Best way to write custom json messages using log4j2

Question

I have been using log4j for different kind of projects and have some experience with log4j2. All implementations used the default appender and layout. Currently i need to wr

Answer 1

The question is about writing a custom json messages using log4j2.

This is possible since version 2.11 of log4j2 version:

https://issues.apache.org/jira/browse/LOG4J2-2190

The new parameter of for JSONLayout is called

objectMessageAsJsonObject

. Sample project files;

log4j2.properties

status = error


appender.ana_whitespace.type = RollingFile
appender.ana_whitespace.name = ana_whitespace
appender.ana_whitespace.fileName = ${sys:es.logs.base_path:-target}${sys:file.separator}ana_whitespace.log
appender.ana_whitespace.layout.type = JsonLayout
appender.ana_whitespace.layout.propertiesAsList = false
appender.ana_whitespace.layout.compact = false
appender.ana_whitespace.layout.eventEol = true
appender.ana_whitespace.layout.objectMessageAsJsonObject = true
appender.ana_whitespace.layout.complete= true
appender.ana_whitespace.layout.properties= true
appender.ana_whitespace.filePattern = ${sys:es.logs.base_path:-target}${sys:file.separator}ana_whitespace-%d{yyyy-MM-dd}.log
appender.ana_whitespace.filter.1.type = MarkerFilter
appender.ana_whitespace.filter.1.onMismatch=DENY
appender.ana_whitespace.filter.1.onMatch=ACCEPT
appender.ana_whitespace.filter.1.marker=ANA_WHITESPACE
appender.ana_whitespace.policies.type = Policies
appender.ana_whitespace.policies.time.type = TimeBasedTriggeringPolicy
appender.ana_whitespace.policies.time.interval = 1
appender.ana_whitespace.policies.time.modulate = true
appender.ana_whitespace.policies.size.type = SizeBasedTriggeringPolicy
appender.ana_whitespace.policies.size.size = 10 MB

rootLogger.level = info
rootLogger.appenderRef.ana_whitespace.ref = ana_whitespace

Example Java code

package de.es.stemmer;

import java.io.IOException;
import java.util.Map;
import java.util.TreeMap;

import org.apache.http.client.ClientProtocolException;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.MarkerManager;
import org.apache.logging.log4j.ThreadContext;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.message.ObjectMessage;

public class JsonLoggerTest {
    final static Logger log = LogManager.getLogger(JsonLoggerTest.class);
    final static Marker MARKER_WHITESPACE = MarkerManager.getMarker("ANA_WHITESPACE");

    public static void main(String[] args) throws ClientProtocolException, IOException {
        System.setProperty("es.logs.base_path", "target");
        System.setProperty("es.logs.cluster_name", "_cluster");
        LoggerContext.getContext().reconfigure();
        ThreadContext.put("orig", "MDC_origValue");
        ThreadContext.put("source", "MDC_sourceSnippet");
        Map map = new TreeMap<>();
        map.put("orig", "msg_origValue");
        map.put("source", "msg_sourceSnippet");
        ObjectMessage msg = new ObjectMessage(map);
        log.info(MARKER_WHITESPACE, msg);
        ThreadContext.remove("orig");
        ThreadContext.remove("source");
    }

}

JSON Log Entry

[
{
  "thread" : "main",
  "level" : "INFO",
  "loggerName" : "de.es.stemmer.JsonLoggerTest",
  "marker" : {
    "name" : "ANA_WHITESPACE"
  },
  "message" : {
    "orig" : "msg_origValue",
    "source" : "msg_sourceSnippet"
  },
  "endOfBatch" : false,
  "loggerFqcn" : "org.apache.logging.log4j.spi.AbstractLogger",
  "instant" : {
    "epochSecond" : 1526576578,
    "nanoOfSecond" : 184000000
  },
  "contextMap" : {
    "orig" : "MDC_origValue",
    "source" : "MDC_sourceSnippet"
  },
  "threadId" : 1,
  "threadPriority" : 5
}

]