Logs sent to console using logback configuration in java app, not visible in Kubernetes using kubectl logs

Question

I read in kubernetes docs somewhere that kubernetes reads application logs from stdout and stderror in pods. I created a new application and configured it to send logs to a remote splunk hec endpoint (using splunk-logback jars) and at the same time to console. So by default, the console logs in logback should go to System.out, which should then be visible using kubectl logs . But it's not happening in my application.

my logback file:

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

<configuration>

    <Appender name="SPLUNK" class="com.splunk.logging.HttpEventCollectorLogbackAppender">
        <url>${splunk_hec_url}</url>
        <token>${splunk_hec_token}</token>
        <index>${splunk_app_token}</index>
        <disableCertificateValidation>true</disableCertificateValidation>
        <batch_size_bytes>1000000</batch_size_bytes>
        <batch_size_count>${batch_size_count}</batch_size_count>
        <send_mode>sequential</send_mode>

        <layout class="ch.qos.logback.classic.PatternLayout">
            <pattern>%msg</pattern>
        </layout>
    </Appender>

    <Appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%msg</pattern>
        </encoder>
    </Appender>

    <Appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="STDOUT" />
    </Appender>

    <root level="INFO">
        <appender-ref ref="SPLUNK"/>
        <appender-ref ref="ASYNC"/>
    </root>

</configuration>

I am able to see the logs in splunk and If I login to the container from backend and start my java application, then also I can see the logs on the terminal that time. But if I let the container start by default on it's own, then the logs are only going to splunk and I can't view them using kubectl logs <POD_NAME>

The kubernetes yml file for my logger app:

apiVersion: v1
kind: Pod
metadata:
    name: logging-pod
    labels:
       app: logging-pod
spec:
  containers:
     - name: logging-container
       image: logger-splunk:latest
       command: ["java", "-jar", "logger-splunk-1.0-SNAPSHOT.jar"]
       resources:
          requests:
             cpu: 1
             memory: 1Gi
          limits:
             cpu: 1
             memory: 1Gi

Answer 1

ok so this finally got resolved. The issue was with the logs not being flushed.

In the PatternLayout the %n was missing. Hence everything was going into some buffer I guess and not reaching the console.