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On Mon, Aug 11, 2014 at 11:02 AM, Yuriy Taraday <yorik.sar at gmail.com> 
wrote:
> On Mon, Aug 11, 2014 at 5:44 AM, Joshua Harlow <harlowja at outlook.com> 
> wrote:
>> One question from me:
>> 
>> Will there be later fixes to remove oslo.config dependency/usage 
>> from oslo.concurrency?
>> 
>> I still don't understand how oslo.concurrency can be used as a 
>> library with the configuration being set in a static manner via 
>> oslo.config (let's use the example of `lock_path` @ 
>> https://github.com/YorikSar/oslo.concurrency/blob/master/oslo/concurrency/lockutils.py#L41). 
>> For example:
>> 
>> Library X inside application Z uses lockutils (via the nice 
>> oslo.concurrency library) and sets the configuration `lock_path` to 
>> its desired settings, then library Y (also a user of 
>> oslo.concurrency) inside same application Z sets the configuration 
>> for `lock_path` to its desired settings. Now both have some unknown 
>> set of configuration they have set and when library X (or Y) 
>> continues to use lockutils they will be using some mix of 
>> configuration (likely some mish mash of settings set by X and Y); 
>> perhaps to a `lock_path` that neither actually wants to be able to 
>> write to...
>> 
>> This doesn't seem like it will end well; and will just cause 
>> headaches during debug sessions, testing, integration and more...
>> 
>> The same question can be asked about the `set_defaults()` function, 
>> how is library Y or X expected to use this (are they?)??
>> 
>> I hope one of the later changes is to remove/fix this??
>> 
>> Thoughts?
>> 
>> -Josh
> 
> I'd be happy to remove lock_path config variable altogether. It's 
> basically never used. There are two basic branches in code wrt 
> lock_path:
> - when you provide lock_path argument to lock (and derivative 
> functions), file-based lock is used and CONF.lock_path is ignored; 
> - when you don't provide lock_path in arguments, semaphore-based lock 
> is used and CONF.lock_path is just a prefix for its name (before 
> hashing).

Agreed, it just seems confusing (and bad) to have parts of the API come 
in from `CONF.lock_path` (or other `CONF.*` options) and other parts of 
the API come in via function parameters. This just makes understanding 
the API and knowing how to interact with it that much harder (after all 
what is the right way of using XYZ feature when it can be changed via a 
out-of-band *hidden* API call via configuration adjustments under the 
covers?)... This makes it really hard to use oslo.concurrency in 
taskflow (and likely other libraries that would like to consume 
oslo.concurrency, seeing that it will be on pypi, I would expect this 
number to grow...) since taskflow would really appreciate and desire to 
have stable APIs that don't change by some configuration that can be 
set by some party via some out-of-band method (for example some other 
library or program calling `set_defaults()`). This kind of way of using 
an API (half of the settings from config, half of the settings from the 
functions API...) may be ok for applications but it's not IMHO ok for 
libraries (or clients) that want to use oslo.concurrency. 

Hopefully it can be fixed some that it works via both ways? Oslo.db I 
believe made this work better by allowing for configuration to come in 
via a configuration object that can be provided by the user of oslo.db, 
this makes the API that oslo.db exposes strongly tied to the attributes 
& documentation of that object. I still don't think thats perfect 
either since its likely that the documentation for what that objects 
attributes should be is not as update to date or easy to change as 
updating function/method documentation...

> I wonder if users even set lock_path in their configs as it has 
> almost no effect. So I'm all for removing it, but...
> From what I understand, every major change in lockutils drags along a 
> lot of headache for everybody (and risk of bugs that would be 
> discovered very late). So is such change really worth it? And if so, 
> it will require very thorough research of lockutils usage patterns.

Sounds like tech debt to me, it always requires work to make something 
better. Are we the type of community that will avoid changing things 
(for the better) because we fear introducing new bugs that may be found 
along the way? I for one hope that we are not that type of community 
(that type of community will die due to its own *fake* fears...).

> 
> -- 
> 
> Kind regards, Yuriy.