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KarstenSchnitterKarstenSchnitter
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Dynamic Filtering for Log4j2
Provides a new filter for dynamic log levels with class name support. The DynamicLevelPrefixLoggerFilter will check the Logger name against a list of prefixes and only change the log level on matching names.
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‎cf-java-logging-support-log4j2/src/main/java/com/sap/hcp/cf/log4j2/filter/DynamicLevelPrefixLoggerFilter.java‎

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package com.sap.hcp.cf.log4j2.filter;
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import org.apache.commons.lang3.StringUtils;
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import org.apache.logging.log4j.Level;
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import org.apache.logging.log4j.Marker;
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import org.apache.logging.log4j.core.LogEvent;
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import org.apache.logging.log4j.core.Logger;
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import org.apache.logging.log4j.core.config.plugins.Plugin;
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import org.apache.logging.log4j.core.config.plugins.PluginFactory;
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import org.apache.logging.log4j.core.filter.AbstractFilter;
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import org.apache.logging.log4j.message.Message;
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import org.apache.logging.log4j.util.ReadOnlyStringMap;
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import org.slf4j.MDC;
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import com.sap.hcp.cf.logging.common.helper.DynamicLogLevelHelper;
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@Plugin(name = "DynamicLevelPrefixLoggerFilter", category = "Core", elementType = "filter", printObject = true)
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public class DynamicLevelPrefixLoggerFilter extends AbstractFilter {
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@Override
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public Result filter(LogEvent event) {
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Level level = event.getLevel();
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Level dynamicLevel = getDynamicLevel(event);
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String loggerFqcn = event.getLoggerFqcn();
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String logLevelPackages = getDynamicPackages(event);
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return filter(level, dynamicLevel, loggerFqcn, logLevelPackages);
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}
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private Level getDynamicLevel(LogEvent event) {
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String logLevel = getContextValue(event, DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_KEY);
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return StringUtils.isNotBlank(logLevel) ? Level.getLevel(logLevel) : null;
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}
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private String getContextValue(LogEvent event, String key) {
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ReadOnlyStringMap contextData = event.getContextData();
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return contextData != null ? contextData.getValue(key) : null;
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}
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private String getDynamicPackages(final LogEvent event) {
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String logLevelPackages = getContextValue(event, DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES);
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return logLevelPackages;
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}
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private Result filter(Level level, Level dynamicLevel, String loggerFqcn, String logLevelPackages) {
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if (dynamicLevel != null && level.isMoreSpecificThan(dynamicLevel)
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&& checkPackages(loggerFqcn, logLevelPackages)) {
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return Result.ACCEPT;
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}
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return Result.NEUTRAL;
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}
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private boolean checkPackages(String loggerFqcn, String logLevelPackages) {
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if (StringUtils.isNotBlank(logLevelPackages)) {
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for (String current : logLevelPackages.split(",")) {
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if (loggerFqcn.startsWith(current)) {
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return true;
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}
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}
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}
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return false;
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}
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@Override
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public Result filter(final Logger logger, final Level level, final Marker marker, final Message msg,
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final Throwable t) {
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return filter(level, getMdcLevel(), logger.getName(), getMdcPackages());
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}
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@Override
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public Result filter(final Logger logger, final Level level, final Marker marker, final Object msg,
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final Throwable t) {
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return filter(level, getMdcLevel(), logger.getName(), getMdcPackages());
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}
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@Override
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public Result filter(final Logger logger, final Level level, final Marker marker, final String msg,
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final Object... params) {
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return filter(level, getMdcLevel(), logger.getName(), getMdcPackages());
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}
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private Level getMdcLevel() {
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String mdcLevel = MDC.get(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_KEY);
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return StringUtils.isNotBlank(mdcLevel) ? Level.getLevel(mdcLevel) : null;
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}
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private String getMdcPackages() {
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return MDC.get(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES);
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}
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@PluginFactory
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public static DynamicLevelPrefixLoggerFilter createFilter() {
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return new DynamicLevelPrefixLoggerFilter();
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}
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}

‎cf-java-logging-support-log4j2/src/test/java/com/sap/hcp/cf/log4j2/filter/DynamicLevelPrefixLoggerFilterTest.java‎

