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skynetservices / skydns

DNS service discovery for etcd
MIT License
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Round-robin localhost priority #213

Open jpillora opened 8 years ago

jpillora commented 8 years ago

I'm not sure if this feature is already possible or if would be possible a result of implementing #178, if so, feel free to close this.

For example, let's say we have:

1.mydatabase.service 10.0.0.1
2.mydatabase.service 10.0.0.2
3.mydatabase.service 10.0.0.3

So mydatabase.service will round-robin through each as expected. However, it would be nice if 10.0.0.2 was priortised at the top for requests coming from 10.0.0.2 as it would prevent unnecessary network traversals. Thoughts?

Edit: This has the benefit of using a localhost instance of a given service when available and falling back to a remote host when not. Note, this scheme can manually implemented for custom clients, however with 3rd party clients using connection pools (redis/rethinkdb) this would not be possible without going into the source and introducing "primary" and "secondary" hostnames.

miekg commented 8 years ago

Interesting feature. But I think this should not be done in the DNS. Why can't you add those 10 addresses to the loopback interface on those hosts? On 26 Jul 2015 08:20, "Jaime Pillora" notifications@github.com wrote:

I'm not sure if this feature is already possible or if would be possible a result of implementing #178 https://github.com/skynetservices/skydns/issues/178, if so, feel free to close this.

For example, let's say we have:

1.mydatabase.service 10.0.0.1 2.mydatabase.service 10.0.0.2 3.mydatabase.service 10.0.0.3

So mydatabase.service will round-robin through each as expected. However, it would be nice if 10.0.0.2 was priortised at the top for requests coming from 10.0.0.2 as it would prevent unnecessary network traversals. Thoughts?

— Reply to this email directly or view it on GitHub https://github.com/skynetservices/skydns/issues/213.

jpillora commented 8 years ago

That would help in the case where a VM died and all containers on a single machine die at once. However, if container A dies, container B would still think A is on localhost. Whereas, if A had its address in skydns then it would expire and B would correctly route to a remote host.