for (ch.qos.logback.classic.Logger logger : loggerContext.getLoggerList()) {
+      Iterator<Appender<ILoggingEvent>> appenderIterator = logger.iteratorForAppenders();
+      while (appenderIterator.hasNext()) {
+        Appender<ILoggingEvent> appender = appenderIterator.next();
+        if (appender instanceof OpenTelemetryAppender) {
+          OpenTelemetryAppender openTelemetryAppender = (OpenTelemetryAppender) appender;
+          return Optional.of(openTelemetryAppender);
+        }
+      }
+    }
+    return Optional.empty();
+  }
+
+  private LogbackAppenderInstaller() {}
+}