Addressed comments

Author: bhattmanish98

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

@@ -203,6 +203,10 @@ public class AbfsConfiguration{
           DefaultValue = DEFAULT_HTTP_READ_TIMEOUT)
   private int httpReadTimeout;
 
+  @IntegerConfigurationValidatorAnnotation(ConfigurationKey = AZURE_EXPECT_100CONTINUE_WAIT_TIMEOUT,
+          DefaultValue = DEFAULT_EXPECT_100CONTINUE_WAIT_TIMEOUT)
+  private int expect100ContinueWaitTimeout;
+
   @IntegerConfigurationValidatorAnnotation(ConfigurationKey = AZURE_OAUTH_TOKEN_FETCH_RETRY_COUNT,
       MinValue = 0,
       DefaultValue = DEFAULT_AZURE_OAUTH_TOKEN_FETCH_RETRY_MAX_ATTEMPTS)
@@ -1033,6 +1037,10 @@ public int getHttpReadTimeout() {
     return this.httpReadTimeout;
   }
 
+  public int getExpect100ContinueWaitTimeout() {
+    return this.expect100ContinueWaitTimeout;
+  }
+
   public long getAzureBlockSize() {
     return this.azureBlockSize;
   }

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

@@ -97,6 +97,13 @@ public final class ConfigurationKeys {
    */
   public static final String AZURE_HTTP_READ_TIMEOUT = "fs.azure.http.read.timeout";
 
+  /**
+   * Config to set HTTP Expect100-Continue Wait Timeout Value for Rest Operations.
+   * Value: {@value}.
+   */
+  public static final String AZURE_EXPECT_100CONTINUE_WAIT_TIMEOUT
+      = "fs.azure.http.expect.100continue.wait.timeout";
+
   //  Retry strategy for getToken calls
   public static final String AZURE_OAUTH_TOKEN_FETCH_RETRY_COUNT = "fs.azure.oauth.token.fetch.retry.max.retries";
   public static final String AZURE_OAUTH_TOKEN_FETCH_RETRY_MIN_BACKOFF = "fs.azure.oauth.token.fetch.retry.min.backoff.interval";

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

@@ -58,6 +58,12 @@ public final class FileSystemConfigurations {
    */
   public static final int DEFAULT_HTTP_READ_TIMEOUT = 30_000; // 30 secs
 
+  /**
+   * Default value of connection request timeout to be used when 100continue is enabled.
+   * Value: {@value}.
+   */
+  public static final int DEFAULT_EXPECT_100CONTINUE_WAIT_TIMEOUT = 3_000; // 3s
+
   // Retry parameter defaults.
   public static final int DEFAULT_AZURE_OAUTH_TOKEN_FETCH_RETRY_MAX_ATTEMPTS = 5;
   public static final int DEFAULT_AZURE_OAUTH_TOKEN_FETCH_RETRY_MIN_BACKOFF_INTERVAL = 0;

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

@@ -93,8 +93,14 @@ static boolean usable() {
     final HttpClientBuilder builder = HttpClients.custom();
     builder.setConnectionManager(connMgr)
         .setRequestExecutor(
+            // In case of Expect:100-continue, the timeout for waiting for
+            // the 100-continue response from the server is set using
+            // ExpectWaitContinueTimeout. For other requests, the read timeout
+            // is set using SocketTimeout.
             new AbfsManagedHttpRequestExecutor(
-                abfsConfiguration.getHttpReadTimeout()))
+                abfsConfiguration.isExpectHeaderEnabled()
+                    ? abfsConfiguration.getExpect100ContinueWaitTimeout()
+                    : abfsConfiguration.getHttpReadTimeout()))
         .disableContentCompression()
         .disableRedirectHandling()
         .disableAutomaticRetries()

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

@@ -257,6 +257,9 @@ private AbfsClient(final URL baseUrl,
         == HttpOperationType.APACHE_HTTP_CLIENT) {
       keepAliveCache = new KeepAliveCache(abfsConfiguration);
 
+      // Warm up the connection pool during client initialization to avoid latency during first request.
+      // Since for every filesystem instance, we create both DFS and Blob client instance,
+      // so warmup is done only for the default client.
       abfsApacheHttpClient = new AbfsApacheHttpClient(
           DelegatingSSLSocketFactory.getDefaultFactory(),
           abfsConfiguration, keepAliveCache, baseUrl,

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

@@ -68,6 +68,9 @@ public AbfsClientHandler(final URL baseUrl,
       final SASTokenProvider sasTokenProvider,
       final EncryptionContextProvider encryptionContextProvider,
       final AbfsClientContext abfsClientContext) throws IOException {
+    // This will initialize the default and ingress service types.
+    // This is needed before crating the clients so that we can do cache warmup
+    // only for default client.
     initServiceType(abfsConfiguration);
     this.dfsAbfsClient = createDfsClient(baseUrl, sharedKeyCredentials,
         abfsConfiguration, null, sasTokenProvider, encryptionContextProvider,

