conditional transforms

[captncraig]

We need to support some additional logic for our import_transforms at stack.

CURRENT:

var TRANSFORM_DOUBLEINT = [
    {low: NYLO, high: NYLO+40, newBase: [NYINT,COINT] },  
    {low: NYHI, high: NYHI+40, newBase: [NYINT,COINT] },  
    {low: COLO, high: COLO+40, newBase: [NYINT,COINT] }, 
    {low: COHI, high: COHI+40, newBase: [NYINT,COINT] }, 
]

We need to conditionally only use one of the newBase entries for wildcard records.
Logic is essentially:

var TRANSFORM_DOUBLEINT = [
    {low: NYLO, high: NYLO+40, newBase: [NYINT(always),COINT(unless *)] },  
    {low: NYHI, high: NYHI+40, newBase: [NYINT(always),COINT(unless *)] },  
    {low: COLO, high: COLO+40, newBase: [NYINT(unless *),COINT(always)] }, 
    {low: COHI, high: COHI+40, newBase: [NYINT(unless *),COINT(always)] }, 
]

I can see a few different ways to implement this:

1. Hack it in

Just handle all * records as a special case and only emit the first newBase transform.

Quick and easy, but completely inflexible, and a bit "magical"

2. Add a field to each rule, double the rules

var TRANSFORM_DOUBLEINT = [
    {low: NYLO, high: NYLO+40, newBase: [NYINT,COINT], ignore:"*" },  
    {low: NYLO, high: NYLO+40, newBase: [NYINT] },
    {low: NYHI, high: NYHI+40, newBase: [NYINT,COINT] , ignore:"*"}, 
    {low: NYHI, high: NYHI+40, newBase: [NYINT] },  
    {low: COLO, high: COLO+40, newBase: [NYINT,COINT], ignore:"*" }, 
    {low: COLO, high: COLO+40, newBase: [COINT] }, 
    {low: COHI, high: COHI+40, newBase: [NYINT,COINT], ignore:"*" },
    {low: COHI, high: COHI+40, newBase: [COINT] }, 
]

Here each rule can have an ignore field to skip it. Since transforms stop looking at rules once we match one, this should behave as expected.

Cons: our home grown hacky transform format for transforms (~~ soup) is not making this easy. But it can be added in.

Also, is the field a regex? Or just do a contains on it? Regex for wildcard means putting in \* which feels kinda odd. Should it just match on the label, or on the fqdn?

[gbrayut]

Another option would be a 'post transform' layer, where we could override any records with a final version. We just need to update *.Stackexchange.com.internal and *.Blogoverflow.com.internal to have a single A record in the primary internal base range, but having a final layer would let us fix up any other discrepancies found in the future.

I am fine with any of these approaches, especially after finding that wildcard records with double A addresses don't follow local subnet prioritization rules.

[captncraig]

3.

Explicitly add records for things the transforms screw up:

var INTERNAL_TTL = 300;
D("internal"...
TTL(INTERNAL_TTL),
A("*.blogoverflow.com", ADDRESS19, TRANSFORM_INT),
A("*.stackexchange.com", ADDRESS16, TRANSFORM_INT),
IMPORT_TRANSFORM(TRANSFORM_DOUBLEINT, 'blogoverflow.com', INTERNAL_TTL),
IMPORT_TRANSFORM(TRANSFORM_DOUBLEINT, "stackexchange.com", INTERNAL_TTL)

Change transform logic to skip a record if it already exists in the target domain.

[tlimoncelli]

Discussion in a hangout concluded that option 3 was the best.