ARROW-2696: [JAVA] enhance AllocationListener with an onFailedAllocation() call

java/memory/src/main/java/org/apache/arrow/memory/AllocationListener.java

@@ -21,15 +21,20 @@
 /**
  * An allocation listener being notified for allocation/deallocation
  * <p>
- * It is expected to be called from multiple threads and as such,
- * provider should take care of making the implementation thread-safe
+ * It might be called from multiple threads if the allocator hierarchy shares a listener, in which
+ * case, the provider should take care of making the implementation thread-safe.
  */
 public interface AllocationListener {
 
   public static final AllocationListener NOOP = new AllocationListener() {
     @Override
     public void onAllocation(long size) {
     }
+
+    @Override
+    public boolean onFailedAllocation(long size, Accountant.AllocationOutcome outcome) {
+      return false;
+    }
   };
 
   /**
@@ -39,4 +44,15 @@ public void onAllocation(long size) {
    */
   void onAllocation(long size);
 
+  /**
+   * Called whenever an allocation failed, giving the caller a chance to create some space in the allocator
+   * (either by freeing some resource, or by changing the limit), and, if successful, allowing the allocator
+   * to retry the allocation.
+   *
+   * @param size     the buffer size that was being allocated
+   * @param outcome  the outcome of the failed allocation. Carries information of what failed
+   * @return true, if the allocation can be retried; false if the allocation should fail
+   */
+  boolean onFailedAllocation(long size, Accountant.AllocationOutcome outcome);
+
 }

java/memory/src/main/java/org/apache/arrow/memory/BaseAllocator.java

@@ -72,7 +72,7 @@ protected BaseAllocator(
     this(parentAllocator.listener, parentAllocator, name, initReservation, maxAllocation);
   }
 
-  private BaseAllocator(
+  protected BaseAllocator(
       final AllocationListener listener,
       final BaseAllocator parentAllocator,
       final String name,
@@ -276,7 +276,13 @@ public ArrowBuf buffer(final int initialRequestSize, BufferManager manager) {
         : initialRequestSize;
     AllocationOutcome outcome = this.allocateBytes(actualRequestSize);
     if (!outcome.isOk()) {
-      throw new OutOfMemoryException(createErrorMsg(this, actualRequestSize, initialRequestSize));
+      if (listener.onFailedAllocation(actualRequestSize, outcome)) {
+        // Second try, in case the listener can do something about it
+        outcome = this.allocateBytes(actualRequestSize);
+      }
+      if (!outcome.isOk()) {
+        throw new OutOfMemoryException(createErrorMsg(this, actualRequestSize, initialRequestSize));
+      }
     }
 
     boolean success = false;
@@ -333,9 +339,18 @@ public BufferAllocator newChildAllocator(
       final String name,
       final long initReservation,
       final long maxAllocation) {
+    return newChildAllocator(name, this.listener, initReservation, maxAllocation);
+  }
+
+  @Override
+  public BufferAllocator newChildAllocator(
+      final String name,
+      final AllocationListener listener,
+      final long initReservation,
+      final long maxAllocation) {
     assertOpen();
 
-    final ChildAllocator childAllocator = new ChildAllocator(this, name, initReservation,
+    final ChildAllocator childAllocator = new ChildAllocator(listener, this, name, initReservation,
         maxAllocation);
 
     if (DEBUG) {

java/memory/src/main/java/org/apache/arrow/memory/BufferAllocator.java

@@ -68,6 +68,17 @@ public interface BufferAllocator extends AutoCloseable {
    */
   public BufferAllocator newChildAllocator(String name, long initReservation, long maxAllocation);
 
+  /**
+   * Create a new child allocator.
+   *
+   * @param name            the name of the allocator.
+   * @param listener        allocation listener for the newly created child
+   * @param initReservation the initial space reservation (obtained from this allocator)
+   * @param maxAllocation   maximum amount of space the new allocator can allocate
+   * @return the new allocator, or null if it can't be created
+   */
+  public BufferAllocator newChildAllocator(String name, AllocationListener listener, long initReservation, long maxAllocation);
+
   /**
    * Close and release all buffers generated from this buffer pool.
    *

java/memory/src/main/java/org/apache/arrow/memory/ChildAllocator.java

@@ -32,6 +32,7 @@ class ChildAllocator extends BaseAllocator {
   /**
    * Constructor.
    *
+   * @param listener        Allocation listener to be used in this child
    * @param parentAllocator parent allocator -- the one creating this child
    * @param name            the name of this child allocator
    * @param initReservation initial amount of space to reserve (obtained from the parent)
@@ -41,11 +42,12 @@ class ChildAllocator extends BaseAllocator {
    *                        allocation policy in force, even less memory may be available
    */
   ChildAllocator(
+      AllocationListener listener,
       BaseAllocator parentAllocator,
       String name,
       long initReservation,
       long maxAllocation) {
-    super(parentAllocator, name, initReservation, maxAllocation);
+    super(listener, parentAllocator, name, initReservation, maxAllocation);
   }
 
