isabella232 / circuitbreaker

Circuit Breakers in Go

circuitbreaker

Circuitbreaker provides an easy way to use the Circuit Breaker pattern in a Go program.

Circuit breakers are typically used when your program makes remote calls. Remote calls can often hang for a while before they time out. If your application makes a lot of these requests, many resources can be tied up waiting for these time outs to occur. A circuit breaker wraps these remote calls and will trip after a defined amount of failures or time outs occur. When a circuit breaker is tripped any future calls will avoid making the remote call and return an error to the client. In the meantime, the circuit breaker will periodically allow some calls to be tried again and will close the circuit if those are successful.

You can read more about this pattern and how it's used at:

• Martin Fowler's bliki
• The Netflix Tech Blog
• Release It!

Installation

  go get github.com/rubyist/circuitbreaker

Examples

Here is a quick example of what circuitbreaker provides

// Creates a circuit breaker that will trip if the function fails 10 times
cb := NewThresholdBreaker(10)

cb.BreakerTripped = func() {
	// This function will be called every time the circuit breaker moves
	// from reset to tripped.
}

cb.BreakerReset = func() {
	// This function will be called every time the circuit breaker moves
	// from tripped to reset.
}

cb.Call(func() error {
	// This is where you'll do some remote call
	// If it fails, return an error
})

Circuitbreaker can also wrap a time out around the remote call.

// Creates a circuit breaker that will trip after 10 failures or time outs
// using a time out of 5 seconds
cb := NewTimeoutBreaker(Time.Second * 5, 10)

// Proceed as above

Circuitbreaker also provides a wrapper around http.Client that will wrap a time out around any request.

// Passing in nil will create a regular http.Client.
// You can also build your own http.Client and pass it in
client := NewHTTPClient(time.Second * 5, 10, nil)
client.BreakerTripped = func() {
	// Perhaps notify your monitoring system
}
client.BreakerReset = func() {
	// Perhaps notify your monitoring system
}

resp, err := client.Get("http://example.com/resource.json")

See the godoc for more examples.

Bugs, Issues, Feedback

Right here on GitHub: https://github.com/rubyist/circuitbreaker