review refactors: apachehttpclient (#17)

pr: #17

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/AbfsConfiguration.java

@@ -395,7 +395,7 @@ public class AbfsConfiguration{
   private int maxApacheHttpClientIoExceptionsRetries;
 
   @IntegerConfigurationValidatorAnnotation(ConfigurationKey = FS_AZURE_APACHE_HTTP_CLIENT_MAX_CACHE_CONNECTION_SIZE,
-      DefaultValue = DEFAULT_HTTP_CLIENT_CONN_MAX_IDLE_CONNECTIONS)
+      DefaultValue = DEFAULT_HTTP_CLIENT_CONN_MAX_CACHED_CONNECTIONS)
   private int maxApacheHttpClientCacheConnections;
 
   @LongConfigurationValidatorAnnotation(ConfigurationKey = FS_AZURE_APACHE_HTTP_CLIENT_IDLE_CONNECTION_TTL,

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/constants/AbfsHttpConstants.java

@@ -165,9 +165,12 @@ public static ApiVersion getCurrentVersion() {
    */
   public static final Integer HTTP_STATUS_CATEGORY_QUOTIENT = 100;
 
+  /**
+   * System property that define maximum number of cached-connection per fileSystem for
+   * ApacheHttpClient. JDK network library uses the same property to define maximum
+   * number of cached-connections at JVM level.
+   */
   public static final String HTTP_MAX_CONN_SYS_PROP = "http.maxConnections";
-  public static final Integer DEFAULT_MAX_CONN_SYS_PROP = 5;
-  public static final int KAC_DEFAULT_CONN_TTL = 5_000;
   public static final String JDK_IMPL = "JDK";
   public static final String APACHE_IMPL = "Apache";
   public static final String JDK_FALLBACK = "JDK_fallback";

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/constants/ConfigurationKeys.java

@@ -319,10 +319,17 @@ public static String accountProperty(String property, String account) {
    * @see FileSystem#openFile(org.apache.hadoop.fs.Path)
    */
   public static final String FS_AZURE_BUFFERED_PREAD_DISABLE = "fs.azure.buffered.pread.disable";
-  /**Defines what network library to use for server IO calls {@value }*/
+  /**Defines what network library to use for server IO calls: {@value}*/
   public static final String FS_AZURE_NETWORKING_LIBRARY = "fs.azure.networking.library";
+  /**
+   * Maximum number of IOExceptions retries for a single server call on ApacheHttpClient.
+   * Breach of this count would turn off future uses of the ApacheHttpClient library
+   * in the JVM lifecycle: {@value}
+   */
   public static final String FS_AZURE_APACHE_HTTP_CLIENT_MAX_IO_EXCEPTION_RETRIES = "fs.azure.apache.http.client.max.io.exception.retries";
+  /**Maximum ApacheHttpClient-connection cache size at filesystem level: {@value}*/
   public static final String FS_AZURE_APACHE_HTTP_CLIENT_MAX_CACHE_CONNECTION_SIZE = "fs.azure.apache.http.client.max.cache.connection.size";
+  /**Maximum idle time for a ApacheHttpClient-connection: {@value}*/
   public static final String FS_AZURE_APACHE_HTTP_CLIENT_IDLE_CONNECTION_TTL = "fs.azure.apache.http.client.idle.connection.ttl";
   private ConfigurationKeys() {}
 }

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/constants/FileSystemConfigurations.java

@@ -174,7 +174,7 @@ public final class FileSystemConfigurations {
 
   public static final long DEFAULT_HTTP_CLIENT_CONN_MAX_IDLE_TIME = 5_000L;
 
-  public static final int DEFAULT_HTTP_CLIENT_CONN_MAX_IDLE_CONNECTIONS = 5;
+  public static final int DEFAULT_HTTP_CLIENT_CONN_MAX_CACHED_CONNECTIONS = 5;
 
   private FileSystemConfigurations() {}
 }

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/contracts/exceptions/AbfsApacheHttpExpect100Exception.java

@@ -18,19 +18,17 @@
 
 package org.apache.hadoop.fs.azurebfs.contracts.exceptions;
 
-import java.io.IOException;
-
 import org.apache.http.HttpResponse;
 
-public class AbfsApacheHttpExpect100Exception extends IOException {
-  private final HttpResponse httpResponse;
+import static org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.EXPECT_100_JDK_ERROR;
 
-  public AbfsApacheHttpExpect100Exception(final String s, final HttpResponse httpResponse) {
-    super(s);
-    this.httpResponse = httpResponse;
-  }
+/**
+ * Exception that marks expect100 handshake error. This exception is thrown when
+ * the expect100 handshake fails with ADLS server sending 4xx or 5xx status code.
+ */
+public class AbfsApacheHttpExpect100Exception extends HttpResponseException {
 
-  public HttpResponse getHttpResponse() {
-    return httpResponse;
+  public AbfsApacheHttpExpect100Exception(final HttpResponse httpResponse) {
+    super(EXPECT_100_JDK_ERROR, httpResponse);
   }
 }

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/contracts/exceptions/HttpResponseException.java

@@ -0,0 +1,22 @@
+package org.apache.hadoop.fs.azurebfs.contracts.exceptions;
+
+import java.io.IOException;
+import java.util.Objects;
+
+import org.apache.http.HttpResponse;
+
+/**
+ * Encapsulates an exception thrown from ApacheHttpClient response parsing.
+ */
+public class HttpResponseException extends IOException {
+  protected final HttpResponse httpResponse;
+  public HttpResponseException(final String s, final HttpResponse httpResponse) {
+    super(s);
+    Objects.requireNonNull(httpResponse, "httpResponse should be non-null");
+    this.httpResponse = httpResponse;
+  }
+
+  public HttpResponse getHttpResponse() {
+    return httpResponse;
+  }
+}