Tacker WSGI/HTTP API layer

This section will cover the internals of Tacker’s HTTP API, and the classes in Tacker that can be used to create Extensions to the Tacker API.

Python web applications interface with webservers through the Python Web Server Gateway Interface (WSGI) - defined in PEP 333


Tackers’s WSGI server is started from the server module and the entry point serve_wsgi is called to build an instance of the TackerApiService, which is then returned to the server module, which spawns a Eventlet GreenPool that will run the WSGI application and respond to requests from clients.

WSGI Application

During the building of the TackerApiService, the _run_wsgi function creates a WSGI application using the load_paste_app function inside config.py - which parses api-paste.ini - in order to create a WSGI app using Paste’s deploy.

The api-paste.ini file defines the WSGI applications and routes - using the Paste INI file format.

The INI file directs paste to instantiate the APIRouter class of Tacker, which contains several methods that map VNFM resources (such as vnfd, vnf) to URLs, and the controller for each resource.

Further reading

Tacker wsgi is based on neutron’s extension. The following doc is still relevant.

Yong Sheng Gong: Deep Dive into Neutron