Collators were previously reencoding the available data and checking the
erasure root.
Replace that with just checking the PoV hash, which consumes much less
CPU and takes less time.
We also don't need to check the `PersistedValidationData` hash, as
collators don't use it.
Reason:
https://github.com/paritytech/polkadot-sdk/issues/575#issuecomment-1806572230
After systematic chunks recovery is merged, collators will no longer do
any reed-solomon encoding/decoding, which has proven to be a great CPU
consumer.
Signed-off-by: alindima <alin@parity.io>
Refactors availability-recovery strategies to allow for easily adding
new hotpaths and failover mechanisms.
The new interface allows for chaining multiple `RecoveryStrategy`-es
together, to cleanly express the relationship between them and share
state and code where neccessary/possible:
This was done in order to aid in implementing new hotpaths like
[systematic chunks
recovery](https://github.com/paritytech/polkadot-sdk/issues/598) and
[fetching from approval
checkers](https://github.com/paritytech/polkadot-sdk/issues/575).
Thanks to this design, intermediate state can be shared between the
strategies. For example, if the systematic chunks recovery retrieved
less than the needed amount of chunks, pass them over to the next
FetchChunks strategy, which will only need to recover the remaining
number of chunks.
Draft example of how a systematic chunk recovery strategy would look:
https://github.com/paritytech/polkadot-sdk/commit/667d870bdf1470525d66c13929d5eac7249dd995
(notice how easy it was to add and reuse code)
Note that this PR doesn't itself add any new strategy, it should fully
preserve backwards compatiblity in terms of functionality. Follow-up PRs
to add new strategies will come.
Alin Dima