IBC-go antedecorator effect on Hermes operation

[adizere]

Crate

ibc-relayer

Summary

There is a new feature that the IBC-go team implemented consisting of a CheckTx decorator
which has intuitively the following side-effects:

1. if a transaction consists of IBC messages all of which are redundant, i.e., all the messages in the tx already executed
   previously, then the decorator prevents the transaction from entering the mempool and
   rejects it before that.
2. if a transactions consists of a mix of redundant and novel IBC messages, then the transactions is accepted and
   the redundant messages are accepted as no-op, while the novel messages execute as usual.

Resources:

• feature changelog
• PR: Reject Redundant Tx Antedecorator cosmos/ibc-go#235

Problem Definition

The basic problem is that we don't know yet how this feature affects Hermes.

Point 1 has the positive side-effect that it will prevent some situations where Hermes wastes fees in the presence of competitive relayers.

Point 2 has the benefit that Hermes (and other relayers) can now adopt a strategy of minimizing the number of messages they put in a tx, so that they minimize wasting gas fees.

Proposal

• We need to make sure that Hermes correctly interprets the broadcast_tx_sync response in situation (1) and correctly drops the operational data (since that consists of redundant messages).

• We also need to make sure we retain backwards compatibility, because some node may not have the antedecorator enabled (or using an older version).

Acceptance Criteria

• Smooth Hermes operations and E2E tests in the presence of the IBC antedecorator

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For Admin Use

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[adizere]

The basic problem is that we don't know yet how this feature affects Hermes.

Many chains have been running with this change already, and experience from production use shows that the antedecorator raises no issue for Hermes.