Logging

Dao provides a flexible logging system that supports multiple output destinations, including standard output, files, and network sockets, with the ability to control output granularity based on severity levels at runtime.

Severity Levels

Log messages are assigned a severity level by the programmer, indicating the importance of each message and allowing the logging system to filter for specific severities during output.

The following is a list of all the available severity levels:

  • TRACE

  • DEBUG

  • INFO

  • WARNING

  • ERROR

  • CRITICAL

Python

To use the logging system within a Python application, import the following:

from daoLog import daoLog
import logging

The example below demonstrates how to create a logger and use it to output logs to the standard output:

_ = daoLog("LoggingApp")

logger = logging.getLogger("LoggingApp")
logger.Trace("trace log")
logger.Debug("debug log")
logger.Info("info log")
logger.Warning("warning log")
logger.Error("error log")
logger.critical("critical log")

By default, the log severity threshold is set to TRACE, therefore all severities will be included in the output. The following shows how to adjust the logging granularity at runtime:

newSeverity: str = "INFO"  # Any supported severity level
logger = logging.getLogger("LoggingApp")
logger.setLevel(newSeverity)

To have the logs also be directed to a file, you simply need to pass the desired output file path when creating the logger:

_ = daoLog("LoggingApp", filename="logFile.log")

By default the logs will now be output to both standard output and the specified file, however you can disable output to standard output by doing the following:

_ = daoLog("LoggingApp", filename="logFile.log", toScreen=False)

Each log contains several pieces of information such as the logger name, a timestamp, the device host name and the severity level - below shows an example output from the logger.

[2025-10-13 09:15:17,286] [HOST-NAME] - __main__ [TRACE] : trace log (daoLog.py:77)
[2025-10-13 09:15:17,286] [HOST-NAME] - __main__ [DEBUG] : debug log (daoLog.py:276)
[2025-10-13 09:15:17,286] [HOST-NAME] - __main__ [INFO] : info log (daoLog.py:277)
[2025-10-13 09:15:17,286] [HOST-NAME] - __main__ [WARNING] : warning log (daoLog.py:278)
[2025-10-13 09:15:17,286] [HOST-NAME] - __main__ [ERROR] : error log  (daoLog.py:279)
[2025-10-13 09:15:17,286] [HOST-NAME] - __main__ [CRITICAL] : critical log (daoLog.py:280)

C++

The C++ logging system queues log messages as they are issued by the application and routes them to the configured output destination on a dedicated background thread, minimizing overhead for real-time applications.

To use the logging system within your C++ application, include the following header:

#include <daoLog.hpp>

The following example shows how to create a logger and output various logs to standard output:

Dao::Log logger("LoggingApp", Dao::Log::DESTINATION::SCREEN);

logger.Trace("trace log");
logger.Debug("debug log");
logger.Info("info log");
logger.Warning("warning log");
logger.Error("error log");
logger.critical("critical log");

By default, the trace and debug logs will be omitted from the output as the default severity threshold is the INFO level and thus lower-severity messages are filtered out. The threshold can be adjusted at runtime depending on the desired granularity of the output, as shown below:

Dao::Log::LEVEL newSeverity = Dao::Log::LEVEL::TRACE; // Any level in Dao::Log::LEVEL
logger.SetLevel(newSeverity);

The logger can instead direct logs to a file instead of standard output. Below shows how to configure the logger object to achieve this.

std::string logFilePath = "logFile.log".
Dao::Log::Logger logger("LoggingApp", Dao::Log::Logger::DESTINATION::FILE, logFilePath);

The logger is also capable of directing the logs over the network using a TCP ZeroMQ socket. A user created ZeroMQ application can then receive these logs on the destination device and be processed as desired. The following shows how to configure the logger to achieve this.

int portNumber = 1234;
std::string ipAddr = "127.0.0.1";
Dao::Log::Logger logger("LoggingApp", Dao::Log::Logger::DESTINATION::NETWORK, ipAddr, portNumber);

The logger formats each log message upon output to the destination. Each log contains several pieces of information such as the logger name, a timestamp, the device host name and the severity level - below shows an example output from the logger.

LoggingApp:25-10-13 10:23:28 [TRACE]    - trace log
LoggingApp:25-10-13 10:23:28 [DEBUG]    - debug log
LoggingApp:25-10-13 10:23:28 [INFO ]    - info log
LoggingApp:25-10-13 10:23:28 [WARNING]  - warning log
LoggingApp:25-10-13 10:23:28 [ERROR]    - error log
LoggingApp:25-10-13 10:23:28 [CRITICAL] - critical log