System Log

After being successfully started, MDX for Kylin will create a directory named logs/. By default all logs generated during MDX for Kylin runtime will be stored in this directory.

Log files

Log files generated by MDX for Kylin is as follows:

mdx.log

The file is MDX access log generated by Semantic server, whose default logging level is INFO.

semantic.log

Semantic main log file, whose default logging level is INFO.

semantic.out

The standard output of Semantic will be redirected to this file.

gateway.log

Gateway main log file, whose default logging level is INFO.

Log Configuration

MDX for Kylin leverages log4j for logging configuration. Users can edit the log4j.properties file in the $MDX_HOME/conf/ directory to configure the logging behavior, such as the splitting rule and the single file size limit. For example:

• The default appender type of semantic.log and mdx.log files is org.apache.log4j.RollingFileAppender, which means creating a new file every time the old file reaches a designated size. To create a new file every day instead, you can set log4j.appender.file and/or log4j.appender.mdx to org.apache.log4j.DailyRollingFileAppender.

• log4j.appender.file.MaxFileSize and log4j.appender.mdx.MaxFileSize define the size limit mentioned above of any semantic.log file or mdx.log file respectively, default 268435456, i.e. 256MB.

• log4j.appender.file.MaxBackupIndex and log4j.appender.mdx.MaxBackupIndex define the max reserved amount of semantic.log files and of mdx.log files respectively, default 10.

After modifications on the log4j.properties file, you should restart MDX for Kylin to apply your changes.

Log debugging

The MDX log contains the caller information of the query ID and API, which can be used to increase the debugging ability.

1. Query ID, MDX query issued by Business Intelligence tools, will generate a unique query ID in MDX, you can trace the relevant information according to the query ID.

1. The caller information of API can be used to locate the user.