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Commiteee2dea

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Added a circuit breaker handler using failsafe (#64)
* Added a circuit breaker handler using failsafe
1 parent14c6e57 commiteee2dea

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2 files changed

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packagecom.stubbornjava.common.undertow.handlers;
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importorg.slf4j.Logger;
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importorg.slf4j.LoggerFactory;
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importio.undertow.server.HttpHandler;
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importio.undertow.server.HttpServerExchange;
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importnet.jodah.failsafe.CircuitBreaker;
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importnet.jodah.failsafe.Failsafe;
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// {{start:handler}}
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publicclassCircuitBreakerHandlerimplementsHttpHandler {
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privatestaticfinalLoggerlog =LoggerFactory.getLogger(CircuitBreakerHandler.class);
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privatefinalCircuitBreakercircuitBreaker;
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privatefinalHttpHandlerdelegate;
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privatefinalHttpHandlerfailureHandler;
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publicCircuitBreakerHandler(CircuitBreakercircuitBreaker,HttpHandlerdelegate,HttpHandlerfailureHandler) {
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super();
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this.circuitBreaker =circuitBreaker;
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this.delegate =delegate;
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this.failureHandler =failureHandler;
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}
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@Override
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publicvoidhandleRequest(HttpServerExchangeexchange)throwsException {
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Failsafe.with(circuitBreaker)
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.withFallback(() ->failureHandler.handleRequest(exchange))
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// We need to call get here instead of execute so we can return the
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// mutated exchange to run checks on it
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.get(() -> {
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delegate.handleRequest(exchange);
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returnexchange;
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});
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}
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}
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// {{end:handler}}
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packagecom.stubbornjava.examples.failsafe;
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importjava.io.IOException;
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importjava.util.concurrent.Executors;
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importjava.util.concurrent.ScheduledExecutorService;
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importjava.util.concurrent.TimeUnit;
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importorg.slf4j.Logger;
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importorg.slf4j.LoggerFactory;
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importcom.stubbornjava.common.HttpClient;
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importcom.stubbornjava.common.undertow.Exchange;
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importcom.stubbornjava.common.undertow.SimpleServer;
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importcom.stubbornjava.common.undertow.handlers.CircuitBreakerHandler;
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importcom.stubbornjava.common.undertow.handlers.CustomHandlers;
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importio.undertow.server.HttpHandler;
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importio.undertow.server.HttpServerExchange;
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importio.undertow.util.StatusCodes;
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importnet.jodah.failsafe.CircuitBreaker;
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importokhttp3.HttpUrl;
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importokhttp3.Request;
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publicclassFailsafeWebserver {
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privatestaticfinalLoggerlog =LoggerFactory.getLogger(FailsafeWebserver.class);
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// {{start:handlers}}
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privatestaticfinalvoidserverError(HttpServerExchangeexchange) {
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exchange.setStatusCode(StatusCodes.INTERNAL_SERVER_ERROR);
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Exchange.body().sendText(exchange,"500 - Internal Server Error");
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}
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// This handler helps simulate errors, bad requests, and successful requests.
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privatestaticfinalvoidcircuitClosed(HttpServerExchangeexchange) {
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booleanerror =Exchange.queryParams().queryParamAsBoolean(exchange,"error").orElse(false);
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booleanexception =Exchange.queryParams().queryParamAsBoolean(exchange,"exception").orElse(false);
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if (error) {
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exchange.setStatusCode(StatusCodes.BAD_REQUEST);
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Exchange.body().sendText(exchange,"Bad Request");
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}elseif (exception) {
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thrownewRuntimeException("boom");
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}else {
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Exchange.body().sendText(exchange,"Circuit is open everything is functioning properly.");
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}
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}
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privatestaticfinalHttpHandlerCIRCUIT_BREAKER_HANDLER;
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static {
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CircuitBreakerbreaker =newCircuitBreaker()
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// Trigger circuit breaker failure on exceptions or bad requests
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.failIf((HttpServerExchangeexchange,Throwableex) -> {
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return (exchange !=null &&StatusCodes.BAD_REQUEST ==exchange.getStatusCode())
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||ex !=null;
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})
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// If 7 out of 10 requests fail Open the circuit
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.withFailureThreshold(7,10)
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// When half open if 3 out of 5 requests succeed close the circuit
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.withSuccessThreshold(3,5)
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// Delay this long before half opening the circuit
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.withDelay(2,TimeUnit.SECONDS)
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.onClose(() ->log.info("Circuit Closed"))
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.onOpen(() ->log.info("Circuit Opened"))
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.onHalfOpen(() ->log.info("Circuit Half-Open"));
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CIRCUIT_BREAKER_HANDLER =newCircuitBreakerHandler(breaker,
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FailsafeWebserver::circuitClosed,
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FailsafeWebserver::serverError);
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}
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// {{end:handlers}}
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// {{start:request}}
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privatestaticvoidrequest(booleanerror,booleanexception) {
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HttpUrlurl =HttpUrl.parse("http://localhost:8080")
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.newBuilder()
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.addQueryParameter("error",String.valueOf(error))
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.addQueryParameter("exception",String.valueOf(exception))
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.build();
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Requestrequest =newRequest.Builder().get().url(url).build();
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try {
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log.info(HttpClient.globalClient().newCall(request).execute().body().string());
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}catch (IOExceptione) {
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e.printStackTrace();
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}
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}
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// {{end:request}}
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// {{start:main}}
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publicstaticvoidmain(String[]args) {
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HttpHandlerexceptionHandler =
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CustomHandlers.exception(CIRCUIT_BREAKER_HANDLER)
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.addExceptionHandler(Throwable.class,FailsafeWebserver::serverError);
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SimpleServerserver =SimpleServer.simpleServer(exceptionHandler);
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server.start();
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// Warm-up the circuit breaker it needs to hit at least max executions
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// Before it will reject anything. This will make that easier.
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for (inti =0;i <10;i++) {
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request(false,false);
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}
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ScheduledExecutorServiceschedExec =Executors.newScheduledThreadPool(1);
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// A simple request that should always succeed
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schedExec.scheduleAtFixedRate(() ->request(false,false),0,500,TimeUnit.MILLISECONDS);
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// Send a batch of 15 bad requests to trigger the circuit breaker
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Runnableerrors = () -> {
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log.info("Executing bad requests!");
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for (inti =0;i <15;i++) {
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request(true,false);
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}
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};
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schedExec.schedule(errors,1,TimeUnit.SECONDS);
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// Send a batch of 15 requests that throw exceptions
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Runnableexceptions = () -> {
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log.info("Executing requests that throw exceptions!");
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for (inti =0;i <15;i++) {
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request(false,true);
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}
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};
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schedExec.schedule(exceptions,5,TimeUnit.SECONDS);
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}
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// {{end:main}}
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}

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