ARQ uses Apache Commons Logging as the API and ships with Log4J as a deployment system. You can use Java 1.4 logging instead.
ARQ does not output any logging messages at level INFO in normal operation. The code uses level TRACE and DEBUG. Running with logging set to an application at INFO will cause no output in normal operation. Output below INFO can be very verbose and is intended mainly to help debug ARQ. WARN and FATAL messages are only used when something is wrong.
The root of all the loggers is com.hp.hpl.jena
.
com.hp.hpl.jena.query
is the application API.
com.hp.hpl.jena.sparql
is the implementation and extensions
points.
If using in Tomcat, or other system that provides complex class loading arrangements, be careful about loading from jars in both the web application and the system directories as this can cause separate logging systems to be created (this may not matter).
The ARQ and RIOT command line utilities look for a file "log4j.properties" in the current directory to control logging during command execution.
Logger Names | Name | Constant | Logger | Use |
---|---|---|---|---|
com.hp.hpl.jena.arq.info |
ARQ.logInfoName |
ARQ.getLoggerInfo() |
General information | |
com.hp.hpl.jena.arq.exec |
ARQ.logExecName |
ARQ.getLoggerExec() |
Execution information |
There is some code to cover simple situations. See the log4j documentation for full details of log4j.
The reading of log4j.properties
from the current directory is achieved
by a call to org.apache.jena.atlas.logging.Log.setlog4j()
.
Example log4j.properties file:
log4j.rootLogger=INFO, stdlog log4j.appender.stdlog=org.apache.log4j.ConsoleAppender ## log4j.appender.stdlog.target=System.err log4j.appender.stdlog.layout=org.apache.log4j.PatternLayout log4j.appender.stdlog.layout.ConversionPattern=%d{HH:mm:ss} %-5p %-25c{1} :: %m%n # Execution logging log4j.logger.com.hp.hpl.jena.arq.info=INFO log4j.logger.com.hp.hpl.jena.arq.exec=INFO # Other log4j.logger.com.hp.hpl.jena=WARN log4j.logger.org.apache.jena=WARN
A Fuseki server output can include ARQ execution logging.
Note: ARQ performs some direct control of logging in the test suite and depends on log4j to compile.
ARQ can log query and update execution details globally or for an individual operations. This adds another level of control on top of the logger level controls.
Explanatory messages are controlled by the Explain.InfoLevel
level in
the execution context.
The logger used is called com.hp.hpl.jena.arq.exec
. Message are sent
at level "info". So for log4j, the following can be set in the
log4j.properties file:
log4j.logger.com.hp.hpl.jena.arq.exec=INFO
The context setting is for key (Java constant) ARQ.symLogExec
. To set
globally:
ARQ.setExecutionLogging(Explain.InfoLevel.ALL) ;
and it may also be set on an individual query execution using its local context.
QueryExecutiuon qExec = QueryExecutionFactory.create(...) ; qExec.getContext().set(ARQ.symLogExec, Explain.InfoLevel.ALL) ;
On the command line:
arq.query --explain --data data file --query=queryfile
The command tdbquery
takes the same --explain
argument.
Information levels
Level | Effect |
---|---|
INFO | Log each query |
FINE | Log each query and its algebra form after optimization |
ALL | Log query, algebra and every dataset access (can be expensive) |
NONE | No information logged |
These can be specified as string, to the command line tools, or using
the constants in Explain.InfoLevel
.
qExec.getContext().set(ARQ.symLogExec, Explain.InfoLevel.FINE) ; arq.query --set arq:logExec=FINE --data data file --query=queryfile