Log4cxx C++ Logging

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Apache Log4cxx is a framework which provides the capability to log messages in a variety of formats to the local console, local files, streamed over a socket or even launch an email based on a hierarchy of notification levels.

Prerequisites:

• autoconf and automake
  • RHEL5: yum install autoconf automake
  • Ubuntu: apt-get install autoconf automake
• libxml2 and libxml2-devel (http://xmlsoft.org/)
  • RHEL5 (2.6.26): yum install libxml2 libxml2-devel
  • Ubuntu 12.04 (2.7.8): sudo apt-get install libxml2 libxml2-dev
  • Ubuntu 8.10 (2.6.32): sudo apt-get install libxml2 libxml2-dev
• gmp (http://swox.com/gmp/)
  • RHEL5 (gmp 4.1.4): yum install gmp
  • Ubuntu 8.10 (4.2.2): sudo apt-get install libgmpxx4 libgmp3-dev
  • Ubuntu 12.04 (2.7.8): sudo apt-get install libgmpxx4ldbl libgmp3-dev
• boost and boost-devel
  • RHEL5 (boost: 1.33.1): yum install boost boost-devel
  • Ubuntu 8.10 (libboost-dev: 1.34.1): sudo apt-get install libboost-dev
  • Ubuntu 12.04 (libboost-dev: 1.46): sudo apt-get install libboost-dev
• cppunit
  • RHEL5 (1.12.0): Download RPMs from RepoForge
    Download packages cppunit and cppunit-devel
  • Ubuntu 8.10 (1.12.1): sudo apt-get install libcppunit-dev
  • Ubuntu 12.04 (1.12.1-4): sudo apt-get install libcppunit-dev
• apr, apr-devel and apr-util, apr-util-devel
  • RHEL5 (1.2.7): yum install apr apr-devel apr-util apr-util-devel
  • Ubuntu 8.10 (1.2.12): sudo apt-get install libapr1 libaprutil1
  • Ubuntu 12.04 (1.4.6-1): sudo apt-get install libapr1 libaprutil1

Log4cxx binary installation:

Ubuntu: sudo apt-get install liblog4cxx10 liblog4cxx10-dev

• Install Java: (Maven is a Java program) See the YoLinux Java installation tutorial
• Install Maven (untar Java jar files. Java program and thus platform independent)
  (Called by XmlBeans configure script and Makefile)
  • Download compiled Java program: http://maven.apache.org/download.html
  • cd /opt
  • wget http://apache.opensourceresources.org/maven/binaries/apache-maven-2.2.1-bin.tar.gz
  • tar xzf apache-maven-2.2.1-bin.tar.gz
    This creates /opt/apache-maven-2.2.1
  • Configuration:
    • Add path to shell environment: export PATH=$PATH:/opt/apache-maven-2.2.1/bin
      This allows execution of the Maven build command mvn
    • If using a proxy, edit /opt/apache-maven-2.2.1/conf/settings.xml
      Set proxy: <proxies> <proxy> ...
  Ubuntu/Debian Note: Maven can also be installed using apt-get: sudo apt-get install maven2

Build and install:

• Apache Log4cxx home page
• download
• tar xzf apache-log4cxx-0.10.0.tar.gz
• cd apache-log4cxx-0.10.0/
• ./configure --prefix=/usr
  Typically I would specify /opt or /usr/local but xmlbeansxx (an XML parser I like) which has a dependency on log4cxx and requires an installation in /usr.
• make
  (will call Maven mvn)
• make install
  This installs:

  /usr/include/log4cxx/...
  /usr/lib/liblog4cxx.so.10.0.0
  /usr/lib/liblog4cxx.la
  /usr/lib/liblog4cxx.a
  /usr/lib/pkgconfig/liblog4cxx.pc
      

error while loading shared libraries: liblog4cxx.so.10: cannot open shared object file: No such file or directory

[prompt]$ ./configure --prefix=/usr LDFLAGS="-L/lib64 -L/usr/lib64"
[prompt]$ make
inputstreamreader.cpp:66: error: 'memmove' was not declared in this scope
make[3]: *** [inputstreamreader.lo] Error 1

• File: apache-log4cxx-0.10.0/src/main/cpp/inputstreamreader.cpp
  Add the include file: #include <string.h>
  Change from:

  #include <log4cxx/logstring.h>
  #include <log4cxx/helpers/inputstreamreader.h>
  #include <log4cxx/helpers/exception.h>
  #include <log4cxx/helpers/pool.h>
  #include <log4cxx/helpers/bytebuffer.h>
      

  to:

  #include <string.h>
  #include <log4cxx/logstring.h>
  #include <log4cxx/helpers/inputstreamreader.h>
  #include <log4cxx/helpers/exception.h>
  #include <log4cxx/helpers/pool.h>
  #include <log4cxx/helpers/bytebuffer.h>
      

