fix: last chunk is retriable (#677)

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Fixes #666 ☕️

google-cloud-storage/src/main/java/com/google/cloud/storage/BlobWriteChannel.java

@@ -120,6 +120,14 @@ public void run() {
                     // For completeness, this case is not possible because it would require retrying
                     // a 400 status code which is not allowed.
                     //
+                    // Case 7: remoteNextByteOffset==-1 && last == true
+                    // Upload is complete and retry occurred in the "last" chunk. Data sent was
+                    // received by the service.
+                    //
+                    // Case 8: remoteNextByteOffset==-1 && last == false
+                    // Upload was completed by another client because this retry did not occur
+                    // during the last chunk.
+                    //
                     // Get remote offset from API
                     long remoteNextByteOffset =
                         getOptions().getStorageRpcV1().getCurrentUploadOffset(getUploadId());
@@ -154,7 +162,8 @@ && driftOffset < getChunkSize()) {
                       // Continue to next chunk
                       retrying = false;
                       return;
-                    } else {
+                    } else if (localNextByteOffset < remoteNextByteOffset
+                        && driftOffset > getChunkSize()) {
                       // Case 5
                       StringBuilder sb = new StringBuilder();
                       sb.append(
@@ -167,6 +176,13 @@ && driftOffset < getChunkSize()) {
                       sb.append("remoteNextByteOffset: ").append(remoteNextByteOffset).append('\n');
                       sb.append("driftOffset: ").append(driftOffset).append("\n\n");
                       throw new StorageException(0, sb.toString());
+                    } else if (remoteNextByteOffset == -1 && last) {
+                      // Case 7
+                      retrying = false;
+                      return;
+                    } else if (remoteNextByteOffset == -1 && !last) {
+                      // Case 8
+                      throw new StorageException(0, "Resumable upload is already complete.");
                     }
                   }
                   // Request was successful and retrying state is now disabled.

google-cloud-storage/src/main/java/com/google/cloud/storage/spi/v1/HttpStorageRpc.java

@@ -766,7 +766,7 @@ public long getCurrentUploadOffset(String uploadId) {
         response = httpRequest.execute();
         int code = response.getStatusCode();
         if (code == 201 || code == 200) {
-          throw new StorageException(0, "Resumable upload is already complete.");
+          return -1;
         }
         StringBuilder sb = new StringBuilder();
         sb.append("Not sure what occurred. Here's debugging information:\n");

google-cloud-storage/src/test/java/com/google/cloud/storage/BlobWriteChannelTest.java

@@ -202,6 +202,64 @@ public void testWriteWithFlushRetryChunkWithDrift() throws IOException {
     assertArrayEquals(buffer.array(), capturedBuffer.getValue());
   }
 
+  @Test
+  public void testWriteWithLastFlushRetryChunkButCompleted() throws IOException {
+    StorageException exception = new StorageException(new SocketException("Socket closed"));
+    ByteBuffer buffer = randomBuffer(MIN_CHUNK_SIZE);
+    Capture<byte[]> capturedBuffer = Capture.newInstance();
+    expect(storageRpcMock.open(BLOB_INFO.toPb(), EMPTY_RPC_OPTIONS)).andReturn(UPLOAD_ID);
+    expect(
+            storageRpcMock.writeWithResponse(
+                eq(UPLOAD_ID),
+                capture(capturedBuffer),
+                eq(0),
+                eq(0L),
+                eq(MIN_CHUNK_SIZE),
+                eq(true)))
+        .andThrow(exception);
+    expect(storageRpcMock.getCurrentUploadOffset(eq(UPLOAD_ID))).andReturn(-1L);
+    replay(storageRpcMock);
+    writer = new BlobWriteChannel(options, BLOB_INFO, EMPTY_RPC_OPTIONS);
+    assertEquals(MIN_CHUNK_SIZE, writer.write(buffer));
+    writer.close();
+    assertFalse(writer.isRetrying());
+    assertFalse(writer.isOpen());
+    // Capture captures entire buffer of a chunk even when not completely used.
+    // Making assert selective up to the size of MIN_CHUNK_SIZE
+    assertArrayEquals(Arrays.copyOf(capturedBuffer.getValue(), MIN_CHUNK_SIZE), buffer.array());
+  }
+
+  @Test
+  public void testWriteWithFlushRetryChunkButCompletedByAnotherClient() throws IOException {
+    StorageException exception = new StorageException(new SocketException("Socket closed"));
+    StorageException completedException =
+        new StorageException(0, "Resumable upload is already complete.");
+    ByteBuffer buffer = randomBuffer(MIN_CHUNK_SIZE);
+    Capture<byte[]> capturedBuffer = Capture.newInstance();
+    expect(storageRpcMock.open(BLOB_INFO.toPb(), EMPTY_RPC_OPTIONS)).andReturn(UPLOAD_ID);
+    expect(
+            storageRpcMock.writeWithResponse(
+                eq(UPLOAD_ID),
+                capture(capturedBuffer),
+                eq(0),
+                eq(0L),
+                eq(MIN_CHUNK_SIZE),
+                eq(false)))
+        .andThrow(exception);
+    expect(storageRpcMock.getCurrentUploadOffset(eq(UPLOAD_ID))).andReturn(-1L);
+    replay(storageRpcMock);
+    writer = new BlobWriteChannel(options, BLOB_INFO, EMPTY_RPC_OPTIONS);
+    writer.setChunkSize(MIN_CHUNK_SIZE);
+    try {
+      writer.write(buffer);
+      fail("Expected completed exception.");
+    } catch (StorageException ex) {
+      assertEquals(ex, completedException);
+    }
+    assertTrue(writer.isRetrying());
+    assertTrue(writer.isOpen());
+  }
+
   @Test
   public void testWriteWithFlush() throws IOException {
     expect(storageRpcMock.open(BLOB_INFO.toPb(), EMPTY_RPC_OPTIONS)).andReturn(UPLOAD_ID);