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Logging

Hermes Frontend, Consumers and Management modules use Logback as an implementation of logging. Any option exposed by Logback can be used to configure it.

Below our production configuration is described.

Pointing to logback.xml location

Simple way to use external logback.xml file is to pass its location using JVM flag:

-Dlogback.configurationFile=/etc/hermes/logback.xml

Example logback.xml file

Sample logback.xml file that will log to file using async appender:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>/var/log/hermes/hermes-frontend.log</file>
        <encoder>
            <Pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level %logger{36} - %msg%n</Pattern>
        </encoder>
        <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
            <fileNamePattern>/var/log/hermes/hermes-frontend-%i.log</fileNamePattern>
            <minIndex>1</minIndex>
            <maxIndex>4</maxIndex>
        </rollingPolicy>

        <triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
            <maxFileSize>100MB</maxFileSize>
        </triggeringPolicy>
    </appender>

    <appender name="ASYNC_FILE" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="FILE" />
    </appender>

    <logger name="org.apache.zookeeper" level="ERROR" />

    <!-- Selector spams ERROR level messages every 100ms on IOException -->
    <logger name="org.apache.kafka.common.network.Selector" level="OFF"/>

    <logger name="kafka" level="WARN"/>

    <root level="INFO">
        <appender-ref ref="ASYNC_FILE" />
    </root>
</configuration>

This configuration is tuned for Frontend, but Consumers and Management config is more or less the same.

Created by Skylab