Add a per-replica, in-memory health tracker for MCP servers and A2A
agents (target_health.go). The tracker records observations from real
proxied traffic (handleTargetProxy, mcp_a2a.go) and federated calls
(mcpFederatedToolsList/mcpFederatedToolsCall, mcp_federation.go), and
derives a three-state readout (unknown, healthy, unhealthy) from a
configurable consecutive-failure threshold. Add TargetHealthConfig to
Config, validated at construction. The tracker never gates routing:
federation and the target proxy keep contacting every configured
server regardless of its recorded health.
Extend proxyResult (routes_passthrough.go) with status and
clientCanceled so handleTargetProxy can classify a proxied response
without proxyUpstream knowing anything about target health.
Add maybeSweepTargetHealth, an opt-in, lazy, single-flight active
probe sweep with no timer and no long-lived goroutine, matching this
plugin's lack of a Close hook under Traefik hot reload. A probe uses
the initialize/close handshake for a Streamable HTTP MCP server, a
plain unread GET for a legacy /sse server, and a GET of the agent card
path for an A2A agent. handleMCPServers and handleAgents now trigger a
sweep at the top of each call.
Claude-Session: https://claude.ai/code/session_01EebV5jyWvYocByNQ3oss1w
