Don't rely (just) on cdnRailId for `withCDN` check

[rvagg]

See FilOzone/filecoin-services#161

Currently we have this code (in two places):

synapse-sdk/src/warm-storage/service.ts

Line 327 in 001e4a3

withCDN: dataSet.cdnRailId > 0, // CDN is enabled if cdnRailId is non-zero (should be more reliable than metadata)

Which turns out to not be true. Termination of a CDN service by FilCDN will:

1. Terminate the rails
2. Reset the metadata to remove withCDN (so it's actually a more reliable indicator than the code comment above suggests)
3. Set cdnEndEpoch to be the current epoch (via the railTerminated callback from Payments) instead of 0

The CDN rail IDs are left intact after this operation.

So we either need to bother with fishing around in metadata, or we should check cdnEndEpoch==0 as well.

[SgtPooki]

TIL you can modify metadata for a dataset.. I should probably use the recommended method in #487

[rvagg]

you can't, this is a privileged operation that happens inside the contract just for this case: https://github.com/FilOzone/filecoin-services/blob/55e6e67371bb8ea1123d422602dd3ee251424bbb/service_contracts/src/FilecoinWarmStorageService.sol#L1054

[hugomrdias]

so its either cdnRailId > 0 && cdnEndEpoch === 0 or metadata ?

[rvagg]

yeah, that'll probably be fine for now, easy issue

[DarkLord017]

In the current WarmStorageView contract, DataSetInfo no longer includes cdnEndEpoch. The Synapse SDK ABI also does not expose this field. So should cdnEndEpoch now be fetched through the Payments contract instead?

The warm-storage tests still reference it in the mock setup, but the contract itself does not even the abi in synapse does not mention it

[rvagg]

Yep, good point. It was removed in FilOzone/filecoin-services#237 as part of their refactor. See here for the reasoning; i.e. they don't have a validator for their rails now so we don't get a railTerminated call.

We could call into the payments contract to look at endEpoch there, but the right approach here I think is to just look at metadata:

1. Metadata is immutable except in this case where withCDN is reliably removed.
2. We have it where we need it, both places where we touch this already have metadata available so we can just check it:

• synapse-sdk/packages/synapse-sdk/src/warm-storage/service.ts

  Line 381 in 6a3b5cc

  withCDN: base.cdnRailId > 0,

• synapse-sdk/packages/synapse-sdk/src/storage/context.ts

  Line 439 in 6a3b5cc

  const withCDN = dataSetInfo.cdnRailId > 0

We can still retain the existing cdnRailId check because it's cheap, but then we can also add a simple utility.

And now that I've spent this much time in this code I'm just going to PR this myself. Sorry @DarkLord017, I know you were probably queueing up for this one, thank you for looking deeper at the issue though.