聊聊resilience4j的CircuitBreakerStateMachine
序
本文主要研究一下resilience4j的CircuitBreakerStateMachine
CircuitBreakerStateMachine
resilience4j-circuitbreaker-0.13.0-sources.jar!/io/github/resilience4j/circuitbreaker/internal/CircuitBreakerStateMachine.java
/**
* A CircuitBreaker finite state machine.
*/
public final class CircuitBreakerStateMachine implements CircuitBreaker {
private static final Logger LOG = LoggerFactory.getLogger(CircuitBreakerStateMachine.class);
private final String name;
private final AtomicReference<CircuitBreakerState> stateReference;
private final CircuitBreakerConfig circuitBreakerConfig;
private final CircuitBreakerEventProcessor eventProcessor;
/**
* Creates a circuitBreaker.
*
* @param name the name of the CircuitBreaker
* @param circuitBreakerConfig The CircuitBreaker configuration.
*/
public CircuitBreakerStateMachine(String name, CircuitBreakerConfig circuitBreakerConfig) {
this.name = name;
this.circuitBreakerConfig = circuitBreakerConfig;
this.stateReference = new AtomicReference<>(new ClosedState(this));
this.eventProcessor = new CircuitBreakerEventProcessor();
}
/**
* Creates a circuitBreaker with default config.
*
* @param name the name of the CircuitBreaker
*/
public CircuitBreakerStateMachine(String name) {
this(name, CircuitBreakerConfig.ofDefaults());
}
/**
* Creates a circuitBreaker.
*
* @param name the name of the CircuitBreaker
* @param circuitBreakerConfig The CircuitBreaker configuration supplier.
*/
public CircuitBreakerStateMachine(String name, Supplier<CircuitBreakerConfig> circuitBreakerConfig) {
this(name, circuitBreakerConfig.get());
}
/**
* Requests permission to call this backend.
*
* @return true, if the call is allowed.
*/
@Override
public boolean isCallPermitted() {
boolean callPermitted = stateReference.get().isCallPermitted();
if (!callPermitted) {
publishCallNotPermittedEvent();
}
return callPermitted;
}
@Override
public void onError(long durationInNanos, Throwable throwable) {
if (circuitBreakerConfig.getRecordFailurePredicate().test(throwable)) {
if (LOG.isDebugEnabled()) {
LOG.debug(String.format("CircuitBreaker '%s' recorded a failure:", name), throwable);
}
publishCircuitErrorEvent(name, durationInNanos, throwable);
stateReference.get().onError(throwable);
} else {
publishCircuitIgnoredErrorEvent(name, durationInNanos, throwable);
}
}
@Override
public void onSuccess(long durationInNanos) {
publishSuccessEvent(durationInNanos);
stateReference.get().onSuccess();
}
/**
* Get the state of this CircuitBreaker.
*
* @return the the state of this CircuitBreaker
*/
@Override
public State getState() {
return this.stateReference.get().getState();
}
/**
* Get the name of this CircuitBreaker.
*
* @return the the name of this CircuitBreaker
*/
@Override
public String getName() {
return this.name;
}
/**
* Get the config of this CircuitBreaker.
*
* @return the config of this CircuitBreaker
*/
@Override
public CircuitBreakerConfig getCircuitBreakerConfig() {
return circuitBreakerConfig;
}
@Override
public Metrics getMetrics() {
return this.stateReference.get().getMetrics();
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
return String.format("CircuitBreaker '%s'", this.name);
}
@Override
public void reset() {
CircuitBreakerState previousState = stateReference.getAndUpdate(currentState -> new ClosedState(this));
if (previousState.getState() != CLOSED) {
publishStateTransitionEvent(StateTransition.transitionBetween(previousState.getState(), CLOSED));
}
publishResetEvent();
}
private void stateTransition(State newState, Function<CircuitBreakerState, CircuitBreakerState> newStateGenerator) {
CircuitBreakerState previousState = stateReference.getAndUpdate(currentState -> {
if (currentState.getState() == newState) {
return currentState;
}
return newStateGenerator.apply(currentState);
});
if (previousState.getState() != newState) {
publishStateTransitionEvent(StateTransition.transitionBetween(previousState.getState(), newState));
}
}
@Override
public void transitionToDisabledState() {
stateTransition(DISABLED, currentState -> new DisabledState(this));
}
@Override
public void transitionToForcedOpenState() {
stateTransition(FORCED_OPEN, currentState -> new ForcedOpenState(this));
}
@Override
public void transitionToClosedState() {
stateTransition(CLOSED, currentState -> new ClosedState(this, currentState.getMetrics()));
}
@Override
public void transitionToOpenState() {
stateTransition(OPEN, currentState -> new OpenState(this, currentState.getMetrics()));
}
@Override
public void transitionToHalfOpenState() {
stateTransition(HALF_OPEN, currentState -> new HalfOpenState(this));
}
//......
