Package io.vertx.circuitbreaker

Interface CircuitBreaker

public interface CircuitBreaker

An implementation of the circuit breaker pattern for Vert.x

Author:

Clement Escoffier

Method Summary

Modifier and Type	Method	Description
CircuitBreaker	close()	Closes the circuit breaker.
CircuitBreaker	closeHandler(Handler<Void> handler)	Sets a Handler to be invoked when the circuit breaker state switches to closed.
static CircuitBreaker	create(String name, Vertx vertx)	Creates a new instance of CircuitBreaker, with default options.
static CircuitBreaker	create(String name, Vertx vertx, CircuitBreakerOptions options)	Creates a new instance of CircuitBreaker.
<T> Future<T>	execute(Handler<Promise<T>> command)	Same as executeWithFallback(Handler, Function) but using the circuit breaker default fallback.
<T> Future<T>	execute(Supplier<Future<T>> command)	Same as executeWithFallback(Supplier, Function) but using the circuit breaker default fallback.
<T> CircuitBreaker	executeAndReport(Promise<T> resultPromise, Handler<Promise<T>> command)	Same as executeAndReportWithFallback(Promise, Handler, Function) but using the circuit breaker default fallback.
<T> CircuitBreaker	executeAndReportWithFallback(Promise<T> resultPromise, Handler<Promise<T>> command, Function<Throwable,T> fallback)	Executes the given operation with the circuit breaker control.
<T> Future<T>	executeWithFallback(Handler<Promise<T>> command, Function<Throwable,T> fallback)	Executes the given operation with the circuit breaker control.
<T> Future<T>	executeWithFallback(Supplier<Future<T>> command, Function<Throwable,T> fallback)	Executes the given operation with the circuit breaker control.
long	failureCount()
default <T> CircuitBreaker	failurePolicy(FailurePolicy<T> failurePolicy)	Configures the failure policy for this circuit-breaker.
<T> CircuitBreaker	fallback(Function<Throwable,T> handler)	Sets a default fallback Function to be invoked when the circuit breaker is open or when failure occurs and CircuitBreakerOptions.isFallbackOnFailure() is enabled.
CircuitBreaker	halfOpenHandler(Handler<Void> handler)	Sets a Handler to be invoked when the circuit breaker state switches to half-open.
String	name()
CircuitBreaker	open()	Explicitly opens the circuit breaker.
CircuitBreaker	openHandler(Handler<Void> handler)	Sets a Handler to be invoked when the circuit breaker state switches to open.
CircuitBreaker	reset()	Resets the circuit breaker state.
CircuitBreaker	retryPolicy(RetryPolicy retryPolicy)	Set a RetryPolicy which computes a delay before a retry attempt.
CircuitBreakerState	state()

Method Detail

create

static CircuitBreaker create(String name,
                             Vertx vertx,
                             CircuitBreakerOptions options)

Creates a new instance of CircuitBreaker.

Parameters:

name - the name

vertx - the Vert.x instance

options - the configuration options

Returns:

the created instance

create

static CircuitBreaker create(String name,
                             Vertx vertx)

Creates a new instance of CircuitBreaker, with default options.

Parameters:

name - the name

vertx - the Vert.x instance

Returns:

the created instance

close

CircuitBreaker close()

Closes the circuit breaker. It stops sending events on its state on the event bus.

This method is not related to the closed state of the circuit breaker. To move the circuit breaker to the closed state, use reset().

openHandler

CircuitBreaker openHandler(Handler<Void> handler)

Sets a Handler to be invoked when the circuit breaker state switches to open.

Parameters:

handler - the handler, must not be null

Returns:

this CircuitBreaker

halfOpenHandler

CircuitBreaker halfOpenHandler(Handler<Void> handler)

Sets a Handler to be invoked when the circuit breaker state switches to half-open.

Parameters:

handler - the handler, must not be null

Returns:

this CircuitBreaker

closeHandler

CircuitBreaker closeHandler(Handler<Void> handler)

Sets a Handler to be invoked when the circuit breaker state switches to closed.

Parameters:

handler - the handler, must not be null

Returns:

this CircuitBreaker

executeWithFallback

<T> Future<T> executeWithFallback(Handler<Promise<T>> command,
                                  Function<Throwable,T> fallback)

Executes the given operation with the circuit breaker control. The operation is generally calling an external system. The operation receives a Promise object as parameter and must call Promise.complete(Object) when the operation has terminated successfully. The operation must also call Promise.fail(Throwable) in case of a failure.

The operation is not invoked if the circuit breaker is open, and the given fallback is called instead. The circuit breaker also monitors whether the operation completes in time. The operation is considered failed if it does not terminate before the configured timeout.

