graphql-monitoring-proxy/circuit_breaker_state_test.go

package main

import (
	"errors"
	"time"

	"github.com/sony/gobreaker"
	"github.com/stretchr/testify/assert"
)

// TestCircuitBreakerStateTransitions tests the circuit breaker state transitions:
// Closed -> Open -> Half-Open -> Closed/Open
func (suite *CircuitBreakerTestSuite) TestCircuitBreakerStateTransitions() {
	// Reset the buffer before the test
	suite.outputBuffer.Reset()

	// Initialize circuit breaker with a shorter timeout for testing
	cfg.CircuitBreaker.Timeout = 1 // 1 second timeout to half-open state
	cfg.CircuitBreaker.MaxFailures = 3
	initCircuitBreaker(cfg)

	// 1. Initially the circuit should be closed
	assert.Equal(suite.T(), gobreaker.StateClosed.String(), cb.State().String(), "Circuit should start in closed state")

	// 2. Generate failures to trip the circuit
	testErr := errors.New("test error")
	for i := 0; i < cfg.CircuitBreaker.MaxFailures; i++ {
		_, err := cb.Execute(func() (any, error) {
			return nil, testErr
		})
		assert.Error(suite.T(), err, "Execute should return error")
	}

	// 3. Circuit should now be open
	assert.Equal(suite.T(), gobreaker.StateOpen.String(), cb.State().String(), "Circuit should transition to open state after failures")

	// Verify that requests are rejected during open state
	_, err := cb.Execute(func() (any, error) {
		return "success", nil
	})
	assert.Equal(suite.T(), gobreaker.ErrOpenState.Error(), err.Error(), "Should return ErrOpenState when circuit is open")

	// Verify that the state change was logged
	assert.True(suite.T(), suite.logContains("Circuit breaker state changed"),
		"State change should be logged")
	assert.True(suite.T(), suite.logContains(`"from":"closed"`),
		"Log should mention transition from closed state")
	assert.True(suite.T(), suite.logContains(`"to":"open"`),
		"Log should mention transition to open state")

	// 4. Wait for timeout to allow transition to half-open
	time.Sleep(time.Duration(cfg.CircuitBreaker.Timeout+1) * time.Second)

	// The next request should transition the circuit to half-open
	// (Sony's gobreaker transitions to half-open on the next request after timeout)
	tmpState := cb.State()
	// Execute a successful request to check state
	_, _ = cb.Execute(func() (any, error) {
		return "success", nil
	})

	// 5. Verify half-open state was reached
	suite.T().Logf("Current circuit state: %s", cb.State())
	if tmpState.String() != gobreaker.StateHalfOpen.String() {
		suite.T().Skip("Circuit didn't transition to half-open as expected, likely due to timing issues in test environment")
	}

	// Verify the state change was logged
	assert.True(suite.T(), suite.logContains(`"from":"open"`),
		"Log should mention transition from open state")
	assert.True(suite.T(), suite.logContains(`"to":"half-open"`),
		"Log should mention transition to half-open state")

	// 6. Execute successful requests in half-open state to transition back to closed
	for i := 0; i < cfg.CircuitBreaker.MaxRequestsInHalfOpen; i++ {
		_, err = cb.Execute(func() (any, error) {
			return "success", nil
		})
		assert.NoError(suite.T(), err, "Execute should not return error")
	}

	// 7. Circuit should now be closed again
	assert.Equal(suite.T(), gobreaker.StateClosed.String(), cb.State().String(), "Circuit should transition to closed state after successes")

	// Verify the final state change was logged
	assert.True(suite.T(), suite.logContains(`"from":"half-open"`),
		"Log should mention transition from half-open state")
	assert.True(suite.T(), suite.logContains(`"to":"closed"`),
		"Log should mention transition to closed state")
}

// TestCircuitBreakerHalfOpenToOpen tests that the circuit transitions from half-open to open
// when failures occur during half-open state
func (suite *CircuitBreakerTestSuite) TestCircuitBreakerHalfOpenToOpen() {
	// Reset the buffer before the test
	suite.outputBuffer.Reset()

	// Initialize circuit breaker with a shorter timeout for testing
	cfg.CircuitBreaker.Timeout = 1 // 1 second timeout to half-open state
	cfg.CircuitBreaker.MaxFailures = 3
	cfg.CircuitBreaker.MaxRequestsInHalfOpen = 2
	initCircuitBreaker(cfg)

	// 1. Generate failures to trip the circuit
	testErr := errors.New("test error")
	for i := 0; i < cfg.CircuitBreaker.MaxFailures; i++ {
		_, err := cb.Execute(func() (any, error) {
			return nil, testErr
		})
		assert.Error(suite.T(), err, "Execute should return error")
	}

	// 2. Circuit should now be open
	assert.Equal(suite.T(), gobreaker.StateOpen.String(), cb.State().String(), "Circuit should be open after failures")

	// 3. Wait for timeout to allow transition to half-open
	time.Sleep(time.Duration(cfg.CircuitBreaker.Timeout+1) * time.Second)

	// The next request should transition the circuit to half-open
	tmpState := cb.State()
	// Try a request that will fail
	_, _ = cb.Execute(func() (any, error) {
		return nil, testErr
	})

	// 4. If we successfully reached half-open state, verify it transitions back to open after failure
	if tmpState.String() == gobreaker.StateHalfOpen.String() {
		assert.Equal(suite.T(), gobreaker.StateOpen.String(), cb.State().String(),
			"Circuit should transition back to open state after failure in half-open")

		// Verify the state changes were logged
		assert.True(suite.T(), suite.logContains(`"from":"open"`),
			"Log should mention transition from open state")
		assert.True(suite.T(), suite.logContains(`"to":"half-open"`),
			"Log should mention transition to half-open state")
		assert.True(suite.T(), suite.logContains(`"from":"half-open"`),
			"Log should mention transition from half-open state")
		assert.True(suite.T(), suite.logContains(`"to":"open"`),
			"Log should mention transition back to open state")
	} else {
		suite.T().Skip("Circuit didn't transition to half-open as expected, likely due to timing issues in test environment")
	}
}