Defines methods for synchronizing data in blocks among all sequencer nodes of a domain.

The write operations sequence and distribute different kinds of requests. They can all be implemented by the same mechanism of sequencing a bytestring, but are kept separately for legacy reasons: The Fabric and Ethereum drivers have separate entry points or messages for the different request kinds.

Sequenced requests are delivered in a stream of RawLedgerBlocks ordered by their block height. The driver must make sure that all sequencer nodes of a domain receive the same stream of RawLedgerBlocks eventually. That is, if one sequencer node receives a block b at block height h, then every other sequencer node has already or will eventually receive b at height h unless the node fails permanently. Each RawLedgerBlock contains com.digitalasset.canton.domain.block.RawLedgerBlock.RawBlockEvents that correspond to the sequenced requests. The com.digitalasset.canton.tracing.TraceContext passed to the write operations should be propagated into the corresponding com.digitalasset.canton.domain.block.RawLedgerBlock.RawBlockEvent.

All write operations are asynchronous: the scala.concurrent.Future may complete before the request is actually sequenced. Under normal circumstances, the request should then also eventually be delivered in a com.digitalasset.canton.domain.block.RawLedgerBlock.RawBlockEvent, but there is no guarantee. A write operation may fail with an exception; in that case, the request must not be sequenced. Every write operation may result in at most one corresponding com.digitalasset.canton.domain.block.RawLedgerBlock.RawBlockEvent.

The SequencerDriver is responsible for assigning timestamps to com.digitalasset.canton.domain.block.RawLedgerBlock.RawBlockEvent.Send events. The assigned timestamps must be close to real-world time given the trust assumptions of the SequencerDriver. For example, assume that the clocks among all honest sequencer nodes are synchronized up to a given skew. Let ts0 be the local sequencer's time when an honest sequencer node calls SequencerDriver.send. Let ts1 be the local sequencer's time when it receives the corresponding com.digitalasset.canton.domain.block.RawLedgerBlock.RawBlockEvent.Send. Then the assigned timestamp ts must satisfy ts0 - skew <= ts <= ts1 + skew.

Several com.digitalasset.canton.domain.block.RawLedgerBlock.RawBlockEvent.Send events may have the same timestamp or go backwards, as long as they remain close to real-world time.