#1519 - Memory leak when using @Cache(enableQueryCache=true) (#1523)

* #1519 - Memory leak when using @Cache(enableQueryCache=true)

* #1519 - Memory leak when using @Cache(enableQueryCache=true)

Remove unused TransactionEventBeans

src/test/java/io/ebean/config/PlatformNoGeneratedKeysTest.java

@@ -93,9 +93,9 @@ public class PlatformNoGeneratedKeysTest {
     return EbeanServerFactory.create(config);
   }
 
-  static class OtherH2Platform extends H2Platform {
+  public static class OtherH2Platform extends H2Platform {
 
-    OtherH2Platform() {
+    public OtherH2Platform() {
       super();
       this.platform = Platform.GENERIC;
     }

src/test/java/org/MainMemoryLeak.java

@@ -0,0 +1,76 @@
+package org;
+
+import io.ebean.Ebean;
+import io.ebean.EbeanServer;
+import io.ebean.EbeanServerFactory;
+import io.ebean.Transaction;
+import io.ebean.annotation.Cache;
+import io.ebean.config.PlatformNoGeneratedKeysTest;
+import io.ebean.config.ServerConfig;
+
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.Lob;
+import java.util.Arrays;
+
+/**
+ *
+ * Test preparation:
+ *
+ * - Enable file based H2 in ebean.properties (line `datasource.h2.databaseUrl=jdbc:h2:file:~/tests`)
+ * - disable logging of io.ebean.SUM/TXN/SQL in logback-test.xml
+ * - remove existing database in ~/tests (do that before each run)
+ * - run this class with `-Xmx1g` jvm argument
+ * - an OOM in iteration ~45000 will occur (45k * 10k chars = 45k * 20k bytes = 900MB)
+ *
+ * remove the line `@Cache(enableQueryCache=true)` - and it will run forever (until disk is full)
+ */
+public class MainMemoryLeak {
+
+  @Cache(enableQueryCache=true)
+  @Entity
+  public static class ECachedBean {
+    @Id
+    private Long id;
+
+    @Lob
+    private String description;
+  }
+
+  public static void main(String[] args) {
+
+    PlatformNoGeneratedKeysTest.OtherH2Platform platform = new PlatformNoGeneratedKeysTest.OtherH2Platform();
+
+    ServerConfig config = new ServerConfig();
+
+    config.setDatabasePlatform(platform);
+    config.addClass(ECachedBean.class);
+    config.loadFromProperties();
+
+    EbeanServer server = EbeanServerFactory.create(config);
+
+    // create a string with 10k chars
+    char[] c = new char[10_000];
+    Arrays.fill(c, 'x');
+
+    try (Transaction txn = server.beginTransaction()) {
+      for (int i = 0; i < 500000; i++) {
+
+        if (i % 1000 == 0) {
+          long mem = Runtime.getRuntime().freeMemory() / 1024 / 1024;
+          if (mem > 1024) {
+            throw new IllegalStateException("-Xmx1g JVM argument expected");
+          }
+          System.out.println("Iteration: " + i + " Free mem: " + mem + " MB");
+        }
+
+        ECachedBean a = new ECachedBean();
+        a.description = new String(c);
+        server.save(a);
+      }
+      System.out.println("Success, no mem limit detected");
+      txn.commit();
+    }
+
+  }
+}