Standalone configuration

[mikz]

Fixes #795

Implements "standalone" configuration, that does not depend on 3scale and can be human-authored YAML document describing internal services and routing between them.

Please note this is just first version and it will be refined as we start using it more.

[davidor]

I think we had a similar problem in Executor and figured out a way to run every phase only once.

[mikz]

It was a bit different problem I think.

Executor does the following:

• call :init and initialize all policies in the current chain
• use PolicyLoader:get_all() to load "all" policies
• call :init on the remaining policies

Now PolicyLoader:get_all() does not return all the policies. Some don't have apicast-policy.json file, so they are not discovered.

So the problem is that the Executor is going to call the :init phase on all policies that it can find but does not expose the information if the phase was already executed. So standalone can't really know if it was already executed or not.

There are two options I see:

• expose information about what phase was executed on what policy in the Executor
• standalone policy should not trigger :init on policies that can be found by PolicyLoader and assume it was done by the Executor module

Wdyt?

[davidor]

I prefer the first one because I think it's more explicit, but I think that both options should be OK.

[mikz]

So after some digging, I realised the problem is a bit deeper.

Executor keeps track of what it executed, but it can't keep track of what nested policy chains executed. Let's say Executor has 3 policies and the 2nd is itself a policy chain with 3 more policies. The Executor would be aware only of the first level.

We would have to figure out how to collect all policies from the executor without calling them.

Maybe I'd rather postpone this until we get more information and see more places where it breaks.

[davidor]

Ah, I didn't think about the nested chains scenario.
OK to postpone it 👍 No need to solve this for a first version.

[davidor]

I agree with the approach taken 👍

My comments are just about minor things. I also think that we need more unit and integration tests.

As you mentioned in your original comment, this is just a first version, so no need to fix everything now.