Struct Connection 

pub struct Connection { /* private fields */ }

An active connection to an MCP server using the Streamable HTTP transport.

Cheaply clonable (one Arc bump). When the last clone is dropped, the inner Arc ref count hits zero, [ConnectionInner::Drop] runs, the listener-cancel DropGuard is dropped, and the SSE listener task is cancelled — exiting any in-flight lines.next_line(), reconnect send(), or backoff sleep immediately without retrying against the now-dead proxy session.

Use the public methods (list_tools, call_tool, list_resources, read_resource, call_tool_as_message, tool_key) for the upstream MCP protocol surface. The inner state (ConnectionInner) is also reachable via Deref for read-only field access (e.g. connection.url, connection.initialize_result.server_info.name), but its methods are private — you must go through Connection.

Implementations

impl Connection

pub fn tool_key(&self) -> String

Returns a key identifying this connection for tool namespacing.

pub fn session_id(&self) -> &str

Returns the session ID for this connection.

pub async fn list_tools(&self) -> Result<Arc<Vec<Tool>>, Arc<Error>>

Returns all tools from the upstream server.

pub async fn call_tool( &self, params: &CallToolRequestParams, ) -> Result<CallToolResult, Error>

Calls a tool on the upstream server.

pub async fn call_tool_as_message( &self, params: &CallToolRequestParams, tool_call_id: String, ) -> Result<ToolMessage, Error>

Calls a tool and converts the result into a [ToolMessage].

pub async fn list_resources(&self) -> Result<Arc<Vec<Resource>>, Arc<Error>>

Returns all resources from the upstream server.

pub async fn subscribe_tools( &self, current: &[Tool], timeout: Duration, ) -> Result<Arc<Vec<Tool>>, Arc<Error>>

Returns the cached tool list as soon as it differs from current, or waits up to timeout for the next notifications/tools/list_changed from the upstream server before re-reading.

Wakes the moment a refresh writer takes the cache write lock, so the post-wake read is guaranteed to observe the new list rather than racing against the install. Safe to call from any number of tasks concurrently.

pub async fn subscribe_resources( &self, current: &[Resource], timeout: Duration, ) -> Result<Arc<Vec<Resource>>, Arc<Error>>

Resource counterpart of Connection::subscribe_tools.

pub async fn read_resource( &self, uri: &str, ) -> Result<ReadResourceResult, Error>

Reads a resource from the upstream server.

pub fn set_on_tools_list_changed<F>(&self, callback: F)

where F: Fn() + Send + Sync + 'static,

Register a callback to fire whenever the upstream emits notifications/tools/list_changed.

Timing: the callback runs after the tool cache’s write lock is acquired but before the network paginate that replaces it. That means readers blocked on the read lock won’t return until the new list is in place, and the callback observes the moment the staleness window opens. The proxy uses this to emit its own notifications/tools/list_changed to downstream clients at the right instant.

Replaces any previously-registered tools-list-changed callback. All clones of this Connection share the same callback slot.

pub fn set_on_resources_list_changed<F>(&self, callback: F)

where F: Fn() + Send + Sync + 'static,

Register a callback to fire whenever the upstream emits notifications/resources/list_changed. Same timing contract as Connection::set_on_tools_list_changed.

Replaces any previously-registered resources-list-changed callback. All clones of this Connection share the same callback slot.

Trait Implementations

impl Clone for Connection

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Connection

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

Formats the value using the given formatter.

impl Deref for Connection

type Target = ConnectionInner

The resulting type after dereferencing.

fn deref(&self) -> &ConnectionInner

Dereferences the value.