fix: update BlobWriteChannelV2 to properly carry forward offset after incremental flush

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

@@ -36,9 +36,9 @@ final class ApiaryUnbufferedWritableByteChannel implements UnbufferedWritableByt
   private final SettableApiFuture<StorageObject> result;
   private final LongConsumer committedBytesCallback;
 
-  private boolean open = true;
+  private boolean open;
   private long cumulativeByteCount;
-  private boolean finished = false;
+  private boolean finished;
 
   ApiaryUnbufferedWritableByteChannel(
       HttpClientContext httpClientContext,
@@ -50,6 +50,9 @@ final class ApiaryUnbufferedWritableByteChannel implements UnbufferedWritableByt
     this.session = ResumableSession.json(httpClientContext, deps, alg, resumableWrite);
     this.result = result;
     this.committedBytesCallback = committedBytesCallback;
+    this.open = true;
+    this.cumulativeByteCount = resumableWrite.getBeginOffset();
+    this.finished = false;
   }
 
   @Override

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

@@ -82,7 +82,7 @@ public WriteChannel restore() {
             entity != null ? Conversions.apiary().blobInfo().encode(entity) : null;
         return new BlobWriteChannelV2.BlobWriteChannelV2State(
                 (HttpStorageOptions) serviceOptions,
-                JsonResumableWrite.of(encode, ImmutableMap.of(), uploadId),
+                JsonResumableWrite.of(encode, ImmutableMap.of(), uploadId, position),
                 position,
                 isOpen,
                 chunkSize,

google-cloud-storage/src/main/java/com/google/cloud/storage/BlobWriteChannelV2.java

@@ -107,6 +107,10 @@ static final class BlobWriteChannelV2State
 
     @Override
     public WriteChannel restore() {
+      JsonResumableWrite resumableWrite = this.resumableWrite;
+      if (position != null) {
+        resumableWrite = resumableWrite.withBeginOffset(position);
+      }
       BlobWriteChannelV2 channel =
           new BlobWriteChannelV2(BlobReadChannelContext.from(options), resumableWrite);
       if (chunkSize != null) {

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

@@ -153,7 +153,7 @@ public void rewindTo(long offset) {
           success = true;
           //noinspection DataFlowIssue  compareTo result will filter out actualSize == null
           return ResumableOperationResult.complete(storageObject, actualSize.longValue());
-        } else if (compare < 0) {
+        } else if (compare > 0) {
           StorageException se =
               JsonResumableSessionFailureScenario.SCENARIO_4_1.toStorageException(
                   uploadId, response, null, toString(storageObject));

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

@@ -16,6 +16,8 @@
 
 package com.google.cloud.storage;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 import com.google.api.services.storage.model.StorageObject;
 import com.google.cloud.storage.spi.v1.StorageRpc;
 import com.google.common.base.MoreObjects;
@@ -41,24 +43,40 @@ final class JsonResumableWrite implements Serializable {
   @MonotonicNonNull private final String signedUrl;
 
   @NonNull private final String uploadId;
+  private final long beginOffset;
 
   private volatile String objectJson;
 
   private JsonResumableWrite(
       StorageObject object,
       Map<StorageRpc.Option, ?> options,
       String signedUrl,
-      @NonNull String uploadId) {
+      @NonNull String uploadId,
+      long beginOffset) {
     this.object = object;
     this.options = options;
     this.signedUrl = signedUrl;
     this.uploadId = uploadId;
+    this.beginOffset = beginOffset;
   }
 
   public @NonNull String getUploadId() {
     return uploadId;
   }
 
+  public long getBeginOffset() {
+    return beginOffset;
+  }
+
+  public JsonResumableWrite withBeginOffset(long newBeginOffset) {
+    checkArgument(
+        newBeginOffset >= beginOffset,
+        "New beginOffset must be >= existing beginOffset (%s >= %s)",
+        newBeginOffset,
+        beginOffset);
+    return new JsonResumableWrite(object, options, signedUrl, uploadId, newBeginOffset);
+  }
+
   @Override
   public boolean equals(Object o) {
     if (this == o) {
@@ -68,15 +86,16 @@ public boolean equals(Object o) {
       return false;
     }
     JsonResumableWrite that = (JsonResumableWrite) o;
-    return Objects.equals(object, that.object)
+    return beginOffset == that.beginOffset
+        && Objects.equals(object, that.object)
         && Objects.equals(options, that.options)
         && Objects.equals(signedUrl, that.signedUrl)
-        && uploadId.equals(that.uploadId);
+        && Objects.equals(uploadId, that.uploadId);
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash(object, options, signedUrl, uploadId);
+    return Objects.hash(object, options, signedUrl, uploadId, beginOffset);
   }
 
