There are several ways to handle diagnostic data which are grouped into the following two types:

log4sendpp offers two formatters to cover the common use cases. Mainly intended for logging to files in a format used by syslog is SimpleFormatter

	At the beginning of each line there is always the timestamp and the log level.
	A log message can spawn multiple lines. A block always starts with an opening bracket and ends with a closing. On multiple lines a dot denotes the continuation lines.

  [ 18:05:37,400ERROR ] first message

  [ 18:05:37,400 ERROR . second message
  . 18:05:37,400 ERROR .second line
  . 18:05:37,400 ERROR . third line
  . 18:05:37,400 ERROR ] forth line

The second format is mainly used when messages are sent to logging applications like Chainsaw which can receive messages in XML format over a network or read regular files.

An example created by XmlFormatter could look like this:

  <log4j:event logger="category2" timestamp="1529829438"
                  sequenceNumber="3" level="INFO" thread="threadname">
    <log4j:message>second message</log4j:message>
    <log4j:throwable>throwablename</log4j:throwable>
    <log4j:NDC>my-ndc</log4j:NDC>
    <log4j:MDC>
      <log4j:data name="mdc1" value="val1" />
      <log4j:data name="mdc2" value="val2" />
    </log4j:MDC>
    <log4j:locationInfo file="filename" line="1234"
                           class="" method="methodname" />
    <log4j:properties>
      <log4j:data name="application" value="test" />
      <log4j:data name="hostname" value="hostname" />
      <log4j:data name="prop1" value="val1" />
    </log4j:properties>
  </log4j:event>

Appenders are used to forward the log messages to their destination. log4sendpp contains two of the most important classes:

For covenient access all the logger helper classes are tied together by a Logger. You can either use a predefined default object with a TcpIpAppender and a FileAppender:

  Logger &logger = Logger::logger();
  logger.ndc().push("trivial context");
  logger.info("info message");
  logger.warn("warn message");

or you can create your own setting:

  Logger mylogger;
  mylogger.setPrimaryAppender(new TcpIpAppender(
                                new XmlFormatter("appname", "localhost"),
                                "localhost"));
  mylogger.setSecondaryAppender(FileAppender app (
                                  new SimpleFormatter("appname"),
                                  "testfile.txt"));

By default two appenders are used. The second is only used if the first fails for some reason. This way you can preferably log over a network and still store everything to a file when there is not network available or the remote log host is not running.

If you want to add location information to trace the file and line it is more convenient to use the logging macros instead of the plain method calls. These macros already contain this information and also request the current nickname from the thread dictionary:

    LOG4SENDPP_TRACE("trace by macro\nline2");
    LOG4SENDPP_DEBUG("debug by macro\nline2\nline3");

There are some more lower level macros which might become interesting if you wish to build your own macro for logging information.

    LOG4SENDPP_MACRO_TI("message throwinfo", "exception name", Logger::Info);
    LOG4SENDPP_MACRO_LI("message location", "category", Logger::Error);
    LOG4SENDPP_MACRO_LTI("message", "category", "exception name", Logger::Error);

An possible application is to create a macro which throws an exception. Before actually throwing the exception you could send the log message to be informed about every thrown exception and the according location.

#define THROW_ASSERTION(txt) \
  { \
    LOG4SENDPP_MACRO_TI(txt, L"Assertion", Logger::LogError); \
    throw Assertion(txt, __FILE__, __LINE__) ; \
  }

	Error messages might be confusing
	All these macros surround the according parameters with a do { ... } while(false) sequence. This is neccessary to be able to use the macros like normal function calls. Otherwise there might be situations in if - statements leading to forbidden code. Unfortunately your compiler may issue confusing error messages regarding this do .. while statement if you place incorrect code into the macro.