Logback Filter - limitative error log message - gradle

Question

Still newbie on springboot, gradle and logback, I need help! I am trying to create my own logback filter.
Main goal is to allow my logger to only send a single log message if some logs with same error message are send by application.
To do it, I just create a basic gradle project to test, with 2 classes.
build.gradle
logback.xml
project_explorer_eclipse
I - My main class which logs some errors
package com.example.CDOP221logback;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.joran.JoranConfigurator;
import ch.qos.logback.core.joran.spi.JoranException;
#SpringBootApplication
public class Cdop221LogbackApplication {
private final static Logger log = LoggerFactory.getLogger("com.example.CDOP221log4j");
public static void main(String[] args) {
SpringApplication.run(Cdop221LogbackApplication.class, args);
LoggerContext context = (LoggerContext)LoggerFactory.getILoggerFactory();
context.reset();
JoranConfigurator config = new JoranConfigurator();
config.setContext(context);
try {
config.doConfigure("/home/mehdi/eclipse-workspace/CDOP-221-logback/logback.xml");
} catch (JoranException e) {
e.printStackTrace();
}
test();
}
private static void test() {
log.debug("Application Cdop221 with LOGBACK logger launch succesful");
log.error("ERROR_1");
log.error("ERROR_1");
log.error("ERROR_1");
log.error("ERROR_1");
log.error("ERROR_1");
log.error("ERROR_1");
log.error("ERROR_1");
log.error("ERROR_1");
int i = 0;
while(i < 100) {
log.error("ERROR_2");
i++;
}
}
}
II - My own appender which has to limit number of log if some entries are the same
package com.logback;
import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.classic.spi.IThrowableProxy;
import ch.qos.logback.classic.spi.LoggingEvent;
import ch.qos.logback.classic.spi.StackTraceElementProxy;
import ch.qos.logback.core.filter.Filter;
import ch.qos.logback.core.spi.FilterReply;
import org.apache.commons.lang3.ArrayUtils;
import org.slf4j.LoggerFactory;
import java.util.HashMap;
import java.util.Map;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
/**
* Improved {#link ch.qos.logback.classic.turbo.DuplicateMessageFilter} with a timeout feature added and time window error stacking #buzzwords
* Indeed if there's some error logs that are the same (same hashcode) they are stacked and sent after {#link DuplicateErrorLogFilter#cacheTimeoutInSec}
*/
public class DuplicateErrorLogFilter extends Filter<ILoggingEvent> {
/**
* Repetition number MDC property
*/
private static final String REP_NB = "repNb";
/**
* The default cache size.
*/
private static final int DEFAULT_CACHE_SIZE = 100;
/**
* The default cache timeout in seconds
*/
private static final int DEFAULT_CACHE_TIMEOUT_IN_SEC = 300;
private String smtpAppenderName;
private int cacheSize = DEFAULT_CACHE_SIZE;
private int cacheTimeoutInSec = DEFAULT_CACHE_TIMEOUT_IN_SEC;
private Map<Integer, FoldingTask> tasks = new ConcurrentHashMap<>(cacheSize);
/**
* Timer that will expire folding tasks
*/
private Timer foldingTimer = new Timer("folding-timer", false);
private final class FoldingTask extends TimerTask {
private Integer key;
private ILoggingEvent lastEvent;
private int foldingCount;
#Override
public void run() {
// Remove current task
tasks.remove(key);
// And send the event to SMTP appender
sendEvent(lastEvent, foldingCount);
}
}
/**
* Append an event that has been folded
*
* #param event the last seen event of this kind
* #param foldingCount how many events were folded
*/
protected void sendEvent(ILoggingEvent event, int foldingCount) {
if (event != null) {
if (foldingCount > 1) {
// Do that to prevent UnsupportedOp from EmptyMap
if (event.getMDCPropertyMap().isEmpty() && event instanceof LoggingEvent) {
((LoggingEvent) event).setMDCPropertyMap(new HashMap<>());
}
event.getMDCPropertyMap().put(REP_NB, "[" + foldingCount + "x]");
}
((Logger) (LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME))).getAppender(smtpAppenderName).doAppend(event);
}
}
public void setSmtpAppenderName(String smtpAppenderName) {
this.smtpAppenderName = smtpAppenderName;
}
public void setCacheSize(int cacheSize) {
this.cacheSize = cacheSize;
}
public void setCacheTimeoutInSec(int cacheTimeoutInSec) {
this.cacheTimeoutInSec = cacheTimeoutInSec;
}
#Override
public void start() {
super.start();
}
#Override
public void stop() {
tasks.clear();
tasks = null;
super.stop();
}
#Override
public FilterReply decide(ILoggingEvent event) {
if (!event.getLevel().isGreaterOrEqual(Level.ERROR)) {
return FilterReply.NEUTRAL;
}
Integer key = eventHashCode(event);
FoldingTask task = tasks.get(key);
if (task == null) {
// First time we encounter this event
task = new FoldingTask();
task.key = key;
// lastEvent will be set at the first folded event
tasks.put(key, task);
// Arm timer for this task
foldingTimer.schedule(task, TimeUnit.SECONDS.toMillis(cacheTimeoutInSec));
// And log this event
return FilterReply.NEUTRAL;
} else {
// Fold this event
task.lastEvent = event;
task.foldingCount++;
return FilterReply.DENY;
}
}
/**
* Compute a signature for an event
*/
private int eventHashCode(ILoggingEvent event) {
IThrowableProxy thrInfo = event.getThrowableProxy();
if (thrInfo == null || ArrayUtils.isEmpty(thrInfo.getStackTraceElementProxyArray())) {
// No stacktrace
String message = event.getFormattedMessage();
return message.hashCode();
}
StackTraceElementProxy[] stack = thrInfo.getStackTraceElementProxyArray();
int hashCode = 0;
for (StackTraceElementProxy str : stack) {
hashCode = 31 * hashCode + str.hashCode();
}
return hashCode;
}
}
So, when I run my code, it doesn't work actually... But I am not really able to identify if it's because of a bad configuration (I am beginner with logback library) or if my code sucks?...
Thank you in advance for your help
result code (doesn't work correctly)

Answer 1

A part is missing from the logback config file (logback.xml) where you connect your filter (DuplicateErrorLogFilter) and logback:
<filter class="com.logback.DuplicateErrorLogFilter"/>
for additional info on how to use filter: https://logback.qos.ch/manual/filters.html