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

@@ -361,7 +361,7 @@ private int cacheExtraConnection(final HttpRoute route,
         } catch (RejectedExecutionException e) {
           LOG.debug("Task rejected for connection creation: {}",
               e.getMessage());
-          return 0;
+          return -1;
         }
       }
 

hadoop-tools/hadoop-azure/src/site/markdown/index.md

@@ -890,8 +890,8 @@ ABFS Driver can use the following networking libraries:
 The networking library can be configured using the configuration `fs.azure.networking.library`
 while initializing the filesystem.
 Following are the supported values:
-- `JDK_HTTP_URL_CONNECTION` : Use JDK networking library [Default]
-- `APACHE_HTTP_CLIENT` : Use Apache HttpClient
+- `JDK_HTTP_URL_CONNECTION` : Use JDK networking library
+- `APACHE_HTTP_CLIENT` : Use Apache HttpClient [Default]
 
 #### <a href="ahc_networking_conf"></a>ApacheHttpClient networking layer configuration Options:
 

hadoop-tools/hadoop-azure/src/test/java/org/apache/hadoop/fs/azurebfs/services/ITestApacheClientConnectionPool.java

@@ -33,6 +33,7 @@
 import org.apache.hadoop.fs.azurebfs.AbstractAbfsIntegrationTest;
 import org.apache.hadoop.fs.azurebfs.AzureBlobFileSystem;
 import org.apache.hadoop.fs.azurebfs.contracts.exceptions.AbfsDriverException;
+import org.apache.hadoop.fs.azurebfs.contracts.exceptions.AzureBlobFileSystemException;
 import org.apache.hadoop.security.ssl.DelegatingSSLSocketFactory;
 import org.apache.hadoop.util.functional.Tuples;
 import org.apache.http.HttpHost;
@@ -45,8 +46,10 @@
 import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
 import org.apache.http.impl.conn.DefaultHttpClientConnectionOperator;
 
+import static org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.APACHE_IMPL;
 import static org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.COLON;
 import static org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.EMPTY_STRING;
+import static org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.JDK_FALLBACK;
 import static org.apache.hadoop.fs.azurebfs.constants.AbfsHttpConstants.KEEP_ALIVE_CACHE_CLOSED;
 import static org.apache.hadoop.fs.azurebfs.constants.ConfigurationKeys.FS_AZURE_METRIC_FORMAT;
 import static org.apache.hadoop.fs.azurebfs.constants.ConfigurationKeys.FS_AZURE_NETWORKING_LIBRARY;
@@ -74,7 +77,9 @@ public void testKacIsClosed() throws Throwable {
     configuration.unset(FS_AZURE_METRIC_FORMAT);
     try (AzureBlobFileSystem fs = (AzureBlobFileSystem) FileSystem.newInstance(
         configuration)) {
-      KeepAliveCache kac = fs.getAbfsStore().getClientHandler().getIngressClient()
+      KeepAliveCache kac = fs.getAbfsStore()
+          .getClientHandler()
+          .getIngressClient()
           .getKeepAliveCache();
       kac.close();
       AbfsDriverException ex = intercept(AbfsDriverException.class,
@@ -149,10 +154,33 @@ public void testApacheClientFallbackDuringConnectionWarmup()
       Assertions.assertThat(AbfsApacheHttpClient.usable())
           .describedAs("Apache HttpClient should be not usable")
           .isFalse();
+      // Make a rest API call to verify that the client falls back to JDK client.
+      AzureBlobFileSystem fs = getFileSystem();
+      verifyClientRequestId(fs, JDK_FALLBACK);
       AbfsApacheHttpClient.setUsable();
+      verifyClientRequestId(fs, APACHE_IMPL);
     }
   }
 
+  /**
+   * Verify that the client request id contains the expected client.
+   * @param fs AzureBlobFileSystem instance
+   * @param expectedClient Expected client in the client request id.
+   * @throws AzureBlobFileSystemException if any failure occurs during the operation.
+   */
+  private void verifyClientRequestId(AzureBlobFileSystem fs,
+      String expectedClient)
+      throws AzureBlobFileSystemException {
+    AbfsRestOperation op = fs.getAbfsStore()
+        .getClient()
+        .getFilesystemProperties(getTestTracingContext(fs, true));
+    String[] clientRequestIdList = op.getResult()
+        .getClientRequestId().split(COLON);
+    Assertions.assertThat(clientRequestIdList[clientRequestIdList.length - 1])
+        .describedAs("Http Client in use should be %s", expectedClient)
+        .isEqualTo(expectedClient);
+  }
+
   private Map.Entry<HttpRoute, AbfsManagedApacheHttpConnection> getTestConnection()
       throws IOException {
     HttpHost host = new HttpHost(getFileSystem().getUri().getHost(),