HBASE-20506 Add doc and test for unused RetryCounter, useful-looking utility

hbase-common/src/main/java/org/apache/hadoop/hbase/util/RetryCounter.java

@@ -24,9 +24,17 @@ import org.apache.yetus.audience.InterfaceAudience;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+/**
+ * Operation retry accounting.
+ * Use to calculate wait period, {@link #getBackoffTimeAndIncrementAttempts()}}, or for performing
+ * wait, {@link #sleepUntilNextRetry()}, in accordance with a {@link RetryConfig}, initial
+ * settings, and a Retry Policy, (See org.apache.hadoop.io.retry.RetryPolicy).
+ * Like <a href=https://github.com/rholder/guava-retrying>guava-retrying</a>.
+ * @since 0.92.0
+ * @see RetryCounterFactory
+ */
 @InterfaceAudience.Private
 public class RetryCounter {
-
   /**
    *  Configuration for a retry counter
    */
@@ -151,10 +159,8 @@ public class RetryCounter {
    */
   public void sleepUntilNextRetry() throws InterruptedException {
     int attempts = getAttemptTimes();
-    long sleepTime = retryConfig.backoffPolicy.getBackoffTime(retryConfig, attempts);
-    if (LOG.isTraceEnabled()) {
-      LOG.trace("Sleeping " + sleepTime + "ms before retry #" + attempts + "...");
-    }
+    long sleepTime = getBackoffTime();
+    LOG.trace("Sleeping {} ms before retry #{}...", sleepTime, attempts);
     retryConfig.getTimeUnit().sleep(sleepTime);
     useRetry();
   }
@@ -174,4 +180,14 @@ public class RetryCounter {
   public int getAttemptTimes() {
     return attempts;
   }
+
+  public long getBackoffTime() {
+    return this.retryConfig.backoffPolicy.getBackoffTime(this.retryConfig, getAttemptTimes());
+  }
+
+  public long getBackoffTimeAndIncrementAttempts() {
+    long backoffTime = getBackoffTime();
+    useRetry();
+    return backoffTime;
+  }
 }

hbase-common/src/test/java/org/apache/hadoop/hbase/util/TestRetryCounter.java

@@ -0,0 +1,55 @@
+/**
+ * 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.hbase.util;
+
+import static junit.framework.TestCase.assertTrue;
+
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.testclassification.MiscTests;
+import org.apache.hadoop.hbase.testclassification.SmallTests;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+* Basic test for some old functionality we don't seem to have used but that looks nice.
+ */
+@Category({MiscTests.class, SmallTests.class})
+public class TestRetryCounter {
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+      HBaseClassTestRule.forClass(TestRetryCounter.class);
+  private static final Logger LOG = LoggerFactory.getLogger(TestRetryCounter.class);
+
+  @Test
+  public void testBasics() throws InterruptedException {
+    int maxAttempts = 10;
+    RetryCounterFactory factory =
+        new RetryCounterFactory(maxAttempts, 10, 1000);
+    RetryCounter retryCounter = factory.create();
+    while (retryCounter.shouldRetry()) {
+      LOG.info("Attempt={}, backoffTime={}", retryCounter.getAttemptTimes(),
+          retryCounter.getBackoffTime());
+      retryCounter.sleepUntilNextRetry();
+    }
+    assertTrue(retryCounter.getAttemptTimes() == maxAttempts);
+  }
+}