Wait for outstanding ORC reads after an error by 0z5a · Pull Request #25075 · NVIDIA/cudf

0z5a · 2026-11-04T18:52:00Z

Description

When an ORC stripe read fails, load_next_stripe_data could leave the function while other host or device reads were still running against the reader's buffers and datasources. This change keeps the device and host read futures in plain std::vector<std::future<...>> with sizes and destinations in parallel vectors, and guards both with cudf::detail::futures_wait_guard, so every submitted read is waited for before an exception leaves the function.

All host reads finish and pass their size checks before any host-to-device copy is queued, the same order fetch_byte_ranges_to_device_async uses. A failed read can then no longer free a host buffer that a queued copy still reads from.

Closes #25012.

Testing

The current version has not been compiled or run. The changed file was formatted with clang-format 20.1.8 (-style=file). An earlier version of this PR included regression tests; they were removed per review.

Checklist

I am familiar with the Contributing Guidelines.
New or existing tests cover these changes.
The documentation is up to date with these changes.

Signed-off-by: Dezhen Lu <dezhen.lu@student.uni-tuebingen.de>

copy-pr-bot · 2026-11-04T18:52:05Z

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coderabbitai · 2026-11-05T22:06:26Z

No actionable comments were generated in the recent review.

Summary

Summary by CodeRabbit

Bug Fixes
- Improved reliability when loading stripe data by validating host- and device-read sizes and reporting discrepancies consistently.
- Host data is now checked before it is copied to the device, and device-read results are checked after the stream completes.
- Improved handling of outstanding asynchronous reads when an error occurs, helping prevent resources from being released before pending operations finish.

The ORC stripe reader now stores host and device read futures separately from their metadata. It waits for outstanding reads on exceptional exits, validates host reads before queuing copies, and checks device-read sizes after stream synchronization.

Changes: ORC stripe read completion

Layer / File(s)	Summary
Track and complete stripe reads `cpp/src/io/orc/reader_impl_chunking.cu`	The reader stores host and device futures separately from expected sizes and destinations, with wait guards for both collections. It awaits and validates host reads before queuing copies, then synchronizes the stream before checking device-read sizes.

Estimated code review effort: 2 (Simple) | ~12 minutes

Severity of issue fixed: Medium

Suggested reviewers: bdice, ttnghia

Merge Risk: Minimal · up to 0647e

The change makes ORC stripe reads finish before an exception leaves the function, which reduces the chance of in-flight reads touching freed buffers. No actionable merge-blocking risk was found. The label and merge-barrier checks still need to be resolved before merge.

Architecture risk: Low · up to 29186

The change affects 1 system.

Changed systems: cpp

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

observed — cpp (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

observed — Modified behavior in cpp/src/io/orc/reader_impl_chunking.cu: Adds the host worker pool utilities header.
observed — Modified behavior in cpp/src/io/orc/reader_impl_chunking.cu: Replaces paired and tuple-based future records with separate vectors for host buffers, host and device futures, expected sizes, and host destinations. Reserves each vector for the read count and adds wait guards for both future collections.
observed — Modified behavior in cpp/src/io/orc/reader_impl_chunking.cu: Read submissions now store futures separately from expected sizes and host destinations. Host reads are all awaited and size-validated before copies are queued, retaining their buffers until the stream sync; device read sizes are then checked against their expected values. Previously, host reads were validated and copied one at a time, and device futures carried their expected sizes in pairs.

Pre-merge checks: 5

Check name	Status	Explanation
Title check		The title clearly describes the main change: waiting for outstanding ORC reads after an error.
Description check		The description explains the ORC read failure, the future-waiting change, and the host-to-device copy ordering.
Linked Issues check		Issue `#25012` requires `load_next_stripe_data` to wait for every submitted host and device read before an exception leaves the function. The implementation stores futures in separate vectors and declar…
Out of Scope Changes check		The whole-PR diff changes only `cpp/src/io/orc/reader_impl_chunking.cu`. It adds the guard include and restructures future and metadata storage in `load_next_stripe_data`. These changes directly suppo…
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…

Full details: Linked Issues check

Explanation

Issue #25012 requires load_next_stripe_data to wait for every submitted host and device read before an exception leaves the function. The implementation stores futures in separate vectors and declares a futures_wait_guard for each vector. The guards wait for remaining valid futures during unwinding. The function also completes and validates all host reads before it queues host-to-device copies. Device read results are checked after stream synchronization. No automated test requirement is stated in #25012; the issue notes that no reproducer exists.

