AKKA Typed SLF4J NOP warning - akka

Question

I am using AKKA Typed 2.6.5 with AKKA HTTP...
and getting below error
SLF4J: No SLF4J providers were found.
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#noProviders for further details.
I have imported every possible sbt repository and tested but still logging is not working.
Any help would be appreciated.

Answer 1

You need to add a dependency to an implementation of the SLF4J API. SLF4J is only an interface, and requires you to provide an implementation of your choice, as described in the documentation linked from the error message.
A popular implementation is Logback. You can include it in your project by adding it to your libraryDependencies:
libraryDependencies += "ch.qos.logback" % "logback-classic" % "1.2.3"
You can configure it by adding a file at src/main/resources/logback.xml with contents like this:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>myapp.log</file>
<immediateFlush>false</immediateFlush>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<fileNamePattern>myapp_%d{yyyy-MM-dd}.log</fileNamePattern>
</rollingPolicy>
<encoder>
<pattern>[%date{ISO8601}] [%level] [%logger] [%marker] [%thread] - %msg MDC: {%mdc}%n</pattern>
</encoder>
</appender>
<appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
<queueSize>8192</queueSize>
<neverBlock>true</neverBlock>
<appender-ref ref="FILE" />
</appender>
<root level="INFO">
<appender-ref ref="ASYNC"/>
</root>
</configuration>
You can configure this to the needs of your application. See the Logback manual for details on configuration. Be sure to use an async appender as demonstrated above, so that logging doesn't result in blocking I/O on your Akka dispatcher threads.
There is more information in the Akka documentation at https://doc.akka.io/docs/akka/current/typed/logging.html#slf4j-backend