zentol commented on a change in pull request #14304:
URL: https://github.com/apache/flink/pull/14304#discussion_r538540769
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File path: docs/deployment/advanced/logging.md
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@@ -59,49 +71,47 @@ For Flink distributions this means you have to
## Configuring logback
-For users and developers alike it is important to control the logging
framework.
-The configuration of the logging framework is exclusively done by
configuration files.
-The configuration file either has to be specified by setting the environment
property `-Dlogback.configurationFile=<file>` or by putting `logback.xml` in
the classpath.
-The `conf` directory contains a `logback.xml` file which can be modified and
is used if Flink is started outside of an IDE and with the provided starting
scripts.
-The provided `logback.xml` has the following form:
-
-{% highlight xml %}
-<configuration>
- <appender name="file" class="ch.qos.logback.core.FileAppender">
- <file>${log.file}</file>
- <append>false</append>
- <encoder>
- <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{60}
%X{sourceThread} - %msg%n</pattern>
- </encoder>
- </appender>
-
- <root level="INFO">
- <appender-ref ref="file"/>
- </root>
-</configuration>
-{% endhighlight %}
+To use Flink with [logback](https://logback.qos.ch/) you must ensure that:
+- `org.apache.logging.log4j:log4j-slf4j-impl` is not on the classpath,
+- `ch.qos.logback:logback-core` and `ch.qos.logback:logback-classic` are on
the classpath.
-In order to control the logging level of
`org.apache.flink.runtime.jobgraph.JobGraph`, for example, one would have to
add the following line to the configuration file.
+In the IDE this means you have to replace such dependencies defined in your
pom, and possibly add exclusions on dependencies that transitively depend on
them.
-{% highlight xml %}
-<logger name="org.apache.flink.runtime.jobgraph.JobGraph" level="DEBUG"/>
-{% endhighlight %}
+For Flink distributions this means you have to
+- remove the `log4j-slf4j-impl` jar from the `lib` directory,
+- add the `logback-core`, and `logback-classic` jars to the `lib` directory.
+
+The Flink distribution ships with the following logback configuration files in
the `conf` directory, which are used automatically if logback is enabled:
+- `logback-session.properties`: used by the command line interface when
starting a Kubernetes/Yarn session cluster (i.e.,
`kubernetes-session.sh`/`yarn-session.sh`)
+- `logback-console.properties`: used for Job-/TaskManagers if they are run in
the foreground (e.g., Kubernetes)
+- `logback.xml`: used for command line interface and Job-/TaskManagers by
default
-For further information on configuring logback see [LOGback's
manual](http://logback.qos.ch/manual/configuration.html).
+<div class="alert alert-info" markdown="span">
+ <strong>Note:</strong> Logback 1.3+ requires SLF4J 2, which is currently not
supported.
+</div>
## Best practices for developers
-The loggers using slf4j are created by calling
+You can create an SLF4J logger by calling
`org.slf4j.LoggerFactory#LoggerFactory.getLogger` with the `Class` of your
class as an argument.
+
+We highly recommend storing this logger in a `private static final` field.
{% highlight java %}
import org.slf4j.LoggerFactory
import org.slf4j.Logger
Review comment:
good idea
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