Full details: Out of Scope Changes check

Explanation

The whole-PR diff changes only cpp/src/io/orc/reader_impl_chunking.cu. It adds the guard include and restructures future and metadata storage in load_next_stripe_data. These changes directly support issue #25012. No unrelated change is demonstrated.

Full details: Docstring Coverage

Explanation

Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 1 functions across 1 files.

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Reviewing files that changed from the base of the PR and between `29186b4` and `0647ea2`.

Files selected for processing: 1

`cpp/src/io/orc/reader_impl_chunking.cu`

Files skipped from review as they are similar to previous changes: 1

cpp/src/io/orc/reader_impl_chunking.cu

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Repository: NVIDIA/cudf

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File: .coderabbit.yaml

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`cpp/src/io/orc/reader_impl_chunking.cu`

`cpp/tests/io/orc_chunked_reader_test.cu`

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mhaseeb123 · 2026-11-06T05:25:40Z

  auto const [read_begin, read_end] =
    merge_selected_ranges(_file_itm_data.stripe_data_read_ranges, load_stripe_range);

+  // Reserve before issuing asynchronous reads: an allocation failure must not


I think this whole block can just be replaced with the use of fetch_bytes_to_device_async in parquet_io_utils.hpp. Thoughts @vuule?

Thanks. I looked at fetch_byte_ranges_to_device_async in parquet_io_utils (I couldn't find a fetch_bytes_to_device_async, so I assume you meant this one). As far as I can tell it doesn't drop in here:

It allocates and returns its own buffers: one padded rmm::device_buffer per datasource, with the requested ranges packed back to back. The ORC reader reads into lvl_stripe_data, which it allocated beforehand as one buffer per (level, stripe), and writes each range at its own dst_pos. The decode code indexes those buffers directly. Using the helper would mean changing how ORC owns and lays out stripe data across the reader, or adding a device-to-device copy for every range.

It is a public cudf::io::parquet API, so ORC would end up depending on the Parquet utilities.

That seemed out of scope for this fix, so I left the call site in place and made it follow the same pattern the helper uses. Device and host futures now each live in a plain std::vector<std::future<...>>, with sizes and destinations in parallel vectors. futures_wait_guard covers both vectors, and all host reads finish and pass the size check before any H2D copy is queued. If you or @vuule would like ORC moved onto a shared helper, I'm happy to do that in a follow-up.

I see. Thanks for looking into it. Let me take a look at this PR again then.

mhaseeb123 · 2026-11-06T05:26:21Z

                                                             cudf::io::compression_type::ZSTD)));
+
+namespace {
+// Promise-backed futures intentionally do not wait in their destructors. The first read


No need for any of these tests here imo

Removed. The test changes are reverted, so the file matches the PR base again.

mhaseeb123 · 2026-11-06T05:27:43Z

+  } catch (...) {
+    // Any successful earlier host copies must finish before their source
+    // buffers are destroyed. Preserve the original exception if sync fails.
+    try {
+      _stream.sync();
+    } catch (...) {
+    }
+    throw;


I am only glancing at it but if needed, this should go either in futures_wait_guard or something similar for reuse

The block is gone. Because host reads now finish and pass their size checks before any copy is queued, a failed read or a size mismatch throws while nothing is in flight that reads from the host buffers. So there is nothing left to sync on the error path, and nothing to move into futures_wait_guard. The remaining edge case is a CUDA error part-way through the copy loop. The helper accepts a similar risk, though it issues one batched copy rather than one copy per range. One trade-off: copies no longer overlap with the remaining host reads, which also matches the helper.

