Circuit Breaker

The circuit breaker protects your services by stopping traffic to failing upstreams. It is configured inside a service block.

State Transitions

The circuit breaker operates in three states:

1. Closed (normal operation). Requests flow to the upstream. When consecutive failures reach the failure_threshold, the circuit transitions to Open.
2. Open (blocking). All requests are rejected immediately. After open_duration_milliseconds elapses, the circuit transitions to HalfOpen.
3. HalfOpen (probing). A limited number of probe requests (half_open_max_requests) are allowed through. If success_threshold probes succeed, the circuit closes again. If any probe fails, the circuit reopens.

circuit_breaker = {
  # Enable or disable the circuit breaker.
  enable                     = true

  # Allow automatic recovery after the open duration.
  enable_auto_recovery       = false

  # Failures before tripping to Open.
  failure_threshold          = 3

  # Milliseconds the circuit stays Open.
  open_duration_milliseconds = 10000

  # Probe requests allowed in HalfOpen.
  half_open_max_requests     = 1

  # Successful probes needed to close the circuit.
  success_threshold          = 2

  # Count HTTP 5xx responses as failures.
  count_http_5xx_as_failure  = false
}

Fields

Field	Type	Default	Description
enable	boolean	true	Enable or disable the circuit breaker.
enable_auto_recovery	boolean	false	Allow the circuit breaker to automatically recover after the open duration.
failure_threshold	integer	5	Number of consecutive failures (transport errors or 5xx) in the Closed state before tripping the circuit to Open.
open_duration_milliseconds	integer	10000	How long, in milliseconds, the circuit remains Open before transitioning to HalfOpen.
half_open_max_requests	integer	1	How many simultaneous probe requests are allowed while in the HalfOpen state.
success_threshold	integer	2	How many successful probes are required in HalfOpen to close the circuit again.
count_http_5xx_as_failure	boolean	true	Whether HTTP 5xx responses from the upstream count as failures for the circuit breaker.