feat(server): add versioned task store and event stream interfaces - #1244
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🧪 Code Coverage (vs
|
| Base | PR | Delta | |
|---|---|---|---|
| src/a2a/server/models.py | 97.83% | 90.16% | 🔴 -7.66% |
| src/a2a/server/tasks/database_task_store.py | 91.19% | 92.45% | 🟢 +1.26% |
| src/a2a/server/cluster/database_event_stream.py (new) | — | 93.88% | — |
| src/a2a/server/cluster/database_task_store.py (new) | — | 95.12% | — |
| src/a2a/server/cluster/event_stream.py (new) | — | 100.00% | — |
| src/a2a/server/cluster/task_store.py (new) | — | 100.00% | — |
| src/a2a/server/cluster/version.py (new) | — | 100.00% | — |
| Total | 93.06% | 93.12% | 🟢 +0.06% |
Generated by coverage-comment.yml
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…ing blocks Introduces the a2a.server.cluster package: the extension points for running the A2A server as multiple replicas behind a load balancer with no task affinity. The package is inert at this commit -- nothing in the runtime imports it yet -- but it also adds a `version` column to the shared tasks schema that database-backed deployments must provision (see the schema bullet). * Optimistic concurrency: TaskVersion, VersionedTaskStore (compare-and-set) whose `get` returns a `StoredTask` (task + version), with ConcurrentTaskModificationError and a LegacyTaskStoreAdapter that runs an existing TaskStore under the versioned interface (last-writer-wins). * Versioned store: VersionedDatabaseTaskStore (CAS on a version column) with a configurable bounded retry (max_attempts / retry_delay_s) for transient DB contention. * Cross-replica event stream: TaskEventStream / VersionedEvent and DatabaseTaskEventStream tailing a transactional task_events outbox. * Schema: nullable `version` column on TaskMixin plus the `task_events` outbox table. Their VALUES are inert for the non-versioned stores (version stays NULL, task_events empty), but DatabaseTaskStore selects and writes every mapped column, so the `version` column must exist in the database. Any database-backed deployment must run `a2a-db` after upgrading -- versioned or not; create_table=True (dev/tests) picks it up automatically.
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Adds a2a.server.cluster, the building blocks for running the A2A server as several replicas, with no need to route a task's requests back to the replica that started it. This PR is purely additive nothing uses the new structures yet.
Key changes:
Tested:
Design discussion: #1224