apache的HttpClient的默认重试机制
maven
<dependency>
<groupId>org.apache.httpcomponentsgroupId>
<artifactId>httpclientartifactId>
<version>4.5.2version>
dependency>异常重试log
2017-01-31 19:31:39.057 INFO 3873 --- [askScheduler-13] o.apache.http.impl.execchain.RetryExec : I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {}->http://192.168.99.100:8080: The target server failed to respond
2017-01-31 19:31:39.058 INFO 3873 --- [askScheduler-13] o.apache.http.impl.execchain.RetryExec : Retrying request to {}->http://192.168.99.100:8080RetryExec
org/apache/http/impl/execchain/RetryExec.java
/**
* Request executor in the request execution chain that is responsible
* for making a decision whether a request failed due to an I/O error
* should be re-executed.
*
* Further responsibilities such as communication with the opposite
* endpoint is delegated to the next executor in the request execution
* chain.
*
*
* @since 4.3
*/
@Immutable
public class RetryExec implements ClientExecChain {
private final Log log = LogFactory.getLog(getClass());
private final ClientExecChain requestExecutor;
private final HttpRequestRetryHandler retryHandler;
public RetryExec(
final ClientExecChain requestExecutor,
final HttpRequestRetryHandler retryHandler) {
Args.notNull(requestExecutor, "HTTP request executor");
Args.notNull(retryHandler, "HTTP request retry handler");
this.requestExecutor = requestExecutor;
this.retryHandler = retryHandler;
}
@Override
public CloseableHttpResponse execute(
final HttpRoute route,
final HttpRequestWrapper request,
final HttpClientContext context,
final HttpExecutionAware execAware) throws IOException, HttpException {
Args.notNull(route, "HTTP route");
Args.notNull(request, "HTTP request");
Args.notNull(context, "HTTP context");
final Header[] origheaders = request.getAllHeaders();
for (int execCount = 1;; execCount++) {
try {
return this.requestExecutor.execute(route, request, context, execAware);
} catch (final IOException ex) {
if (execAware != null && execAware.isAborted()) {
this.log.debug("Request has been aborted");
throw ex;
}
if (retryHandler.retryRequest(ex, execCount, context)) {
if (this.log.isInfoEnabled()) {
this.log.info("I/O exception ("+ ex.getClass().getName() +
") caught when processing request to "
+ route +
": "
+ ex.getMessage());
}
if (this.log.isDebugEnabled()) {
this.log.debug(ex.getMessage(), ex);
}
if (!RequestEntityProxy.isRepeatable(request)) {
this.log.debug("Cannot retry non-repeatable request");
throw new NonRepeatableRequestException("Cannot retry request " +
"with a non-repeatable request entity", ex);
}
request.setHeaders(origheaders);
if (this.log.isInfoEnabled()) {
this.log.info("Retrying request to " + route);
}
} else {
if (ex instanceof NoHttpResponseException) {
final NoHttpResponseException updatedex = new NoHttpResponseException(
route.getTargetHost().toHostString() + " failed to respond");
updatedex.setStackTrace(ex.getStackTrace());
throw updatedex;
} else {
throw ex;
}
}
}
}
}
}DefaultHttpRequestRetryHandler
org/apache/http/impl/client/DefaultHttpRequestRetryHandler.java
/**
* The default {@link HttpRequestRetryHandler} used by request executors.
*
* @since 4.0
*/
@Immutable
public class DefaultHttpRequestRetryHandler implements HttpRequestRetryHandler {
public static final DefaultHttpRequestRetryHandler INSTANCE = new DefaultHttpRequestRetryHandler();
/** the number of times a method will be retried */
private final int retryCount;
/** Whether or not methods that have successfully sent their request will be retried */
private final boolean requestSentRetryEnabled;
private final Setextends IOException>> nonRetriableClasses;
/**
* Create the request retry handler using the specified IOException classes
*
* @param retryCount how many times to retry; 0 means no retries
* @param requestSentRetryEnabled true if it's OK to retry requests that have been sent
* @param clazzes the IOException types that should not be retried
* @since 4.3
*/
protected DefaultHttpRequestRetryHandler(
final int retryCount,
final boolean requestSentRetryEnabled,
final Collectionextends IOException>> clazzes) {
super();
this.retryCount = retryCount;
this.requestSentRetryEnabled = requestSentRetryEnabled;
this.nonRetriableClasses = new HashSetextends IOException>>();
for (final Classextends IOException> clazz: clazzes) {
this.nonRetriableClasses.add(clazz);
}
}
/**
* Create the request retry handler using the following list of
* non-retriable IOException classes:
*
* - InterruptedIOException
* - UnknownHostException
* - ConnectException
* - SSLException
*
* @param retryCount how many times to retry; 0 means no retries
* @param requestSentRetryEnabled true if it's OK to retry non-idempotent requests that have been sent
*/
@SuppressWarnings("unchecked")
public DefaultHttpRequestRetryHandler(final int retryCount, final boolean requestSentRetryEnabled) {
this(retryCount, requestSentRetryEnabled, Arrays.asList(
InterruptedIOException.class,
UnknownHostException.class,
ConnectException.class,
SSLException.class));
}
/**
* Create the request retry handler with a retry count of 3, requestSentRetryEnabled false
* and using the following list of non-retriable IOException classes:
*
* - InterruptedIOException
* - UnknownHostException
* - ConnectException
* - SSLException
*
*/
public DefaultHttpRequestRetryHandler() {
this(3, false);
}
/**
* Used {@code retryCount} and {@code requestSentRetryEnabled} to determine
* if the given method should be retried.
*/
@Override
public boolean retryRequest(
final IOException exception,
final int executionCount,
final HttpContext context) {
Args.notNull(exception, "Exception parameter");
Args.notNull(context, "HTTP context");
if (executionCount > this.retryCount) {
// Do not retry if over max retry count
return false;
}
if (this.nonRetriableClasses.contains(exception.getClass())) {
return false;
} else {
for (final Classextends IOException> rejectException : this.nonRetriableClasses) {
if (rejectException.isInstance(exception)) {
return false;
}
}
}
final HttpClientContext clientContext = HttpClientContext.adapt(context);
final HttpRequest request = clientContext.getRequest();
if(requestIsAborted(request)){
return false;
}
if (handleAsIdempotent(request)) {
// Retry if the request is considered idempotent
return true;
}
if (!clientContext.isRequestSent() || this.requestSentRetryEnabled) {
// Retry if the request has not been sent fully or
// if it's OK to retry methods that have been sent
return true;
}
// otherwise do not retry
return false;
}
/**
* @return {@code true} if this handler will retry methods that have
* successfully sent their request, {@code false} otherwise
*/
public boolean isRequestSentRetryEnabled() {
return requestSentRetryEnabled;
}
/**
* @return the maximum number of times a method will be retried
*/
public int getRetryCount() {
return retryCount;
}
/**
* @since 4.2
*/
protected boolean handleAsIdempotent(final HttpRequest request) {
return !(request instanceof HttpEntityEnclosingRequest);
}
/**
* @since 4.2
*
* @deprecated (4.3)
*/
@Deprecated
protected boolean requestIsAborted(final HttpRequest request) {
HttpRequest req = request;
if (request instanceof RequestWrapper) { // does not forward request to original
req = ((RequestWrapper) request).getOriginal();
}
return (req instanceof HttpUriRequest && ((HttpUriRequest)req).isAborted());
}
} 默认重试3次，三次都失败则抛出NoHttpResponseException或其他异常
doc
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Apache HttpComponents