Java tutorial
package org.apache.hadoop.gateway.rm.dispatch; /** * 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. */ import org.apache.hadoop.gateway.dispatch.DefaultDispatch; import org.apache.hadoop.gateway.filter.AbstractGatewayFilter; import org.apache.hadoop.gateway.ha.provider.HaProvider; import org.apache.hadoop.gateway.ha.provider.impl.HaServiceConfigConstants; import org.apache.hadoop.gateway.i18n.messages.MessagesFactory; import org.apache.hadoop.gateway.rm.i18n.RMMessages; 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.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; class RMHaBaseDispatcher extends DefaultDispatch { private static final String FAILOVER_COUNTER_ATTRIBUTE = "dispatch.ha.failover.counter"; private static final String RETRY_COUNTER_ATTRIBUTE = "dispatch.ha.retry.counter"; private static final String LOCATION = "Location"; private static final RMMessages LOG = MessagesFactory.get(RMMessages.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 String resourceRole = null; private HttpResponse inboundResponse = null; /** * * @return HttpReponse used for unit testing so we * can inject inboundResponse before calling executeRequest method */ private HttpResponse getInboundResponse() { HttpResponse response = this.inboundResponse; this.setInboundResponse(null); return response; } void setInboundResponse(HttpResponse inboundResponse) { this.inboundResponse = inboundResponse; } void setHaProvider(HaProvider haProvider) { this.haProvider = haProvider; } private HaProvider haProvider; void setMaxFailoverAttempts(int maxFailoverAttempts) { this.maxFailoverAttempts = maxFailoverAttempts; } void setFailoverSleep(int failoverSleep) { this.failoverSleep = failoverSleep; } void setMaxRetryAttempts(int maxRetryAttempts) { this.maxRetryAttempts = maxRetryAttempts; } void setRetrySleep(int retrySleep) { this.retrySleep = retrySleep; } void setResourceRole(String resourceRole) { this.resourceRole = resourceRole; } @Override protected void executeRequest(HttpUriRequest outboundRequest, HttpServletRequest inboundRequest, HttpServletResponse outboundResponse) throws IOException { HttpResponse inboundResponse = this.getInboundResponse(); try { if (this.getInboundResponse() == null) { 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 { int status = inboundResponse.getStatusLine().getStatusCode(); if (status == 403 || status == 307) { 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("This is standby RM")) { 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()); URI uri; String outboundURIs; AtomicInteger counter = (AtomicInteger) inboundRequest.getAttribute(FAILOVER_COUNTER_ATTRIBUTE); if (counter == null) { counter = new AtomicInteger(0); } inboundRequest.setAttribute(FAILOVER_COUNTER_ATTRIBUTE, counter); outboundURIs = outboundRequest.getURI().toString(); if (counter.incrementAndGet() <= maxFailoverAttempts) { //null out target url so that rewriters run again inboundRequest.setAttribute(AbstractGatewayFilter.TARGET_REQUEST_URL_ATTRIBUTE_NAME, null); uri = getUriFromInbound(inboundRequest, inboundResponse, outboundURIs); ((HttpRequestBase) outboundRequest).setURI(uri); if (failoverSleep > 0) { try { Thread.sleep(failoverSleep); } catch (InterruptedException e) { LOG.failoverSleepFailed(this.resourceRole, e); } } executeRequest(outboundRequest, inboundRequest, outboundResponse); } else { LOG.maxFailoverAttemptsReached(maxFailoverAttempts, this.resourceRole); if (inboundResponse != null) { writeOutboundResponse(outboundRequest, inboundRequest, outboundResponse, inboundResponse); } else { throw new IOException(exception); } } } URI getUriFromInbound(HttpServletRequest inboundRequest, HttpResponse inboundResponse, String outboundURIs) { URI uri; if (outboundURIs != null) { markFailedURL(outboundURIs); } try { if (inboundResponse != null) { // We get redirection URI, failover condition we don't // need to consult list of host. String host = inboundResponse.getFirstHeader(LOCATION).getValue(); LOG.failoverRedirect(host); uri = URI.create(host); } else { // inboundRequest was null previous active node is down // get next URI in list to try. uri = getDispatchUrl(inboundRequest); } } catch (Exception ex) { uri = getDispatchUrl(inboundRequest); } haProvider.setActiveURL(this.resourceRole, uri.toString()); return uri; } private void markFailedURL(String outboundURIs) { haProvider.markFailedURL(this.resourceRole, outboundURIs); } 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(this.resourceRole, e); } } executeRequest(outboundRequest, inboundRequest, outboundResponse); } else { LOG.maxRetryAttemptsReached(maxRetryAttempts, this.resourceRole, outboundRequest.getURI().toString()); if (inboundResponse != null) { writeOutboundResponse(outboundRequest, inboundRequest, outboundResponse, inboundResponse); } else { throw new IOException(exception); } } } }