2 changed files with 227 additions and 11 deletions
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/* |
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* Copyright 1999-2019 Seata.io Group. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package cc.niushuai.dididone.util; |
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import java.net.NetworkInterface; |
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import java.util.Enumeration; |
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import java.util.HashMap; |
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import java.util.List; |
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import java.util.Map; |
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import java.util.Random; |
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import java.util.concurrent.atomic.AtomicLong; |
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import java.util.stream.Collectors; |
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/** |
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* @author funkye |
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* @author selfishlover |
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*/ |
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public class IntSnowflake { |
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private static final IntSnowflake snowflake = new IntSnowflake(0L); |
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public static int next_id() { |
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return (int) snowflake.nextId(); |
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} |
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public static String next_id_str() { |
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return snowflake.nextId() + ""; |
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} |
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/** |
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* Start time cut (2020-05-03) |
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*/ |
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private final long twepoch = 1588435200000L; |
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/** |
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* The number of bits occupied by workerId |
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*/ |
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private final int workerIdBits = 8; |
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/** |
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* The number of bits occupied by timestamp |
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*/ |
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private final int timestampBits = 12; |
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/** |
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* The number of bits occupied by sequence |
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*/ |
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private final int sequenceBits = 12; |
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/** |
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* Maximum supported machine id, the result is 1023 |
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*/ |
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private final int maxWorkerId = ~(-1 << workerIdBits); |
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/** |
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* mask that help to extract timestamp and sequence from a long |
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*/ |
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private final long timestampAndSequenceMask = ~(-1L << (timestampBits + sequenceBits)); |
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/** |
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* business meaning: machine ID (0 ~ 1023) |
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* actual layout in memory: |
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* highest 1 bit: 0 |
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* middle 10 bit: workerId |
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* lowest 53 bit: all 0 |
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*/ |
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private long workerId; |
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/** |
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* timestamp and sequence mix in one Long |
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* highest 11 bit: not used |
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* middle 41 bit: timestamp |
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* lowest 12 bit: sequence |
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*/ |
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private AtomicLong timestampAndSequence; |
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/** |
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* instantiate an IdWorker using given workerId |
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* |
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* @param workerId if null, then will auto assign one |
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*/ |
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public IntSnowflake(Long workerId) { |
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initTimestampAndSequence(); |
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initWorkerId(workerId); |
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} |
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/** |
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* init first timestamp and sequence immediately |
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*/ |
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protected void initTimestampAndSequence() { |
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long timestamp = getNewestTimestamp(); |
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long timestampWithSequence = timestamp << sequenceBits; |
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this.timestampAndSequence = new AtomicLong(timestampWithSequence); |
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} |
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/** |
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* init workerId |
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* |
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* @param workerId if null, then auto generate one |
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*/ |
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protected void initWorkerId(Long workerId) { |
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if (workerId == null) { |
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workerId = generateWorkerId(); |
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} |
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if (workerId > maxWorkerId || workerId < 0) { |
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String message = String.format("worker Id can't be greater than %d or less than 0", maxWorkerId); |
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throw new IllegalArgumentException(message); |
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} |
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this.workerId = workerId << (timestampBits + sequenceBits); |
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} |
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/** |
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* get next UUID(base on snowflake algorithm), which look like: |
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* highest 1 bit: always 0 |
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* next 10 bit: workerId |
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* next 41 bit: timestamp |
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* lowest 12 bit: sequence |
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* |
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* @return UUID |
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*/ |
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public long nextId() { |
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waitIfNecessary(); |
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long next = timestampAndSequence.incrementAndGet(); |
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long timestampWithSequence = next & timestampAndSequenceMask; |
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return workerId | timestampWithSequence; |
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} |
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/** |
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* block current thread if the QPS of acquiring UUID is too high |
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* that current sequence space is exhausted |
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*/ |
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private void waitIfNecessary() { |
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long currentWithSequence = timestampAndSequence.get(); |
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long current = currentWithSequence >>> sequenceBits; |
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long newest = getNewestTimestamp(); |
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if (current >= newest) { |
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try { |
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Thread.sleep(5); |
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} catch (InterruptedException ignore) { |
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// don't care
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} |
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} |
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} |
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/** |
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* get newest timestamp relative to twepoch |
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*/ |
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private long getNewestTimestamp() { |
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return System.currentTimeMillis() - twepoch; |
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} |
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/** |
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* auto generate workerId, try using mac first, if failed, then randomly generate one |
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* |
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* @return workerId |
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*/ |
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private long generateWorkerId() { |
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try { |
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return generateWorkerIdBaseOnMac(); |
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} catch (Exception e) { |
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return generateRandomWorkerId(); |
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} |
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} |
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/** |
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* use lowest 10 bit of available MAC as workerId |
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* |
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* @return workerId |
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* @throws Exception when there is no available mac found |
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*/ |
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private long generateWorkerIdBaseOnMac() throws Exception { |
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Enumeration<NetworkInterface> all = NetworkInterface.getNetworkInterfaces(); |
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while (all.hasMoreElements()) { |
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NetworkInterface networkInterface = all.nextElement(); |
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boolean isLoopback = networkInterface.isLoopback(); |
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boolean isVirtual = networkInterface.isVirtual(); |
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if (isLoopback || isVirtual) { |
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continue; |
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} |
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byte[] mac = networkInterface.getHardwareAddress(); |
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return ((mac[4] & 0B11) << 8) | (mac[5] & 0xFF); |
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} |
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throw new RuntimeException("no available mac found"); |
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} |
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/** |
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* randomly generate one as workerId |
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* |
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* @return workerId |
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*/ |
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private long generateRandomWorkerId() { |
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return new Random().nextInt(maxWorkerId + 1); |
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} |
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public static void main(String[] args) { |
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Map<Integer, Integer> map = new HashMap<>(); |
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for (int i = 0; i < 100000000; i++) { |
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long id = next_id(); |
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map.put((int) id, (map.getOrDefault(id, 0) + 1)); |
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} |
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List<Integer> collect = map.values().stream().filter(item -> item > 0).collect(Collectors.toList()); |
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System.out.println(map.size()); |
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System.out.println(collect); |
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} |
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} |
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