IP float via APIs instead of ARP?

[gregfr]

Greetings
Could this project allow to move a floating fail over IP with an IP call instead of a local ARP burst?
Thanks in advance
Regards

[johnsudaar]

Just to be sure i understand your request correctly what you'd want is to:

• Disable gratuitous ARP requests
• Let LinK notify another sofware component (via webhook or something else) when an IP should be routed on a new host ?

[EtienneM]

@gregfr can you confirm or clarify your issue? So that we can investigate how and if we want to achieve this

[gregfr]

Sorry I totally forgot about that, but my need is still there.

That's exactly how you said: calling the datacenter API to have them correctly route the IP.

Regards

[johnsudaar]

I guess that's something that we could do pretty easily. I think that we could do that in a 2 step plan:

1. Add an option to disable any operation on the NIC (gARP and IP assignation)
2. Add Hooks on the STANDBY, MASTER and FAILING state of a VIP

For step 2. even if we technically should integrate some major providers APIs to make ENI switch host it sounds like an integration hell, every provider has its own quirks and every user might want to use that API differently.
I think that we should instead provide a simpler API on LinK and let the API calls implementation to the user. So hooks would just call an arbitrary binary on the filesystem (path provided by the user).

The call would then pass 3 args:

• The ID of the VIP (vip-aaaa-bbbbb-cccc-dddd)
• The IP adresse concerned (with mask) (10.0.0.1/32)
• The current state of the IP (STANDBY, MASTER, FAILING)
• The previous state of the IP (STANDBY, MASTER, FAILING)

Both the stdin and stderr of the script should be redirected to LinK logs and the script should have an execution timeout (configurable via the environment).

What do you think @EtienneM @gregfr ?

Edit: Add the previous state of the IP after @EtienneM suggestion.

[EtienneM]

Thanks @johnsudaar for the explanation of how we could handle it. The plan looks good to me but I would wait for @gregfr inputs before proceeding with it. Just to make sure it fits his needs.

Just a question about the arguments provided to the hook script. Don't we want to also provide the previous state? There may be some cases someone wants to know this information

[johnsudaar]

I agree. We could add it as 4th argument.

[gregfr]

@johnsudaar thanks a lot for the followup :D
That would be great to have that hook system 👍
On the top of my head, it would be nice to allow a custom parameter (like some ID of the IPFO in the hosting scheme) to allow a more generic hook to be written (especially if some hooks are provided by the Project, there should be provider-specific parameters).