Eureka vs ELB with Genie cluster

[Jelez Raditchkov]

Can ELB in VPC be used for a cluster of Genie nodes in ASG where ELB checks are enabled? What are the caveats?
What more does Eureka ptovide than ELB?
If ELB can be used then what serttings should be set/unset in Genie?

Also are jobs coordinated via the MySQL database across a cluster of genie instances?

Thank you!

[Tom Gianos]

Hi Jalez,

For the way Genie 2 is designed an ELB is likely not going to work very well. This is because the job files are written to local disk and need to be accessed on the node they're written to. If you put the cluster behind an ELB and it attempts to round robin requests and users attempt to access their results they would get a lot of 404's. You might be able to get around this with some sticky sessions and better yet some sort of mounted file system across your cluster but as of this writing a tool like EFS hasn't gone GA.

For Genie 2 Eureka provides a way for applications to discover nodes in the ASG while also allowing those nodes to be accessed directly. It doesn't directly provide any load balancing unless combined with something like Ribbon or other client side load balancing logic.

All that said it is interesting you ask this question at this time as we're getting very close to releasing Genie 3. Genie 3 has been redesigned to address this exact shortcoming and become even more of a distributed system. Internally at Netflix we are running our test versions of Genie 3 behind a HTTPS endpoint ELB, with security via SAML and OAuth2 and https session sharing via Redis. Genie now has the ability to forward requests around the cluster if an ELB proxied request goes to the wrong node. Eventually we want to make the web tier of Genie completely stateless and run all jobs on a backend cluster while mounting a filesystem onto the web nodes and worker nodes. We're not there yet but with 3.1 we likely will be.

That said if you're looking to use an ELB and any of the above features look interesting to you I would suggest looking at Genie 3 in the develop branch. We don't have any documentation yet as we're still in active development and haven't had a chance but hope to soon.

Let us know if this helps or not or if you have further questions.

Thanks,

Tom