[GitHub] [flink] dawidwys commented on a change in pull request #14719: [FLINK-21072] Refactor the SnapshotStrategy hierarchy

[GitBox <gi...@apache.org>]

dawidwys commented on a change in pull request #14719:
URL: https://github.com/apache/flink/pull/14719#discussion_r563884695



##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/SnapshotStrategyRunner.java
##########
@@ -0,0 +1,132 @@
+/*
+ * 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.flink.runtime.state;
+
+import org.apache.flink.core.fs.CloseableRegistry;
+import org.apache.flink.runtime.checkpoint.CheckpointOptions;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nonnull;
+
+import java.util.concurrent.RunnableFuture;
+
+/**
+ * A class to execute a {@link SnapshotStrategy}. It can execute a strategy either synchronously or
+ * asynchronously. It takes care of common logging and resource cleaning.
+ *
+ * @param <T> type of the snapshot result.
+ */
+public final class SnapshotStrategyRunner<T extends StateObject, SR extends SnapshotResources> {
+    /** Flag to tell how the strategy should be executed. */
+    public enum ExecutionType {
+        SYNCHRONOUS,
+        ASYNCHRONOUS
+    }
+
+    private static final Logger LOG = LoggerFactory.getLogger(SnapshotStrategyRunner.class);
+
+    private static final String LOG_SYNC_COMPLETED_TEMPLATE =
+            "{} ({}, synchronous part) in thread {} took {} ms.";
+    private static final String LOG_ASYNC_COMPLETED_TEMPLATE =
+            "{} ({}, asynchronous part) in thread {} took {} ms.";
+
+    /**
+     * Descriptive name of the snapshot strategy that will appear in the log outputs and {@link
+     * #toString()}.
+     */
+    @Nonnull private final String description;
+
+    @Nonnull private final SnapshotStrategy<T, SR> snapshotStrategy;
+    @Nonnull private final CloseableRegistry cancelStreamRegistry;
+
+    @Nonnull private final ExecutionType executionType;
+
+    public SnapshotStrategyRunner(
+            @Nonnull String description,
+            @Nonnull SnapshotStrategy<T, SR> snapshotStrategy,
+            @Nonnull CloseableRegistry cancelStreamRegistry,
+            @Nonnull ExecutionType executionType) {
+        this.description = description;
+        this.snapshotStrategy = snapshotStrategy;
+        this.cancelStreamRegistry = cancelStreamRegistry;
+        this.executionType = executionType;
+    }
+
+    @Nonnull
+    public final RunnableFuture<SnapshotResult<T>> snapshot(
+            long checkpointId,
+            long timestamp,
+            @Nonnull CheckpointStreamFactory streamFactory,
+            @Nonnull CheckpointOptions checkpointOptions)
+            throws Exception {
+        long startTime = System.currentTimeMillis();
+        SR snapshotResources = snapshotStrategy.syncPrepareResources(checkpointId);
+        logCompletedInternal(LOG_SYNC_COMPLETED_TEMPLATE, streamFactory, startTime);
+        SnapshotStrategy.SnapshotResultSupplier<T> asyncSnapshot =
+                snapshotStrategy.asyncSnapshot(
+                        snapshotResources,
+                        checkpointId,
+                        timestamp,
+                        streamFactory,
+                        checkpointOptions);
+
+        switch (executionType) {
+            case SYNCHRONOUS:
+                return DoneFuture.of(asyncSnapshot.get(cancelStreamRegistry));

Review comment:
       Good catch. I think this is actually a bug, as it is using a different one. With this registry the main checkpointing thread(from which the `snapshot` method is executed) might not get cancelled before shutting down the io streams.
   
   I will rewrite the code to always go through the `AsyncSnapshotTask`




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