I am observing an issue when sending logs to both log4j2 and logback using kafka.

Here is the code of my very simple Springboot app:

@SpringBootApplication
public class QuestionApplication {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(QuestionApplication.class, args);
        HelloWorld helloWorld = new HelloWorld();
        HelloWorld.createLogs();
    }
}

public class HelloWorld {

    private static final Logger logger = LoggerFactory.getLogger(HelloWorld.class);

    public static void createLogs() throws JsonProcessingException {
        int k = 0;
        boolean b = true;
        while (b) {
            try{
                if(Math.random() > 0.5){
                    logger.info("ISSUE HERE -> custom logs and send log  messages  to Kafka topic at " +
                            DateTimeFormatter.ofPattern("HH:mm:ss").format(LocalDateTime.now()));
                    int i =  2 / 0;
                    b = k < Integer.MAX_VALUE;
                    Thread.sleep(1000);
                } else{
                }
            } catch (Exception re){
                throw new RuntimeException("ISSUE HERE (custom log) error in try " + k, re);
            } finally {
                try {
                    int j = 2 / 0;
                } catch (Exception e) {
                    logger.error("ISSUE HERE (custom log) error in finally " + k, e);
                }
            }
            k++;
        }
    }
}

Project ONE with just log4j2 + kafka appender
With the above code, in a first project, I need to send the logs to a Kafka topic.
To do so, I am using the following dependencies:

  <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
                <dependency>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-log4j2</artifactId>
                </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-clients</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-log4j-appender</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-layout-template-json</artifactId>
        </dependency>

And this log4j2.xml file (not logback-spring.xml)

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="info" name="spring-boot-kafka-log">
    <Appenders>
        <Kafka name="Kafkalol" topic="question">
            <PatternLayout>
                <Pattern>
{
  "some field": "1.0",
  "parameters": {
    "class": "%logger",
    "message": "%message"
  }
}
                </Pattern>
            </PatternLayout>
            <Property name="bootstrap.servers">localhost:9093</Property>
        </Kafka>
        <Async name="Async">
            <AppenderRef ref="Kafkalol"/>
        </Async>

        <Console name="stdout" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} %-5p [%-7t] %F:%L - %m%n"/>
        </Console>

    </Appenders>
    <Loggers>
        <Root level="INFO">
            <AppenderRef ref="Kafkalol"/>
            <AppenderRef ref="stdout"/>
        </Root>
        <Logger name="org.apache.kafka" level="WARN" /><!-- avoid recursive logging -->
    </Loggers>
</Configuration>

This WORKS and I am able to see all logs in the kafka topics.
By all logs, I mean my custom logs (from logger.info()) and the springboot logs

Project TWO with just logback + loki appender
With the same above java code, in a second project, I need to send the logs to a loki instance.
To do so, I am using the following dependencies:

   <dependency>
            <groupId>com.github.loki4j</groupId>
            <artifactId>loki-logback-appender</artifactId>
            <version>1.6.0-m1</version>
        </dependency>
        <dependency>
            <groupId>io.micrometer</groupId>
            <artifactId>micrometer-core</artifactId>
        </dependency>

and this is the logback-spring.xml (not log4j2.xml)

<?xml version="1.0" encoding="UTF-8"?>
<configuration debug="true">

    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>
                %d{yyyy-MM-dd HH:mm:ss} ${PID} %-5level --- [%thread] [${name},%X{traceId:-},%X{spanId:-}] %logger{36} : %msg%n
            </pattern>
        </encoder>
    </appender>

    <appender name="LOKI" class="com.github.loki4j.logback.Loki4jAppender">
        <metricsEnabled>true</metricsEnabled>
        <http>
            <url>https://logs-prod-006.grafana.net/loki/api/v1/push</url>
            <auth>
                <username>813123</username>
                <password>123</password>
            </auth>
        </http>
        <format>
            <label>
                <pattern>name=${name},host=${HOSTNAME},level=%level,pid=${PID},thread=%thread</pattern>
                <readMarkers>true</readMarkers>
            </label>
            <message>
                <pattern>
{
  "somefield":"1.0",
  "playload": {
    "pid":"${PID}",
    "class":"%logger",
    "thread":"%thread",
    "traceId":"%X{traceId}",
    "spanId":"%X{spanId}",
    "message":"%message"
  }
}
                </pattern>
            </message>
            <sortByTime>true</sortByTime>
        </format>
        <verbose>false</verbose>
    </appender>

    <root level="INFO">
        <appender-ref ref="STDOUT"/>
        <appender-ref ref="LOKI"/>
    </root>

</configuration>

This WORKS and I am able to see all logs in grafana loki.
By all logs, I mean my custom logs (from logger.info()) and the springboot logs

Now, in project THREE, I need to combine both, I need to send my logs to both kafka and loki.

Therefore, I added both log4j2.xml and the logback-spring.xml to my resources folder.
I combined all dependencies into one pom, and ran the program

I was expecting to see all logs in both locations.

However, the results are:

• All logs (the logger.info() logs + the default springboot logs are in grafana loki

• But only the default springboot logs are in the kafka topic, missing the custom logs.

By springboot log, I am referring to something like:

2024-12-13T04:35:32.364+08:00  INFO 4394 --- [  main] [ ] org.example.EventApplication             : No active profile set, falling back to 1 default profile: "default"

Question, may I ask why the custom logs ended up in only grafana logs, but not Kafka?

What to do so I can see all logs in both places?