• File: apache-log4cxx-0.10.0/src/main/cpp/socketoutputstream.cpp
  Add the include file: #include <string.h>

• File: apache-log4cxx-0.10.0/src/examples/cpp/console.cpp
  Add the include file: #include <stdio.h>
  Add the include file: #include <string.h>

you may have neglected to install the packages apr-devel and apr-util-devel.
Install (RHEL5 example): rpm -ivh apr-devel-1.2.7-11.el5_3.1.i386.rpm apr-util-devel-1.2.7-7.el5_3.2.i386.rpm

/usr/lib/libaprutil-1.so: could not read symbols: File in wrong format

• Add the following directives to the configure script: ./configure --prefix=/usr LDFLAGS="-L/lib64 -L/usr/lib64"
• Set the following environment variable: export LDFLAGS="-L/lib64 -L/usr/lib64"
• Edit the gcc/g++ compile/link statement and add the following directives: -L/lib64 -L/usr/lib64

• Installed from binary packages:
  • g++ testLog4cxx.cpp -lapr-1 -laprutil-1 -llog4cxx
• Installed from source:
  • 64 bit: g++ testLog4cxx.cpp -I/opt/include /opt/lib64/liblog4cxx.a -lapr-1 -laprutil-1
  • 32 bit: g++ testLog4cxx.cpp -I/opt/include /opt/lib/liblog4cxx.a -lapr-1 -laprutil-1

TRACE main - this is a debug message for detailed code discovery. Value=5
DEBUG main - this is a debug message.
INFO  main - this is a info message, ignore. Value=5
WARN  main - this is a warn message, not too bad.
ERROR main - this is a error message, something serious is happening.
FATAL main - this is a fatal message!!!
INFO  functionA - Executing functionA.
INFO  functionA - Executing functionA.

Log4cxx can log to the console and log file as shown above. It can also log in XML format or a specified format, it can log time intervals with each interval logged to its' own log file (time based logs with TimeBasedRollingPolicy) or log to files of a specified size where upon reaching the size limit, it logs to a new file (size based logs set MaxFileSize). Log4cxx can log to the Linux syslogd (local or remote) or to a socket stream. Email alerts can be sent (e.g. send email upon total extreme failure). Logs can be sent via ODBC to MySQL or Postgres.

Add the "appender" definition and "root" "appender-ref" snippets below to the above configuration file.

• Set file size limit MaxFileSize to 5KB
• Keep five rolling log files with MaxBackupIndex: appxSizeBasedLog.log.1, ... appxSizeBasedLog.log.5
  Log4cxx will operate "round robin" and overwrite the previous log file.

The best approach is to use the XML configuration file and the DOMConfigurator class to read it. XML and this class can support more complex configurations which may include Filters, custom ErrorHandlers, nested appenders, etc ... For some, the Java properties style configuration file is their preference but note that some advanced features are not supported. Note that log4cxx and log4j both support XML config files.

log4j.rootLogger=INFO, rootConsoleAppender, rootFileAppender
# Name of appender is the fully.qualified.name.of.appender.class
log4j.appender.rootConsoleAppender=org.apache.log4j.ConsoleAppender
log4j.appender.rootConsoleAppender.layout=org.apache.log4j.PatternLayout
log4j.appender.rootConsoleAppender.layout.ConversionPattern=%d %-5p [%c] - %m%n

log4j.appender.rootFileAppender=org.apache.log4j.FileAppender
log4j.appender.rootFileAppender.layout=org.apache.log4j.PatternLayout
log4j.appender.rootFileAppender.layout.ConversionPattern=%d %-5p [%c] - %m%n
log4j.appender.rootFileAppender.File=test.log
# set whether to overwrite or append to the file
log4j.appender.rootFileAppender.Append=false

2013-08-22 19:44:01,033 INFO  [main] - this is a info message, ignore. Value=5
2013-08-22 19:44:01,033 WARN  [main] - this is a warn message, not too bad.
2013-08-22 19:44:01,033 ERROR [main] - this is a error message, something serious is happening.
2013-08-22 19:44:01,033 FATAL [main] - this is a fatal message!!!
2013-08-22 19:44:01,033 INFO  [functionA] - Executing functionA.

Apache Chainsaw is a Java GUI application for viewing log files. It can accept streaming logs or view a log file.

• Apache Chainsaw home page

Chainsaw will filter, color code and display log messages. When streaming log messages over a socket, use the XMLLayout sent with the XMLSocketAppender. The screenshot below is showing two applications streaming log messages to two "receivers" configured in Chainsaw.

Controls on the left panel set the logging focus to the log pointers of your choice. Right click on the logger pointer and select "Focus on logger-ptr-name" to turn off all other logger pointers you don't want to see including logging from the Chainsaw application itself.

