From d415696e01dede022a9c91b036dec4dd831510d3 Mon Sep 17 00:00:00 2001 From: Looly Date: Wed, 6 Apr 2022 23:50:56 +0800 Subject: [PATCH] add randomSequence support --- CHANGELOG.md | 1 + .../java/cn/hutool/core/lang/Snowflake.java | 68 +++++++++++++------ .../cn/hutool/core/lang/SnowflakeTest.java | 31 ++++++++- 3 files changed, 77 insertions(+), 23 deletions(-) diff --git a/CHANGELOG.md b/CHANGELOG.md index bc4cb1a7b..e82677009 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -10,6 +10,7 @@ ### 🐣新特性 * 【core 】 CopyOptions支持以Lambda方式设置忽略属性列表（pr#590@Gitee） * 【core 】 增加中文姓名正则及其校验（pr#592@Gitee） +* 【core 】 Snowflake支持sequence使用随机数（issue#I51EJY@Gitee） ### 🐞Bug修复 * 【core 】 修复UserAgentUtil识别Linux出错（issue#I50YGY@Gitee） diff --git a/hutool-core/src/main/java/cn/hutool/core/lang/Snowflake.java b/hutool-core/src/main/java/cn/hutool/core/lang/Snowflake.java index 1ba75e310..c9eeac826 100644 --- a/hutool-core/src/main/java/cn/hutool/core/lang/Snowflake.java +++ b/hutool-core/src/main/java/cn/hutool/core/lang/Snowflake.java @@ -2,6 +2,7 @@ package cn.hutool.core.lang; import cn.hutool.core.date.SystemClock; import cn.hutool.core.util.IdUtil; +import cn.hutool.core.util.RandomUtil; import cn.hutool.core.util.StrUtil; import java.io.Serializable; @@ -61,16 +62,30 @@ public class Snowflake implements Serializable { // 时间毫秒数左移22位 private static final long TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATA_CENTER_ID_BITS; // 序列掩码，用于限定序列最大值不能超过4095 - @SuppressWarnings("FieldCanBeLocal") private static final long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS);// 4095 + /** + * 初始化时间点 + */ private final long twepoch; private final long workerId; private final long dataCenterId; private final boolean useSystemClock; - // 允许的时钟回拨数 + /** + * 允许的时钟回拨毫秒数 + */ private final long timeOffset; + /** + * 当在低频模式下时，序号始终为0，导致生成ID始终为偶数
+ * 此属性用于限定一个随机上限，在不同毫秒下生成序号时，给定一个随机数，避免偶数问题。
+ * 注意次数必须小于{@link #SEQUENCE_MASK}，{@code 0}表示不使用随机数。
+ * 这个上限不包括值本身。 + */ + private final long randomSequenceLimit; + /** + * 自增序号，当高频模式下时，同一毫秒内生成N个ID，则这个序号在同一毫秒下，自增以避免ID重复。 + */ private long sequence = 0L; private long lastTimestamp = -1L; @@ -84,7 +99,7 @@ public class Snowflake implements Serializable { /** * 构造 * - * @param workerId 终端ID + * @param workerId 终端ID */ public Snowflake(long workerId) { this(workerId, IdUtil.getDataCenterId(MAX_DATA_CENTER_ID)); @@ -127,26 +142,30 @@ public class Snowflake implements Serializable { * @param workerId 工作机器节点id * @param dataCenterId 数据中心id * @param isUseSystemClock 是否使用{@link SystemClock} 获取当前时间戳 - * @param timeOffset 允许时间回拨的毫秒数 - * @since 5.7.3 + * @param timeOffset 允许时间回拨的毫秒数 + * @since 5.8.0 */ public Snowflake(Date epochDate, long workerId, long dataCenterId, boolean isUseSystemClock, long timeOffset) { - if (null != epochDate) { - this.twepoch = epochDate.getTime(); - } else{ - // Thu, 04 Nov 2010 01:42:54 GMT - this.twepoch = DEFAULT_TWEPOCH; - } - if (workerId > MAX_WORKER_ID || workerId < 0) { - throw new IllegalArgumentException(StrUtil.format("worker Id can't be greater than {} or less than 0", MAX_WORKER_ID)); - } - if (dataCenterId > MAX_DATA_CENTER_ID || dataCenterId < 0) { - throw new IllegalArgumentException(StrUtil.format("datacenter Id can't be greater than {} or less than 