[GitHub] merlimat commented on a change in pull request #1309: Refactored OrderedSafeExecutor and OrderedScheduler

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merlimat commented on a change in pull request #1309: Refactored OrderedSafeExecutor and OrderedScheduler
URL: https://github.com/apache/bookkeeper/pull/1309#discussion_r178176919
 
 

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 File path: bookkeeper-common/src/main/java/org/apache/bookkeeper/common/util/OrderedSafeExecutor.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.bookkeeper.common.util;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+
+import io.netty.util.concurrent.DefaultThreadFactory;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Future;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import lombok.extern.slf4j.Slf4j;
+
+import org.apache.bookkeeper.stats.Gauge;
+import org.apache.bookkeeper.stats.NullStatsLogger;
+import org.apache.bookkeeper.stats.OpStatsLogger;
+import org.apache.bookkeeper.stats.StatsLogger;
+import org.apache.commons.lang.StringUtils;
+
+/**
+ * This class provides 2 things over the java {@link ExecutorService}.
+ *
+ * <p>1. It takes {@link SafeRunnable objects} instead of plain Runnable objects.
+ * This means that exceptions in scheduled tasks wont go unnoticed and will be
+ * logged.
+ *
+ * <p>2. It supports submitting tasks with an ordering key, so that tasks submitted
+ * with the same key will always be executed in order, but tasks across
+ * different keys can be unordered. This retains parallelism while retaining the
+ * basic amount of ordering we want (e.g. , per ledger handle). Ordering is
+ * achieved by hashing the key objects to threads by their {@link #hashCode()}
+ * method.
+ */
+@Slf4j
+public class OrderedSafeExecutor implements ExecutorService {
 
 Review comment:
   Yes, makes sense. 
   
   Also, regarding `SafeRunnable`, I think we should be doing that internally, just taking a `Runnable`, though that's another story from this PR.

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