From b821702b8dc03575419a5b583611b68ad2691ccc Mon Sep 17 00:00:00 2001
From: Koen De Groote <kdg.private@gmail.com>
Date: Fri, 31 Mar 2017 13:30:01 +0200
Subject: [PATCH] Moving defaultservercache implementation to use nanoseconds
 to determine whether or not something needs to be evicted from the cache.
 (#998)

The old implementation used System.currentTimeMillis(), which might be unreliable, for instance during a jump in DST.
Thanks @rPraml for noticing and suggesting the fix.
---
 .../ebeaninternal/api/ScopedTransaction.java   |  1 -
 .../server/cache/DefaultServerCache.java       | 18 +++++++++---------
 .../server/persist/BatchedPstmtHolder.java     |  1 -
 .../server/transaction/JdbcTransaction.java    |  1 -
 4 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/src/main/java/io/ebeaninternal/api/ScopedTransaction.java b/src/main/java/io/ebeaninternal/api/ScopedTransaction.java
index 145491135..fdd2914c5 100644
--- a/src/main/java/io/ebeaninternal/api/ScopedTransaction.java
+++ b/src/main/java/io/ebeaninternal/api/ScopedTransaction.java
@@ -13,7 +13,6 @@ import io.ebeaninternal.server.persist.BatchControl;
 import io.ebeanservice.docstore.api.DocStoreTransaction;
 
 import javax.persistence.PersistenceException;
-import java.io.IOException;
 import java.sql.Connection;
 import java.sql.SQLException;
 
diff --git a/src/main/java/io/ebeaninternal/server/cache/DefaultServerCache.java b/src/main/java/io/ebeaninternal/server/cache/DefaultServerCache.java
index 5a12d19d8..47cb08a09 100644
--- a/src/main/java/io/ebeaninternal/server/cache/DefaultServerCache.java
+++ b/src/main/java/io/ebeaninternal/server/cache/DefaultServerCache.java
@@ -8,8 +8,8 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.Serializable;
+import java.util.List;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.Iterator;
 import java.util.Map;
@@ -276,19 +276,19 @@ public class DefaultServerCache implements ServerCache {
     long trimmedByTTL = 0;
     long trimmedByLRU = 0;
 
-    ArrayList<CacheEntry> activeList = new ArrayList<>(map.size());
+    List<CacheEntry> activeList = new ArrayList<>(map.size());
 
-    long idleExpire = System.currentTimeMillis() - (maxIdleSecs * 1000);
-    long ttlExpire = System.currentTimeMillis() - (maxSecsToLive * 1000);
+    long idleExpireNano =  startNanos - TimeUnit.SECONDS.toNanos(maxIdleSecs);
+    long ttlExpireNano = startNanos - TimeUnit.SECONDS.toNanos(maxSecsToLive);
 
     Iterator<CacheEntry> it = map.values().iterator();
     while (it.hasNext()) {
       CacheEntry cacheEntry = it.next();
-      if (maxIdleSecs > 0 && idleExpire > cacheEntry.getLastAccessTime()) {
+      if (maxIdleSecs > 0 && idleExpireNano > cacheEntry.getLastAccessTime()) {
         it.remove();
         trimmedByIdle++;
 
-      } else if (maxSecsToLive > 0 && ttlExpire > cacheEntry.getCreateTime()) {
+      } else if (maxSecsToLive > 0 && ttlExpireNano > cacheEntry.getCreateTime()) {
         it.remove();
         trimmedByTTL++;
 
@@ -301,7 +301,7 @@ public class DefaultServerCache implements ServerCache {
       trimmedByLRU = activeList.size() - maxSize;
       if (trimmedByLRU > 0) {
         // sort into last access time ascending
-        Collections.sort(activeList, BY_LAST_ACCESS);
+        activeList.sort(BY_LAST_ACCESS);
         int trimSize = getTrimSize();
         for (int i = trimSize; i < activeList.size(); i++) {
           // remove if still in the cache
@@ -365,7 +365,7 @@ public class DefaultServerCache implements ServerCache {
     public CacheEntry(Object key, Object value) {
       this.key = key;
       this.value = value;
-      this.createTime = System.currentTimeMillis();
+      this.createTime = System.nanoTime();
       this.lastAccessTime = createTime;
     }
 
@@ -381,7 +381,7 @@ public class DefaultServerCache implements ServerCache {
      */
     public Object getValue() {
       // long assignment should be atomic these days (Ref Cliff Click)
-      lastAccessTime = System.currentTimeMillis();
+      lastAccessTime = System.nanoTime();
       return value;
     }
 
diff --git a/src/main/java/io/ebeaninternal/server/persist/BatchedPstmtHolder.java b/src/main/java/io/ebeaninternal/server/persist/BatchedPstmtHolder.java
index b47b41a36..b981614ed 100644
--- a/src/main/java/io/ebeaninternal/server/persist/BatchedPstmtHolder.java
+++ b/src/main/java/io/ebeaninternal/server/persist/BatchedPstmtHolder.java
@@ -3,7 +3,6 @@ package io.ebeaninternal.server.persist;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import javax.persistence.PersistenceException;
 import java.sql.PreparedStatement;
 import java.sql.SQLException;
 import java.util.LinkedHashMap;
diff --git a/src/main/java/io/ebeaninternal/server/transaction/JdbcTransaction.java b/src/main/java/io/ebeaninternal/server/transaction/JdbcTransaction.java
index 9b9d31ce7..ae3404b82 100644
--- a/src/main/java/io/ebeaninternal/server/transaction/JdbcTransaction.java
+++ b/src/main/java/io/ebeaninternal/server/transaction/JdbcTransaction.java
@@ -22,7 +22,6 @@ import org.slf4j.LoggerFactory;
 
 import javax.persistence.PersistenceException;
 import javax.persistence.RollbackException;
-import java.io.IOException;
 import java.sql.Connection;
 import java.sql.SQLException;
 import java.util.ArrayList;