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Posted to github@beam.apache.org by "scwhittle (via GitHub)" <gi...@apache.org> on 2026/03/23 13:01:43 UTC
[PR] [Java] Optimize StreamUtils to avoid copying bytes [beam]
scwhittle opened a new pull request, #37912:
URL: https://github.com/apache/beam/pull/37912
We can avoid unnecessary thread-local and output stream allocation when available matches the actual size of the input stream. This is a common case with length limited wrapped input streams of a ByteArrayInputStream.
The optimization for known input streams types was broken when it was wrapped by an UnownedOutputStream.
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Re: [PR] [Java] Optimize StreamUtils to avoid copying bytes [beam]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #37912:
URL: https://github.com/apache/beam/pull/37912#issuecomment-4111506672
Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment `assign set of reviewers`
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Re: [PR] [Java] Optimize StreamUtils to avoid copying bytes [beam]
Posted by "scwhittle (via GitHub)" <gi...@apache.org>.
scwhittle commented on PR #37912:
URL: https://github.com/apache/beam/pull/37912#issuecomment-4110616594
Example profile showing issue:
<img width="2401" height="801" alt="image" src="https://github.com/user-attachments/assets/b7a84073-d5cb-4983-8f19-eed575c9f9d2" />
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Re: [PR] [Java] Optimize StreamUtils to avoid copying bytes [beam]
Posted by "arunpandianp (via GitHub)" <gi...@apache.org>.
arunpandianp commented on code in PR #37912:
URL: https://github.com/apache/beam/pull/37912#discussion_r2987482744
##########
sdks/java/core/src/main/java/org/apache/beam/sdk/util/StreamUtils.java:
##########
@@ -35,34 +37,67 @@ private StreamUtils() {}
private static final int BUF_SIZE = 8192;
- private static ThreadLocal<SoftReference<byte[]>> threadLocalBuffer = new ThreadLocal<>();
+ private static final ThreadLocal<SoftReference<byte[]>> threadLocalBuffer = new ThreadLocal<>();
/** Efficient converting stream to bytes. */
public static byte[] getBytesWithoutClosing(InputStream stream) throws IOException {
+ // Unwrap the stream so the below optimizations based upon class type function properly.
+ // We don't use mark or reset in this function.
+ while (stream instanceof UnownedInputStream) {
+ stream = ((UnownedInputStream) stream).getWrappedStream();
+ }
+
if (stream instanceof ExposedByteArrayInputStream) {
// Fast path for the exposed version.
return ((ExposedByteArrayInputStream) stream).readAll();
- } else if (stream instanceof ByteArrayInputStream) {
+ }
+ if (stream instanceof ByteArrayInputStream) {
// Fast path for ByteArrayInputStream.
byte[] ret = new byte[stream.available()];
stream.read(ret);
return ret;
}
- // Falls back to normal stream copying.
+
+ // Most inputs are fully available so we attempt to first read directly
+ // into a buffer of the right size, assuming available reflects all the bytes.
+ int available = stream.available();
+ @Nullable ByteArrayOutputStream outputStream = null;
+ if (available > 0 && available < 1024 * 1024) {
+ byte[] initialBuffer = new byte[available];
+ int initialReadSize = stream.read(initialBuffer);
+ if (initialReadSize == -1) {
+ return new byte[0];
+ }
+ int nextChar = stream.read();
Review Comment:
nit: nextByte?
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Re: [PR] [Java] Optimize StreamUtils to avoid copying bytes [beam]
Posted by "gemini-code-assist[bot] (via GitHub)" <gi...@apache.org>.
gemini-code-assist[bot] commented on PR #37912:
URL: https://github.com/apache/beam/pull/37912#issuecomment-4110445760
## Summary of Changes
Hello, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request significantly enhances the performance of stream-to-byte array conversion by intelligently avoiding redundant memory allocations and data copying. It addresses a specific inefficiency where stream optimizations were bypassed due to wrapping, and introduces a new direct-read mechanism for streams with predictable sizes. The changes aim to improve the overall efficiency of byte array operations within the SDK.
### Highlights
* **Stream Optimization**: Optimized the `getBytesWithoutClosing` method in `StreamUtils` to avoid unnecessary byte copying and thread-local/output stream allocation, especially when the input stream's `available()` method accurately reflects its size.
* **UnownedInputStream Handling**: Introduced logic to unwrap `UnownedInputStream` instances, ensuring that underlying stream optimizations (e.g., for `ByteArrayInputStream`) are correctly applied even when wrapped.
* **Direct Buffer Allocation**: Implemented a new fast path that attempts to read directly into a pre-sized byte array if the stream's `available()` size is positive and within a reasonable limit, further reducing allocations.
* **API Enhancement**: Added a `getWrappedStream()` method to `UnownedInputStream` to facilitate unwrapping.
* **Test Coverage**: Expanded unit tests for `StreamUtils` to cover various scenarios, including `UnownedInputStream` wrapping, limited streams, and streams with misleading `available()` values, ensuring the new optimizations and fixes behave as expected. A test was also added to `CoderUtilsTest` to verify `ByteArrayCoder` avoids copying.
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Re: [PR] [Java] Optimize StreamUtils to avoid copying bytes [beam]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #37912:
URL: https://github.com/apache/beam/pull/37912#issuecomment-4124770195
Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control. If you'd like to restart, comment `assign set of reviewers`
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Re: [PR] [Java] Optimize StreamUtils to avoid copying bytes [beam]
Posted by "scwhittle (via GitHub)" <gi...@apache.org>.
scwhittle merged PR #37912:
URL: https://github.com/apache/beam/pull/37912
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Re: [PR] [Java] Optimize StreamUtils to avoid copying bytes [beam]
Posted by "scwhittle (via GitHub)" <gi...@apache.org>.
scwhittle commented on PR #37912:
URL: https://github.com/apache/beam/pull/37912#issuecomment-4124762178
R: @arunpandianp
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