Debugging Neutron Command line Client

These instructions assume you have installed Neutron command client in a Linux environment. If you have other operating systems, the debugging process might be a slightly different, however, the general rules should still apply.

Neutron command line client is very much like other Linux commands, it outputs errors in the standard output, which is the monitor.

If you get an error, you can always read the error message and generally it give you very good hints about what might be wrong.

For example, if you execute neutron net-list on the command line without authentication, the error message might look like this:

ERROR: You must provide a username via either --os-username or env[OS_USERNAME]

The above message indicates you need to be authenticated before you can use the API. The authentication requires some environment variables to be set. To set these environment variables you can either source the script file obtained from NeCTAR Dashboard or you can override it by using command line options.

Please refer to Networking Getting Started article.

You can always execute man neutron or simply neutron help to get more help information and to learn each supported options.

If you find a useful command, you can also execute nova help command, this will give your more specific help for the command.

Debugging Neutron Python API

Debugging Neutron Python API takes more effects as it depends on how familiar with Python programming and what development environment you use.

The below provides some basic information about how you debug the Neutron Python API.

You can debug your python code using Python debugger called pdb and you can find more information here.

The below code uses pdb debuuger to debug a python file contains clinet python API code.


Once you executed the above code, the command line will be stopped on the first line of code and you can use some commands to control the execution flow.

Some useful ones to use are:

bset a breakpoint
ccontinue debugging until you hit a breakpoint
sstep through the code
nto go to next line of code
llist source code for the current file
unavigate up a stack frame
dnavigate down a stack frame
pto print the value of an expression in the current context

Debugging Via HTTP

The both of command line API and python API are restful web service client. Thus the requests are all made by using HTTP and you can always refer to OpenStack Service End for further references about what should be presented in the HTTP requests. The Neutron API uses requests library to send and receive HTTP requests/responses.

For command line client, you can add --debug option to print out HTTP request header and HTTP response header, which give you a lot of more insight information. To verify parameters in the request header, you can refer to OpenStack service API to see what are expected.

To enable debugging information on the standard out for Python API, you can add the below code:


import logging
logger = logging.getLogger("neutronclient")


The will print the same output as adding --debug option for command line API.

Debugging via Source Code

If the above techniques are still not helpful, you can always look at the source code to find the problems.

The below source file structure is based on the installation in Ubuntu.

The command line neutron command is located in '/usr/bin/neutron'. By looking at this file, you should get a idea of how the various options are interpreted. This file acts as an interface for Python API.

The Python API files are located under '/usr/lib/python2.7/dist-packages/neutronclient/v2_0/' and the most important file to look at is ''. This file does all the request preparation, sending request and receiving response. It is also used by the command line Neutron client.

NeCTAR Support

If still having issues, you can always go to the NecTAR HelpDesk to log a support ticket and support staff are more than happy to help you.