On 18 Mar 2014, at 01:32, Joshua Harlow <[email protected]> wrote:
> To further this lets continue working on 
> https://etherpad.openstack.org/p/taskflow-mistral and see if we can align 
> somehow

Sure.

> (I hope it's not to late to do this,

Never late IMO.

> seeing that there appears to be a lot of resistance from the mistral 
> community to change.

Could you please let us know how you made this conclusion? I’m frankly 
surprised.. It’s not just my curiosity or something, I want to keep improving 
in what I’m doing.


Generally, just to clarify the situation let me provide our vision of what 
we’re doing at the very high level.

As mentioned many times, we’re still building a PoC. Yes, it turned out to take 
longer which is totally fine since we’ve done a lot of research, lots of coding 
exercises, talks, discussions with our customers. We’ve involved several new 
contributors from two different companies, they have their requirements and use 
cases too. We’ve gathered a lot of specific requirements to what should be a 
workflow engine. This all was the exact intention of that phase of the project: 
understand better what we should build. If you look at Mistral list of 
blueprints you’ll see around 40 of them where 80-90% of them come from real 
needs of real projects. And not everything is still captured in BPs because 
something is still not shaped well enough in our minds.

Thought #1: In POC we’ve been concentrating on use cases and requirements. 
Implementation has been secondary.

TaskFlow or anything else just hasn’t mattered a lot so far. But, at the same 
time, I want to remind that in December we tried to use TaskFlow to implement 
the very basic functionality in Mistral (only dependency based model). 
Honestly, we failed to produce a result that we would be satisfied with since 
TaskFlow lacked, for example, the ability to run tasks in an asynchronous 
manner. This was not a problem at all, this is the real world. So I created a 
BP to address that problem in TaskFlow ([0]). So we decided to proceed with it 
with an intent to rejoin later.
And may be even the most important reason not to use TaskFlow was that we did 
want to have a clear research. We found that less productive to try to build a 
project around an existing library than concentrating on use cases and 
high-level requirements. From my experience, it never works well since in your 
thinking you always stick to limitations of that lib and assumptions made in it.

So we actually talked to people a lot (including Josh) and provided this 
reasoning when this question raised again. Reaction was nearly always positive 
and made a lot of sense to customers and developers.

Thought #2: A library shouldn't drive a project where it’s used.

Project needs should define the requirements to a library. Even being adopted 
in lots of places (this is apparently not true for TaskFlow right now which is 
fully understandable, a pretty young project as well) a library is just one of 
many tools used within a project. But not vice versa.

Thought #3. We 100% admit we’re not ready for incubation right now.

We prepared an incubation request already with most of the formal requirements 
met by the project. And even thought the interest to Mistral is serious (at 
least 5-6 projects intent to use it, one already started playing and 
prototyping with Mistral) we want to be honest with the community in that we’re 
not really ready for incubation since even our own solid understanding of core 
requirements and API/DSL is only on its way. This is just one more argument 
that spending significant time on thinking how to fit TaskFlow into our 
unstable Mistral vision is not affordable for us at the moment. Despite of 
that, last week we started spending that time after Josh started bombing us 
with his concerns :).


If that’s all harsh, sorry. We’re interested in keeping in touch with Josh and 
others.

[0] https://blueprints.launchpad.net/taskflow/+spec/async-tasks

Renat Akhmerov
@ Mirantis Inc.

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