feat(gax): add rewindable stream buffer for chunk recovery #14423
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| /* | ||
| * Copyright 2026 Google LLC | ||
| * | ||
| * Redistribution and use in source and binary forms, with or without | ||
| * modification, are permitted provided that the following conditions are | ||
| * met: | ||
| * | ||
| * * Redistributions of source code must retain the above copyright | ||
| * notice, this list of conditions and the following disclaimer. | ||
| * * Redistributions in binary form must reproduce the above | ||
| * copyright notice, this list of conditions and the following disclaimer | ||
| * in the documentation and/or other materials provided with the | ||
| * distribution. | ||
| * * Neither the name of Google LLC nor the names of its | ||
| * contributors may be used to endorse or promote products derived from | ||
| * this software without specific prior written permission. | ||
| * | ||
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | ||
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | ||
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | ||
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | ||
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | ||
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | ||
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | ||
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | ||
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | ||
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | ||
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||
| */ | ||
| package com.google.api.gax.rpc; | ||
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|
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| import static com.google.common.base.Preconditions.checkArgument; | ||
| import static com.google.common.base.Preconditions.checkNotNull; | ||
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|
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| import com.google.common.io.ByteStreams; | ||
| import java.io.IOException; | ||
| import java.io.InputStream; | ||
| import org.jspecify.annotations.NullMarked; | ||
|
|
||
| /** | ||
| * Manages a single-chunk buffer over an {@link InputStream} for resumable uploads. | ||
| * | ||
| * <p>The buffer holds at most one chunk of data in a reused backing array. It supports forward | ||
| * compaction and topping up upon recovery realignment, and enforces the boundary condition that | ||
| * requests to rewind before the buffer's base offset fail with an unrecoverable {@link | ||
| * FailedPreconditionException}. | ||
| */ | ||
| @NullMarked | ||
| final class RewindableStreamBuffer { | ||
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| private final InputStream inputStream; | ||
| private final int chunkSize; | ||
| private final String uploadUrl; | ||
| private final byte[] buffer; | ||
|
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| private long bufferBaseOffset; | ||
| private int payloadLength; | ||
| private boolean isFinal; | ||
| private boolean streamExhausted; | ||
|
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| RewindableStreamBuffer(InputStream inputStream, int chunkSize, String uploadUrl) { | ||
| this.inputStream = checkNotNull(inputStream, "inputStream must not be null"); | ||
| checkArgument(chunkSize > 0, "chunkSize must be > 0"); | ||
| this.chunkSize = chunkSize; | ||
| this.uploadUrl = checkNotNull(uploadUrl, "uploadUrl must not be null"); | ||
| this.buffer = new byte[chunkSize]; | ||
| this.bufferBaseOffset = 0L; | ||
| this.payloadLength = 0; | ||
| this.isFinal = false; | ||
| this.streamExhausted = false; | ||
| } | ||
|
|
||
| /** | ||
| * Advances the buffer from the stream starting at {@code targetOffset}, reading up to chunk size. | ||
| * | ||
| * @param targetOffset the absolute stream offset corresponding to the start of this chunk | ||
| * @throws IOException if reading from the stream fails | ||
| */ | ||
| void fill(long targetOffset) throws IOException { | ||
| this.bufferBaseOffset = targetOffset; | ||
| this.payloadLength = ByteStreams.read(inputStream, buffer, 0, chunkSize); | ||
| this.isFinal = (payloadLength < chunkSize); | ||
| if (this.isFinal) { | ||
| this.streamExhausted = true; | ||
| } | ||
| } | ||
|
|
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| /** | ||
| * Realigns the buffer window to {@code committedOffset}. | ||
| * | ||
| * <p>Compacts forward within the existing buffer to discard already-committed bytes, and then | ||
| * tops up the buffer to capacity from the underlying stream. | ||
| * | ||
| * @param committedOffset the server's committed byte offset | ||
| * @throws FailedPreconditionException if {@code committedOffset} is below the buffer's base | ||
| * offset or beyond the current buffer window | ||
| * @throws IOException if reading from the stream fails | ||
| */ | ||
| void realignTo(long committedOffset) throws IOException { | ||
|
Contributor
There was a problem hiding this comment. The |
||
| if (committedOffset < bufferBaseOffset) { | ||
| throw UploadErrors.protocolViolation( | ||
| String.format( | ||
| "Server committed offset %d is below buffer base offset %d for upload URL %s; cannot" | ||
| + " rewind stream before buffer base", | ||
| committedOffset, bufferBaseOffset, uploadUrl)); | ||
| } | ||
|
|
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| if (committedOffset > bufferBaseOffset + payloadLength) { | ||
| throw UploadErrors.protocolViolation( | ||
| String.format( | ||
| "Server committed offset %d is beyond current buffer window [%d, %d] for upload URL" | ||
| + " %s", | ||
| committedOffset, bufferBaseOffset, bufferBaseOffset + payloadLength, uploadUrl)); | ||
| } | ||
|
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| int committedWithinBuffer = (int) (committedOffset - bufferBaseOffset); | ||
| int remainingBytes = payloadLength - committedWithinBuffer; | ||
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| if (remainingBytes > 0 && committedWithinBuffer > 0) { | ||
| System.arraycopy(buffer, committedWithinBuffer, buffer, 0, remainingBytes); | ||
| } | ||
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| this.bufferBaseOffset = committedOffset; | ||
| this.payloadLength = remainingBytes; | ||
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| if (!streamExhausted && payloadLength < chunkSize) { | ||
| int space = chunkSize - payloadLength; | ||
| int additionalRead = ByteStreams.read(inputStream, buffer, payloadLength, space); | ||
| payloadLength += additionalRead; | ||
| if (additionalRead < space) { | ||
| streamExhausted = true; | ||
| } | ||
| } | ||
|
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| this.isFinal = streamExhausted; | ||
| } | ||
|
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| byte[] getBuffer() { | ||
| return buffer; | ||
| } | ||
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| int getPayloadLength() { | ||
| return payloadLength; | ||
| } | ||
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| long getBufferBaseOffset() { | ||
| return bufferBaseOffset; | ||
| } | ||
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| boolean isFinal() { | ||
| return isFinal; | ||
| } | ||
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| boolean isEmpty() { | ||
| return payloadLength == 0; | ||
| } | ||
| } | ||
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Unconditionally calling
streamBuffer.fill(currentOffset)on every chunk transmission will overwrite the compacted and topped-up bytes in the buffer if the buffer was previously realigned (e.g., during recovery realignment). This leads to silent data corruption because the stream will be read from its current position (which is ahead ofcurrentOffset), resulting in incorrect bytes being uploaded atcurrentOffset. We should only callfillif the buffer does not already contain the data forcurrentOffset.