}
- CircuitBreakerStateMachine實現了CircuitBreakerStateMachine介面
- AtomicReference<CircuitBreakerState>用來記錄當前斷路器的狀態
- 狀態轉換介面內部都呼叫了stateTransition方法，裡頭主要是更新AtomicReference<CircuitBreakerState>以及釋出事件
- stateTransition以及reset方法裡頭都呼叫了StateTransition.transitionBetween來發布事件
- CircuitBreakerEventProcessor用來處理事件
CircuitBreakerState
resilience4j-circuitbreaker-0.13.0-sources.jar!/io/github/resilience4j/circuitbreaker/internal/CircuitBreakerState.java
/**
* Abstract state of the CircuitBreaker state machine.
*/
abstract class CircuitBreakerState{
CircuitBreakerStateMachine stateMachine;
CircuitBreakerState(CircuitBreakerStateMachine stateMachine) {
this.stateMachine = stateMachine;
}
abstract boolean isCallPermitted();
abstract void onError(Throwable throwable);
abstract void onSuccess();
abstract CircuitBreaker.State getState();
abstract CircuitBreakerMetrics getMetrics();
/**
* Should the CircuitBreaker in this state publish events
* @return a boolean signaling if the events should be published
*/
boolean shouldPublishEvents(CircuitBreakerEvent event){
return event.getEventType().forcePublish || getState().allowPublish;
}
}
- CircuitBreakerState與CircuitBreakerStateMachine二者相互儲存各自的引用
- CircuitBreakerState的子類有OpenState、HalfOpenState、ForcedOpenState、ClosedState、DisabledState
- 每個子類的onError、onSuccess方法自己判斷是否進行狀態轉移，如果要轉移會呼叫CircuitBreakerStateMachine的transitionTo開頭的方法
StateTransition.transitionBetween
resilience4j-circuitbreaker-0.13.0-sources.jar!/io/github/resilience4j/circuitbreaker/CircuitBreaker.java
/**
* State transitions of the CircuitBreaker state machine.
*/
enum StateTransition {
CLOSED_TO_OPEN(State.CLOSED, State.OPEN),
CLOSED_TO_DISABLED(State.CLOSED, State.DISABLED),
CLOSED_TO_FORCED_OPEN(State.CLOSED, State.FORCED_OPEN),
HALF_OPEN_TO_CLOSED(State.HALF_OPEN, State.CLOSED),
HALF_OPEN_TO_OPEN(State.HALF_OPEN, State.OPEN),
HALF_OPEN_TO_DISABLED(State.HALF_OPEN, State.DISABLED),
HALF_OPEN_TO_FORCED_OPEN(State.HALF_OPEN, State.FORCED_OPEN),
OPEN_TO_CLOSED(State.OPEN, State.CLOSED),
OPEN_TO_HALF_OPEN(State.OPEN, State.HALF_OPEN),
OPEN_TO_DISABLED(State.OPEN, State.DISABLED),
OPEN_TO_FORCED_OPEN(State.OPEN, State.FORCED_OPEN),
FORCED_OPEN_TO_CLOSED(State.FORCED_OPEN, State.CLOSED),
FORCED_OPEN_TO_OPEN(State.FORCED_OPEN, State.OPEN),
FORCED_OPEN_TO_DISABLED(State.FORCED_OPEN, State.DISABLED),
FORCED_OPEN_TO_HALF_OPEN(State.FORCED_OPEN, State.HALF_OPEN),
DISABLED_TO_CLOSED(State.DISABLED, State.CLOSED),
DISABLED_TO_OPEN(State.DISABLED, State.OPEN),
DISABLED_TO_FORCED_OPEN(State.DISABLED, State.FORCED_OPEN),
DISABLED_TO_HALF_OPEN(State.DISABLED, State.HALF_OPEN);
private final State fromState;
private final State toState;
private static final Map<Tuple2<State, State>, StateTransition> STATE_TRANSITION_MAP =
Arrays
.stream(StateTransition.values())
.collect(Collectors.toMap(v -> Tuple.of(v.fromState, v.toState), Function.identity()));
private boolean matches(State fromState, State toState) {
return this.fromState == fromState && this.toState == toState;
}
public static StateTransition transitionBetween(State fromState, State toState){
final StateTransition stateTransition = STATE_TRANSITION_MAP.get(Tuple.of(fromState, toState));
if(stateTransition == null) {
throw new IllegalStateException(
String.format("Illegal state transition from %s to %s", fromState.toString(), toState.toString()));
}
return stateTransition;
}
StateTransition(State fromState, State toState) {
this.fromState = fromState;
this.toState = toState;
}
public State getFromState() {
return fromState;
}
public State getToState() {
return toState;
}
@Override
public String toString(){
return String.format("State transition from %s to %s", fromState, toState);
