a2a.server.cluster.task_store module

exception a2a.server.cluster.task_store.ConcurrentTaskModificationError(task_id: str)

Bases: Exception

Raised by VersionedTaskStore.save when prev_version is stale.

class a2a.server.cluster.task_store.LegacyTaskStoreAdapter(store: TaskStore)

Bases: VersionedTaskStore

Runs an unversioned TaskStore under the VersionedTaskStore interface.

async delete(task_id: str, context: ServerCallContext) → None

Deletes a task via the wrapped store.

async get(task_id: str, context: ServerCallContext) → StoredTask | None

Gets from the wrapped store, pairing the result with MISSING.

async list(params: ListTasksRequest, context: ServerCallContext) → ListTasksResponse

Lists tasks via the wrapped store.

async save(task: Task, *, event: Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent | None, prev: Task | None, prev_version: TaskVersion, context: ServerCallContext) → TaskVersion

Saves via the wrapped store; ignores version args, returns MISSING.

property store: TaskStore

The wrapped task store.

class a2a.server.cluster.task_store.StoredTask(task: Task, version: TaskVersion)

Bases: object

A task together with the version it was read at.

task: Task
version: TaskVersion
class a2a.server.cluster.task_store.VersionedTaskStore

Bases: ABC

A TaskStore variant with snapshot versioning to prevent concurrent re-writes.

abstractmethod async delete(task_id: str, context: ServerCallContext) → None

Deletes a task from the store by ID.

abstractmethod async get(task_id: str, context: ServerCallContext) → StoredTask | None

Retrieves a task with its version, or None if it does not exist.

abstractmethod async list(params: ListTasksRequest, context: ServerCallContext) → ListTasksResponse

Retrieves a list of tasks from the store.

abstractmethod async save(task: Task, *, event: Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent | None, prev: Task | None, prev_version: TaskVersion, context: ServerCallContext) → TaskVersion

Persists task and returns its new version.

Parameters:

  • task – The task state to persist.

  • event – The event that produced this state, or None for a direct write.

  • prev – The task as previously read, for implementations that diff.

  • prev_version – The version task was derived from. Implementations MUST raise ConcurrentTaskModificationError if the currently stored version differs. TaskVersion.MISSING marks a first write. A write moving task to CANCELED overwrites a non-terminal stored task without a version check, and raises ConcurrentTaskModificationError if the stored task is already terminal or absent.

  • context – The server call context (used to resolve the owner).

Returns:

The new TaskVersion for the persisted task.

Raises:

ConcurrentTaskModificationError – If prev_version is stale.