This method returns a Future object to retrieve the status and result of the operation, with the status being a success or a failure. If the fallback is called, the returned future is successfully completed with the value returned from the fallback. If the fallback throws an exception, the returned future is marked as failed.

Type Parameters:

T - the type of result

Parameters:

command - the operation

fallback - the fallback function; gets an exception as parameter and returns the fallback result

Returns:

a future object completed when the operation or the fallback completes

executeWithFallback

<T> Future<T> executeWithFallback(Supplier<Future<T>> command,
                                  Function<Throwable,T> fallback)

Executes the given operation with the circuit breaker control. The operation is generally calling an external system. The operation receives a Promise object as parameter and must call Promise.complete(Object) when the operation has terminated successfully. The operation must also call Promise.fail(Throwable) in case of a failure.

The operation is not invoked if the circuit breaker is open, and the given fallback is called instead. The circuit breaker also monitors whether the operation completes in time. The operation is considered failed if it does not terminate before the configured timeout.

This method returns a Future object to retrieve the status and result of the operation, with the status being a success or a failure. If the fallback is called, the returned future is successfully completed with the value returned from the fallback. If the fallback throws an exception, the returned future is marked as failed.

Type Parameters:

T - the type of result

Parameters:

command - the operation

fallback - the fallback function; gets an exception as parameter and returns the fallback result

Returns:

a future object completed when the operation or the fallback completes

execute

<T> Future<T> execute(Handler<Promise<T>> command)

Same as executeWithFallback(Handler, Function) but using the circuit breaker default fallback.

Type Parameters:

T - the type of result

Parameters:

command - the operation

Returns:

a future object completed when the operation or its fallback completes

execute

<T> Future<T> execute(Supplier<Future<T>> command)

Same as executeWithFallback(Supplier, Function) but using the circuit breaker default fallback.

Type Parameters:

T - the type of result

Parameters:

command - the operation

Returns:

a future object completed when the operation or its fallback completes

executeAndReport

<T> CircuitBreaker executeAndReport(Promise<T> resultPromise,
                                    Handler<Promise<T>> command)

Same as executeAndReportWithFallback(Promise, Handler, Function) but using the circuit breaker default fallback.

Type Parameters:

T - the type of result

Parameters:

resultPromise - the promise on which the operation result is reported

command - the operation

Returns:

this CircuitBreaker

executeAndReportWithFallback

<T> CircuitBreaker executeAndReportWithFallback(Promise<T> resultPromise,
                                                Handler<Promise<T>> command,
                                                Function<Throwable,T> fallback)

Executes the given operation with the circuit breaker control. The operation is generally calling an external system. The operation receives a Promise object as parameter and must call Promise.complete(Object) when the operation has terminated successfully. The operation must also call Promise.fail(Throwable) in case of a failure.

The operation is not invoked if the circuit breaker is open, and the given fallback is called instead. The circuit breaker also monitors whether the operation completes in time. The operation is considered failed if it does not terminate before the configured timeout.

Unlike executeWithFallback(Handler, Function), this method does not return a Future object, but lets the caller pass a Promise object on which the result is reported. If the fallback is called, the promise is successfully completed with the value returned by the fallback function. If the fallback throws an exception, the promise is marked as failed.

Type Parameters:

T - the type of result

Parameters:

resultPromise - the promise on which the operation result is reported

command - the operation

fallback - the fallback function; gets an exception as parameter and returns the fallback result

Returns:

this CircuitBreaker

fallback

<T> CircuitBreaker fallback(Function<Throwable,T> handler)

Sets a default fallback Function to be invoked when the circuit breaker is open or when failure occurs and CircuitBreakerOptions.isFallbackOnFailure() is enabled.

The function gets the exception as parameter and returns the fallback result.

Parameters:

handler - the fallback handler

Returns:

this CircuitBreaker

failurePolicy

default <T> CircuitBreaker failurePolicy(FailurePolicy<T> failurePolicy)

Configures the failure policy for this circuit-breaker.

Returns:

the current CircuitBreaker

See Also:

FailurePolicy

reset

CircuitBreaker reset()

Resets the circuit breaker state. The number of recent failures is set to 0 and if the state is half-open, it is set to closed.

Returns:

this CircuitBreaker

open

CircuitBreaker open()

Explicitly opens the circuit breaker.

Returns:

this CircuitBreaker

state

CircuitBreakerState state()

Returns:

the current state of this circuit breaker

failureCount

long failureCount()

Returns:

the current number of recorded failures

name

String name()

Returns:

the name of this circuit breaker

retryPolicy

CircuitBreaker retryPolicy(RetryPolicy retryPolicy)

Set a RetryPolicy which computes a delay before a retry attempt.