}
}
- StateTransition定義了一系列狀態轉換的路徑
- StateTransition.transitionBetween方法會對這些狀態轉換進行校驗，不合法的丟擲IllegalStateException
CircuitBreakerEventProcessor
resilience4j-circuitbreaker-0.13.0-sources.jar!/io/github/resilience4j/circuitbreaker/internal/CircuitBreakerStateMachine.java
private class CircuitBreakerEventProcessor extends EventProcessor<CircuitBreakerEvent> implements EventConsumer<CircuitBreakerEvent>, EventPublisher {
@Override
public EventPublisher onSuccess(EventConsumer<CircuitBreakerOnSuccessEvent> onSuccessEventConsumer) {
registerConsumer(CircuitBreakerOnSuccessEvent.class, onSuccessEventConsumer);
return this;
}
@Override
public EventPublisher onError(EventConsumer<CircuitBreakerOnErrorEvent> onErrorEventConsumer) {
registerConsumer(CircuitBreakerOnErrorEvent.class, onErrorEventConsumer);
return this;
}
@Override
public EventPublisher onStateTransition(EventConsumer<CircuitBreakerOnStateTransitionEvent> onStateTransitionEventConsumer) {
registerConsumer(CircuitBreakerOnStateTransitionEvent.class, onStateTransitionEventConsumer);
return this;
}
@Override
public EventPublisher onReset(EventConsumer<CircuitBreakerOnResetEvent> onResetEventConsumer) {
registerConsumer(CircuitBreakerOnResetEvent.class, onResetEventConsumer);
return this;
}
@Override
public EventPublisher onIgnoredError(EventConsumer<CircuitBreakerOnIgnoredErrorEvent> onIgnoredErrorEventConsumer) {
registerConsumer(CircuitBreakerOnIgnoredErrorEvent.class, onIgnoredErrorEventConsumer);
return this;
}
@Override
public EventPublisher onCallNotPermitted(EventConsumer<CircuitBreakerOnCallNotPermittedEvent> onCallNotPermittedEventConsumer) {
registerConsumer(CircuitBreakerOnCallNotPermittedEvent.class, onCallNotPermittedEventConsumer);
return this;
}
@Override
public void consumeEvent(CircuitBreakerEvent event) {
super.processEvent(event);
}
}
- CircuitBreakerEventProcessor繼承了EventProcessor，處理CircuitBreakerEvent事件
- CircuitBreakerEventProcessor也實現了EventConsumer以及EventPublisher介面
- onSuccess、onError、onStateTransition、onReset、onIgnoredError、onCallNotPermitted裡頭呼叫了registerConsumer方法
- consumeEvent裡頭則是呼叫了processEvent方法
EventProcessor
resilience4j-core-0.13.0-sources.jar!/io/github/resilience4j/core/EventProcessor.java
public class EventProcessor<T> implements EventPublisher<T> {
protected volatile boolean consumerRegistered;
private volatile EventConsumer<T> onEventConsumer;
private ConcurrentMap<Class<? extends T>, EventConsumer<Object>> eventConsumers = new ConcurrentHashMap<>();
public boolean hasConsumers(){
return consumerRegistered;
}
@SuppressWarnings("unchecked")
public <E extends T> void registerConsumer(Class<? extends E> eventType, EventConsumer<E> eventConsumer){
consumerRegistered = true;
eventConsumers.put(eventType, (EventConsumer<Object>) eventConsumer);
}
@SuppressWarnings("unchecked")
public <E extends T> boolean processEvent(E event) {
boolean consumed = false;
if(onEventConsumer != null){
onEventConsumer.consumeEvent(event);
consumed = true;
}
if(!eventConsumers.isEmpty()){
EventConsumer<T> eventConsumer = (EventConsumer<T>) eventConsumers.get(event.getClass());
if(eventConsumer != null){
eventConsumer.consumeEvent(event);
consumed = true;
}
}
return consumed;
}
@Override
public void onEvent(EventConsumer<T> onEventConsumer) {
consumerRegistered = true;
this.onEventConsumer = onEventConsumer;
}
}
- registerConsumer方法主要是往eventConsumers設定事件型別的消費者
- processEvent方法主要是查詢相應的事件消費者去處理事件
EventPublisher
resilience4j-circuitbreaker-0.13.0-sources.jar!/io/github/resilience4j/circuitbreaker/CircuitBreaker.java
/**
* An EventPublisher can be used to register event consumers.
