[ECO-5447][LiveObjects] Use server-provided timestamp to sweep old tombstones

[sacOO7]

• Fixed LiveObject: server-provided timestamp to sweep old tombstones #1117

Summary by CodeRabbit

• New Features

  • Added support for tracking deletion timestamps for live objects and map entries, improving accuracy and traceability of object removal events.

• Bug Fixes

  • Ensured that tombstone (deletion) timestamps are consistently set based on available data, falling back to the current time if not provided.

• Tests

  • Expanded and updated tests to validate correct handling of deletion events and accurate timestamp assignment for tombstoned objects and map entries.

[coderabbitai]

Walkthrough

This change introduces a server-provided serialTimestamp field to ObjectMessage and ObjectMapEntry classes, integrates its handling throughout serialization, deserialization, and state management logic, and updates tombstone timestamping to use this value where available. Related method signatures and test cases are updated accordingly to support and verify this new timestamp propagation.

Changes

Cohort / File(s)	Change Summary
Add serialTimestamp to core data classes live-objects/src/main/kotlin/io/ably/lib/objects/ObjectMessage.kt	Added nullable serialTimestamp property to ObjectMessage and ObjectMapEntry for server-provided tombstone timestamps.
Serialization/Deserialization updates live-objects/src/main/kotlin/io/ably/lib/objects/serialization/MsgpackSerialization.kt	Integrated serialTimestamp into Msgpack serialization/deserialization for both ObjectMessage and ObjectMapEntry.
Sync pool and manager logic updates live-objects/src/main/kotlin/io/ably/lib/objects/ObjectsManager.kt	Changed sync data pool to store ObjectMessage instead of ObjectState; updated usages to propagate serialTimestamp.
Base object and state handling live-objects/src/main/kotlin/io/ably/lib/objects/type/BaseLiveObject.kt	Updated applyObjectSync, applyObjectState, and tombstone methods to handle serialTimestamp and pass it to lifecycle logic.
LiveCounter logic and manager live-objects/src/main/kotlin/io/ably/lib/objects/type/livecounter/DefaultLiveCounter.kt, live-objects/src/main/kotlin/io/ably/lib/objects/type/livecounter/LiveCounterManager.kt	Updated state/operation application to accept and use serialTimestamp for tombstoning; added helper for update calculation.
LiveMap logic and manager live-objects/src/main/kotlin/io/ably/lib/objects/type/livemap/DefaultLiveMap.kt, live-objects/src/main/kotlin/io/ably/lib/objects/type/livemap/LiveMapManager.kt	Updated state/operation application and tombstoning to use serialTimestamp when available; improved timestamp accuracy.
Integration and unit tests for timestamp/tombstone logic live-objects/src/test/kotlin/io/ably/lib/objects/integration/DefaultLiveObjectsTest.kt, live-objects/src/test/kotlin/io/ably/lib/objects/integration/helpers/Utils.kt, live-objects/src/test/kotlin/io/ably/lib/objects/unit/TestHelpers.kt, live-objects/src/test/kotlin/io/ably/lib/objects/unit/objects/ObjectsManagerTest.kt, live-objects/src/test/kotlin/io/ably/lib/objects/unit/type/livecounter/DefaultLiveCounterTest.kt, live-objects/src/test/kotlin/io/ably/lib/objects/unit/type/livecounter/LiveCounterManagerTest.kt, live-objects/src/test/kotlin/io/ably/lib/objects/unit/type/livemap/DefaultLiveMapTest.kt, live-objects/src/test/kotlin/io/ably/lib/objects/unit/type/livemap/LiveMapManagerTest.kt	Updated and expanded tests to verify correct propagation and usage of serialTimestamp for tombstoned objects and entries; added helpers and new test cases for timestamp handling.

Sequence Diagram(s)

sequenceDiagram
    participant Server
    participant Client
    participant ObjectsManager
    participant LiveObject
    participant LiveCounterManager/LiveMapManager

    Server->>Client: Sends ObjectMessage with serialTimestamp
    Client->>ObjectsManager: Receives ObjectMessage (with serialTimestamp)
    ObjectsManager->>LiveObject: applyObjectSync(ObjectMessage)
    LiveObject->>LiveCounterManager/LiveMapManager: applyState(objectState, serialTimestamp)
    LiveCounterManager/LiveMapManager->>LiveObject: Update tombstonedAt with serialTimestamp (if present)

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Assessment against linked issues

Objective	Addressed	Explanation
Add server-provided timestamp (serialTimestamp) for tombstone handling in LiveObject and all related logic (ECO-5447, #1117)	✅
Ensure tombstone timestamps use server-provided value where present, fallback to system time otherwise (ECO-5447, #1117)	✅
Update serialization/deserialization and all state/operation methods to propagate and use serialTimestamp (ECO-5447, #1117)	✅
Update and add tests to verify correct tombstone timestamp handling and propagation (ECO-5447, #1117)	✅

Suggested reviewers

• ttypic

Poem

A server’s clock now guides the tomb,
With serial timestamps sealing doom.
Our objects sleep, their time precise,
Swept away in code so nice.
The tests all cheer, the logic shines,
🕰️⏳—in Kotlin lines!
—From your CodeRabbit, with happy rhymes.

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