Add devref that explains fullstack testing and its direction

The goal of this doc is to communicate what are full stack tests,
how they benefit you and when would you write such a test.

Additionally I'd like to communicate the way forward, and gather
feedback about any areas in the code that can benefit from full
stack tests, and any additional thoughts!

Change-Id: Ifd4ff9be0ed0184a49df6566d238c31a328cd23f
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Assaf Muller 2015-06-02 12:21:11 -04:00
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Neutron Full Stack Testing
The idea behind "fullstack" testing is to fill a gap between unit + functional
tests and Tempest. Tempest tests are expensive to run, difficult to run in
a multi node environment, and are often very high level and provide little
indication to what is wrong, only that something is wrong. Developers further
benefit from full stack testing as it can sufficiently simulate a real
environment and provide a rapidly reproducible way to verify code as you're
still writing it.
Full stack tests set up their own Neutron processes (Server & agents). They
assume a working Rabbit and MySQL server before the run starts. Instructions
on how to run fullstack tests on a VM are available at TESTING.rst:
Each test defines its own topology (What and how many servers and agents should
be running).
Since the test runs on the machine itself, full stack testing enables
"white box" testing. This means that you can, for example, create a router
through the API and then assert that a namespace was created for it.
Full stack tests run in the Neutron tree with Neutron resources alone. You
may use the Neutron API (Keystone is set to NOAUTH so that it's out of the
picture). VMs may be simulated with a helper class that contains a container-
like object in its own namespace and IP address. It has helper methods to send
different kinds of traffic. The "VM" may be connected to br-int or br-ex,
to simulate internal or external traffic.
Full stack testing can simulate multi node testing by starting an agent
multiple times. Specifically, each node would have its own copy of the
OVS/DHCP/L3 agents, all configured with the same "host" value. Each OVS agent
is connected to its own pair of br-int/br-ex, and those bridges are then
.. image:: images/fullstack-multinode-simulation.png
1) You'd like to test the interaction between Neutron components (Server
and agents) and have already tested each component in isolation via unit or
functional tests. You should have many unit tests, fewer tests to test
a component and even fewer to test their interaction. Edge cases should
not be tested with full stack testing.
2) You'd like to increase coverage by testing features that require multi node
testing such as l2pop, L3 HA and DVR.
3) You'd like to test agent restarts. We've found bugs in the OVS, DHCP and
L3 agents and haven't found an effective way to test these scenarios. Full
stack testing can help here as the full stack infrastructure can restart an
agent during the test.
Short Term Goals
* Multinode & Stability:
- Interconnect the internal and external bridges
- Convert the L3 HA failover functional test to a full stack test
- Write a test for DHCP HA / Multiple DHCP agents per network
* Write DVR tests
* Write L3 HA tests
* Write a test that validates L3 HA + l2pop integration after is fixed.
* Write a test that validates DVR + L3 HA integration after is fixed.
None of these tasks currently have owners. Feel free to send patches!
After these tests are merged, it should be fair to start asking contributors to
add full stack tests when appropriate in the patches themselves and not after
the fact as there will probably be something to copy/paste from.
Long Term Goals
* Currently we configure the OVS agent with VLANs segmentation (Only because
it's easier). This allows us to validate most functionality, but we might
need to support tunneling somehow.
* How do advanced services use the full stack testing infrastructure? I'd
assume we treat all of the infrastructure classes as a publicly consumed
API and have the XaaS repos import and use them.
* Currently we configure the Neutron server with the ML2 plugin and the OVS
mechanism driver. We may modularize the topology configuration further to
allow to rerun full stack tests against different Neutron plugins or ML2
mechanism drivers.

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In the Developer Guide, you will find information on Neutron's lower level
programming APIs. There are sections that cover the core pieces of Neutron,
including its database, message queue, and scheduler components. There are
also subsections that describe specific plugins inside Neutron.
also subsections that describe specific plugins inside Neutron. Finally,
the developer guide includes information about Neutron testing infrastructure.
Programming HowTos and Tutorials
@ -51,6 +52,12 @@ Neutron Internals
.. toctree::
:maxdepth: 3
Module Reference

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Please see neutron/doc/source/devref/fullstack_testing.rst.