0", MAX_DATA_CENTER_ID)); - } - this.workerId = workerId; - this.dataCenterId = dataCenterId; + this(epochDate, workerId, dataCenterId, isUseSystemClock, timeOffset, 0); + } + + /** + * @param epochDate 初始化时间起点（null表示默认起始日期）,后期修改会导致id重复,如果要修改连workerId dataCenterId，慎用 + * @param workerId 工作机器节点id + * @param dataCenterId 数据中心id + * @param isUseSystemClock 是否使用{@link SystemClock} 获取当前时间戳 + * @param timeOffset 允许时间回拨的毫秒数 + * @param randomSequenceLimit 限定一个随机上限，在不同毫秒下生成序号时，给定一个随机数，避免偶数问题，0表示无随机，上限不包括值本身。 + * @since 5.8.0 + */ + public Snowflake(Date epochDate, long workerId, long dataCenterId, + boolean isUseSystemClock, long timeOffset, long randomSequenceLimit) { + this.twepoch = (null != epochDate) ? epochDate.getTime() : DEFAULT_TWEPOCH; + this.workerId = Assert.checkBetween(workerId, 0, MAX_WORKER_ID); + this.dataCenterId = Assert.checkBetween(dataCenterId, 0, MAX_DATA_CENTER_ID); this.useSystemClock = isUseSystemClock; this.timeOffset = timeOffset; + this.randomSequenceLimit = Assert.checkBetween(randomSequenceLimit, 0, SEQUENCE_MASK); } /** @@ -187,10 +206,10 @@ public class Snowflake implements Serializable { public synchronized long nextId() { long timestamp = genTime(); if (timestamp < this.lastTimestamp) { - if(this.lastTimestamp - timestamp < timeOffset){ + if (this.lastTimestamp - timestamp < timeOffset) { // 容忍指定的回拨，避免NTP校时造成的异常 timestamp = lastTimestamp; - } else{ + } else { // 如果服务器时间有问题(时钟后退) 报错。 throw new IllegalStateException(StrUtil.format("Clock moved backwards. Refusing to generate id for {}ms", lastTimestamp - timestamp)); } @@ -203,7 +222,12 @@ public class Snowflake implements Serializable { } this.sequence = sequence; } else { - sequence = 0L; + // issue#I51EJY + if (randomSequenceLimit > 1) { + sequence = RandomUtil.randomLong(randomSequenceLimit); + } else { + sequence = 0L; + } } lastTimestamp = timestamp; diff --git a/hutool-core/src/test/java/cn/hutool/core/lang/SnowflakeTest.java b/hutool-core/src/test/java/cn/hutool/core/lang/SnowflakeTest.java index f41512233..ca02e5e67 100644 --- a/hutool-core/src/test/java/cn/hutool/core/lang/SnowflakeTest.java +++ b/hutool-core/src/test/java/cn/hutool/core/lang/SnowflakeTest.java @@ -59,7 +59,7 @@ public class SnowflakeTest { Set ids = new ConcurrentHashSet<>(); ThreadUtil.concurrencyTest(100, () -> { - for (int i = 0; i < 5000; i++) { + for (int i = 0; i < 50000; i++) { if(false == ids.add(snowflake.nextId())){ throw new UtilException("重复ID！"); } @@ -74,4 +74,33 @@ public class SnowflakeTest { Assert.assertEquals(19, StrUtil.toString(l).length()); } } + + @Test + @Ignore + public void snowflakeRandomSequenceTest(){ + final Snowflake snowflake = new Snowflake(null, 0, 0, + false, Snowflake.DEFAULT_TIME_OFFSET, 2); + for (int i = 0; i < 1000; i++) { + final long id = snowflake.nextId(); + Console.log(id); + ThreadUtil.sleep(10); + } + } + + @Test + @Ignore + public void uniqueOfRandomSequenceTest(){ + // 测试并发环境下生成ID是否重复 + final Snowflake snowflake = new Snowflake(null, 0, 0, + false, Snowflake.DEFAULT_TIME_OFFSET, 100); + + Set ids = new ConcurrentHashSet<>(); + ThreadUtil.concurrencyTest(100, () -> { + for (int i = 0; i < 50000; i++) { + if(false == ids.add(snowflake.nextId())){ + throw new UtilException("重复ID！"); + } + } + }); + } }