From 92a7cad6ddcea4be48ac82cc40f88302b88614d2 Mon Sep 17 00:00:00 2001
From: lookingatstarts <lookingatstarts@gmail.com>
Date: Thu, 15 Oct 2020 23:07:56 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BF=AE=E5=A4=8Dbug:=20SnowflakeIDGenImpl#til?=
 =?UTF-8?q?NextMillis=E6=96=B9=E6=B3=95=EF=BC=8C=E7=AD=89=E5=BE=85?=
 =?UTF-8?q?=E4=B8=8B=E4=B8=AA=E6=AF=AB=E7=A7=92=E6=97=B6=EF=BC=8C=E5=A6=82?=
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---
 .../leaf/snowflake/SnowflakeIDGenImpl.java    | 26 ++++++++++++++++---
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/leaf-core/src/main/java/com/sankuai/inf/leaf/snowflake/SnowflakeIDGenImpl.java b/leaf-core/src/main/java/com/sankuai/inf/leaf/snowflake/SnowflakeIDGenImpl.java
index b4f813b2..53595f70 100644
--- a/leaf-core/src/main/java/com/sankuai/inf/leaf/snowflake/SnowflakeIDGenImpl.java
+++ b/leaf-core/src/main/java/com/sankuai/inf/leaf/snowflake/SnowflakeIDGenImpl.java
@@ -5,10 +5,12 @@
 import com.sankuai.inf.leaf.common.Result;
 import com.sankuai.inf.leaf.common.Status;
 import com.sankuai.inf.leaf.common.Utils;
+import com.sankuai.inf.leaf.snowflake.exception.CheckLastTimeException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.util.Random;
+import java.util.concurrent.TimeUnit;
 
 public class SnowflakeIDGenImpl implements IDGen {
 
@@ -94,12 +96,28 @@ public synchronized Result get(String key) {
 
     }
 
-    protected long tilNextMillis(long lastTimestamp) {
-        long timestamp = timeGen();
-        while (timestamp <= lastTimestamp) {
+    /**
+     * 等待下个毫秒，防止等待期间系统时钟被回调，导致方法一直轮询
+     */
+    protected long tilNextMillis(long lastTimestamp){
+        long timestamp;
+        long offset;
+        while (true) {
             timestamp = timeGen();
+            offset = lastTimestamp-timestamp;
+            if(offset<0){
+                return timestamp;
+            }
+            if(offset>=5) { // 系统时钟回调时间大于5ms
+                throw new CheckLastTimeException("timestamp check error,last timestamp " + lastTimestamp + ",now " + timestamp);
+            }
+            if(offset>=2){ // 系统时钟回调时间大于等于2ms
+                try {
+                    TimeUnit.MILLISECONDS.sleep(offset);
+                } catch (InterruptedException ignore) {
+                }
+            }
         }
-        return timestamp;
     }
 
     protected long timeGen() {