   @Override
@@ -86,6 +105,7 @@ public String toString() {
         .add("options", options)
         .add("signedUrl", signedUrl)
         .add("uploadId", uploadId)
+        .add("beginOffset", beginOffset)
         .toString();
   }
 
@@ -112,11 +132,11 @@ private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundE
   }
 
   static JsonResumableWrite of(
-      StorageObject req, Map<StorageRpc.Option, ?> options, String uploadId) {
-    return new JsonResumableWrite(req, options, null, uploadId);
+      StorageObject req, Map<StorageRpc.Option, ?> options, String uploadId, long beginOffset) {
+    return new JsonResumableWrite(req, options, null, uploadId, beginOffset);
   }
 
-  static JsonResumableWrite of(String signedUrl, String uploadId) {
-    return new JsonResumableWrite(null, null, signedUrl, uploadId);
+  static JsonResumableWrite of(String signedUrl, String uploadId, long beginOffset) {
+    return new JsonResumableWrite(null, null, signedUrl, uploadId, beginOffset);
   }
 }

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

@@ -243,7 +243,7 @@ public Blob createFrom(BlobInfo blobInfo, Path path, int bufferSize, BlobWriteOp
             optionsMap,
             retryAlgorithmManager.getForResumableUploadSessionCreate(optionsMap));
     JsonResumableWrite jsonResumableWrite =
-        JsonResumableWrite.of(encode, optionsMap, uploadIdSupplier.get());
+        JsonResumableWrite.of(encode, optionsMap, uploadIdSupplier.get(), 0);
 
     JsonResumableSession session =
         ResumableSession.json(
@@ -671,7 +671,7 @@ public StorageWriteChannel writer(BlobInfo blobInfo, BlobWriteOption... options)
             optionsMap,
             retryAlgorithmManager.getForResumableUploadSessionCreate(optionsMap));
     JsonResumableWrite jsonResumableWrite =
-        JsonResumableWrite.of(encode, optionsMap, uploadIdSupplier.get());
+        JsonResumableWrite.of(encode, optionsMap, uploadIdSupplier.get(), 0);
     return new BlobWriteChannelV2(BlobReadChannelContext.from(getOptions()), jsonResumableWrite);
   }
 
@@ -688,7 +688,7 @@ public StorageWriteChannel writer(URL signedURL) {
         ResumableMedia.startUploadForSignedUrl(
             getOptions(), signedURL, forResumableUploadSessionCreate);
     JsonResumableWrite jsonResumableWrite =
-        JsonResumableWrite.of(signedUrlString, uploadIdSupplier.get());
+        JsonResumableWrite.of(signedUrlString, uploadIdSupplier.get(), 0);
     return new BlobWriteChannelV2(BlobReadChannelContext.from(getOptions()), jsonResumableWrite);
   }
 

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

@@ -113,7 +113,8 @@ public void rewindWillQueryStatusOnlyWhenDirty() throws Exception {
       URI endpoint = fakeHttpServer.getEndpoint();
       String uploadUrl = String.format("%s/upload/%s", endpoint.toString(), UUID.randomUUID());
 
-      JsonResumableWrite resumableWrite = JsonResumableWrite.of(null, ImmutableMap.of(), uploadUrl);
+      JsonResumableWrite resumableWrite =
+          JsonResumableWrite.of(null, ImmutableMap.of(), uploadUrl, 0);
       JsonResumableSession session =
           new JsonResumableSession(
               httpClientContext, RETRYING_DEPENDENCIES, RETRY_ALGORITHM, resumableWrite);
@@ -167,7 +168,8 @@ public void retryAttemptWillReturnQueryResultIfPersistedSizeMatchesSpecifiedEndO
       URI endpoint = fakeHttpServer.getEndpoint();
       String uploadUrl = String.format("%s/upload/%s", endpoint.toString(), UUID.randomUUID());
 