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package com.sap.hcp.cf.log4j2.filter;
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import static org.hamcrest.Matchers.is;
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import static org.junit.Assert.assertThat;
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import java.net.URL;
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import java.util.HashMap;
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import org.apache.logging.log4j.Level;
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import org.apache.logging.log4j.core.Filter.Result;
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import org.apache.logging.log4j.core.LoggerContext;
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import org.apache.logging.log4j.core.appender.CountingNoOpAppender;
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import org.apache.logging.log4j.core.config.ConfigurationSource;
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import org.apache.logging.log4j.core.config.xml.XmlConfiguration;
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import org.apache.logging.log4j.core.impl.JdkMapAdapterStringMap;
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import org.apache.logging.log4j.core.impl.Log4jLogEvent;
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import org.junit.Test;
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import org.slf4j.MDC;
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import com.sap.hcp.cf.logging.common.helper.DynamicLogLevelHelper;
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public class DynamicLevelPrefixLoggerFilterTest {
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private static final String KNOWN_PREFIX = "known.prefix";
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private static final String UNKNOWN_PREFIX = "unknown.prefix";
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private final JdkMapAdapterStringMap contextData;
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private final DynamicLevelPrefixLoggerFilter filter = new DynamicLevelPrefixLoggerFilter();
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public DynamicLevelPrefixLoggerFilterTest() {
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HashMap<String, String> customMDC = new HashMap<>();
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customMDC.put(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_KEY, "DEBUG");
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customMDC.put(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES, KNOWN_PREFIX);
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this.contextData = new JdkMapAdapterStringMap(customMDC);
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}
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@Test
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public void acceptsOnKnownPackage() throws Exception {
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Log4jLogEvent event = Log4jLogEvent.newBuilder().setLoggerFqcn(KNOWN_PREFIX + "acceptsOnKnownPackage")
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.setContextData(contextData).setLevel(Level.INFO).build();
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assertThat(filter.filter(event), is(Result.ACCEPT));
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}
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@Test
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public void neutralOnUnknownPackage() throws Exception {
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Log4jLogEvent event = Log4jLogEvent.newBuilder().setLoggerFqcn(UNKNOWN_PREFIX + "neutralOnUnknownPackage")
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.setContextData(contextData).setLevel(Level.INFO).build();
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assertThat(filter.filter(event), is(Result.NEUTRAL));
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}
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@Test
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public void neutralOnLowerLevel() throws Exception {
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Log4jLogEvent event = Log4jLogEvent.newBuilder().setLoggerFqcn(KNOWN_PREFIX + "neutralOnUnknownPackage")
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.setContextData(contextData).setLevel(Level.TRACE).build();
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assertThat(filter.filter(event), is(Result.NEUTRAL));
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}
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@Test
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public void neutralOnUnconfiguredLevelKey() throws Exception {
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HashMap<String, String> customMDC = new HashMap<>();
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customMDC.put(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES, KNOWN_PREFIX);
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JdkMapAdapterStringMap missingLevelKey = new JdkMapAdapterStringMap(customMDC);
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Log4jLogEvent event = Log4jLogEvent.newBuilder().setLoggerFqcn(KNOWN_PREFIX + "neutralOnUnknownPackage")
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.setContextData(missingLevelKey).setLevel(Level.INFO).build();
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assertThat(filter.filter(event), is(Result.NEUTRAL));
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}
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@Test
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public void neutralOnUnconfiguredPrefix() throws Exception {
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HashMap<String, String> customMDC = new HashMap<>();
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customMDC.put(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES, KNOWN_PREFIX);
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JdkMapAdapterStringMap missingPrefixes = new JdkMapAdapterStringMap(customMDC);
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Log4jLogEvent event = Log4jLogEvent.newBuilder().setLoggerFqcn(KNOWN_PREFIX + "neutralOnUnknownPackage")
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.setContextData(missingPrefixes).setLevel(Level.INFO).build();
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assertThat(filter.filter(event), is(Result.NEUTRAL));
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}
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@Test
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public void integratesIntoConfiguration() throws Exception {
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LoggerContext loggerContext = new LoggerContext("integratesIntoConfiguration");
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URL configLocation = getClass().getResource("log4j2-test.xml");
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ConfigurationSource configurationSource = ConfigurationSource.fromUri(configLocation.toURI());
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XmlConfiguration configuration = new XmlConfiguration(loggerContext, configurationSource);
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loggerContext.start(configuration);
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org.apache.logging.log4j.core.Logger logger = loggerContext
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.getLogger(KNOWN_PREFIX + "integratesIntoConfiguration");
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CountingNoOpAppender appender = new CountingNoOpAppender("integratesIntoConfiguration", null);
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logger.addAppender(appender);
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logger.debug("test-integration-message-at-debug");
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assertThat(appender.getCount(), is(0L));
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logger.info("test-integration-message-at-info");
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assertThat(appender.getCount(), is(1L));
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MDC.put(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_KEY, "DEBUG");
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MDC.put(DynamicLogLevelHelper.MDC_DYNAMIC_LOG_LEVEL_PREFIXES, KNOWN_PREFIX);
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logger.debug("test-integration-message-at-debug");
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assertThat(appender.getCount(), is(2L));
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loggerContext.close();
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}
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}

‎cf-java-logging-support-log4j2/src/test/resources/com/sap/hcp/cf/log4j2/filter/log4j2-test.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<Configuration status="warn" strict="true"
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packages="com.sap.hcp.cf.log4j2.converter,com.sap.hcp.cf.log4j2">
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<DynamicLevelPrefixLoggerFilter />
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<Appenders>
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<Console name="Console" target="SYSTEM_OUT">
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<PatternLayout
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pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
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</Console>
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</Appenders>
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<Loggers>
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<Root level="info">
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<AppenderRef ref="Console" />
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</Root>
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</Loggers>
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</Configuration>

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