x/anvil
Code Issues Proposed changes

Change to address some of the questions that are coming up.

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Joshua Harlow 2012-01-26 12:23:14 -08:00
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@ -215,3 +215,46 @@ You can override environment variables used in *stack* by editing *stack.ini* or
To adjust logging edit the *conf/logging.ini* file which controls the logging levels and handlers.
* You can also change which logging file name python will select ([format defined here](http://docs.python.org/dev/library/logging.config.html)) by setting the environment variable *LOG_FILE*.
# Q/A
## Why are we doing this?
1. The current devstack v1 seems to be growing into something it was never meant to be and is becoming hard to understand.
1. A python implementation will:
* Reign the above in and match closely how the other openstack components are developed, tested and code reviewed.
* Keep openstack on one language, thus reducing the language complexity aspect.
1. Additional features/nice to haves were added:
* Ability to uninstall/start/stop the different components.
* Command line help and descriptions of components.
* An object oriented model that can be *easily* examined to figure out what a component requires for setup/config/install/starting/stopping.
1. It can be a place where distributions will come to determine exactly what packages where used for a given openstack release (thus the reason why full versions are important).
1. It can also be a place where you find out what openstack components have dependencies on other components:
* For example: glance depends on keystone, glance depends on a database, keystone depends on a database...
## Why not just rely on package management dependency systems?
1. Having the dependency's handled by the distribtion package management system makes it **hard** for others to know what **exactly** is installed and what should exactly be installed.
* This is important just in general since not everyone is on ubuntu 11.10 (or later), especially for development.
* This is one of the *key* problems that we are trying to solve, since developers are on systems other than ubuntu and those individuals/companies want to contribute to openstack.
* How can these individuals/companies do that if they can't easily get a development system with dependencies installed up and running. This issue
seems like it was starting to be addressed by devstack v1 with apt package lists but this does not seem complete enough as knowing the exact
versions of packages is also very important for other distributions to know what version they should provide.
Thus the reason for having dependencies + versions (not a complete dependency graph) listed.
1. It allows developers to have reproducibility.
* For example when a bug is filed against diablo (or other release/milestone), the developer can easily figure out exactly what packages where installed for whichever distribution that bug was filed against
This allows that developer to recreate the bug (or have a chance at recreated it) and rule out dependency issues causing that bug.
1. Those dependency management systems do not always work the same, so the intricacies of how they work can be isolated in the devstack code.
## Why not just rely on dep or rpm files?
1. Devstack was created for developers and these developers will most likely be using trunk code.
1. Some of the intricacies with getting openstack running, the configs setup, ..., are not as simple as just over-writing some config files (some require actual logic to determine what to do).
* This is why its not as simple as just having a set of debian packages or rpm's that hand-code this logic in there packaging language.
1. This also violates the *key* principle that openstack seems to be sticking to, that of of keeping openstack projects under python if at all possible.
**Past experience**
Something yahoo has learned from doing this many different ways (more than you want to know) is that in the end when having a production level software that can be installed (repeatedly) requires at information on exactly what versions/packages/dependencies are needed. If a distribution automatically updates a package version without the openstack community knowing & approving that change and we didn't list the versions then it may crash openstack (or at least invalidate tests that the openstack community has tested with a given set of dependencies+versions).
That is one of the major wins for versions and dependency lists. Since openstack will be developed and deployed on more than one distribution having a central place where people know exactly what packages + versions worked for a release (or for development) seems pretty important (especially as the project matures). This may be an *inversion* of currently how it works but it seems better to fix this now than later when it becomes even more of a problem.