Circuit Breaker Pattern
Prevent cascading failures by temporarily blocking calls to failing services, enabling fast failure responses and automatic recovery.
Pattern Overview
The Circuit Breaker pattern is a fault tolerance design pattern that prevents an application from repeatedly trying to execute an operation that's likely to fail. It monitors for failures and, when failures reach a certain threshold, the circuit breaker trips, and all further calls to the circuit breaker return with an error, without the protected call being made at all.
When to Use
- • External service calls
- • Database connections
- • Network requests
- • Any operation that can fail
When Not to Use
- • Critical business logic
- • Operations that must succeed
- • Local operations
- • Simple error handling
System Architecture
The circuit breaker acts as a proxy between the client and the service, monitoring the success and failure of calls and automatically opening the circuit when failures exceed the threshold.
Circuit Flow
The circuit breaker operates in three states: Closed (normal operation), Open (fast fail), and Half-Open (testing recovery). This sequence diagram shows how requests flow through each state.
State Machine
The circuit breaker state machine shows the transitions between different states based on success/failure conditions and timeouts.
Implementation Example
A typical implementation includes state management, failure counting, timeout handling, and health checking to ensure proper circuit breaker operation.
Benefits
- Prevents cascading failures
- Fast failure responses
- Automatic recovery mechanism
- Improves system resilience
Trade-offs
- Additional latency in some cases
- Complex state management
- Potential for false positives
- Configuration complexity
Best Practices
Configuration
- • Set appropriate failure thresholds
- • Configure timeout durations
- • Use exponential backoff
- • Monitor circuit breaker metrics
Implementation
- • Use libraries like Hystrix or Resilience4j
- • Implement proper fallback strategies
- • Add comprehensive logging
- • Test failure scenarios