| /** |
| * 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.yarn.server.timelineservice.storage.common; |
| |
| import java.util.concurrent.atomic.AtomicLong; |
| |
| import org.apache.hadoop.yarn.api.records.ApplicationId; |
| |
| /** |
| * Utility class that allows HBase coprocessors to interact with unique |
| * timestamps. |
| */ |
| public class TimestampGenerator { |
| |
| /* |
| * if this is changed, then reading cell timestamps written with older |
| * multiplier value will not work |
| */ |
| public static final long TS_MULTIPLIER = 1000000L; |
| |
| private final AtomicLong lastTimestamp = new AtomicLong(); |
| |
| /** |
| * Returns the current wall clock time in milliseconds, multiplied by the |
| * required precision. |
| * |
| * @return current timestamp. |
| */ |
| public long currentTime() { |
| // We want to align cell timestamps with current time. |
| // cell timestamps are not be less than |
| // System.currentTimeMillis() * TS_MULTIPLIER. |
| return System.currentTimeMillis() * TS_MULTIPLIER; |
| } |
| |
| /** |
| * Returns a timestamp value unique within the scope of this |
| * {@code TimestampGenerator} instance. For usage by HBase |
| * {@code RegionObserver} coprocessors, this normally means unique within a |
| * given region. |
| * |
| * Unlikely scenario of generating a non-unique timestamp: if there is a |
| * sustained rate of more than 1M hbase writes per second AND if region fails |
| * over within that time range of timestamps being generated then there may be |
| * collisions writing to a cell version of the same column. |
| * |
| * @return unique timestamp. |
| */ |
| public long getUniqueTimestamp() { |
| long lastTs; |
| long nextTs; |
| do { |
| lastTs = lastTimestamp.get(); |
| nextTs = Math.max(lastTs + 1, currentTime()); |
| } while (!lastTimestamp.compareAndSet(lastTs, nextTs)); |
| return nextTs; |
| } |
| |
| /** |
| * Returns a timestamp multiplied with TS_MULTIPLIER and last few digits of |
| * application id. |
| * |
| * Unlikely scenario of generating a timestamp that is a duplicate: If more |
| * than a 1M concurrent apps are running in one flow run AND write to same |
| * column at the same time, then say appId of 1M and 1 will overlap |
| * with appId of 001 and there may be collisions for that flow run's |
| * specific column. |
| * |
| * @param incomingTS Timestamp to be converted. |
| * @param appId Application Id. |
| * @return a timestamp multiplied with TS_MULTIPLIER and last few digits of |
| * application id |
| */ |
| public static long getSupplementedTimestamp(long incomingTS, String appId) { |
| long suffix = getAppIdSuffix(appId); |
| long outgoingTS = incomingTS * TS_MULTIPLIER + suffix; |
| return outgoingTS; |
| |
| } |
| |
| private static long getAppIdSuffix(String appIdStr) { |
| if (appIdStr == null) { |
| return 0L; |
| } |
| ApplicationId appId = ApplicationId.fromString(appIdStr); |
| long id = appId.getId() % TS_MULTIPLIER; |
| return id; |
| } |
| |
| /** |
| * truncates the last few digits of the timestamp which were supplemented by |
| * the TimestampGenerator#getSupplementedTimestamp function. |
| * |
| * @param incomingTS Timestamp to be truncated. |
| * @return a truncated timestamp value |
| */ |
| public static long getTruncatedTimestamp(long incomingTS) { |
| return incomingTS / TS_MULTIPLIER; |
| } |
| } |