Integration of TOS: Add common Chain.

hadoop-cloud-storage-project/hadoop-tos/src/main/java/org/apache/hadoop/fs/tosfs/common/Chain.java

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+/*
+ * 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.tosfs.common;
+
+import org.apache.hadoop.fs.tosfs.util.CommonUtils;
+import org.apache.hadoop.thirdparty.com.google.common.collect.Queues;
+import org.apache.hadoop.util.Lists;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.util.Deque;
+import java.util.List;
+import java.util.Queue;
+import java.util.function.Predicate;
+
+public class Chain<T extends Closeable> implements Closeable {
+  private static final Logger LOG = LoggerFactory.getLogger(Chain.class);
+
+  private final List<IOException> suppressed = Lists.newArrayList();
+  private final Queue<ItemFactory<T>> queue;
+  private final Predicate<IOException> shouldContinue;
+  private T curItem;
+
+  private Chain(Deque<ItemFactory<T>> queue, Predicate<IOException> shouldContinue) {
+    this.queue = queue;
+    this.shouldContinue = shouldContinue;
+    this.curItem = null;
+  }
+
+  public <R> R run(Task<T, R> task) throws IOException {
+    while (true) {
+      if (curItem == null && !nextItem()) {
+        IOException ex = new IOException("Failed to run task after attempt all items");
+        suppressed.forEach(ex::addSuppressed);
+        throw ex;
+      }
+
+      try {
+        return task.run(curItem);
+      } catch (IOException e) {
+        LOG.debug("Encounter exception while running task with item {}", curItem, e);
+        // Resetting the current caller to be null, for triggering the next round election.
+        if (curItem != null) {
+          CommonUtils.runQuietly(curItem::close);
+          curItem = null;
+        }
+        suppressed.add(e);
+
+        if (shouldContinue != null && !shouldContinue.test(e)) {
+          IOException ex = new IOException("Failed to run the chain since the encountered error not retryable.");
+          suppressed.forEach(ex::addSuppressed);
+          throw ex;
+        }
+      }
+    }
+  }
+
+  public T curItem() {
+    return curItem;
+  }
+
+  private boolean nextItem() {
+    if (curItem != null) {
+      CommonUtils.runQuietly(curItem::close);
+      curItem = null;
+    }
+
+    while (!queue.isEmpty()) {
+      ItemFactory<T> nextFactory = queue.poll();
+      try {
+        curItem = nextFactory.newItem();
+        return true;
+      } catch (IOException e) {
+        curItem = null;
+        LOG.debug("Failed to create new item", e);
+        suppressed.add(e);
+      }
+    }
+
+    return false;
+  }
+
+  @Override
+  public void close() throws IOException {
+    if (curItem != null) {
+      curItem.close();
+    }
+  }
+
+  public interface ItemFactory<T extends Closeable> {
+    T newItem() throws IOException;
+  }
+
+  public interface Task<T extends Closeable, R> {
+    R run(T call) throws IOException;
+  }
+
+  public static class Builder<T extends Closeable> {
+    private final Deque<ItemFactory<T>> factories = Queues.newArrayDeque();
+    private Predicate<IOException> shouldContinue;
+
+    public Builder<T> addFirst(ItemFactory<T> factory) {
+      factories.addFirst(factory);
+      return this;
+    }
+
+    public Builder<T> addLast(ItemFactory<T> factory) {
+      factories.addLast(factory);
+      return this;
+    }
+
+    public Builder<T> shouldContinue(Predicate<IOException> shouldContinue) {
+      this.shouldContinue = shouldContinue;
+      return this;
+    }
+
+    public Chain<T> build() throws IOException {
+      Chain<T> chain = new Chain<>(factories, shouldContinue);
+
+      // Do nothing in the chain task to initialize the first item.
+      chain.run(item -> null);
+      return chain;
+    }
+  }
+
+  public static <T extends Closeable> Builder<T> builder() {
+    return new Builder<>();
+  }
+}
+