HADOOP-17337. S3A NetworkBinding has a runtime dependency on shaded httpclient. (#2599)

Contributed by Steve Loughran.

Change-Id: I0471322fc88d8bc3896ac439aefb31e6a856936c

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/impl/ConfigureShadedAWSSocketFactory.java

@@ -0,0 +1,47 @@
+/*
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.fs.s3a.impl;
+
+import javax.net.ssl.HostnameVerifier;
+import java.io.IOException;
+
+import com.amazonaws.ClientConfiguration;
+import com.amazonaws.thirdparty.apache.http.conn.ssl.SSLConnectionSocketFactory;
+
+import org.apache.hadoop.security.ssl.DelegatingSSLSocketFactory;
+
+/**
+ * This interacts with the Shaded httpclient library used in the full
+ * AWS SDK. If the S3A client is used with the unshaded SDK, this
+ * class will not link.
+ */
+public class ConfigureShadedAWSSocketFactory implements
+    NetworkBinding.ConfigureAWSSocketFactory {
+
+  @Override
+  public void configureSocketFactory(final ClientConfiguration awsConf,
+      final DelegatingSSLSocketFactory.SSLChannelMode channelMode)
+      throws IOException {
+    DelegatingSSLSocketFactory.initializeDefaultFactory(channelMode);
+    awsConf.getApacheHttpClientConfig().setSslSocketFactory(
+        new SSLConnectionSocketFactory(
+            DelegatingSSLSocketFactory.getDefaultFactory(),
+            (HostnameVerifier) null));
+  }
+}

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/impl/NetworkBinding.java

@@ -19,14 +19,10 @@
 package org.apache.hadoop.fs.s3a.impl;
 
 import java.io.IOException;
-import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 import java.net.URI;
 import java.net.URISyntaxException;
 
-import javax.net.ssl.HostnameVerifier;
-import javax.net.ssl.SSLSocketFactory;
-
 import com.amazonaws.ClientConfiguration;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -43,20 +39,21 @@ import static org.apache.hadoop.fs.s3a.Constants.SSL_CHANNEL_MODE;
 /**
  * Configures network settings when communicating with AWS services.
  */
-public class NetworkBinding {
+public final class NetworkBinding {
 
   private static final Logger LOG =
           LoggerFactory.getLogger(NetworkBinding.class);
-  private static final String AWS_SOCKET_FACTORY_CLASSNAME = "com.amazonaws" +
-          ".thirdparty.apache.http.conn.ssl.SSLConnectionSocketFactory";
+  private static final String BINDING_CLASSNAME = "org.apache.hadoop.fs.s3a.impl.ConfigureShadedAWSSocketFactory";
+
+  private NetworkBinding() {
+  }
 
   /**
    * Configures the {@code SSLConnectionSocketFactory} used by the AWS SDK.
    * A custom Socket Factory can be set using the method
    * {@code setSslSocketFactory()}.
-   * If {@code SSLConnectionSocketFactory} cannot be found on the classpath, the value
-   * of {@link org.apache.hadoop.fs.s3a.Constants#SSL_CHANNEL_MODE} is ignored.
-   *
+   * Uses reflection to do this via {@link ConfigureShadedAWSSocketFactory}
+   * so as to avoid 
    * @param conf the {@link Configuration} used to get the client specified
    *             value of {@code SSL_CHANNEL_MODE}
    * @param awsConf the {@code ClientConfiguration} to set the
@@ -84,28 +81,33 @@ public class NetworkBinding {
 
     DelegatingSSLSocketFactory.initializeDefaultFactory(channelMode);
     try {
-      // Look for AWS_SOCKET_FACTORY_CLASSNAME on the classpath and instantiate
-      // an instance using the DelegatingSSLSocketFactory as the
-      // SSLSocketFactory.
-      Class<?> sslConnectionSocketFactory = Class.forName(
-              AWS_SOCKET_FACTORY_CLASSNAME);
-      Constructor<?> factoryConstructor =
-              sslConnectionSocketFactory.getDeclaredConstructor(
-                      SSLSocketFactory.class, HostnameVerifier.class);
-      awsConf.getApacheHttpClientConfig().setSslSocketFactory(
-              (com.amazonaws.thirdparty.apache.http.conn.ssl.
-                      SSLConnectionSocketFactory) factoryConstructor
-                      .newInstance(DelegatingSSLSocketFactory
-                                      .getDefaultFactory(),
-                              (HostnameVerifier) null));
+      // use reflection to load in our own binding class.
+      // this is *probably* overkill, but it is how we can be fully confident
+      // that no attempt will be made to load/link to the AWS Shaded SDK except
+      // within this try/catch block
+      Class<? extends ConfigureAWSSocketFactory> clazz =
+          (Class<? extends ConfigureAWSSocketFactory>) Class.forName(BINDING_CLASSNAME);
+      clazz.getConstructor()
+          .newInstance()
+          .configureSocketFactory(awsConf, channelMode);
     } catch (ClassNotFoundException | NoSuchMethodException |
             IllegalAccessException | InstantiationException |
             InvocationTargetException | LinkageError  e) {
       LOG.debug("Unable to create class {}, value of {} will be ignored",
-              AWS_SOCKET_FACTORY_CLASSNAME, SSL_CHANNEL_MODE, e);
+          BINDING_CLASSNAME, SSL_CHANNEL_MODE, e);
     }
   }
 
+  /**
+   * Interface used to bind to the socket factory, allows the code which
+   * works with the shaded AWS libraries to exist in their own class.
+   */
+  interface ConfigureAWSSocketFactory {
+    void configureSocketFactory(ClientConfiguration awsConf,
+        DelegatingSSLSocketFactory.SSLChannelMode channelMode)
+        throws IOException;
+  }
+
   /**
    * Given an S3 bucket region as returned by a bucket location query,
    * fix it into a form which can be used by other AWS commands.