Struct McpClientCache 

pub struct McpClientCache { /* private fields */ }

Bounded cache of McpClient instances keyed by the command-line string. Keeps a Vec of (key, client) pairs in usage order — most-recently-used at the back. On cache miss past cap, the front (oldest) entry is dropped.

Why a Vec rather than a HashMap + linked list: cap is small (16 by default) so linear scan is cheaper than the pointer chase, and a Vec lets us own the Clients directly instead of through RefCell/Arc.

Subprocess death is detected lazily: when call_tool fails the offending entry is dropped. Next call to the same server respawns. A handler that sits idle long enough for upstream MCP servers to be killed by ops will see one Err per server before recovering.

Implementations

impl McpClientCache

pub fn with_capacity(cap: usize) -> Self

pub fn call( &mut self, server: &str, tool: &str, args: Value, ) -> Result<Value, String>

Send a tools/call to the named server, spawning the subprocess on cache miss and reusing it on hit. Returns the server’s result JSON or an error message; on error, the offending client is dropped so the next call respawns.

pub fn len(&self) -> usize

Number of cached subprocesses. Useful for tests and observability; not on the hot path.

pub fn is_empty(&self) -> bool

Trait Implementations

impl Default for McpClientCache

fn default() -> Self

Returns the “default value” for a type.