adjust decider to not retry client errors

[dbu]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	kindof
Deprecations?	no
Related tickets	fixes #80
Documentation	-
License	MIT

What's in this PR?

Do not retry if the error is caused by the server returning a HTTP error code indicating that the request was bad.

Why?

There is no point in retrying those.

Checklist

• Updated CHANGELOG.md to describe BC breaks / deprecations | new feature | bugfix

To Do

• Unless the exception plugin is used, this plugin only acts on network errors. Should we also look at the response and retry if the response code is >= 500? => see Retry Plugin should also retry responses with status 5xx #126
• Add test in spec

[joelwurtz]

Not sure why this is needed ? Since only the ErrorPlugin transform to HttpException AFAIK. Also you can configure the ErrorPlugin to only throw when response status code is >= 500.

[dbu]

@joelwurtz indeed the response exception is an edge case, the expected exceptions are transfer problems. but i think it still does make sense.

however, what would be more relevant is to look at non exception responses to check them for server side errors and retry those as well.

[Nyholm]

I like this.

I also think it is strange that we only consider exceptions. Why dont we also check the response? Ie this plugin is useless without the ErrorPlugin.

[joelwurtz]

we should certainly change the decider function to accept a ResponseInterface inside it then

[dbu]

i created #126 to discuss handling server error responses in addition to exceptions. please give your input there.

ok if we merge the tweak for exception handling here separately?

[dbu]

this is only about the exception - okay if we merge it?

[Nyholm]

Thank you