Logging

Both SLS and the Network Emulator provide logging functionality that can be configured to a certain level. MaxiNet's logging is partially available through the Network Emulator.

SLS

SLS uses the log4j logging framework. netSLS provides a default configuration that logs everything on INFO-level to the console. To change the logging behavior modify the file sls/hadoop/etc/hadoop/log4j.properties.

Also refer to the official log4j documentation.

Network Emulator

The Network Emulator uses the logging framework from the python standard library. To change its behavior modify the file network_emulator/logging.cfg. The default behavior logs everything on INFO-level with exception to the following modules: ssh_tools, Testing, MaxiNet (they are set to WARNING-level).

To change the global output level, set the logging output to a file etc., change the global stream handler:

[handler_stream_handler]
class=StreamHandler
level=DEBUG
formatter=formatter
args=(sys.stdout,)

For advanced tasks, as creating an individual logger for a certain module, refer to the official documentation.

MaxiNet

As mentioned above, MaxiNet's logging is only partially available through the Network Emulator:
All logging of the core parts (FronendServer, WorkerClient) is done on the hosts running these services and configured by the corresponding MaxiNet.cfg files.

However, the logging of the MaxiNet experiment (application), which is started inside the Network Emulator, is handled by the Network Emulator and can be configured in the network_emulator/logging.cfg file.
To change the desired log level or to assign its output to another handler, modify the corresponding block:

[logger_MaxiNet]
qualname=MaxiNet
level=WARNING
handlers=stream_handler

Transport API

The logging of the transport API is a rather special case as the scripts of the transport API are executed as background processes on the MaxiNet workers. To be able to obtain output from these scripts they are placed in background by the daemonize script (network_emulator/transport_bin/daemonize), which writes the processes' stdout and stderr to files named by their PIDs (by default /tmp/netSLS/processes/$PID on the MaxiNet workers).
In case a process of the transport API fails, the Network Emulator fetches the corresponding output file an prints is content using the logger.

These output files are not removed, until the simulation is restarted. So for debugging purposes the files can be examined manually on the respective workers.