[LOG4J2-2375] When KafkaAppender is used with other KafkaProducer, there is a problem.

• Type: Bug
• Status: Open
• Priority: Critical
• Resolution: Unresolved
• Affects Version/s: 2.11.0
• Component/s: Appenders

Environment

scala 2.12.6 
kafka 1.1.0 
log4j2 2.11.0

• Assignee: Unassigned
• Reporter: zhangjk
• Created: 16/Jul/18 07:58
• Updated: 24/Jul/18 07:38

Description

hi:

When i use the log4j2's KafkaAppender , I found a bug.  the property CONFIG of the ProducerConfig is null.

here's my code:

log4j2.xml

<Appenders>
    <Kafka name="Kafka" topic="test" key ="KafkaTestKey">
        <PatternLayout pattern="%d{yyyy.MM.dd 'at' HH:mm:ss z} %-5level %class{36} %L %M - %msg%xEx%n"/>
        <Property name="bootstrap.servers">localhost:9092</Property>
    </Kafka>
</Appenders>

the main class:

object KafkaTest extends App {
  // this is scala code.
  // create a KafkaProducer
  val p = new Producer
}

producer code:

class Producer {
  val props = {
    val p = new Properties()
    ....
    p
  }

  val producer = {
    val p = new KafkaProducer[Integer, String](props)
    p
  }
}

The reason for this BUG is that:  the `new Producer` is first initialized, and the `ProducerConfig` has a static method block, and it called the `CommonClientConfigs` class. in the `CommonClientConfigs` class,  it has a static Log property, so, this will initialize the Log4j2's configuration, and this will call a startup method of the Appender, it actually calls the KafkaAppender's method. and then the method create a new `KafkaProducer`, this will create a new `ProducerConfig` instance, but the static method block is not completed, so the `CONFIG` is null.  this cause the `NullPointerException`  

my english is bad, so , hope to understand what i mean