*/
interface EventPublisher extends io.github.resilience4j.core.EventPublisher<CircuitBreakerEvent> {
EventPublisher onSuccess(EventConsumer<CircuitBreakerOnSuccessEvent> eventConsumer);
EventPublisher onError(EventConsumer<CircuitBreakerOnErrorEvent> eventConsumer);
EventPublisher onStateTransition(EventConsumer<CircuitBreakerOnStateTransitionEvent> eventConsumer);
EventPublisher onReset(EventConsumer<CircuitBreakerOnResetEvent> eventConsumer);
EventPublisher onIgnoredError(EventConsumer<CircuitBreakerOnIgnoredErrorEvent> eventConsumer);
EventPublisher onCallNotPermitted(EventConsumer<CircuitBreakerOnCallNotPermittedEvent> eventConsumer);
}
- 這個EventPublisher介面繼承了io.github.resilience4j.core.EventPublisher，邏輯上有點混亂
- 這些on方法分別處理了CircuitBreakerOnSuccessEvent、CircuitBreakerOnErrorEvent、CircuitBreakerOnStateTransitionEvent、CircuitBreakerOnResetEvent、CircuitBreakerOnIgnoredErrorEvent、CircuitBreakerOnCallNotPermittedEvent事件
CircuitBreakerEvent
resilience4j-circuitbreaker-0.13.0-sources.jar!/io/github/resilience4j/circuitbreaker/event/CircuitBreakerEvent.java
/**
* An event which is created by a CircuitBreaker.
*/
public interface CircuitBreakerEvent {
/**
* Returns the name of the CircuitBreaker which has created the event.
*
* @return the name of the CircuitBreaker which has created the event
*/
String getCircuitBreakerName();
/**
* Returns the type of the CircuitBreaker event.
*
* @return the type of the CircuitBreaker event
*/
Type getEventType();
/**
* Returns the creation time of CircuitBreaker event.
*
* @return the creation time of CircuitBreaker event
*/
ZonedDateTime getCreationTime();
/**
* Event types which are created by a CircuitBreaker.
*/
enum Type {
/** A CircuitBreakerEvent which informs that an error has been recorded */
ERROR(false),
/** A CircuitBreakerEvent which informs that an error has been ignored */
IGNORED_ERROR(false),
/** A CircuitBreakerEvent which informs that a success has been recorded */
SUCCESS(false),
/** A CircuitBreakerEvent which informs that a call was not permitted because the CircuitBreaker state is OPEN */
NOT_PERMITTED(false),
/** A CircuitBreakerEvent which informs the state of the CircuitBreaker has been changed */
STATE_TRANSITION(true),
/** A CircuitBreakerEvent which informs the CircuitBreaker has been reset */
RESET(true),
/** A CircuitBreakerEvent which informs the CircuitBreaker has been forced open */
FORCED_OPEN(false),
/** A CircuitBreakerEvent which informs the CircuitBreaker has been disabled */
DISABLED(false);
public final boolean forcePublish;
Type(boolean forcePublish) {
this.forcePublish = forcePublish;
}
}
}
- CircuitBreakerEvent介面定義了事件的Type列舉
- 規範了getCircuitBreakerName、getEventType、getCreationTime方法
AbstractCircuitBreakerEvent
resilience4j-circuitbreaker-0.13.0-sources.jar!/io/github/resilience4j/circuitbreaker/event/AbstractCircuitBreakerEvent.java
abstract class AbstractCircuitBreakerEvent implements CircuitBreakerEvent {
private final String circuitBreakerName;
private final ZonedDateTime creationTime;
AbstractCircuitBreakerEvent(String circuitBreakerName) {
this.circuitBreakerName = circuitBreakerName;
this.creationTime = ZonedDateTime.now();
}
@Override
public String getCircuitBreakerName() {
return circuitBreakerName;
}
@Override
public ZonedDateTime getCreationTime() {
return creationTime;
}
}
- 定義了circuitBreakerName、creationTime屬性
- 重寫了getCircuitBreakerName、getCreationTime方法
- ircuitBreakerOnSuccessEvent、CircuitBreakerOnErrorEvent、CircuitBreakerOnStateTransitionEvent、CircuitBreakerOnResetEvent、CircuitBreakerOnIgnoredErrorEvent、CircuitBreakerOnCallNotPermittedEvent都是從AbstractCircuitBreakerEvent繼承而來，個別的自定義了自己的屬性，主要是重寫getEventType以及toString方法
小結
- CircuitBreakerStateMachine裡頭維護了一個AtomicReference<CircuitBreakerState>引用，對應的onError及onSuccess方法都委託給改引用對應的狀態的onError以及onSuccess方法
- 子類的onError以及onSuccess方法方法則自行判斷是否需要進行狀態切換以及切換到什麼狀態，自己呼叫CircuitBreakerStateMachine的transitionTo開頭的方法，來改變AtomicReference<CircuitBreakerState>的值(
藉助子類的各自實現來化解狀態轉換的複雜邏輯)，同時釋出一些事件。
doc
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