Create only one private route table when single_nat_gateway is true

[lorengordon]

Right now, this module is creating a route table for every subnet even when there is a single NAT Gateway. This is unnecessary, as all the route tables are using the same NAT Gateway, and multiple subnets can be associated with the same route table.

I propose that when the user elects to use a single NAT Gateway, all the private subnets should be associated with just a single private route table.

[sarcasticadmin]

I just ran into this myself, I only needed a single NAT instance and therefore assumed that would only create a single routing table across all the private subnets (3 subnets in my case). Unfortunately I was still left with 3 private routing tables. I'd like to see this module support a single private routing table 👍

[yardensachs]

Any update on this?
@lorengordon's fork looks very good. can you create a pr and merge it?

[antonbabenko]

@yardensachs I should be able to take a look at this during upcoming weekends.

[antonbabenko]

Apparently, it will be during next weekends... sorry for the delay!

[yardensachs]

Thanks

[mhumeSF]

What's the use case where you would create multiple private subnets across azs when using only a single nat.

[yardensachs]

@mhumeSF because you may want to launch instances across multiple azs

[mhumeSF]

Sorry, I'm an idiot. I see now. Just be aware that traffic between the nat and instances across AZs will incur cross-az data charges. (A cautionary tale)

[antonbabenko]

Sorry for the delay, finding time to do a proper review and manual testing is not the easiest part of the work. Patience and nudge usually help :)

v1.29.0 has been just released.

[yardensachs]

@antonbabenko thank you!

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