[Apiman-user] Feedback wanted: Allowing policies to modify PolicyFailures emitted by *other* policies in chain

[Marc Savy]

As I had no negative feedback, this has been merged (along with
tests). It should be in the next release.

On 4 July 2018 at 20:44, Marc Savy <marc.savy at redhat.com> wrote:
> Hi,
>
> I have a prototype of this available for people to try (forgive any
> scrappiness, this will be tidied before the final version is merged):
>
> https://github.com/apiman/apiman/pull/686/files
>
> It works as follows:
>
> Let's imagine our policy chain again.
> [CORS, PolicyA, PolicyB]
>
> * If a policy failure occurs in the *request* chain, the entire
> response chain will be executed (in the usual reverse order) with
> #processFailure
>
> Imagine PolicyA throws a failure on the request leg, then each of the
> policies will have a chance to modify the failure object in the
> following order:
> [PolicyB, PolicyA, CORS]
>
> * If a policy failure occurs during the *response* chain, then only
> the remaining policies will have a chance to process the failure.
>
> This seemed like the most sensible/practical design to me -- happy to
> hear feedback, though.
>
> Here's an example of a policy using this proposed functionality:
>     https://gist.github.com/msavy/b872efa7f08929d19a420ea68ec3f584
>
>
> Regards,
> Marc
>
> On 12 April 2018 at 19:42, Marc Savy <marc.savy at redhat.com> wrote:
>>  Marvin Oßwald filed a really interesting issue:
>> https://issues.jboss.org/browse/APIMAN-1300
>>
>> In short, if we imagine a policy chain like this:
>>
>> [CORS, PolicyA, PolicyB]
>>
>> Even if PolicyB emits a failure, then the CORS policy would likely
>> still want to be able to process the PolicyFailure to add the relevant
>> headers (otherwise a SPA type app like Angular would break).
>>
>> This seems like a valid use-case.
>>
>> Ideally I'd like to tackle this without breaking any existing interfaces.
>>
>> A couple of quick ideas:
>>
>> * Add a new interface that policies like CORS could implement that
>> indicates it wants to do this kind of processing. E.g.
>> IFailureProcessor or similar with a simple method signature like
>> #process(PolicyFailure failureToModify).
>>
>> * An annotation: essentially the same as above, but with a
>> @WhateverWeCallIt annotation on the method that does the processing.