Tx metadata included in fee calculations

[rvl]

Context

ADP-307

Adding metadata to transactions increases their size on chain. Therefore metadata incurs fees.

Decision

1. Include metadata in any call to computeTxSize.

Acceptance Criteria

1. Adding metadata to a transaction must increase its size, and therefore its fee.

---

Development

As above.

QA

1. Added unit test "metadata incurs fees" to lib/shelley/test/unit/Cardano/Wallet/Shelley/TransactionSpec.hs ⇒ PR Add unit test for transaction metadata fee calculation #2108.
2. Added integration test "TRANS_ESTIMATE_xxx - fee estimation includes metadata" to lib/core-integration/src/Test/Integration/Scenario/API/Shelley/Transactions.hs ⇒ PR Tx metadata API integration tests #2096.

[piotr-iohk]

I have managed to brake it:

It seems that estimating fee with too large metadata (and actually sendindg such tx too) results in 500:

• metadata used: meta-fee.txt

Result:

Code = 500,
Message = Something went wrong

In the log there is:

[2020-09-03 11:01:12.86 UTC] [RequestId 0] [POST] /v2/wallets/1ceb45b37a94c7022837b5ca14045f11a5927c65/payment-fees
generated a coin selection with an excessively large fee.
actual fee: 3.194 Ada
coin selection:
  inputs: - 1st d1727eae (~ 22490393 @ 0150e277...8094ee36)
  withdrawal: -0
  reclaim: -0
  outputs: - 1000000 @ 013e8da9...8094ee36
  change: [18296768]
  deposit: -0

CallStack (from HasCallStack):
  error, called at src/Cardano/Wallet/Primitive/Fee.hs:182:9 in cardano-wallet-core-2020.8.3-EUxOQdVGrF0B4QcgxDCOoV:Cardano.Wallet.Primitive.Fee
  adjustForFee, called at src/Cardano/Wallet.hs:1288:24 in cardano-wallet-core-2020.8.3-EUxOQdVGrF0B4QcgxDCOoV:Cardano.Wallet

I have created PR extending tx meta tests -> #2110.
TRANSMETA_CREATE_03, TRANSMETA_ESTIMATE_03 - seem to cover that case there and are currently failing.

[KtorZ]

Awe crap. I think that's because the guard which checks whether metadata are too large occurs only when one tries to submit the transaction, which happens after this invariant is triggered. We should move the transaction size guard earlier in the pipeline.

[piotr-iohk]

BTW, Seems that latency benchamark failed for the same reason -> https://buildkite.com/input-output-hk/cardano-wallet-nightly/builds/630#f25ae394-5bd6-4422-ae66-12bf6700a0b3

[piotr-iohk]

lgtm.
The issue no longer occurs. When metadata is too big error message is presented for both: sending tx and fee estimation:

Code = 400,
Message = {"code":"transaction_is_too_big","message":"I am afraid that the transaction you're trying to submit is too large! The network allows transactions only as large as 16384 bytes! As it stands, the current transaction only allows me to select up to 0 inputs. Note that I am selecting inputs randomly, so retrying *may work* provided I end up choosing bigger inputs sufficient to cover the transaction cost. Alternatively, try sending to less recipients or with smaller metadata."}