A convenient log system was necessary to monitor distributed applications.
The NDFS-II provides log information from servers, duplicators and client nodes. These pieces of information can be very useful to identify problems in applications or to display status information. The log outputs are by default sent to the standard output stream and the Control Center, but it is also possible to redirect the log output to:
a file. Each server, client node or duplicators has one log file.
the system logger of your operating system.
Enabling log outputs is done from the command line or the Control Center. From the command line, when launching a client node or the server, add parameters to specify redirections:
To log to a file, add --sf logfile=/the/full/path/of/the/file. The log of the server or client node will be saved in the file indicated using an absolute path. When logging into a file is activated for a server, the file logging is as well activated for duplicators. The log files for duplicators are stored in the same folder as where the server saves its log. The files are named dup_IdOfTheFlow-TypeOfTheFlow.log. For example, if a client node creates a flow of type Flow_Audio_Array with the connection ID mic1. The log file of the duplicator handling this flow is named dup_mic1-Flow_Audio_Array.log.
To log to the system logger, add --sf syslog=1 when you launch a server or a client node. The log options for the server are propagated to duplicators running on the same host.
Note: The Log System has not been fully tested yet and therefore is disabled by default. If you want to gather the logs from the Control Center, you need to enable this capability when launching data flow servers or client nodes. It can be done by giving this extra parameter to the data flow server or client nodes:
--sf logforward=1
The log severity can also be set up when launching servers or client nodes. The severity level applied to a server will also be applied to the duplicator running on the same host. The severity of each client node can be set up individually.
Here are the 3 error levels in detail ascending order:
error: this is the default mode. Only errors and important messages are displayed.
warning: This mode is providing more output information.
debug. This mode provides very detailed information. It is intended for developers.
In order to change the default log severity, you need to specify it when starting a server or a client node. Adding the loglevel parameter on the command line does it. In the example below, the client is started with the debug severity.
consumer1 --sf clientname=new name --sf loglevel=debug
It is possible for the user to use the log capabilities of the NDFS-II for his own usage within a client node. By doing so, logs generated from client nodes will therefore be visible from the Control Center, and be stored in a file or sent to the system logger if required.
We use the ACE logging capabilities to implement the NDFS-II log system, hence the method is actually an ACE macro.
ACE_DEBUG( (USER_PREFIX ACE_TEXT("The message displays a string: %s and an integer: %d\n"),
myString, myInteger) );The formatting directives used (%d, %s…) are mostly similar to the one used by the standard printf() function. For more specific formatting directive, please have a look at the ACE documentation.