Struct EventStream 

pub struct EventStream { /* private fields */ }

Event Stream aggregate enforcing gapless version numbers

Inspired by SierraDB’s watermark pattern for consistent event sourcing. Ensures no gaps in version sequences, critical for proper event replay.

SierraDB Pattern

• Watermark tracks “highest continuously confirmed sequence”
• Prevents gaps that would break event sourcing guarantees
• Uses optimistic locking for concurrency control

Invariants

• Versions start at 1 and increment sequentially
• No gaps allowed in version sequence
• Watermark <= max version always
• All versions below watermark are confirmed (gapless)

Implementations

impl EventStream

pub fn new(stream_id: EntityId) -> Self

Create a new event stream

pub fn reconstruct( stream_id: EntityId, partition_key: PartitionKey, current_version: u64, watermark: u64, events: Vec<Event>, expected_version: Option<u64>, created_at: DateTime<Utc>, updated_at: DateTime<Utc>, ) -> Result<Self>

Reconstruct an EventStream from persistent storage

Used by repository implementations to restore streams from database. Bypasses validation since data is already validated at creation time.

Arguments

• stream_id: Entity ID of the stream
• partition_key: Pre-computed partition assignment
• current_version: Latest version number
• watermark: Highest continuously confirmed version
• events: All events in the stream
• expected_version: Optional optimistic lock version
• created_at: Stream creation timestamp
• updated_at: Last modification timestamp

pub fn append_event(&mut self, event: Event) -> Result<u64>

Append an event with optimistic locking

SierraDB Pattern

• Checks expected_version matches current_version
• Prevents concurrent modification conflicts
• Ensures gapless version sequence

pub fn expect_version(&mut self, version: u64)

Set expected version for next append (optimistic locking)

pub fn clear_expected_version(&mut self)

Clear expected version

pub fn events_from(&self, from_version: u64) -> Vec<&Event>

Get events from version (inclusive)

pub fn is_gapless(&self) -> bool

Check if stream has gapless versions up to watermark

pub fn stream_id(&self) -> &EntityId

pub fn partition_key(&self) -> &PartitionKey

pub fn current_version(&self) -> u64

pub fn watermark(&self) -> u64

pub fn event_count(&self) -> usize

pub fn created_at(&self) -> DateTime<Utc>

pub fn updated_at(&self) -> DateTime<Utc>

pub fn expected_version(&self) -> Option<u64>

pub fn tenant_id(&self) -> Option<&TenantId>

Get the tenant ID for this stream

Returns the tenant_id from the first event, or None if the stream is empty. All events in a stream should belong to the same tenant.

pub fn has_consistent_tenant(&self) -> bool

Validate that all events in the stream belong to the same tenant

Returns true if the stream is empty or all events have the same tenant_id. This is a safety check to detect tenant isolation violations.

pub fn validate_event_tenant(&self, event: &Event) -> Result<()>

Validate that an event belongs to this stream’s tenant

Returns an error if:

• The stream has events and the new event’s tenant doesn’t match

This ensures tenant isolation at the stream level.

pub fn append_event_with_tenant_check(&mut self, event: Event) -> Result<u64>

Append an event with tenant validation

Like append_event, but also validates tenant consistency. Prevents cross-tenant event appends for security.

Trait Implementations

impl Clone for EventStream

fn clone(&self) -> EventStream

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for EventStream

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for EventStream

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for EventStream

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.