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日本男女操逼在线观看 _聊聊feign的Retryer

本文主要研究一下feign的Retryer

聊聊feign的Retryer

Retryer

feign-core-10.2.3-sources.jar!/feign/Retryer.java

public interface Retryer extends Cloneable {
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/**
* if retry is permitted, return (possibly after sleeping). Otherwise propagate the exception.
*/
void continueOrPropagate(RetryableException e);
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Retryer clone();
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class Default implements Retryer {
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private final int maxAttempts;
private final long period;
private final long maxPeriod;
int attempt;
long sleptForMillis;
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public Default() {
this(100, SECONDS.toMillis(1), 5);
}
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public Default(long period, long maxPeriod, int maxAttempts) {
this.period = period;
this.maxPeriod = maxPeriod;
this.maxAttempts = maxAttempts;
this.attempt = 1;
}
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// visible for testing;
protected long currentTimeMillis() {
return System.currentTimeMillis();
}
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public void continueOrPropagate(RetryableException e) {
if (attempt++ >= maxAttempts) {
throw e;
}
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long interval;
if (e.retryAfter() != null) {
interval = e.retryAfter().getTime() - currentTimeMillis();
if (interval > maxPeriod) {
interval = maxPeriod;
}
if (interval < 0) {
return;
}
} else {
interval = nextMaxInterval();
}
try {
Thread.sleep(interval);
} catch (InterruptedException ignored) {
Thread.currentThread().interrupt();
throw e;
}
sleptForMillis += interval;
}
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/**
* Calculates the time interval to a retry attempt. <br>
* The interval increases exponentially with each attempt, at a rate of nextInterval *= 1.5
* (where 1.5 is the backoff factor), to the maximum interval.
*
* @return time in nanoseconds from now until the next attempt.
*/
long nextMaxInterval() {
long interval = (long) (period * Math.pow(1.5, attempt - 1));
return interval > maxPeriod ? maxPeriod : interval;
}
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@Override
public Retryer clone() {
return new Default(period, maxPeriod, maxAttempts);
}
}
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/**
* Implementation that never retries request. It propagates the RetryableException.
*/
Retryer NEVER_RETRY = new Retryer() {
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@Override
public void continueOrPropagate(RetryableException e) {
throw e;
}
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@Override
public Retryer clone() {
return this;
}
};
}
  • Retryer继承了Cloneable接口,它定义了continueOrPropagate、clone方法;它内置了一个名为Default以及名为NEVER_RETRY的实现
  • Default有period、maxPeriod、maxAttempts参数可以设置,默认构造器使用的period为100,maxPeriod为1000,maxAttempts为5;continueOrPropagate方法首先判断attempt是否达到阈值,达到则抛出异常,否则进一步计算interval,然后进行sleep
  • NEVER_RETRY的continueOrPropagate直接抛出异常,而clone方法直接返回当前实例

SynchronousMethodHandler

feign-core-10.2.3-sources.jar!/feign/SynchronousMethodHandler.java

final class SynchronousMethodHandler implements MethodHandler {
//......
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public Object invoke(Object[] argv) throws Throwable {
RequestTemplate template = buildTemplateFromArgs.create(argv);
Retryer retryer = this.retryer.clone();
while (true) {
try {
return executeAndDecode(template);
} catch (RetryableException e) {
try {
retryer.continueOrPropagate(e);
} catch (RetryableException th) {
Throwable cause = th.getCause();
if (propagationPolicy == UNWRAP && cause != null) {
throw cause;
} else {
throw th;
}
}
if (logLevel != Logger.Level.NONE) {
logger.logRetry(metadata.configKey(), logLevel);
}
continue;
}
}
}
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//......
}
  • SynchronousMethodHandler的invoke的方法首先使用retryer.clone()创建一个retryer,然后在捕获到RetryableException的时候,会执行retryer.continueOrPropagate(e)

