Configuring and logging

Overview

Questions

• What are QMI configuration and log files?

Objectives

• Know how to create a basic configuration file.

QMI Configuration and log file

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Many aspects of QMI are configurable via a configuration file. The syntax of this file is very similar to JSON, but unlike JSON, the configuration file may contain comments starting with a # character. By default, QMI attempts to read the configuration from a file named qmi.conf in the home directory (i.e. ‘/home/<user_profile>’ in Linux or ‘C:\Users\<user_name>’ folder on Windows). If you want to use a different file name or location, you can specify the configuration file path with the config_file= argument of qmi.start() or in the environment variable QMI_CONFIG. Let’s create a configuration file qmi.conf at the course directory with the following contents:

JSON

{
    # Log level for messages to the console.
    "logging": {
        "console_loglevel": "INFO"
        # "logfile": "log.log"
    }
    # Directory to write main log file.
    # "log_dir": "~/qmi_course/log"
}

This configuration file changes the log level for messages that appear on your terminal. By default, QMI prints only warnings and error messages. Our new configuration also enables printing of informational messages. For further details about logging options, see documentation on qmi.core.logging_init module. Test the new configuration file in a new Python session:

PYTHON

import qmi
qmi.start("hello_world", config_file="qmi.conf")
qmi.stop()

If the configuration file is found and written correctly, QMI should print a bunch of log messages on the terminal after the call to start. If you don’t see any output, you might have to give full path location for the config_file= argument to, or try setting the QMI_CONFIG environment variable with:

export QMI_CONFIG=`pwd`/qmi.conf

Or in powershell

POWERSHELL

$Env:QMI_CONFIG = Join-Path $pwd "\qmi.conf"

At your home directory should also now be a file called qmi.log. The file works as a log for QMI programs. You will find in this file a log of actions you took until now while testing your first examples. The logging can be disabled by giving input parameter init_logging=False for qmi.start(). We will add more settings to the configuration file as we progress through this tutorial.

Let’s try the different options to change the QMI log file name and logging location. Try, for example, uncommenting the “logfile” and “log_dir” options in your qmi.conf file. Then run again the test in Python and see if the location and file name of the log file did change. Note that JSON is very picky about the use of commas. There must be a comma between multiple elements in the same group, but there may not be a comma after the last element of a group.

You can also try commenting out these lines again and to use the QMI_HOME environment variable by setting it with:

export QMI_HOME=`pwd`

Key Points

• qmi.conf has a JSON-like structure, but allows comments starting with ‘#’
• qmi.conf location can be given as an argument to qmi.start by setting QMI_CONFIG environment variable
• Log levels are set within “logging” keyword section
• Default name and location of the log file are qmi.log and the user’s home directory
• These can be changed using “logfile” and “log_dir” options in qmi.conf, but also by setting QMI_HOME environment variable.