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Logging

Lyna logs with Log4j 2. It reads its logging setup from config/log4j2.xml.

When the file is missing, Lyna writes the starting file below on its first start and uses it. After that the file is yours: Lyna never changes it again.

Where the file is read from​

The start script reads JAVA_OPTS. The Docker image sets it to:

JAVA_OPTS="-Dlog4j.configurationFile=config/log4j2.xml"

Running from a release, set the same yourself. See from source.

A starting file​

Logs to the console and to logs/app.log, and keeps ten days of old logs:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" shutdownHook="disable" packages="de.chojo.logutil.appender">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="[%d{HH:mm:ss}][%p{length=3}][%c{1}] %m%n"/>
        </Console>
        <RollingFile name="File" fileName="logs/app.log" filePattern="logs/app-%d{yyyy-MM-dd}.log">
            <PatternLayout pattern="[%d{HH:mm:ss}][%p{length=3}][%15.15c{1}] %m%ex%n"/>
            <Policies>
                <OnStartupTriggeringPolicy/>
                <TimeBasedTriggeringPolicy/>
            </Policies>
            <DefaultRolloverStrategy max="10"/>
        </RollingFile>
    </Appenders>
    <Loggers>
        <Logger name="net.dv8tion.jda" level="INFO"/>
        <Logger name="org.eclipse.jetty" level="INFO"/>
        <Logger name="com.zaxxer.hikari" level="INFO"/>
        <Root level="INFO">
            <AppenderRef ref="Console"/>
            <AppenderRef ref="File"/>
        </Root>
    </Loggers>
</Configuration>

logs/ is relative to the working directory, /app/logs in the Docker image. Mount it if you want to keep the files.

Errors in a Discord channel​

Errors an operator should see are logged with the marker NOTIFY_ADMIN: a failed mail check, a receipt Lyna couldn't read, a failed database request, a crashed command. You can send exactly those to a Discord channel through a webhook.

Create a webhook in the channel's settings under Integrations, then add an appender and a reference to it:

<Appenders>
    <!-- the appenders from above -->
    <DiscordWebhook name="DiscordError" url="https://discord.com/api/webhooks/...">
        <MarkerFilter marker="NOTIFY_ADMIN" onMatch="ACCEPT" onMismatch="DENY"/>
    </DiscordWebhook>
</Appenders>
<Loggers>
    <Root level="INFO">
        <AppenderRef ref="Console"/>
        <AppenderRef ref="File"/>
        <AppenderRef ref="DiscordError"/>
    </Root>
</Loggers>

The packages="de.chojo.logutil.appender" attribute on <Configuration> is what makes DiscordWebhook known. Keep it.

note

The webhook address is a secret too. Anybody who has it can post into that channel.