Add support for outputting slf4j markers in the default configuration

src/main/java/com/spotify/logging/LoggingConfigurator.java

@@ -189,6 +189,24 @@ public static void configureDefaults(final String ident, final Level level) {
    */
   public static void configureDefaults(
       final String ident, final Level level, final ReplaceNewLines replaceNewLines) {
+    configureDefaults(ident, level, replaceNewLines, false);
+  }
+
+  /**
+   * Configure logging with default behaviour and log to stderr. If the SPOTIFY_SYSLOG_HOST or
+   * SPOTIFY_SYSLOG_PORT environment variable is defined, the syslog appender will be used,
+   * otherwise console appender will be.
+   *
+   * @param ident The logging identity.
+   * @param level logging level to use.
+   * @param replaceNewLines configures new lines replacement in the messages
+   * @param appendMarkers append markers to the log message
+   */
+  public static void configureDefaults(
+      final String ident,
+      final Level level,
+      final ReplaceNewLines replaceNewLines,
+      final boolean appendMarkers) {
     // Call configureSyslogDefaults if the SPOTIFY_SYSLOG_HOST or SPOTIFY_SYSLOG_PORT env var is
     // set. If this causes a problem, we could introduce a configureConsoleDefaults method which
     // users could call instead to avoid this behavior.
@@ -205,7 +223,7 @@ public static void configureDefaults(
     final LoggerContext context = setupLoggerContext(rootLogger, ident);
 
     // Setup stderr output
-    rootLogger.addAppender(getStdErrAppender(context, replaceNewLines));
+    rootLogger.addAppender(getStdErrAppender(context, replaceNewLines, appendMarkers));
 
     // Setup logging level
     rootLogger.setLevel(level.logbackLevel);
@@ -380,16 +398,20 @@ public static SentryAppender addSentryAppender(
    * Create a stderr appender.
    *
    * @param context The logger context to use.
+   * @param appendMarkers append markers to the log message
    * @return An appender writing to stderr.
    */
   private static Appender<ILoggingEvent> getStdErrAppender(
-      final LoggerContext context, final ReplaceNewLines replaceNewLines) {
+      final LoggerContext context,
+      final ReplaceNewLines replaceNewLines,
+      final boolean appendMarkers) {
 
     // Setup format
     final PatternLayoutEncoder encoder = new PatternLayoutEncoder();
     encoder.setContext(context);
     encoder.setPattern(
         "%date{HH:mm:ss.SSS} %property{ident}[%property{pid}]: %-5level [%thread] %logger{0}: "
+            + (appendMarkers ? "[%marker] " : "")
             + ReplaceNewLines.getMsgPattern(replaceNewLines)
             + "%n");
     encoder.setCharset(StandardCharsets.UTF_8);
@@ -487,7 +509,7 @@ static void configure(final JewelCliLoggingOptions opts) {
       rootLogger.addAppender(
           getSyslogAppender(context, syslogHost, syslogPort, ReplaceNewLines.OFF));
     } else {
-      rootLogger.addAppender(getStdErrAppender(context, ReplaceNewLines.OFF));
+      rootLogger.addAppender(getStdErrAppender(context, ReplaceNewLines.OFF, false));
     }
 
     // Setup default logging level

src/test/java/com/spotify/logging/LoggingConfiguratorTest.java

@@ -49,6 +49,7 @@
 import ch.qos.logback.classic.net.SyslogAppender;
 import ch.qos.logback.core.ConsoleAppender;
 import ch.qos.logback.core.status.Status;
+import com.spotify.logging.LoggingConfigurator.ReplaceNewLines;
 import com.spotify.logging.logback.CustomLogstashEncoder;
 import io.sentry.logback.SentryAppender;
 import net.logstash.logback.composite.loggingevent.ArgumentsJsonProvider;
@@ -178,6 +179,30 @@ public void shouldConfigureDefaultWithIdentAndLevelWhenSyslogEnvVarIsNotSet() {
     assertDefault("some-ident", Level.DEBUG);
   }
 
+  @Test
+  public void shouldConfigureDefaultWithMarkerSupport() {
+    LoggingConfigurator.configureDefaults(
+        "some-ident", LoggingConfigurator.Level.DEBUG, ReplaceNewLines.OFF, true);
+    final Logger rootLogger = (Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
+    final ConsoleAppender<?> stderr = (ConsoleAppender<?>) rootLogger.getAppender("stderr");
+    assertTrue(stderr.getEncoder() instanceof PatternLayoutEncoder);
+    assertEquals(
+        "%date{HH:mm:ss.SSS} %property{ident}[%property{pid}]: %-5level [%thread] %logger{0}: [%marker] %msg%n",
+        ((PatternLayoutEncoder) stderr.getEncoder()).getPattern());
+  }
+
+  @Test
+  public void shouldConfigureDefaultWithoutMarkerSupport() {
+    LoggingConfigurator.configureDefaults(
+        "some-ident", LoggingConfigurator.Level.DEBUG, ReplaceNewLines.OFF, false);
+    final Logger rootLogger = (Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
+    final ConsoleAppender<?> stderr = (ConsoleAppender<?>) rootLogger.getAppender("stderr");
+    assertTrue(stderr.getEncoder() instanceof PatternLayoutEncoder);
+    assertEquals(
+        "%date{HH:mm:ss.SSS} %property{ident}[%property{pid}]: %-5level [%thread] %logger{0}: %msg%n",
+        ((PatternLayoutEncoder) stderr.getEncoder()).getPattern());
+  }
+
   @Test
   public void shouldConfigureLogstashEncoderWhenEnvVarIsSetToTrue() {
     environmentVariables.set("USE_JSON_LOGGING", "true");