Write an acknowledgement that member has processed earlier timestamps. Only the latest timestamp needs to be stored. Earlier timestamps can be overwritten. Acknowledgements of earlier timestamps should be ignored.

Whether the sequencer store operates is used for a block sequencer or a standalone database sequencer.

In case of single instance sequencer we can use in-memory fanout buffer for events

Maximum memory usage by the events in the buffer before it starts dropping events. If set to 0, caching is disabled and all requests go to the underlying store (e.g. database).

Count records currently stored by the sequencer. Used for pruning tests.

No implementation as only required for crash recovery

Prevents member from sending and reading from the sequencer, and allows unread data for this member to be pruned. It however won't stop any sends addressed to this member.

Fetch the lower bound of events that can be read. Returns None if all events can be read.

There can be no other sequencers sharing this storage

Fetch previous event timestamp for a member for a given inclusive timestamp.

Read the watermark for this sequencer and its online/offline status. Currently only used for testing.

Flag that we're going offline (likely due to a shutdown)

Mark the sequencer as online and return a timestamp for when this sequencer can start safely producing events.

Return the latest acknowledgements for all members

For a given member and timestamp, return the latest timestamp of a potential topology change, that reached both the sequencer and the member. To be used by the topology snapshot awaiting, should there be a topology change expected to need to be taken into account for timestampExclusive sequencing timestamp.

Locate a timestamp relative to the earliest available event based on a skip index starting at 0. Useful to monitor the progress of pruning and for pruning in batches.

Lookup an existing member id for the given member. Will return a cached value if available. Return scala.None if no id exists.

Lookup member directly without caching.

This store does not support multiple concurrent instances so will do nothing.

For a given member find the timestamp of the last event that the member has received before timestampExclusive.

Prune as much data as safely possible from before the given timestamp.

Prune events before the given timestamp

Prune payloads before the given timestamp

Read all events of which a member is a recipient from the provided timestamp but no greater than the earliest watermark. Passing both member and memberId to avoid a database query for the lookup.

Internal non-buffered implementation of readEvents.

The state returned here is used to initialize a separate database sequencer (that does not share the same database as this one) using initializeFromSnapshot such that this new sequencer has enough information (registered members, previous event timestamps, etc) to be able to process new events from the same point as this sequencer to the same clients. This is typically used by block sequencers that use the database sequencer as local storage such that they will process the same events in the same order and they need to be able to spin up new block sequencers from a specific point in time.

Register the provided member. Should be idempotent if member is already registered and return the existing id.

Reset the watermark to an earlier value, i.e. in case of working as a part of block sequencer. Also sets the sequencer as offline. If current watermark value is before ts, it will be left unchanged. If a watermark doesn't yet exist, it won't be inserted, because it would effectively mean setting it to a future value.

Return the minimum watermark across all online sequencers

Save a series of events to the store. Callers should determine batch size. No batching is done within the store. Callers MUST ensure that event-ids are unique as no errors will be returned if a duplicate is present (for the sequencer writer see sequencer.PartitionedTimestampGenerator for use with their instance index).

Save an updated lower bound of events that can be read. Must be equal or greater than any prior set lower bound.

Save a series of payloads to the store. Is up to the caller to determine a reasonable batch size and no batching is done within the store.

Write the watermark that we promise not to write anything earlier than. Does not indicate that there is an event written by this sequencer for this timestamp as there may be no activity at the sequencer, but updating the timestamp allows the sequencer to indicate that it's still alive. Return an error if we find our sequencer is offline.

Build a status object representing the current state of the sequencer.

Set the "pruned" previous event timestamp for a member. This timestamp is used to serve the oldest (earliest) event that sequencer has for the member:

• after pruning
• after the sequencer's onboarding

Validate that the commit mode of a session is inline with the configured expected commit mode. Return a human readable message about the mismatch in commit modes if not.