Dynamic prefix filtering for Logback

Provides a new TurboFilter for dynamic log level support with support for class names.
The DynamicLevelPrefixLoggerTurboFilter will check the Logger name against a list of
prefixes and only change the log level on matching names.

Author: KarstenSchnitter

cf-java-logging-support-core/src/main/java/com/sap/hcp/cf/logging/common/helper/DynamicLogLevelHelper.java

@@ -7,5 +7,6 @@ public class DynamicLogLevelHelper {
      * from mdc
      */
     public static final String MDC_DYNAMIC_LOG_LEVEL_KEY = "dynamic_log_level";
+	public static final String MDC_DYNAMIC_LOG_LEVEL_PREFIXES = "dynamic_log_level_prefixes";
 
 }

cf-java-logging-support-logback/src/main/java/com/sap/hcp/cf/logback/filter/DynamicLevelPrefixLoggerTurboFilter.java

@@ -0,0 +1,38 @@
+package com.sap.hcp.cf.logback.filter;
+
+import org.apache.commons.lang3.StringUtils;
+import org.slf4j.MDC;
+import org.slf4j.Marker;
+
+import com.sap.hcp.cf.logging.common.helper.DynamicLogLevelHelper;
+
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.turbo.TurboFilter;
+import ch.qos.logback.core.spi.FilterReply;
+
+public class DynamicLevelPrefixLoggerTurboFilter extends TurboFilter {
+
+	@Override
+	public FilterReply decide(final Marker marker, final Logger logger, final Level level, final String format,
+			final Object[] params, final Throwable t) {
+		final String logLevel = MDC.get(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_KEY);
+		if (logLevel != null && level.isGreaterOrEqual(Level.toLevel(logLevel)) && checkPackages(logger)) {
+			return FilterReply.ACCEPT;
+		}
+		return FilterReply.NEUTRAL;
+	}
+
+	private boolean checkPackages(final Logger logger) {
+		final String logLevelPackages = MDC.get(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES);
+		if (StringUtils.isNotBlank(logLevelPackages)) {
+			for (String current : logLevelPackages.split(",")) {
+				if (logger.getName().startsWith(current)) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+}

cf-java-logging-support-logback/src/test/java/com/sap/hcp/cf/logback/filter/DynamicLevelPrefixLoggerTurboFilterTest.java

@@ -0,0 +1,81 @@
+package com.sap.hcp.cf.logback.filter;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.MDC;
+
+import com.sap.hcp.cf.logging.common.helper.DynamicLogLevelHelper;
+
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.classic.turbo.TurboFilter;
+import ch.qos.logback.core.read.ListAppender;
+import ch.qos.logback.core.spi.FilterReply;
+
+public class DynamicLevelPrefixLoggerTurboFilterTest {
+
+	private static final String KNOWN_PREFIX = "known.prefix";
+	private static final String UNKNOWN_PREFIX = "unknown.prefix";
+
+	private LoggerContext loggerContext = new LoggerContext();
+	private TurboFilter filter = new DynamicLevelPrefixLoggerTurboFilter();
+
+	@Before
+	public void setUp() {
+		MDC.clear();
+		MDC.put(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_KEY, "DEBUG");
+		MDC.put(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES, KNOWN_PREFIX);
+		loggerContext.addTurboFilter(filter);
+	}
+
+	@Test
+	public void acceptsOnKnownPackage() throws Exception {
+		Logger logger = loggerContext.getLogger(KNOWN_PREFIX + "acceptsOnKnownPackage");
+		assertThat(filter.decide(null, logger, Level.INFO, null, null, null), is(FilterReply.ACCEPT));
+	}
+
+	@Test
+	public void neutralOnUnknownPackage() throws Exception {
+		Logger logger = loggerContext.getLogger(UNKNOWN_PREFIX + "neutralOnUnknownPackage");
+		assertThat(filter.decide(null, logger, Level.INFO, null, null, null), is(FilterReply.NEUTRAL));
+	}
+
+	@Test
+	public void neutralOnLowerLevel() throws Exception {
+		Logger logger = loggerContext.getLogger(KNOWN_PREFIX + "neutralOnUnknownPackage");
+		assertThat(filter.decide(null, logger, Level.TRACE, null, null, null), is(FilterReply.NEUTRAL));
+	}
+
+	@Test
+	public void neutralOnUnconfiguredLevelKey() throws Exception {
+		MDC.remove(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_KEY);
+		Logger logger = loggerContext.getLogger(KNOWN_PREFIX + "neutralOnUnknownPackage");
+		assertThat(filter.decide(null, logger, Level.INFO, null, null, null), is(FilterReply.NEUTRAL));
+	}
+
+	@Test
+	public void neutralOnUnconfiguredPrefix() throws Exception {
+		MDC.remove(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES);
+		Logger logger = loggerContext.getLogger(KNOWN_PREFIX + "neutralOnUnknownPackage");
+		assertThat(filter.decide(null, logger, Level.INFO, null, null, null), is(FilterReply.NEUTRAL));
+	}
+
+	@Test
+	public void integratesIntoConfiguration() throws Exception {
+		Logger logger = loggerContext.getLogger(KNOWN_PREFIX + "integratesIntoConfiguration");
+		ListAppender<ILoggingEvent> appender = new ListAppender<ILoggingEvent>();
+		appender.start();
+		logger.addAppender(appender);
+		logger.info("test-integration-message");
+		assertThat(appender.list, hasSize(1));
+		assertThat(appender.list.get(0).getMessage(), is(equalTo("test-integration-message")));
+		appender.stop();
+	}
+}