check if data size exceeds java array vm limit when it is copied in jni (#3850)

Summary:
to address issue #3849
Closes https://github.com/facebook/rocksdb/pull/3850

Differential Revision: D8695487

Pulled By: sagar0

fbshipit-source-id: 04baeb2127663934ed1321fe6d9a9ec23c86e16b

java/rocksjni/portal.h

@@ -4292,25 +4292,12 @@ class JniUtil {
      * @param bytes The bytes to copy
      *
      * @return the Java byte[] or nullptr if an exception occurs
+     * 
+     * @throws RocksDBException thrown 
+     *   if memory size to copy exceeds general java specific array size limitation.
      */
     static jbyteArray copyBytes(JNIEnv* env, std::string bytes) {
-      const jsize jlen = static_cast<jsize>(bytes.size());
-
-      jbyteArray jbytes = env->NewByteArray(jlen);
-      if(jbytes == nullptr) {
-        // exception thrown: OutOfMemoryError
-        return nullptr;
-      }
-
-      env->SetByteArrayRegion(jbytes, 0, jlen,
-        const_cast<jbyte*>(reinterpret_cast<const jbyte*>(bytes.c_str())));
-      if(env->ExceptionCheck()) {
-        // exception thrown: ArrayIndexOutOfBoundsException
-        env->DeleteLocalRef(jbytes);
-        return nullptr;
-      }
-
-      return jbytes;
+      return createJavaByteArrayWithSizeCheck(env, bytes.c_str(), bytes.size());
     }
 
     /**
@@ -4473,26 +4460,39 @@ class JniUtil {
 
       return jbyte_strings;
     }
-
+    
     /**
-     * Copies bytes from a rocksdb::Slice to a jByteArray
-     *
-     * @param env A pointer to the java environment
-     * @param bytes The bytes to copy
-     *
-     * @return the Java byte[] or nullptr if an exception occurs
-     */
-    static jbyteArray copyBytes(JNIEnv* env, const Slice& bytes) {
-      const jsize jlen = static_cast<jsize>(bytes.size());
-
+      * Copies bytes to a new jByteArray with the check of java array size limitation.
+      *
+      * @param bytes pointer to memory to copy to a new jByteArray
+      * @param size number of bytes to copy
+      *
+      * @return the Java byte[] or nullptr if an exception occurs
+      * 
+      * @throws RocksDBException thrown 
+      *   if memory size to copy exceeds general java array size limitation to avoid overflow.
+      */
+    static jbyteArray createJavaByteArrayWithSizeCheck(JNIEnv* env, const char* bytes, const size_t size) {
+      // Limitation for java array size is vm specific
+      // In general it cannot exceed Integer.MAX_VALUE (2^31 - 1)
+      // Current HotSpot VM limitation for array size is Integer.MAX_VALUE - 5 (2^31 - 1 - 5)
+      // It means that the next call to env->NewByteArray can still end with 
+      // OutOfMemoryError("Requested array size exceeds VM limit") coming from VM
+      static const size_t MAX_JARRAY_SIZE = (static_cast<size_t>(1)) << 31;
+      if(size > MAX_JARRAY_SIZE) {
+        rocksdb::RocksDBExceptionJni::ThrowNew(env, "Requested array size exceeds VM limit");
+        return nullptr;
+      }
+      
+      const jsize jlen = static_cast<jsize>(size);
       jbyteArray jbytes = env->NewByteArray(jlen);
       if(jbytes == nullptr) {
-        // exception thrown: OutOfMemoryError
+        // exception thrown: OutOfMemoryError	
         return nullptr;
       }
-
+      
       env->SetByteArrayRegion(jbytes, 0, jlen,
-        const_cast<jbyte*>(reinterpret_cast<const jbyte*>(bytes.data())));
+        const_cast<jbyte*>(reinterpret_cast<const jbyte*>(bytes)));
       if(env->ExceptionCheck()) {
         // exception thrown: ArrayIndexOutOfBoundsException
         env->DeleteLocalRef(jbytes);
@@ -4502,6 +4502,21 @@ class JniUtil {
       return jbytes;
     }
 
+    /**
+     * Copies bytes from a rocksdb::Slice to a jByteArray
+     *
+     * @param env A pointer to the java environment
+     * @param bytes The bytes to copy
+     *
+     * @return the Java byte[] or nullptr if an exception occurs
+     * 
+     * @throws RocksDBException thrown 
+     *   if memory size to copy exceeds general java specific array size limitation.
+     */
+    static jbyteArray copyBytes(JNIEnv* env, const Slice& bytes) {
+      return createJavaByteArrayWithSizeCheck(env, bytes.data(), bytes.size());
+    }
+
     /*
      * Helper for operations on a key and value
      * for example WriteBatch->Put

java/src/main/java/org/rocksdb/ColumnFamilyHandle.java

@@ -28,8 +28,10 @@ public class ColumnFamilyHandle extends RocksObject {
    * Gets the name of the Column Family.
    *
    * @return The name of the Column Family.
+   *
+   * @throws RocksDBException if an error occurs whilst retrieving the name.
    */
-  public byte[] getName() {
+  public byte[] getName() throws RocksDBException {
     return getName(nativeHandle_);
   }
 
