Debugging SciDB: Log levels

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SciDB log files contain a wealth of information and are super useful for various purposes (e.g. debugging issues, identifying query optimizations).

To change the SciDB logging level, go to:

sudo vi /opt/scidb/18.1/share/scidb/log4cxx.properties

The important lines are below:

###
# Levels: TRACE < DEBUG < INFO < WARN < ERROR < FATAL
###
# ...
log4j.rootLogger=WARN, file

log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=scidb.log
log4j.appender.file.MaxFileSize=100MB

In the above config file,

  • the log level is set at WARN
  • log files are rolled after they reach 100 MB. (By default, the last 10 such files are stored)

NOTE: If you change the log-level, you will need to restart SciDB for the change to take effect.

SciDB log levels

At INFO log level, one can

  • see queries submitted to SciDB
  • see query evaluation times

INFO level is recommended for production settings.

At DEBUG log level, one can

  • do the above, plus
  • view the Plan for query submitted to SciDB
  • view time spent in different parts of the engine

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