The controls on the right panel define the log levels for the application.

The Apache Chainsaw log viewer runs in a socket server configuration while the log producing application runs as a socket client. Thus start and configure Chainsaw before the application generating the log messages or "restart the receivers" in Chainsaw before starting the applications to be logged.

The Log4cxx configuration below will set-up the application to be the socket client which will attach to the Chainsaw socket server.

• Right click on "Receivers"
• Select option "New Receivers"
• Select "New XMLSocketReceiver" (This will open up a new dialog window shown below)
• Populate the options:
  • active: false (default)
  • class: org.apache.log4j.net.XMLSocketReceiver (default)
  • decoder: org.apache.log4j.xml.XMLDecoder
  • name: name-of-application-you-are-logging
  • paused: false (default)
  • port: 4448 (default)
  • threshold: TRACE (Select from TRACE, DEBUG, INFO, WARN, ERROR, FATAL, OFF, ALL)

When restarting applications logging with XMLSocketReceiver appender, you must reset the chainsaw socket server receivers. After the applications have attached logged, and exited (closed the socket connections), one must right click “Receivers” and restart the receivers to relaunch the socket servers if one is to restart the applications and begin logging again.

Other user configurations: Select the "chainsaw-log" tab to display the logging pane. From here the configuration menu is available from the tool bar "Current tab" + "LogPanel preferences ...".

The application Log4cxx configuration to log to the console as well as to connect and stream XML log messages to Chainsaw:

Other Logger Display Programs:

Apache Chainsaw is my personal preference as it can display streaming logs from multiple programs, can ingest log files and works. Many of the programs listed below have their personal strengths but often omit a key basic feature possessed by Chainsaw.

cd /opt
tar xzf lilith-0.9.43-bin.tgz
/opt/lilith-0.9.43/bin/lilith

cd /opt
sudo unzip /home/greg/Downloads/logview4j-1.0.3.zip
cd /opt/logview4j-1.0.3; java -jar logview4j-1.0.3.jar

cd /opt
unzip olv-2013-01-24.zip
cd /opt/olv-2013-01-24
/opt/olv-2013-01-24/olv.sh

cd /opt
unzip vigilog-1.3.1-assembly.zip

#!/bin/bash
if [ -d /usr/java/latest ]
then
  PATH=/usr/java/latest/bin:$PATH
  export JAVA_HOME=/usr/java/latest
  export CLASSPATH=/usr/java/latest/lib/tools.jar:./
  export MANPATH=$JAVA_HOME/man:/opt/man:$MANPATH
fi

cd /opt/vigilog-1.3.1
java -jar vigilog-1.3.1.jar

Log4cxx can be configured using a configuration file or by using API calls. As a feature to add robustess to the application, it is often wise to allow an application to continue with some simple basic log4cxx configuration if the configuration file is absent.

Log4cxx includes appenders to write to the console, files, sockets, etc. Log4cxx can be extended to include your own custom appender to write log messages to a medium of your choice such as a message queue or NoSQL data store.

The following is an example of a simple custom appender upon which one may generate a useful Log4cxx appender specific to their needs. The solution includes a new C++ class which derives from the SkeletonAppender class. This class is compiled and linked with your application even though you do not instantiate an object from this class. It is the Log4cxx framework which instantiates and invokes the appender based on the configuration file directives.

The main program testLog4cxx.cpp from the prior example above, will work. There is no change to the code. Invocation of the new appender is through the configuration file which references the new appender. The new appender does have to be linked with the application in order to be available.

Compile and static link: g++ testLog4cxx.cpp MyCustomAppender.cpp -I/opt/include /opt/lib/liblog4cxx.a -lapr-1 -laprutil-1

Note that the registration of the appender is done by using the macro IMPLEMENT_LOG4CXX_OBJECT(MyCustomAppender) This macro adds factory classes for the appenders to a hashmap which utilizes libdl to load the appender dynamically when it is called for use in the configuration file. (This is how they do it: libdl and dynamic linking)

The following configuration file will invoke the custom appender.

• Python script to performa diff between two log files - Compare the log messages but ignore certain fields that are different every time, like the time stamp.
• Add new custom logging fields
• Apache log4cxx Home Page

Books:

	C++ How to Program by Harvey M. Deitel, Paul J. Deitel ISBN #0131857576, Prentice Hall Fifth edition. The first edition of this book (and Professor Sheely at UTA) taught me to program C++. It is complete and covers all the nuances of the C++ language. It also has good code examples. Good for both learning and reference.
	Logging and Log Management: The Authoritative Guide to Understanding the Concepts Surrounding Logging and Log Management by Anton Chuvakian, Kevin Schmidt ISBN #1597496359, Syngress First edition (December 13, 2012) Logging and Log Management helps to simplify the process of effectively analyzing large volumes of diverse logs.