Keep device and host read futures in their own vectors with sizes and destinations alongside, so futures_wait_guard applies directly without range projections. Finish and size-check all host reads before queuing any host-to-device copy, as fetch_byte_ranges_to_device_async does. A failed read can then no longer free a host buffer that a queued copy still uses, so the try/catch with the extra stream sync is removed. Remove the regression tests added earlier, per review. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: 0z5a <dezhen.lu@student.uni-tuebingen.de>

vyasr · 2026-11-10T00:21:53Z

@mhaseeb123 @ttnghia #25153 is solving the same problem. Is there anything that should be pulled from that PR into this one, or vice versa so we can merge the other?

mhaseeb123 · 2026-11-10T05:16:24Z

@mhaseeb123 @ttnghia #25153 is solving the same problem. Is there anything that should be pulled from that PR into this one, or vice versa so we can merge the other?

@vyasr Thanks for the xref. Looks like both PRs are identical except the other one has an extra test which seems a bit redundant. We could just keep the one that was opened first (looks like it's this one).

Update: I have closed #25153 for now marking it as duplicate.

mhaseeb123 · 2026-11-10T05:15:06Z

+  std::vector<std::future<std::unique_ptr<datasource::buffer>>> host_read_tasks;
+  std::vector<std::size_t> host_read_sizes;
+  std::vector<uint8_t*> host_read_dsts;
+  host_read_buffers.reserve(num_reads);


Suggested change

host_read_buffers.reserve(num_reads);

host_read_buffers.reserve(num_reads);

Applied in 0647ea2, thanks.

mhaseeb123 · 2026-11-10T05:15:16Z

+  host_read_tasks.reserve(num_reads);
+  host_read_sizes.reserve(num_reads);
+  host_read_dsts.reserve(num_reads);
+  cudf::detail::futures_wait_guard device_read_tasks_guard{device_read_tasks};


Suggested change

cudf::detail::futures_wait_guard device_read_tasks_guard{device_read_tasks};

cudf::detail::futures_wait_guard device_read_tasks_guard{device_read_tasks};

Applied in 0647ea2, thanks.

Apply both review suggestions: separate the read-vector declarations, the reserve calls and the futures_wait_guard declarations with blank lines. Whitespace only. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: 0z5a <dezhen.lu@student.uni-tuebingen.de>

0z5a · 2026-11-10T08:42:04Z

Thanks @vyasr for the xref and @mhaseeb123 for taking another look. I applied both suggestions in 0647ea2. The setup block is now grouped the same way as in #25153, and the ORC change in the two PRs is the same apart from variable names and comments. Credit to @bodapatisaikrishna: #25153 had the separate future and metadata vectors before this PR moved to them. The only thing #25153 has that this PR doesn't is the FuturesWaitGuardDrainsMultipleFutureVectors unit test. I left it out since it overlaps with the existing FuturesWaitGuardWaitsForPendingFutures. If you'd like it here, I'm happy to cherry-pick it with a Co-authored-by trailer for @bodapatisaikrishna.

mhaseeb123 · 2026-11-10T20:20:09Z

I think this is okay as is. @ttnghia would you like to take a look at this PR instead

Wait for outstanding ORC reads after an error

f9925b6

Signed-off-by: Dezhen Lu <dezhen.lu@student.uni-tuebingen.de>

github-actions Bot assigned 0z5a Nov 4, 2026

github-actions Bot added the libcudf Affects libcudf (C++/CUDA) code. label Nov 4, 2026

0z5a marked this pull request as ready for review November 5, 2026 22:01

0z5a requested a review from a team as a code owner November 5, 2026 22:01

0z5a requested review from mhaseeb123 and shrshi November 5, 2026 22:01

coderabbitai Bot reviewed Nov 5, 2026

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mhaseeb123 requested a review from vuule November 6, 2026 05:19

mhaseeb123 reviewed Nov 6, 2026

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mhaseeb123 requested changes Nov 6, 2026

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mhaseeb123 reviewed Nov 6, 2026

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mhaseeb123 removed the request for review from shrshi November 6, 2026 05:28

coderabbitai Bot mentioned this pull request Nov 8, 2026

Wait for in-flight reads on failure in ORC chunked reader #25153

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mhaseeb123 approved these changes Nov 10, 2026

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	host_read_buffers.reserve(num_reads);

	host_read_buffers.reserve(num_reads);

	cudf::detail::futures_wait_guard device_read_tasks_guard{device_read_tasks};

	cudf::detail::futures_wait_guard device_read_tasks_guard{device_read_tasks};

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