circuit_breaker

circuit_breaker closes new connections for a while when the rest of the chain keeps failing, for example when redirect or load_balancer cannot dial the upstream. Clients fail fast instead of waiting for dial timeouts.

server:
  tcp:
    middlewares:
      db_breaker:
        circuit_breaker:
          failure_ratio: 0.5
          min_requests: 10
          window: 10s
          open_duration: 30s
      db:
        load_balancer:
          servers:
            - address: 10.0.0.1:5432
    routers:
      postgres:
        entrypoints: [postgres]
        middlewares: [db_breaker, db]

Field	Default	Description
failure_ratio	0.5	Opens the circuit when failed / total connections in window reaches it.
min_requests	10	Connections needed in window before the ratio is checked.
window	10s	Rolling window of counted connections.
open_duration	30s	How long connections are rejected after the circuit opens.
half_open_requests	1	Probe connections let through after open_duration. All must succeed to close the circuit.

A connection fails when the rest of the chain returns an error, such as a dial error. Rejections of later filters (rate_limit, ip_deny_list...) are not counted. Rejected connections are closed and logged at debug level.

Place circuit_breaker right before the terminal middleware. The HTTP circuit_breaker works the same way on responses.