Struct HotReloadAgentCardHandler 

pub struct HotReloadAgentCardHandler { /* private fields */ }

An agent card handler that supports hot-reloading.

The current AgentCard is stored behind an Arc<RwLock<_>> so that it can be atomically swapped while the server continues to serve requests.

This type implements AgentCardProducer, so it can be plugged directly into a DynamicAgentCardHandler for full HTTP caching support.

Implementations

impl HotReloadAgentCardHandler

pub fn new(card: AgentCard) -> Self

Creates a new handler with the given initial AgentCard.

pub fn current(&self) -> AgentCard

Returns a snapshot of the current AgentCard.

This acquires a short-lived read lock and clones the card.

Panics

Panics if the internal RwLock is poisoned (another thread panicked while holding the write lock).

pub fn update(&self, card: AgentCard)

Replaces the current agent card with card.

All subsequent requests will see the new card immediately.

Panics

Panics if the internal RwLock is poisoned.

pub fn reload_from_file(&self, path: &Path) -> ServerResult<()>

Reloads the agent card from a JSON file at path.

The file is read synchronously (agent card files are expected to be small). On success the internal card is replaced atomically.

Errors

Returns ServerError::Internal if the file cannot be read or parsed.

pub fn reload_from_json(&self, json: &str) -> ServerResult<()>

Reloads the agent card from a JSON string.

On success the internal card is replaced atomically.

Errors

Returns ServerError::Serialization if json is not valid agent card JSON.

pub fn spawn_poll_watcher( &self, path: &Path, interval: Duration, ) -> JoinHandle<()>

Spawns a background task that periodically checks whether the file at path has been modified and reloads the agent card when it has.

The watcher compares the file’s modification time on each tick and only re-reads the file when the timestamp changes. This is cross-platform and requires no OS-specific file notification APIs.

Returns a tokio::task::JoinHandle that can be used to abort the watcher (via JoinHandle::abort).

pub fn spawn_signal_watcher(&self, path: &Path) -> JoinHandle<()>

Spawns a background task that reloads the agent card from path whenever the process receives SIGHUP.

This is the traditional Unix mechanism for configuration reload and integrates well with process managers (systemd, supervisord, etc.).

Returns a tokio::task::JoinHandle that can be used to abort the watcher (via JoinHandle::abort).

Panics

Panics if the tokio signal handler cannot be registered (e.g. if the runtime was built without the signal feature).

Trait Implementations

impl AgentCardProducer for HotReloadAgentCardHandler

fn produce<'a>( &'a self, ) -> Pin<Box<dyn Future<Output = A2aResult<AgentCard>> + Send + 'a>>

Produces an AgentCard for the current request.

impl Clone for HotReloadAgentCardHandler

fn clone(&self) -> HotReloadAgentCardHandler

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for HotReloadAgentCardHandler

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

Formats the value using the given formatter.