javac ast indices: flush index on low memory

jps/jps-builders/src/org/jetbrains/jps/backwardRefs/BackwardReferenceIndexWriter.java

@@ -15,6 +15,7 @@
  */
 package org.jetbrains.jps.backwardRefs;
 
+import com.intellij.openapi.util.LowMemoryWatcher;
 import com.intellij.util.Function;
 import com.intellij.util.SystemProperties;
 import com.intellij.util.containers.ContainerUtil;
@@ -34,7 +35,10 @@ import org.jetbrains.jps.model.java.compiler.JavaCompilers;
 
 import java.io.File;
 import java.io.IOException;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Set;
 
 import static com.sun.tools.javac.code.Flags.PRIVATE;
 
@@ -45,10 +49,23 @@ public class BackwardReferenceIndexWriter {
 
   private final CompilerBackwardReferenceIndex myIndex;
   private final boolean myRebuild;
+  private final LowMemoryWatcher myMemWatcher;
+  private final Object myCloseLock = new Object();
+  private boolean myClosed;
 
   private BackwardReferenceIndexWriter(CompilerBackwardReferenceIndex index, boolean rebuild) {
     myIndex = index;
     myRebuild = rebuild;
+    myMemWatcher = LowMemoryWatcher.register(new Runnable() {
+      @Override
+      public void run() {
+        synchronized (myCloseLock) {
+          if (!myClosed) {
+            myIndex.flush();
+          }
+        }
+      }
+    });
   }
 
   public static void closeIfNeed() {
@@ -94,10 +111,6 @@ public class BackwardReferenceIndexWriter {
     return SystemProperties.getBooleanProperty(PROP_KEY, false);
   }
 
-  void close() {
-    myIndex.close();
-  }
-
   synchronized LightRef.JavaLightClassRef asClassUsage(Symbol name) {
     return new LightRef.JavaLightClassRef(myIndex.getByteSeqEum().enumerate(bytes(name)));
   }
@@ -207,6 +220,14 @@ public class BackwardReferenceIndexWriter {
     }
   }
 
+  private void close() {
+    synchronized (myCloseLock) {
+      myClosed = true;
+      myMemWatcher.stop();
+      myIndex.close();
+    }
+  }
+
   private void directlyWriteHierarchyIndices(CompilerBackwardReferenceIndex.LightDefinition classId, LightRef.JavaLightClassRef[] superIds) {
     for (LightRef.JavaLightClassRef superId : superIds) {
       myIndex.getBackwardHierarchyMap().put(superId, classId);

jps/jps-builders/src/org/jetbrains/jps/backwardRefs/CompilerBackwardReferenceIndex.java

@@ -203,6 +203,17 @@ public class CompilerBackwardReferenceIndex {
     }
   }
 
+  void flush() {
+    myBackwardHierarchyMap.flush(false);
+    myBackwardReferenceMap.flush(false);
+    myBackwardClassDefinitionMap.flush(false);
+    myHierarchyMap.flush(false);
+    myReferenceMap.flush(false);
+    myClassDefinitionMap.flush(false);
+    myNameEnumerator.force();
+    myFilePathEnumerator.force();
+  }
+
   public static void removeIndexFiles(File buildDir) {
     final File indexDir = getIndexDir(buildDir);
     if (indexDir.exists()) {