Implement failover for singleServer with failover

src/main/java/com/arangodb/internal/http/HttpCommunication.java

@@ -40,6 +40,8 @@
  */
 public class HttpCommunication {
 
+private static final int ERROR_REDIRECT = 307;
+
 public static class Builder {
 
 private final HostHandler hostHandler;
@@ -120,7 +122,18 @@ public void disconnect() throws IOException {
 
 public Response execute(final Request request, final HostHandle hostHandle, final boolean closeConnection)
 throws ArangoDBException, IOException {
-return execute(request, connectionPool.connection(hostHandle), closeConnection);
+final HttpConnection connection = connectionPool.connection(hostHandle);
+try {
+return execute(request, connection, closeConnection);
+} catch (final ArangoDBException e) {
+final Integer responseCode = e.getResponseCode();
+if (responseCode != null && responseCode == ERROR_REDIRECT) {
+connectionPool.closeConnectionOnError(connection);
+return execute(request, hostHandle, closeConnection);
+} else {
+throw e;
+}
+}
 }
 
 protected Response execute(final Request request, final HttpConnection connection, final boolean closeConnection)

src/main/java/com/arangodb/internal/http/HttpConnection.java

@@ -175,9 +175,18 @@ public void close() throws IOException {
 client.close();
 }
 
+@Override
+public void closeOnError() throws IOException {
+hostHandler.fail();
+close();
+}
+
 public Response execute(final Request request) throws ArangoDBException, IOException {
 host = hostHandler.get();
 while (true) {
+if (host == null) {
+throw new ArangoDBException("Was not able to connect to any host");
+}
 try {
 final String url = buildUrl(buildBaseUrl(host), request);
 final HttpRequestBase httpRequest = buildHttpRequestBase(request, url);

src/main/java/com/arangodb/internal/net/Connection.java

@@ -21,6 +21,7 @@
 package com.arangodb.internal.net;
 
 import java.io.Closeable;
+import java.io.IOException;
 
 import com.arangodb.internal.Host;
 
@@ -32,4 +33,6 @@ public interface Connection extends Closeable {
 
 Host getHost();
 
+void closeOnError() throws IOException;
+
 }

src/main/java/com/arangodb/internal/net/ConnectionPool.java

@@ -23,6 +23,7 @@
 import java.io.IOException;
 import java.util.LinkedList;
 
+import com.arangodb.ArangoDBException;
 import com.arangodb.internal.Host;
 
 /**
@@ -75,4 +76,21 @@ public void disconnect() throws IOException {
 }
 }
 
+public void closeConnection(final C connection) {
+try {
+connection.close();
+connections.remove(connection);
+} catch (final IOException e) {
+throw new ArangoDBException(e);
+}
+}
+
+public void closeConnectionOnError(final C connection) {
+try {
+connection.closeOnError();
+connections.remove(connection);
+} catch (final IOException e) {
+throw new ArangoDBException(e);
+}
+}
 }

src/main/java/com/arangodb/internal/velocystream/VstCommunication.java

@@ -51,6 +51,7 @@
 public abstract class VstCommunication<R, C extends VstConnection> {
 
 private static final int ERROR_STATUS = 300;
+private static final int ERROR_REDIRECT = 307;
 
 private static final Logger LOGGER = LoggerFactory.getLogger(VstCommunication.class);
 
@@ -95,7 +96,18 @@ public void disconnect() throws IOException {
 
 public R execute(final Request request, final HostHandle hostHandle, final boolean closeConnection)
 throws ArangoDBException {
-return execute(request, connectionPool.connection(hostHandle), closeConnection);
+final C connection = connectionPool.connection(hostHandle);
+try {
+return execute(request, connection, closeConnection);
+} catch (final ArangoDBException e) {
+final Integer responseCode = e.getResponseCode();
+if (responseCode != null && responseCode == ERROR_REDIRECT) {
+connectionPool.closeConnectionOnError(connection);
+return execute(request, hostHandle, closeConnection);
+} else {
+throw e;
+}
+}
 }
 
 protected abstract R execute(final Request request, C connection, boolean closeConnection) throws ArangoDBException;
@@ -116,10 +128,10 @@ protected void checkError(final Response response) throws ArangoDBException {
 }
 }
 
-protected Response createResponse(final Message messsage) throws VPackParserException {
-final Response response = util.deserialize(messsage.getHead(), Response.class);
-if (messsage.getBody() != null) {
-response.setBody(messsage.getBody());
+protected Response createResponse(final Message message) throws VPackParserException {
+final Response response = util.deserialize(message.getHead(), Response.class);
+if (message.getBody() != null) {
+response.setBody(message.getBody());
 }
 return response;
 }

src/main/java/com/arangodb/internal/velocystream/internal/VstConnection.java

@@ -96,6 +96,9 @@ public synchronized void open() throws IOException {
 }
 host = hostHandler.get();
 while (true) {
+if (host == null) {
+throw new ArangoDBException("Was not able to connect to any host");
+}
 if (LOGGER.isDebugEnabled()) {
 LOGGER.debug(String.format("Open connection to %s", host));
 }
@@ -190,6 +193,12 @@ public synchronized void close() {
 }
 }
 
+@Override
+public synchronized void closeOnError() {
+hostHandler.fail();
+close();
+}
+
 private synchronized void sendProtocolHeader() throws IOException {
 if (LOGGER.isDebugEnabled()) {
 LOGGER.debug(String.format("Send velocystream protocol header to %s", socket));