RetryableException

feign-core-10.2.3-sources.jar!/feign/RetryableException.java

public class RetryableException extends FeignException {
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private static final long serialVersionUID = 1L;
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private final Long retryAfter;
private final HttpMethod httpMethod;
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/**
* @param retryAfter usually corresponds to the {@link feign.Util#RETRY_AFTER} header.
*/
public RetryableException(int status, String message, HttpMethod httpMethod, Throwable cause,
Date retryAfter) {
super(status, message, cause);
this.httpMethod = httpMethod;
this.retryAfter = retryAfter != null ? retryAfter.getTime() : null;
}
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/**
* @param retryAfter usually corresponds to the {@link feign.Util#RETRY_AFTER} header.
*/
public RetryableException(int status, String message, HttpMethod httpMethod, Date retryAfter) {
super(status, message);
this.httpMethod = httpMethod;
this.retryAfter = retryAfter != null ? retryAfter.getTime() : null;
}
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/**
* Sometimes corresponds to the {@link feign.Util#RETRY_AFTER} header present in {@code 503}
* status. Other times parsed from an application-specific response. Null if unknown.
*/
public Date retryAfter() {
return retryAfter != null ? new Date(retryAfter) : null;
}
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public HttpMethod method() {
return this.httpMethod;
}
}
  • RetryableException继承了FeignException,它的构造器会接收retryAfter,该参数可以为null

FeignException

feign-core-10.2.3-sources.jar!/feign/FeignException.java

public class FeignException extends RuntimeException {
//......
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static FeignException errorReading(Request request, Response response, IOException cause) {
return new FeignException(
response.status(),
format("%s reading %s %s", cause.getMessage(), request.httpMethod(), request.url()),
cause,
request.requestBody().asBytes());
}
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//......
}
  • FeignException定义了errorReading静态方法,它创建的是FeignException

ErrorDecoder

feign-core-10.2.3-sources.jar!/feign/codec/ErrorDecoder.java

public interface ErrorDecoder {
//......
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public static class Default implements ErrorDecoder {
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private final RetryAfterDecoder retryAfterDecoder = new RetryAfterDecoder();
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@Override
public Exception decode(String methodKey, Response response) {
FeignException exception = errorStatus(methodKey, response);
Date retryAfter = retryAfterDecoder.apply(firstOrNull(response.headers(), RETRY_AFTER));
if (retryAfter != null) {
return new RetryableException(
response.status(),
exception.getMessage(),
response.request().httpMethod(),
exception,
retryAfter);
}
return exception;
}
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private <T> T firstOrNull(Map<String, Collection<T>> map, String key) {
if (map.containsKey(key) && !map.get(key).isEmpty()) {
return map.get(key).iterator().next();
}
return null;
}
}
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static class RetryAfterDecoder {
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static final DateFormat RFC822_FORMAT =
new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss 'GMT'", US);
private final DateFormat rfc822Format;
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RetryAfterDecoder() {
this(RFC822_FORMAT);
}
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RetryAfterDecoder(DateFormat rfc822Format) {
this.rfc822Format = checkNotNull(rfc822Format, "rfc822Format");
}
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protected long currentTimeMillis() {
return System.currentTimeMillis();
}
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/**
* returns a date that corresponds to the first time a request can be retried.
*
* @param retryAfter String in
* <a href="https://tools.ietf.org/html/rfc2616#section-14.37" >Retry-After format</a>
*/
public Date apply(String retryAfter) {
if (retryAfter == null) {
return null;
}
if (retryAfter.matches("^[0-9]+$")) {
long deltaMillis = SECONDS.toMillis(Long.parseLong(retryAfter));
return new Date(currentTimeMillis() + deltaMillis);
}
synchronized (rfc822Format) {
try {
return rfc822Format.parse(retryAfter);
} catch (ParseException ignored) {
return null;
}
}
}
}
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//......
}
  • ErrorDecoder提供了Default的默认实现,其decode方法会使用RetryAfterDecoder来计算retryAfter值,在该值不为null时会返回RetryableException;RetryAfterDecoder的apply方法会根据retryAfter来计算retryAfter日期,该retryAfter参数是从response的名为Retry-After的header读取而来

小结

  • Retryer继承了Cloneable接口,它定义了continueOrPropagate、clone方法;它内置了一个名为Default以及名为NEVER_RETRY的实现
  • Default有period、maxPeriod、maxAttempts参数可以设置,默认构造器使用的period为100,maxPeriod为1000,maxAttempts为5;continueOrPropagate方法首先判断attempt是否达到阈值,达到则抛出异常,否则进一步计算interval,然后进行sleep
  • NEVER_RETRY的continueOrPropagate直接抛出异常,而clone方法直接返回当前实例

doc

  • Retryer