-      JsonResumableWrite resumableWrite = JsonResumableWrite.of(null, ImmutableMap.of(), uploadUrl);
+      JsonResumableWrite resumableWrite =
+          JsonResumableWrite.of(null, ImmutableMap.of(), uploadUrl, 0);
       JsonResumableSession session =
           new JsonResumableSession(
               httpClientContext, RETRYING_DEPENDENCIES, RETRY_ALGORITHM, resumableWrite);
@@ -234,7 +236,8 @@ public void rewindOfContentIsRelativeToItsBeginOffsetOfTheOverallObject() throws
       URI endpoint = fakeHttpServer.getEndpoint();
       String uploadUrl = String.format("%s/upload/%s", endpoint.toString(), UUID.randomUUID());
 
-      JsonResumableWrite resumableWrite = JsonResumableWrite.of(null, ImmutableMap.of(), uploadUrl);
+      JsonResumableWrite resumableWrite =
+          JsonResumableWrite.of(null, ImmutableMap.of(), uploadUrl, 0);
       JsonResumableSession session =
           new JsonResumableSession(
               httpClientContext, RETRYING_DEPENDENCIES, RETRY_ALGORITHM, resumableWrite);

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

@@ -216,7 +216,8 @@ protected Restorable<?>[] restorableObjects() {
             JsonResumableWrite.of(
                 Conversions.apiary().blobInfo().encode(BlobInfo.newBuilder("b", "n").build()),
                 ImmutableMap.of(),
-                "upload-id"));
+                "upload-id",
+                0));
     return new Restorable<?>[] {readerV2, writer};
   }
 

google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITBlobWriteChannelTest.java

@@ -16,6 +16,7 @@
 
 package com.google.cloud.storage.it;
 
+import static com.google.cloud.storage.TestUtils.xxd;
 import static com.google.common.truth.Truth.assertThat;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.Assert.assertArrayEquals;
@@ -27,6 +28,7 @@
 import com.google.api.client.json.JsonParser;
 import com.google.api.gax.rpc.FixedHeaderProvider;
 import com.google.cloud.NoCredentials;
+import com.google.cloud.RestorableState;
 import com.google.cloud.WriteChannel;
 import com.google.cloud.conformance.storage.v1.InstructionList;
 import com.google.cloud.conformance.storage.v1.Method;
@@ -53,6 +55,7 @@
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.util.Arrays;
 import java.util.Optional;
 import java.util.logging.Logger;
 import org.junit.Test;
@@ -153,6 +156,39 @@ public void changeChunkSizeAfterWrite() throws IOException {
     }
   }
 
+  @Test
+  public void restoreProperlyPlumbsBeginOffset() throws IOException {
+    BlobInfo info = BlobInfo.newBuilder(bucket, generator.randomObjectName()).build();
+    int _256KiB = 256 * 1024;
+
+    byte[] bytes1 = DataGenerator.base64Characters().genBytes(_256KiB);
+    byte[] bytes2 = DataGenerator.base64Characters().genBytes(73);
+
+    int allLength = bytes1.length + bytes2.length;
+    byte[] expected = Arrays.copyOf(bytes1, allLength);
+    System.arraycopy(bytes2, 0, expected, bytes1.length, bytes2.length);
+    String xxdExpected = xxd(expected);
+
+    RestorableState<WriteChannel> capture;
+    {
+      WriteChannel writer = storage.writer(info, BlobWriteOption.doesNotExist());
+      writer.setChunkSize(_256KiB);
+      writer.write(ByteBuffer.wrap(bytes1));
+      // explicitly do not close writer, it will finalize the session
+      capture = writer.capture();
+    }
+
+    assertThat(capture).isNotNull();
+    WriteChannel restored = capture.restore();
+    restored.write(ByteBuffer.wrap(bytes2));
+    restored.close();
+
+    byte[] readAllBytes = storage.readAllBytes(info.getBlobId());
+    assertThat(readAllBytes).hasLength(expected.length);
+    String xxdActual = xxd(readAllBytes);
+    assertThat(xxdActual).isEqualTo(xxdExpected);
+  }
+
   private void doJsonUnexpectedEOFTest(int contentSize, int cappedByteCount) throws IOException {
     String blobPath = String.format("%s/%s/blob", generator.randomObjectName(), NOW_STRING);