#276 Add log4jtcp appender

[Jan Rüegg]

It would be great (and should not be a big effort) to create a log4j tcp appender. With this, it would be very easy to use a good logging tool like http://code.google.com/p/otroslogviewer/ out of the box. (otroslogviewer supports tcp log4j streams, but no udp.)

[Václav Haisman]

It should be possible to add this. However, first I would like to know if there is any description of the protocol/payload formatting on the stream?

[Václav Haisman]

Is it his: http://logging.apache.org/log4j/2.x/manual/layouts.html#XMLLayout

[Jan Rüegg]

Actually, I can already make it work, when forwarding the udp stream to tcp with socat:

Logger:
http://code.google.com/p/otroslogviewer/
Tools -> start socket listener -> config "log4j xml" + port "8080"

Source code:
uncomment in hal/baselogger.cpp:
#include <log4cplus log4judpappender.h="">
log4cplus::helpers::SharedObjectPtr<log4cplus::Appender> networkAppender(new log4cplus::Log4jUdpAppender("localhost", 8080));
log4cplus::Logger::getRoot().addAppender(networkAppender);

Udp -> TCP:
http://www.dest-unreach.org/socat/
(windows: http://blog.gentilkiwi.com/programmes/socat#englishversion)
command:
socat -v udp4-listen:8080,fork tcp:localhost:8080

I guess this should make it pretty straightforward to adapt the existing log4j udp logger to use tcp...

[Jan Rüegg]

I just looked at the source code: Basically, taking the "socketappender.cxx", renaming it to "log4jtcpappender.cxx" and replacing (in the append function) this:

helpers::SocketBuffer buffer(LOG4CPLUS_MAX_MESSAGE_SIZE - sizeof(unsigned int));
convertToBuffer (buffer, event, serverName);
helpers::SocketBuffer msgBuffer(LOG4CPLUS_MAX_MESSAGE_SIZE);

msgBuffer.appendInt(static_cast<unsigned>(buffer.getSize()));
msgBuffer.appendBuffer(buffer);

with this from the log4judpappender.cxx append function:

tstring & str = formatEvent (event);

internal::appender_sratch_pad & appender_sp
    = internal::get_appender_sp ();
tostringstream & buffer = appender_sp.oss;
detail::clear_tostringstream (buffer);

buffer << LOG4CPLUS_TEXT("<log4j:event logger=\"")
       << outputXMLEscaped (event.getLoggerName())
       << LOG4CPLUS_TEXT("\" level=\"")
       // TODO: Some escaping of special characters is needed here.
       << outputXMLEscaped (getLogLevelManager().toString(event.getLogLevel()))
       << LOG4CPLUS_TEXT("\" timestamp=\"")
       << event.getTimestamp().getFormattedTime(LOG4CPLUS_TEXT("%s%q"))
       << LOG4CPLUS_TEXT("\" thread=\"") << event.getThread()
       << LOG4CPLUS_TEXT("\">")

       << LOG4CPLUS_TEXT("<log4j:message>")
       // TODO: Some escaping of special characters is needed here.
       << outputXMLEscaped (str)
       << LOG4CPLUS_TEXT("</log4j:message>")

       << LOG4CPLUS_TEXT("<log4j:NDC>")
       // TODO: Some escaping of special characters is needed here.
       << outputXMLEscaped (event.getNDC())
       << LOG4CPLUS_TEXT("</log4j:NDC>")

       << LOG4CPLUS_TEXT("<log4j:locationInfo class=\"\" file=\"")
       // TODO: Some escaping of special characters is needed here.
       << outputXMLEscaped (event.getFile())
       << LOG4CPLUS_TEXT("\" method=\"")
       << outputXMLEscaped (event.getFunction())
       << LOG4CPLUS_TEXT("\" line=\"")
       << event.getLine()
       << LOG4CPLUS_TEXT("\"/>")
       << LOG4CPLUS_TEXT("</log4j:event>");

LOG4CPLUS_TSTRING_TO_STRING (buffer.str ()).swap (appender_sp.chstr);

should be enough to make it work...

[Jan Rüegg]

Would a patch help to speed things up? It would be great to have this functionality, and I don't think its a lot of work. But I can try to do it myself maybe...