Logstash : ERROR RollingFileManager

Hello,
Logstash worked normally until this morning I don't understand why it doesn't work anymore here's the error parts of the logs, it seems that it's related to the log4j2.properties (wich i never modified) and some permissions for the log files.
logstash[31806]: 2019-11-27 05:36:42,840 main ERROR Could not create plugin of type class org.apache.logging.log4j.core.appender.RollingFileAppender for element RollingFile: java.lang.IllegalStateException: ManagerFactory [org.apache.logging.log4j.core.appender.rolling.RollingFileManager$RollingFileManagerFactory@2e8828b5] unable to create manager for [/var/log/logstash/logstash-slowlog-plain.log] with data [org.apache.logging.log4j.core.appender.rolling.RollingFileManager$FactoryData@5910aa2e[pattern=/var/log/logstash/logstash-slowlog-plain-%d{yyyy-MM-dd}-%i.log.gz, append=true, bufferedIO=true, bufferSize=8192, policy=CompositeTriggeringPolicy(policies=[TimeBasedTriggeringPolicy(nextRolloverMillis=0, interval=1, modulate=true), SizeBasedTriggeringPolicy(size=104857600)]), strategy=DefaultRolloverStrategy(min=1, max=30, useMax=true), advertiseURI=null, layout=[%d{ISO8601}][%-5p][%-25c] %m%n, filePermissions=null, fileOwner=null]] java.lang.IllegalStateException: ManagerFactory [org.apache.logging.log4j.core.appender.rolling.RollingFileManager$RollingFileManagerFactory@2e8828b5] unable to create manager for [/var/log/logstash/logstash-slowlog-plain.log] with data [org.apache.logging.log4j.core.appender.rolling.RollingFileManager$FactoryData@5910aa2e[pattern=/var/log/logstash/logstash-slowlog-plain-%d{yyyy-MM-dd}-%i.log.gz, append=true, bufferedIO=true, bufferSize=8192, policy=CompositeTriggeringPolicy(policies=[TimeBasedTriggeringPolicy(nextRolloverMillis=0, interval=1, modulate=true), SizeBasedTriggeringPolicy(size=104857600)]), strategy=DefaultRolloverStrategy(min=1, max=30, useMax=true), advertiseURI=null, layout=[%d{ISO8601}][%-5p][%-25c] %m%n, filePermissions=null, fileOwner=null]]",

       ` main ERROR RollingFileManager (/var/log/logstash/logstash-slowlog-plain.log) java.io.FileNotFoundException: /var/log/logstash/logstash-slowlog-plain.log (Permission non accordée) java.io.FileNotFoundException: /var/log/logstash/logstash-slowlog-plain.log (Permission non accordée)",`

is there something that i need to change in the log4j2.properties file ?

Check the permissions on /var/log/logstash and make sure that you have permissions to write to it.

I believe that some logstash version updates revert the group ownership of /var/log/logstash from logstash back to root. Logging then fails until I change it back.