how to use Kafka 0.8 Log4j appender

Question

I am trying to run Kafka-0.8 Log4j appender and I am unable to make it. I want my application to send log directly to kafka via Log4j appender.

Here is my log4j.properties. I couldn`t find any proper encoder, so I just configure it to use default encoder. (e.g I commented the line.)

log4j.rootLogger=INFO, stdout, KAFKA

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

log4j.appender.KAFKA=kafka.producer.KafkaLog4jAppender
log4j.appender.KAFKA.layout=org.apache.log4j.PatternLayout
log4j.appender.KAFKA.layout.ConversionPattern=%-5p: %c - %m%n
log4j.appender.KAFKA.BrokerList=hnode01:9092
log4j.appender.KAFKA.Topic=DKTestEvent

#log4j.appender.KAFKA.SerializerClass=kafka.log4j.AppenderStringEncoder

And this is my sample application.

import org.apache.log4j.Logger;
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.PropertyConfigurator;

public class HelloWorld {

        static Logger logger = Logger.getLogger(HelloWorld.class.getName());

        public static void main(String[] args) {
            PropertyConfigurator.configure(args[0]);

            logger.info("Entering application.");
            logger.debug("Debugging!.");
            logger.info("Exiting application.");
        }
}

I used maven for compiling. I included kafka_2.8.2-0.8.0 and log4j_1.2.17 in my pom.xml

And I am getting these error:

INFO [main] (Logging.scala:67) - Verifying properties
INFO [main] (Logging.scala:67) - Property metadata.broker.list is overridden to hnode01:9092
INFO [main] (Logging.scala:67) - Property serializer.class is overridden to kafka.serializer.StringEncoder
INFO [main] (HelloWorld.java:14) - Entering application.
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 0 for 1 topic(s) Set(DKTestEvent)
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 1 for 1 topic(s) Set(DKTestEvent)
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 2 for 1 topic(s) Set(DKTestEvent)
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 3 for 1 topic(s) Set(DKTestEvent)
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 4 for 1 topic(s) Set(DKTestEvent)
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 5 for 1 topic(s) Set(DKTestEvent)
.
.
.
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 60 for 1 topic(s) Set(DKTestEvent)
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 61 for 1 topic(s) Set(DKTestEvent)
INFO [main] (HelloWorld.java:14) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 62 for 1 topic(s) Set(DKTestEvent)
INFO [main] (Logging.scala:67) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 63 for 1 topic(s) Set(DKTestEvent)
INFO [main] (Logging.scala:67) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 64 for 1 topic(s) Set(DKTestEvent)
INFO [main] (Logging.scala:67) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 65 for 1 topic(s) Set(DKTestEvent)
INFO [main] (Logging.scala:67) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 66 for 1 topic(s) Set(DKTestEvent)
INFO [main] (Logging.scala:67) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 67 for 1 topic(s) Set(DKTestEvent)
.
.
.
INFO [main] (Logging.scala:67) - Fetching metadata from broker id:0,host:hnode01,port:9092 with correlation id 534 for 1 topic(s) Set(DKTestEvent)
ERROR [main] (Logging.scala:67) - 
ERROR [main] (Logging.scala:67) - 
ERROR [main] (Logging.scala:67) - 
ERROR [main] (Logging.scala:67) - 
ERROR [main] (Logging.scala:67) - 
ERROR [main] (Logging.scala:67) - 
java.lang.StackOverflowError
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:643)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:643)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
at org.apache.log4j.spi.ThrowableInformation.getThrowableStrRep(ThrowableInformation.java:87)
at org.apache.log4j.spi.LoggingEvent.getThrowableStrRep(LoggingEvent.java:413)
at org.apache.log4j.WriterAppender.subAppend(WriterAppender.java:313)
at org.apache.log4j.WriterAppender.append(WriterAppender.java:162)
at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:66)
at org.apache.log4j.Category.callAppenders(Category.java:206)
at org.apache.log4j.Category.forcedLog(Category.java:391)
at org.apache.log4j.Category.error(Category.java:322)
at kafka.utils.Logging$$anonfun$swallowError$1.apply(Logging.scala:105)
at kafka.utils.Logging$$anonfun$swallowError$1.apply(Logging.scala:105)
at kafka.utils.Utils$.swallow(Utils.scala:189)
at kafka.utils.Logging$class.swallowError(Logging.scala:105)
at kafka.utils.Utils$.swallowError(Utils.scala:46)
at kafka.producer.async.DefaultEventHandler.handle(DefaultEventHandler.scala:67)
at kafka.producer.Producer.send(Producer.scala:76)
at kafka.producer.KafkaLog4jAppender.append(KafkaLog4jAppender.scala:96)
at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:66)
at org.apache.log4j.Category.callAppenders(Category.java:206)
at org.apache.log4j.Category.forcedLog(Category.java:391)
at org.apache.log4j.Category.info(Category.java:666)
at kafka.utils.Logging$class.info(Logging.scala:67)
at kafka.client.ClientUtils$.info(ClientUtils.scala:31)
at kafka.client.ClientUtils$.fetchTopicMetadata(ClientUtils.scala:51)
at kafka.producer.BrokerPartitionInfo.updateInfo(BrokerPartitionInfo.scala:82)
at kafka.producer.async.DefaultEventHandler$$anonfun$handle$1.apply$mcV$sp(DefaultEventHandler.scala:67)
at kafka.utils.Utils$.swallow(Utils.scala:187)
at kafka.utils.Logging$class.swallowError(Logging.scala:105)
at kafka.utils.Utils$.swallowError(Utils.scala:46)
at kafka.producer.async.DefaultEventHandler.handle(DefaultEventHandler.scala:67)
at kafka.producer.Producer.send(Producer.scala:76)
at kafka.producer.KafkaLog4jAppender.append(KafkaLog4jAppender.scala:96)
at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:66)
.
.
.

I am getting above error continuously if i don`t terminate the program.

If I miss something, kindly let me know.

Answer 1

I think Jonas has identified the problem, that is the Kafka producer logging is also getting logged to the Kafka appender causing an infinite loop and eventual stack overflow (no pun intended) You can configure all Kafka logs to go to a different appender. The following shows sending the output to stdout:

log4j.logger.kafka=INFO, stdout

So you should end up with the following in your log4j.properties

log4j.rootLogger=INFO, stdout, KAFKA
log4j.logger.kafka=INFO, stdout
log4j.logger.HelloWorld=INFO, KAFKA