Review fixes for log4j-appender-2.17:library (open-telemetry#18191)

Co-authored-by: otelbot <197425009+otelbot@users.noreply.github.com>

Author: otelbot[bot]

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

@@ -28,16 +28,16 @@ class LogEventToReplay implements LogEvent {
   // Log4j 2 reuses LogEvent object, so we make a copy of all the fields that are used during export
   // in order to be able to replay the log event later.
 
-  private final String loggerName;
+  @Nullable private final String loggerName;
   private final Message message;
   private final Level level;
   private final Instant instant;
-  private final Throwable thrown;
-  private final Marker marker;
+  @Nullable private final Throwable thrown;
+  @Nullable private final Marker marker;
   private final ReadOnlyStringMap contextData;
   private final String threadName;
   private final long threadId;
-  private final StackTraceElement source;
+  @Nullable private final StackTraceElement source;
 
   LogEventToReplay(LogEvent logEvent, boolean captureCodeAttributes) {
     this.loggerName = logEvent.getLoggerName();
@@ -71,7 +71,7 @@ class LogEventToReplay implements LogEvent {
 
   @Override
   public LogEvent toImmutable() {
-    return null;
+    return this;
   }
 
   @SuppressWarnings("deprecation") // Override
@@ -91,6 +91,7 @@ public ThreadContext.ContextStack getContextStack() {
     return null;
   }
 
+  @Nullable
   @Override
   public String getLoggerFqcn() {
     return null;
@@ -101,11 +102,13 @@ public Level getLevel() {
     return level;
   }
 
+  @Nullable
   @Override
   public String getLoggerName() {
     return loggerName;
   }
 
+  @Nullable
   @Override
   public Marker getMarker() {
     return marker;
@@ -118,14 +121,15 @@ public Message getMessage() {
 
   @Override
   public long getTimeMillis() {
-    return 0;
+    return instant.getEpochMillisecond();
   }
 
   @Override
   public Instant getInstant() {
     return instant;
   }
 
+  @Nullable
   @Override
   public StackTraceElement getSource() {
     return source;
@@ -146,11 +150,13 @@ public int getThreadPriority() {
     return 0;
   }
 
+  @Nullable
   @Override
   public Throwable getThrown() {
     return thrown;
   }
 
+  @Nullable
   @Override
   public ThrowableProxy getThrownProxy() {
     return null;
@@ -182,13 +188,14 @@ private static class MessageCopy implements Message {
     private static final long serialVersionUID = 1L;
     private final String formattedMessage;
     private final String format;
-    private final Object[] parameters;
-    private final Throwable throwable;
+    @Nullable private final Object[] parameters;
+    @Nullable private final Throwable throwable;
 
     MessageCopy(Message message) {
       this.formattedMessage = message.getFormattedMessage();
       this.format = message.getFormat();
-      this.parameters = message.getParameters();
+      Object[] parameters = message.getParameters();
+      this.parameters = parameters == null ? null : parameters.clone();
       this.throwable = message.getThrowable();
     }
 
@@ -202,11 +209,13 @@ public String getFormat() {
       return format;
     }
 
+    @Nullable
     @Override
     public Object[] getParameters() {
       return parameters;
     }
 
+    @Nullable
     @Override
     public Throwable getThrowable() {
       return throwable;

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

@@ -63,7 +63,7 @@ public class OpenTelemetryAppender extends AbstractAppender {
   static final String PLUGIN_NAME = "OpenTelemetry";
 
   private final LogEventMapper<ReadOnlyStringMap> mapper;
-  private volatile OpenTelemetry openTelemetry;
+  @Nullable private volatile OpenTelemetry openTelemetry;
 
   private final BlockingQueue<LogEventToReplay> eventsToReplay;
   private final AtomicBoolean replayLimitWarningLogged = new AtomicBoolean();
@@ -112,7 +112,7 @@ public static class Builder<B extends Builder<B>> extends AbstractAppender.Build
     @PluginBuilderAttribute private boolean captureCodeAttributes;
     @PluginBuilderAttribute private boolean captureMapMessageAttributes;
     @PluginBuilderAttribute private boolean captureMarkerAttribute;
-    @PluginBuilderAttribute private String captureContextDataAttributes;
+    @Nullable @PluginBuilderAttribute private String captureContextDataAttributes;
     @PluginBuilderAttribute private boolean captureEventName;
     @PluginBuilderAttribute private int numLogsCapturedBeforeOtelInstall;
 
@@ -187,10 +187,10 @@ public B setCaptureEventName(boolean captureEventName) {
     }
 
     /**
-     * Log telemetry is emitted after the initialization of the OpenTelemetry Logback appender with
-     * an {@link OpenTelemetry} object. This setting allows you to modify the size of the cache used
-     * to replay the logs that were emitted prior to setting the OpenTelemetry instance into the
-     * Logback appender.
+     * Log telemetry is emitted after the initialization of the OpenTelemetry Log4j appender with an
+     * {@link OpenTelemetry} object. This setting allows you to modify the size of the cache used to
+     * replay the logs that were emitted prior to setting the OpenTelemetry instance into the
+     * OpenTelemetry Log4j appender.
      */
     @CanIgnoreReturnValue
     public B setNumLogsCapturedBeforeOtelInstall(int numLogsCapturedBeforeOtelInstall) {
@@ -239,15 +239,15 @@ private OpenTelemetryAppender(
       boolean captureCodeAttributes,
       boolean captureMapMessageAttributes,
       boolean captureMarkerAttribute,
-      String captureContextDataAttributes,
+      @Nullable String captureContextDataAttributes,
       boolean captureEventName,
       int numLogsCapturedBeforeOtelInstall,
-      OpenTelemetry openTelemetry) {
+      @Nullable OpenTelemetry openTelemetry) {
     super(name, filter, layout, ignoreExceptions, properties);
 
-    DeclarativeConfigProperties comonConfig =
+    DeclarativeConfigProperties commonConfig =
         DeclarativeConfigUtil.getInstrumentationConfig(openTelemetry, "common");
-    boolean v3Preview = comonConfig.getBoolean("v3_preview", false);
+    boolean v3Preview = commonConfig.getBoolean("v3_preview", false);
 
     this.mapper =
         new LogEventMapper<>(
@@ -268,7 +268,7 @@ private OpenTelemetryAppender(
     }
   }
 
-  private static List<String> splitAndFilterBlanksAndNulls(String value) {
+  private static List<String> splitAndFilterBlanksAndNulls(@Nullable String value) {
     if (value == null) {
       return emptyList();
     }

instrumentation/log4j/log4j-appender-2.17/metadata.yaml

@@ -36,6 +36,9 @@ configurations:
       Controls which MDC attributes to capture. Use "*" to capture all MDC attributes or provide a
       comma-separated list of specific keys.
     type: list
+    examples:
+      - "*"
+      - "key1,key2"
     default: ''
     examples:
       - "custom-mdc-key"