HADOOP-8748. Refactor DFSClient retry utility methods to a new class in org.apache.hadoop.io.retry. Contributed by Arun C Murthy

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1378969 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -320,6 +320,9 @@ Branch-2 ( Unreleased changes )
     HADOOP-8075. Lower native-hadoop library log from info to debug.
     (Hızır Sefa İrken via eli)
 
+    HADOOP-8748. Refactor DFSClient retry utility methods to a new class
+    in org.apache.hadoop.io.retry.  (Arun C Murthy via szetszwo)
+
   BUG FIXES
 
     HADOOP-8372. NetUtils.normalizeHostName() incorrectly handles hostname

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/retry/RetryUtils.java

@@ -0,0 +1,164 @@
+/**
+ * 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.io.retry;
+
+import java.io.IOException;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.ipc.RemoteException;
+
+import com.google.protobuf.ServiceException;
+
+public class RetryUtils {
+  public static final Log LOG = LogFactory.getLog(RetryUtils.class);
+  
+  /**
+   * Return the default retry policy set in conf.
+   * 
+   * If the value retryPolicyEnabledKey is set to false in conf,
+   * use TRY_ONCE_THEN_FAIL.
+   * 
+   * Otherwise, get the MultipleLinearRandomRetry policy specified in the conf
+   * and then
+   * (1) use multipleLinearRandomRetry for
+   *     - remoteExceptionToRetry, or
+   *     - IOException other than RemoteException, or
+   *     - ServiceException; and
+   * (2) use TRY_ONCE_THEN_FAIL for
+   *     - non-remoteExceptionToRetry RemoteException, or
+   *     - non-IOException.
+   *     
+   *
+   * @param conf
+   * @param retryPolicyEnabledKey     conf property key for enabling retry
+   * @param defaultRetryPolicyEnabled default retryPolicyEnabledKey conf value 
+   * @param retryPolicySpecKey        conf property key for retry policy spec
+   * @param defaultRetryPolicySpec    default retryPolicySpecKey conf value
+   * @param remoteExceptionToRetry    The particular RemoteException to retry
+   * @return the default retry policy.
+   */
+  public static RetryPolicy getDefaultRetryPolicy(
+      Configuration conf,
+      String retryPolicyEnabledKey,
+      boolean defaultRetryPolicyEnabled,
+      String retryPolicySpecKey,
+      String defaultRetryPolicySpec,
+      final Class<? extends Exception> remoteExceptionToRetry
+      ) {
+    
+    final RetryPolicy multipleLinearRandomRetry = 
+        getMultipleLinearRandomRetry(
+            conf, 
+            retryPolicyEnabledKey, defaultRetryPolicyEnabled, 
+            retryPolicySpecKey, defaultRetryPolicySpec
+            );
+    
+    if (LOG.isDebugEnabled()) {
+      LOG.debug("multipleLinearRandomRetry = " + multipleLinearRandomRetry);
+    }
+
+    if (multipleLinearRandomRetry == null) {
+      //no retry
+      return RetryPolicies.TRY_ONCE_THEN_FAIL;
+    } else {
+      return new RetryPolicy() {
+        @Override
+        public RetryAction shouldRetry(Exception e, int retries, int failovers,
+            boolean isMethodIdempotent) throws Exception {
+          if (e instanceof ServiceException) {
+            //unwrap ServiceException
+            final Throwable cause = e.getCause();
+            if (cause != null && cause instanceof Exception) {
+              e = (Exception)cause;
+            }
+          }
+
+          //see (1) and (2) in the javadoc of this method.
+          final RetryPolicy p;
+          if (e instanceof RemoteException) {
+            final RemoteException re = (RemoteException)e;
+            p = remoteExceptionToRetry.getName().equals(re.getClassName())?
+                multipleLinearRandomRetry: RetryPolicies.TRY_ONCE_THEN_FAIL;
+          } else if (e instanceof IOException || e instanceof ServiceException) {
+            p = multipleLinearRandomRetry;
+          } else { //non-IOException
+            p = RetryPolicies.TRY_ONCE_THEN_FAIL;
+          }
+
+          if (LOG.isDebugEnabled()) {
+            LOG.debug("RETRY " + retries + ") policy="
+                + p.getClass().getSimpleName() + ", exception=" + e);
+          }
+          LOG.info("RETRY " + retries + ") policy="
+              + p.getClass().getSimpleName() + ", exception=" + e);
+          return p.shouldRetry(e, retries, failovers, isMethodIdempotent);
+        }
+
+        @Override
+        public String toString() {
+          return "RetryPolicy[" + multipleLinearRandomRetry + ", "
+              + RetryPolicies.TRY_ONCE_THEN_FAIL.getClass().getSimpleName()
+              + "]";
+        }
+      };
+    }
+  }
+
+  /**
+   * Return the MultipleLinearRandomRetry policy specified in the conf,
+   * or null if the feature is disabled.
+   * If the policy is specified in the conf but the policy cannot be parsed,
+   * the default policy is returned.
+   * 
+   * Retry policy spec:
+   *   N pairs of sleep-time and number-of-retries "s1,n1,s2,n2,..."
+   * 
+   * @param conf
+   * @param retryPolicyEnabledKey     conf property key for enabling retry
+   * @param defaultRetryPolicyEnabled default retryPolicyEnabledKey conf value 
+   * @param retryPolicySpecKey        conf property key for retry policy spec
+   * @param defaultRetryPolicySpec    default retryPolicySpecKey conf value
+   * @return the MultipleLinearRandomRetry policy specified in the conf,
+   *         or null if the feature is disabled.
+   */
+  public static RetryPolicy getMultipleLinearRandomRetry(
+      Configuration conf,
+      String retryPolicyEnabledKey,
+      boolean defaultRetryPolicyEnabled,
+      String retryPolicySpecKey,
+      String defaultRetryPolicySpec
+      ) {
+    final boolean enabled = 
+        conf.getBoolean(retryPolicyEnabledKey, defaultRetryPolicyEnabled);
+    if (!enabled) {
+      return null;
+    }
+
+    final String policy = conf.get(retryPolicySpecKey, defaultRetryPolicySpec);
+
+    final RetryPolicy r = 
+        RetryPolicies.MultipleLinearRandomRetry.parseCommaSeparatedString(
+            policy);
+    return (r != null) ? 
+        r : 
+        RetryPolicies.MultipleLinearRandomRetry.parseCommaSeparatedString(
+        defaultRetryPolicySpec);
+  }
+}