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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.flink.runtime.state;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nonnull;

/**
 * Abstract base class for implementing {@link SnapshotStrategy}, that gives a consistent logging across state backends.
 *
 * @param  type of the snapshot result.
 */
public abstract class AbstractSnapshotStrategy implements SnapshotStrategy> {

	private static final Logger LOG = LoggerFactory.getLogger(AbstractSnapshotStrategy.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
	protected final String description;

	protected AbstractSnapshotStrategy(@Nonnull String description) {
		this.description = description;
	}

	/**
	 * Logs the duration of the synchronous snapshot part from the given start time.
	 */
	public void logSyncCompleted(@Nonnull Object checkpointOutDescription, long startTime) {
		logCompletedInternal(LOG_SYNC_COMPLETED_TEMPLATE, checkpointOutDescription, startTime);
	}

	/**
	 * Logs the duration of the asynchronous snapshot part from the given start time.
	 */
	public void logAsyncCompleted(@Nonnull Object checkpointOutDescription, long startTime) {
		logCompletedInternal(LOG_ASYNC_COMPLETED_TEMPLATE, checkpointOutDescription, startTime);
	}

	private void logCompletedInternal(
		@Nonnull String template,
		@Nonnull Object checkpointOutDescription,
		long startTime) {

		long duration = (System.currentTimeMillis() - startTime);

		LOG.debug(
			template,
			description,
			checkpointOutDescription,
			Thread.currentThread(),
			duration);
	}

	@Override
	public String toString() {
		return "SnapshotStrategy {" + description + "}";
	}
}