Sample implementation of a Circuit Breaker pattern with Azure Functions

Circuit breaker

Implementing a circuit breaker prevent calling an operation which is likely to fail. More information on this pattern here.

Implementation

This repositories contains two Azure functions and one extensions library.

• The Functions.Extensions.CircuitBreaker library contains the attribute to append to the azure function implementing the circuit breaker and some services to interact with the state of a circuit. The CircuitBreakerAttribute checks if the circuit is opened before executing the function and returns a 403 in this case. When the function has been executed, it pushes a message to a queue to notify of the result of the function. This message will be handled by the Functions.Circuit breaker function.

• The Functions.CircuitBreaker project is an Azure function making the state of the circuit evolve. It contains one queue trigger which is executed when a message is added to a queue by the CircuitBreakerAttribute and a timer trigger to handle the transition to the half-open state.

• The Functions.Sample project is an Azure function exposing one API failing on odd minutes. This API is marked with a CircuitBreakerAttribute which defines the configuration to use for the circuit of this function.