Struct RequestHandler 

pub struct RequestHandler { /* private fields */ }

Available on crate features a2a-v1 and server only.

Shared dispatch layer for A2A v1.0.0 operations.

Maps operation names to executor/store calls. Used by both the JSON-RPC handler and the REST handler.

When constructed with a adk_runner::RunnerConfig via RequestHandler::with_runner, message_send and message_stream invoke the agent through the ADK Runner for real LLM generation. Without a runner config, they perform state transitions only (useful for protocol-level testing).

Implementations

impl RequestHandler

pub fn new( executor: Arc<V1Executor>, task_store: Arc<dyn TaskStore>, push_sender: Arc<dyn PushNotificationSender>, agent_card: Arc<RwLock<CachedAgentCard>>, ) -> RequestHandler

Creates a new request handler without a runner (stub mode).

pub fn with_runner( executor: Arc<V1Executor>, task_store: Arc<dyn TaskStore>, push_sender: Arc<dyn PushNotificationSender>, agent_card: Arc<RwLock<CachedAgentCard>>, runner_config: Arc<RunnerConfig>, ) -> RequestHandler

Creates a new request handler with a runner for real LLM invocation.

pub async fn message_send(&self, msg: Message) -> Result<Task, A2aError>

Sends a message, creating a task and processing it through the executor.

When a runner config is present, invokes the agent through the ADK Runner for real LLM generation. The LLM response is recorded as an artifact on the task. Without a runner, performs state transitions only.

Errors

Returns an error if task creation, state transitions, or store operations fail.

pub async fn message_stream( &self, msg: Message, ) -> Result<Pin<Box<dyn Stream<Item = Result<StreamResponse, A2aError>> + Send>>, A2aError>

Sends a streaming message, returning a stream of SSE events.

Drives the agent and translates its events as they arrive:

Agent event	A2A event
first, before any output	Task, then TaskStatusUpdateEvent — Working
content with partial = true	TaskArtifactUpdateEvent — append, not last chunk
content with partial = false	TaskArtifactUpdateEvent — final chunk
stream ends	TaskStatusUpdateEvent — Completed
stream errors	TaskStatusUpdateEvent — Failed

Chunks of one response share an artifact ID so a client can reassemble them, which is the same contract adk-python and adk-go implement over their A2A SDKs.

With no runner configured the task is created and completed without agent output, which keeps discovery-only deployments working.

Errors

Returns an error if task creation fails. Failures once streaming has begun are reported as a Failed status event, since the response has already started.

pub async fn tasks_get( &self, task_id: &str, history_len: Option<u32>, ) -> Result<Task, A2aError>

Retrieves a task by ID from the task store.

Optionally limits the number of history messages returned.

Errors

Returns A2aError::TaskNotFound if the task does not exist.

pub async fn tasks_cancel(&self, task_id: &str) -> Result<Task, A2aError>

Cancels a task by transitioning it to CANCELED state.

Validates that the task is not already in a terminal state before canceling.

Errors

Returns A2aError::TaskNotFound if the task does not exist, or A2aError::TaskNotCancelable if the task is in a terminal state.

pub async fn tasks_list( &self, params: ListTasksParams, ) -> Result<Vec<Task>, A2aError>

Lists tasks matching the given parameters.

Supports filtering by context_id, state, and pagination via page_size.

pub async fn tasks_subscribe( &self, task_id: &str, ) -> Result<Pin<Box<dyn Stream<Item = Result<StreamResponse, A2aError>> + Send>>, A2aError>

Returns the current state of a task as a short stream, then closes.

Important: this is a point-in-time snapshot, not a live subscription. It emits the task and its current status and then ends; it does not deliver subsequent updates. A client that needs live updates should use message/stream, which streams the agent’s events as they are produced.

A real re-attach would require a per-task event queue that outlives the request, which the A2A SDKs in adk-python and adk-go provide and this hand-rolled server does not yet.

Errors

Returns A2aError::TaskNotFound if the task does not exist, or A2aError::TaskNotCancelable if the task already reached a terminal state.

pub async fn push_config_create( &self, task_id: &str, config: TaskPushNotificationConfig, ) -> Result<TaskPushNotificationConfig, A2aError>

Creates a push notification configuration for a task.

Assigns a server-generated config ID and stores the config on the task.

Errors

Returns A2aError::TaskNotFound if the task does not exist.

pub async fn push_config_get( &self, task_id: &str, config_id: &str, ) -> Result<TaskPushNotificationConfig, A2aError>

Retrieves a push notification configuration by task ID and config ID.

Errors

Returns A2aError::TaskNotFound if the task or config does not exist.

pub async fn push_config_list( &self, task_id: &str, ) -> Result<Vec<TaskPushNotificationConfig>, A2aError>

Lists all push notification configurations for a task.

Errors

Returns A2aError::TaskNotFound if the task does not exist.

pub async fn push_config_delete( &self, task_id: &str, config_id: &str, ) -> Result<(), A2aError>

Deletes a push notification configuration.

Errors

Returns A2aError::TaskNotFound if the task or config does not exist.

pub async fn agent_card_extended(&self) -> Result<AgentCard, A2aError>

Returns the extended agent card.

Errors

Returns A2aError::ExtendedAgentCardNotConfigured if no card is set.

pub fn executor(&self) -> &Arc<V1Executor>

Returns a reference to the underlying executor.

pub fn task_store(&self) -> &Arc<dyn TaskStore>

Returns a reference to the underlying task store.