Specs to make maxRetries configurable for endpoints and route-services

[domdom82]

• A short explanation of the proposed change:

Fixes #285

This is the companion PR for making max-retries configurable in gorouter

• It needs to be merged together with its companion to make use of the new properties.
• Gorouter submodule has to be bumped as well
• A default value for max-retries is set to 3, retaining the original setting
• For backends, a value of 0 may be set, which implies "retry until success or no more endpoints remain
• For route services, a minimum value of 1 must be maintained, because there is no endpoint list and thus no natural end to retries.

• An explanation of the use cases your change solves

See companion PR

• Instructions to functionally test the behavior change using operator interfaces (BOSH manifest, logs, curl, and metrics)

See companion PR

• Expected result after the change

See companion PR

• Current result before the change

See companion PR

• Links to any other associated PRs

cloudfoundry/gorouter#335

• I have viewed signed and have submitted the Contributor License Agreement

• I have made this pull request to the develop branch

• I have run all the unit tests using scripts/run-unit-tests-in-docker

• (Optional) I have run Routing Acceptance Tests and Routing Smoke Tests on bosh lite

• (Optional) I have run CF Acceptance Tests on bosh lite

[ameowlia]

Hi @domdom82,

Thank you for submitting this! I am deploying it now to test. I appreciate that you split up backend retries and route-service retries. Good catch.

My main critique is the use of the word "retries". You use the word "retries" here, but what I actually think you mean is "tries" or "attempts". To me, zero retries would imply that gorouter tries once, and then never tries again.

I think there are two options here:

1. change "retries" to "connection attempts" or something similar. I prefer this option.
   • In this case I think having 0 mean unlimited makes sense.
2. use the word "retries" and change the code to actually mean retries.
   • make the default for backends 2 (3 attempts total)
   • however then you can't use 0 to mean unlimited (or you could, but it would get rid of the option for 1 try only)

[domdom82]

@ameowlia thanks for your review. funny enough, we just had the same discussion and came up with "attempts" instead of "retries". so 👍 to that!

[nicregez]

@ameowlia We renamed maxRetries to maxAttempts (see today's second commit on the branch). The rename is aligned with gorouter PR-335 of course.

For backend calls, maxAttempts value of "0" means infinite. For route-services, a value of "0" is prevented.

We thoroughly tested the behaviour of gorouter in one of our CF deployments and did not encounter any unexpected behaviour.

May we kindly as you to merge both PRs? Thank you!