 

java/memory/src/test/java/org/apache/arrow/memory/TestBaseAllocator.java

@@ -222,7 +222,122 @@ public void testRootAllocator_createChildDontClose() throws Exception {
     }
   }
 
-  private static void allocateAndFree(final BufferAllocator allocator) {
+  // Allocation listener
+  // It counts the number of times it has been invoked, and how much memory allocation it has seen
+  // When set to 'expand on fail', it attempts to expand the associated allocator's limit
+  private static final class TestAllocationListener implements AllocationListener {
+    private int numCalls;
+    private long totalMem;
+    private boolean expandOnFail;
+    BufferAllocator expandAlloc;
+    long expandLimit;
+
+    TestAllocationListener() {
+      this.numCalls = 0;
+      this.totalMem = 0;
+      this.expandOnFail = false;
+      this.expandAlloc = null;
+      this.expandLimit = 0;
+    }
+
+    @Override
+    public void onAllocation(long size) {
+      numCalls++;
+      totalMem += size;
+    }
+
+    @Override
+    public boolean onFailedAllocation(long size,  Accountant.AllocationOutcome outcome) {
+      if (expandOnFail) {
+        expandAlloc.setLimit(expandLimit);
+        return true;
+      }
+      return false;
+    }
+
+    void setExpandOnFail(BufferAllocator expandAlloc, long expandLimit) {
+      this.expandOnFail = true;
+      this.expandAlloc = expandAlloc;
+      this.expandLimit = expandLimit;
+    }
+
+    int getNumCalls() {
+      return numCalls;
+    }
+
+    long getTotalMem() {
+      return totalMem;
+    }
+  }
+
+  @Test
+  public void testRootAllocator_listeners() throws Exception {
+    TestAllocationListener l1 = new TestAllocationListener();
+    assertEquals(0, l1.getNumCalls());
+    assertEquals(0, l1.getTotalMem());
+    TestAllocationListener l2 = new TestAllocationListener();
+    assertEquals(0, l2.getNumCalls());
+    assertEquals(0, l2.getTotalMem());
+    // root and first-level child share the first listener
+    // second-level and third-level child share the second listener
+    try (final RootAllocator rootAllocator = new RootAllocator(l1, MAX_ALLOCATION)) {
+      try (final BufferAllocator c1 = rootAllocator.newChildAllocator("c1", 0, MAX_ALLOCATION)) {
+        final ArrowBuf buf1 = c1.buffer(16);
+        assertNotNull("allocation failed", buf1);
+        assertEquals(1, l1.getNumCalls());
+        assertEquals(16, l1.getTotalMem());
+        buf1.release();
+        try (final BufferAllocator c2 = c1.newChildAllocator("c2", l2, 0, MAX_ALLOCATION)) {
+          final ArrowBuf buf2 = c2.buffer(32);
+          assertNotNull("allocation failed", buf2);
+          assertEquals(1, l1.getNumCalls());
+          assertEquals(16, l1.getTotalMem());
+          assertEquals(1, l2.getNumCalls());
+          assertEquals(32, l2.getTotalMem());
+          buf2.release();
+          try (final BufferAllocator c3 = c2.newChildAllocator("c3", 0, MAX_ALLOCATION)) {
+            final ArrowBuf buf3 = c3.buffer(64);
+            assertNotNull("allocation failed", buf3);
+            assertEquals(1, l1.getNumCalls());
+            assertEquals(16, l1.getTotalMem());
+            assertEquals(2, l2.getNumCalls());
+            assertEquals(32 + 64, l2.getTotalMem());
+            buf3.release();
+          }
+        }
+      }
+    }
+  }
+
+  @Test
+  public void testRootAllocator_listenerAllocationFail() throws Exception {
+    TestAllocationListener l1 = new TestAllocationListener();
+    assertEquals(0, l1.getNumCalls());
+    assertEquals(0, l1.getTotalMem());
+    // Test attempts to allocate too much from a child whose limit is set to half of the max allocation
+    // The listener's callback triggers, expanding the child allocator's limit, so then the allocation succeeds
+    try (final RootAllocator rootAllocator = new RootAllocator(MAX_ALLOCATION)) {
+      try (final BufferAllocator c1 = rootAllocator.newChildAllocator("c1", l1,0, MAX_ALLOCATION / 2)) {
+        try {
+          c1.buffer(MAX_ALLOCATION);
+          fail("allocated memory beyond max allowed");
+        } catch (OutOfMemoryException e) {
+          // expected
+        }
+        assertEquals(0, l1.getNumCalls());
+        assertEquals(0, l1.getTotalMem());
+
+        l1.setExpandOnFail(c1, MAX_ALLOCATION);
+        ArrowBuf arrowBuf = c1.buffer(MAX_ALLOCATION);
+        assertNotNull("allocation failed", arrowBuf);
+        assertEquals(1, l1.getNumCalls());
+        assertEquals(MAX_ALLOCATION, l1.getTotalMem());
+        arrowBuf.release();
+      }
+    }
+  }
+
+    private static void allocateAndFree(final BufferAllocator allocator) {
     final ArrowBuf arrowBuf = allocator.buffer(512);
     assertNotNull("allocation failed", arrowBuf);
     arrowBuf.release();