Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * <p/> * http://www.apache.org/licenses/LICENSE-2.0 * <p/> * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.hadoop.gateway.hdfs.dispatch; import org.apache.hadoop.gateway.config.Configure; import org.apache.hadoop.gateway.filter.AbstractGatewayFilter; import org.apache.hadoop.gateway.ha.provider.HaProvider; import org.apache.hadoop.gateway.ha.provider.HaServiceConfig; import org.apache.hadoop.gateway.ha.provider.impl.HaServiceConfigConstants; import org.apache.hadoop.gateway.hdfs.i18n.WebHdfsMessages; import org.apache.hadoop.gateway.i18n.messages.MessagesFactory; import org.apache.http.HttpResponse; import org.apache.http.client.methods.HttpRequestBase; import org.apache.http.client.methods.HttpUriRequest; import org.apache.http.entity.BufferedHttpEntity; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.net.URI; import java.util.concurrent.atomic.AtomicInteger; public class WebHdfsHaDispatch extends HdfsHttpClientDispatch { private static final String FAILOVER_COUNTER_ATTRIBUTE = "dispatch.ha.failover.counter"; private static final String RETRY_COUNTER_ATTRIBUTE = "dispatch.ha.retry.counter"; public static final String RESOURCE_ROLE = "WEBHDFS"; private static final WebHdfsMessages LOG = MessagesFactory.get(WebHdfsMessages.class); private int maxFailoverAttempts = HaServiceConfigConstants.DEFAULT_MAX_FAILOVER_ATTEMPTS; private int failoverSleep = HaServiceConfigConstants.DEFAULT_FAILOVER_SLEEP; private int maxRetryAttempts = HaServiceConfigConstants.DEFAULT_MAX_RETRY_ATTEMPTS; private int retrySleep = HaServiceConfigConstants.DEFAULT_RETRY_SLEEP; private HaProvider haProvider; /** * @throws javax.servlet.ServletException */ public WebHdfsHaDispatch() throws ServletException { super(); } @Override public void init() { super.init(); if (haProvider != null) { HaServiceConfig serviceConfig = haProvider.getHaDescriptor().getServiceConfig(RESOURCE_ROLE); maxFailoverAttempts = serviceConfig.getMaxFailoverAttempts(); failoverSleep = serviceConfig.getFailoverSleep(); maxRetryAttempts = serviceConfig.getMaxRetryAttempts(); retrySleep = serviceConfig.getRetrySleep(); } } public HaProvider getHaProvider() { return haProvider; } @Configure public void setHaProvider(HaProvider haProvider) { this.haProvider = haProvider; } @Override protected void executeRequest(HttpUriRequest outboundRequest, HttpServletRequest inboundRequest, HttpServletResponse outboundResponse) throws IOException { HttpResponse inboundResponse = null; try { inboundResponse = executeOutboundRequest(outboundRequest); writeOutboundResponse(outboundRequest, inboundRequest, outboundResponse, inboundResponse); } catch (StandbyException e) { LOG.errorReceivedFromStandbyNode(e); failoverRequest(outboundRequest, inboundRequest, outboundResponse, inboundResponse, e); } catch (SafeModeException e) { LOG.errorReceivedFromSafeModeNode(e); retryRequest(outboundRequest, inboundRequest, outboundResponse, inboundResponse, e); } catch (IOException e) { LOG.errorConnectingToServer(outboundRequest.getURI().toString(), e); failoverRequest(outboundRequest, inboundRequest, outboundResponse, inboundResponse, e); } } /** * Checks for specific outbound response codes/content to trigger a retry or failover */ @Override protected void writeOutboundResponse(HttpUriRequest outboundRequest, HttpServletRequest inboundRequest, HttpServletResponse outboundResponse, HttpResponse inboundResponse) throws IOException { if (inboundResponse.getStatusLine().getStatusCode() == 403) { BufferedHttpEntity entity = new BufferedHttpEntity(inboundResponse.getEntity()); inboundResponse.setEntity(entity); ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); inboundResponse.getEntity().writeTo(outputStream); String body = new String(outputStream.toByteArray()); if (body.contains("StandbyException")) { throw new StandbyException(); } if (body.contains("SafeModeException") || body.contains("RetriableException")) { throw new SafeModeException(); } } super.writeOutboundResponse(outboundRequest, inboundRequest, outboundResponse, inboundResponse); } private void failoverRequest(HttpUriRequest outboundRequest, HttpServletRequest inboundRequest, HttpServletResponse outboundResponse, HttpResponse inboundResponse, Exception exception) throws IOException { LOG.failingOverRequest(outboundRequest.getURI().toString()); AtomicInteger counter = (AtomicInteger) inboundRequest.getAttribute(FAILOVER_COUNTER_ATTRIBUTE); if (counter == null) { counter = new AtomicInteger(0); } inboundRequest.setAttribute(FAILOVER_COUNTER_ATTRIBUTE, counter); if (counter.incrementAndGet() <= maxFailoverAttempts) { haProvider.markFailedURL(RESOURCE_ROLE, outboundRequest.getURI().toString()); //null out target url so that rewriters run again inboundRequest.setAttribute(AbstractGatewayFilter.TARGET_REQUEST_URL_ATTRIBUTE_NAME, null); URI uri = getDispatchUrl(inboundRequest); ((HttpRequestBase) outboundRequest).setURI(uri); if (failoverSleep > 0) { try { Thread.sleep(failoverSleep); } catch (InterruptedException e) { LOG.failoverSleepFailed(RESOURCE_ROLE, e); } } executeRequest(outboundRequest, inboundRequest, outboundResponse); } else { LOG.maxFailoverAttemptsReached(maxFailoverAttempts, RESOURCE_ROLE); if (inboundResponse != null) { writeOutboundResponse(outboundRequest, inboundRequest, outboundResponse, inboundResponse); } else { throw new IOException(exception); } } } private void retryRequest(HttpUriRequest outboundRequest, HttpServletRequest inboundRequest, HttpServletResponse outboundResponse, HttpResponse inboundResponse, Exception exception) throws IOException { LOG.retryingRequest(outboundRequest.getURI().toString()); AtomicInteger counter = (AtomicInteger) inboundRequest.getAttribute(RETRY_COUNTER_ATTRIBUTE); if (counter == null) { counter = new AtomicInteger(0); } inboundRequest.setAttribute(RETRY_COUNTER_ATTRIBUTE, counter); if (counter.incrementAndGet() <= maxRetryAttempts) { if (retrySleep > 0) { try { Thread.sleep(retrySleep); } catch (InterruptedException e) { LOG.retrySleepFailed(RESOURCE_ROLE, e); } } executeRequest(outboundRequest, inboundRequest, outboundResponse); } else { LOG.maxRetryAttemptsReached(maxRetryAttempts, RESOURCE_ROLE, outboundRequest.getURI().toString()); if (inboundResponse != null) { writeOutboundResponse(outboundRequest, inboundRequest, outboundResponse, inboundResponse); } else { throw new IOException(exception); } } } }