@@ -71,14 +73,22 @@ public class ColumnFamilyHandle extends RocksObject {
     }
 
     final ColumnFamilyHandle that = (ColumnFamilyHandle) o;
-    return rocksDB_.nativeHandle_ == that.rocksDB_.nativeHandle_ &&
-        getID() == that.getID() &&
-        Arrays.equals(getName(), that.getName());
+    try {
+      return rocksDB_.nativeHandle_ == that.rocksDB_.nativeHandle_ &&
+          getID() == that.getID() &&
+          Arrays.equals(getName(), that.getName());
+    } catch (RocksDBException e) {
+      throw new RuntimeException("Cannot compare column family handles", e);
+    }
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash(getName(), getID(), rocksDB_.nativeHandle_);
+    try {
+      return Objects.hash(getName(), getID(), rocksDB_.nativeHandle_);
+    } catch (RocksDBException e) {
+      throw new RuntimeException("Cannot calculate hash code of column family handle", e);
+    }
   }
 
   /**
@@ -96,7 +106,7 @@ public class ColumnFamilyHandle extends RocksObject {
     }
   }
 
-  private native byte[] getName(final long handle);
+  private native byte[] getName(final long handle) throws RocksDBException;
   private native int getID(final long handle);
   private native ColumnFamilyDescriptor getDescriptor(final long handle) throws RocksDBException;
   @Override protected final native void disposeInternal(final long handle);

java/src/main/java/org/rocksdb/WriteBatch.java

@@ -65,8 +65,11 @@ public class WriteBatch extends AbstractWriteBatch {
    * Retrieve the serialized version of this batch.
    *
    * @return the serialized representation of this write batch.
+   *
+   * @throws RocksDBException if an error occurs whilst retrieving
+   *   the serialized batch data.
    */
-  public byte[] data() {
+  public byte[] data() throws RocksDBException {
     return data(nativeHandle_);
   }
 
@@ -253,7 +256,7 @@ public class WriteBatch extends AbstractWriteBatch {
       final int serializedLength);
   private native void iterate(final long handle, final long handlerHandle)
       throws RocksDBException;
-  private native byte[] data(final long nativeHandle);
+  private native byte[] data(final long nativeHandle) throws RocksDBException;
   private native long getDataSize(final long nativeHandle);
   private native boolean hasPut(final long nativeHandle);
   private native boolean hasDelete(final long nativeHandle);

java/src/test/java/org/rocksdb/RocksDBTest.java

@@ -4,9 +4,11 @@
 //  (found in the LICENSE.Apache file in the root directory).
 package org.rocksdb;
 
+import org.junit.Assume;
 import org.junit.ClassRule;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.rules.TemporaryFolder;
 
 import java.util.*;
@@ -143,6 +145,39 @@ public class RocksDBTest {
     }
   }
 
+  @Rule
+  public ExpectedException thrown = ExpectedException.none();
+
+  @Test
+  public void getOutOfArrayMaxSizeValue() throws RocksDBException {
+    final int numberOfValueSplits = 10;
+    final int splitSize = Integer.MAX_VALUE / numberOfValueSplits;
+
+    Runtime runtime = Runtime.getRuntime();
+    long neededMemory = ((long)(splitSize)) * (((long)numberOfValueSplits) + 3);
+    boolean isEnoughMemory = runtime.maxMemory() - runtime.totalMemory() > neededMemory;
+    Assume.assumeTrue(isEnoughMemory);
+
+    final byte[] valueSplit = new byte[splitSize];
+    final byte[] key = "key".getBytes();
+
+    thrown.expect(RocksDBException.class);
+    thrown.expectMessage("Requested array size exceeds VM limit");
+
+    // merge (numberOfValueSplits + 1) valueSplit's to get value size exceeding Integer.MAX_VALUE
+    try (final StringAppendOperator stringAppendOperator = new StringAppendOperator();
+         final Options opt = new Options()
+                 .setCreateIfMissing(true)
+                 .setMergeOperator(stringAppendOperator);
+         final RocksDB db = RocksDB.open(opt, dbFolder.getRoot().getAbsolutePath())) {
+      db.put(key, valueSplit);
+      for (int i = 0; i < numberOfValueSplits; i++) {
+        db.merge(key, valueSplit);
+      }
+      db.get(key);
+    }
+  }
+
   @Test
   public void multiGet() throws RocksDBException, InterruptedException {
     try (final RocksDB db = RocksDB.open(dbFolder.getRoot().getAbsolutePath());