Log Grouping

General Idea

The OSGi logging service provides logging facilities and a mechanism to forward application logs to files. There is a default log group, in which all the logs are written. However, writing all logs to a single file or a group of files according to the maximum file size can make navigating through logs a bit difficult, with viewing so much mixed data. To make searching for logs a lot easier, a new feature is added:

• every log service client – a bundle or a group of bundles, configures its own log file with its own rotation policy.

Definitions

For the purposes of separating the output to multiple log files, a concept of log grouping is introduced using the following definitions:

• groups – Bundles are separated into groups. A group is defined by its name, the name of its logging file and optionally by its folder for logging, relative to the bin/vms/jdk folder. Each group logs into its own folder using its own file logging configuration.The supported configuration properties are described in the sections below.

• default log group – There is always a default group for logging, in which all logs are written. Its name is log and its logging file is log.txt, stored in the ../bin/vms/jdk/logs folder.

• custom log groups – The user can define their own specific log groups in a log groups properties file. The format of a single section corresponding to a log group with its name, file base and folder is the following:

log.group.name=<group_name>   # Name of the group - required.

log.dir=<folder_path>   # the folder in which log files will be stored, relative to bin/vms/jdk - required.

log.file.base=<file_name>   # the file name of the logging file - required.

bundle.symbolicNames=<list_of_bundles>   # a comma-separated list of bundle names in the group - required. A suffix wildcard ('*') is supported to include multiple bundles.

• log groups file – The log grouping file is a properties file. It is separated into sections with the above format by a new line, as well as by some empty or comment lines as in the sample below. The log groups file is specified by the mbs.log.groups.file system property with default value of ../log_groups.prs.

Enable/Disable Default Log Grouping

The default log group behavior can be disabled by setting the system property mbs.log.appender.default.strict to true – in this case all logs are forwarded to the group of their bundles.

Some bundles may remain outside any group and even outside the default one, when the system property is set to true, and some bundles may be in multiple groups.

Configurations

Default Log Group Configuration

The default log group is configured by mbs.log.FileLogAppender.Default PID.

The following configuration properties are supported:

• enabled – This property turns file logging on/off.

  Only default log group is turned on by default.

• maxFileSize – This property sets the maximum size of the log file. It is 32768 by default.

  This method will not immediately trim the current log file to the specified size if it already exceeds it.

• maxBackupCount – This property sets the maximum allowed number of backups. This method also deletes the backup files, that exceed the specified maximum. Set the value to zero if you want to remove all backups. Its default value is 4.
• entriesThreshold – This property controls how often the log file is flushed to the disk. If you set the value to 100, the file is flushed after each 100th entry. The value is 100 by default.
• timeThreshold – This property controls how often the log file is flushed to the disk. If you set the value to 10000, the file is flushed every 10 seconds. The default value is 10000.
• logsDir – This property sets the log file directory. It works only for the default log group.

Custom Log Groups Configuration

Each log group is configured separately using mbs.log.FileLogAppender.<group_name> as PID and com.prosyst.mbs.impl.services.log.FileLogAppender as factory PID in two ways:

• using web console

• using static configuration properties file in ../osgi/config/common/com.prosyst.mbs.impl.services.log.FileLogAppender – e.g. for the Bosch related bundles from the sample below you have to create in this folder mbs.log.FileLogAppender.bosch.properties file, with the following content:

#version=2.0

enabled:boolean=true

timeThreshold:int=10

Samples

• A log groups file with four custom log groups sections – its content corresponds to the logs folder structure:

# OSGi specification bundles

log.group.name=osgi

log.dir=logs

log.file.base=osgi

bundle.symbolicNames=com.prosyst.mbs.osgi.*

# Bosch IoT Core bundles

log.group.name=core

log.dir=logs

log.file.base=core

bundle.symbolicNames=com.prosyst.mbs.core.*

# HDM bundles

log.group.name=hdm

log.dir=logs/hdm

log.file.base=hdm

bundle.symbolicNames=com.prosyst.mbs.hdm.*

# Bosch specific bundles

log.group.name=bosch

log.dir=logs/bosch

log.file.base=bosch

bundle.symbolicNames=de.bosch.*, com.bosch.*