So I know I haven't convinced everyone to love bzr yet ... but as they are a large python project with command line and config file options - and plugins - perhaps looking at the infrastructure/design they use might be a good idea?
Also, the work derks did with cement might be of help. I believe both are designed to do things similar to how you are discussing them below (although different, of course - we're all python devs, there's no way we're going to actually do things the same. :) ) Monty (what Eric is saying makes sense to me - but I don't have a whole bunch of stake either way here- I am a fan of reusing solutions that exist where possible though of course) On 07/28/2010 01:24 PM, Eric Day wrote: > Hi Vish, > > If we want to keep things modular and have runtime module selection > like you mention, we probably need to rethink flags. Using gflags > may not be an option unless we can somehow make 'undefok=' a global > option. In other project (that was not in Python, so no code to help), > the flow is: > > * Enforce the use of module names in the options. For example, for > generic queue module options use --queue.*, for libvirt module > options, use --libvirt.*. If we want to make this seamless, we > would probably need to use something else instead gflags or create > a wrapper to enforce the required behavior. > > * Import the core option manager, first thing that happens when > starting a binary. > > * Parse all options, separating each out into the modules they belong > to. We don't know what is valid yet, but we can at least group by module. > > * Load any required modules via normal 'import' lines. They can verify > options for their module space. > > * Have some core flags that specify which modules to load, for example, > use rabbit vs fakerabbit. Then 'import' the selected optional modules. > > * As optional modules load, let them verify the module namespace > options just like the required modules did. > > * Any options for modules that were not loaded are just ignored. > > Thoughts on this? It has worked out quite well in the other C++ project > for me, and with Python it would be even easier to put together. :) > > -Eric > > On Wed, Jul 28, 2010 at 11:13:40AM -0700, Vishvananda Ishaya wrote: >> I'm having some annoyances with gflags which I'd like to air out here. >> Maybe we can come to a consensus about how to move forward with them. I >> find gflags annoying in the following ways: >> a) flags are irritating for global settings. Settings that apply to the >> project as a whole have to be set in multiple places so that the binaries >> all get them properly. This can be fixed somewhat by a shared flagfile. >> For example: >> /etc/nova/nova-manage.conf: >> --flagfile=/etc/nova/nova-common.conf # shared settings >> --otherflag=true #manage specific settings >> The problem here is that the shared settings can only include settings >> that are imported by EVERY binary, or one of the binaries will choke. So >> if you have a flag that 4 of 5 binaries use, you either have to set it in >> four flagfiles or put it in common with an ugly undefok= line. This all >> seems nasty to me. Other possibilities include moving truly >> common/settings related flags into the common flags.py so that they are >> available to all binaries. It all seems a bit hackish. >> b) including files for flags only >> There are places where we need access to a flag, but we aren't actually >> making calls in the file. Pyflakes and pylint complain about unused >> imports. Perhaps we fix this by moving these flags into common flagfile? >> c) dependency injection >> This is related to the issue above. If we are dynamically loading >> specific drivers (for example the auth driver or a datastore backend) as >> specified by a flag, the import is often done later than the parent file >> is imported. Therefore using flags to configure settings for the driver >> will fail, because the binary recognizing the flags is dependent on the >> file that contains the flags being imported. Workarounds here include >> finding a different method for dependency injection, hacking flags to >> search for flags in injected dependencies somehow, or configuring drivers >> differently than the rest of the system. >> So I see 3 options for moving forward >> 1) ditch gflags completely and use a different method for specifying >> settings >> 2) use a combination of some kind of settings file for general >> configuration, and flags for specific runtime settings/hacks >> 3) find good standard practices/workarounds for the above issues >> Thoughts? >> Vish > >> _______________________________________________ >> Mailing list: https://launchpad.net/~nova >> Post to : [email protected] >> Unsubscribe : https://launchpad.net/~nova >> More help : https://help.launchpad.net/ListHelp > > > _______________________________________________ > Mailing list: https://launchpad.net/~nova > Post to : [email protected] > Unsubscribe : https://launchpad.net/~nova > More help : https://help.launchpad.net/ListHelp > _______________________________________________ Mailing list: https://launchpad.net/~nova Post to : [email protected] Unsubscribe : https://launchpad.net/~nova More help : https://help.launchpad.net/ListHelp
