Log4j logging from a Neo4j server extension - neo4j

Question

My unmanaged server extension uses slf4j-log4j logging. When log4j.properties is bundled with the extension, logging works fine.
When it's not bundled but instead placed in Neo4j's conf directory, I assumed
wrapper.java.additional=-Dlog4j.configuration=file:conf/log4j.properties
from neo4j-wrapper.conf would ensure that it's picked up.
However, I don't see the log file being created or the specified log level being used.
The config file must be correct because it works as designed when bundled with the extension.
Adding -Dlog4j.debug as suggested in other posts adds no further information.
Is there something I've missed? I'm using Neo4j 2.1.3 on Mac OS X

Answer 1

Neo4j internally has the logback jars aboard, so every logging using slf4j will be handled by logback.
My approach to logging from an unmanaged extension is as follows:
Set up your logger in the unmanaged extension have a dependency on slf4j-api (do not add and other slf4j implementations to the classpath) and use the logger like this:
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
private static final Logger logger = LoggerFactory.getLogger(com.mycompany.UnmanagedExtension.class);
Modify conf/custom-logback.xml and amend at the end:
<appender name="EXTENSIONLOG" class="ch.qos.logback.core.FileAppender">
<file>extensions.log</file>
<encoder>
<pattern>%date{yyyy-MM-dd HH:mm:ss.SSSZ} %-5level [%logger{15}]: %message%n</pattern>
</encoder>
</appender>
<logger name="com.mycompany" level="debug">
<appender-ref ref="EXTENSIONLOG"/>
</logger>
conf/custom-logback.xml is included by Neo4j's internal logback configuration, see https://github.com/neo4j/neo4j/blob/master/community/kernel/src/main/resources/neo4j-logback.xml