Spring Boot and Logging with External Tomcat only outputs startup log - spring-boot

Question

My Spring boot 2 app is not showing any log message when is running. I can only see the startup log. This app is deployed as WAR in the production server and I configured the log to output to a file:
logging.file = app.log
logging.level.root=WARN
logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR
logging.pattern.console= %d{yyyy-MM-dd HH:mm:ss} - %msg%n
In my local I can see whatever debug message I include in my code but in the server I can't. I only see the application startup trace.
My config to generate the file is the provided by official guideance. And the tomcat dependency in the app.war:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
Do you have any idea of what is happening? It is strange. The log file is generating in the server ( we deploy it in a docker container ) but after the app is running, no more log is output to the file.

Answer 1

By default Spring Boot logs on INFO level, which should include ERROR.
As per Spring boot logging guide 79.1.1 Configure Logback for File-only Output
If you want to disable console logging and write output only to a file, you need a custom logback-spring.xml that imports file-appender.xml but not console-appender.xml, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<include resource="org/springframework/boot/logging/logback/defaults.xml" />
<property name="LOG_FILE" value="${LOG_FILE:-${LOG_PATH:-${LOG_TEMP:-${java.io.tmpdir:-/tmp}}/}spring.log}"/>
<include resource="org/springframework/boot/logging/logback/file-appender.xml" />
<root level="INFO">
<appender-ref ref="FILE" />
</root>
</configuration>
You also need to add logging.file to your application.properties which you have alraedy added.