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feat(pubsub): implement publish hedging to reduce tail latency - #13735

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tonyyyycui merged 49 commits into
googleapis:mainfrom
tonyyyycui:publish-hedging-settings
Sep 14, 2026
Merged

tonyyyycui merged 49 commits into
googleapis:mainfrom
tonyyyycui:publish-hedging-settings

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@tonyyyycui

@tonyyyycui tonyyyycui commented Jul 13, 2026 •

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This PR implements publish hedging in the Java Cloud Pub/Sub Publisher. Specifically, it adds support for scheduling "hedged" publish attempts when a publish call is slow to respond. A token-based method is utilized to rate-limit hedged requests and a coordinator is used to manage/cancel concurrent requests to prevent duplicate publishes.

@tonyyyycui
tonyyyycui requested review from a team as code owners July 13, 2026 17:31

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Code Review

This pull request introduces a hedging mechanism for the Pub/Sub Publisher, adding HedgeSettings for configuration and a thread-safe HedgeTokenBucket to limit hedged requests. The feedback suggests replacing the synchronized methods in HedgeTokenBucket with explicit ReentrantLock to reduce lock contention and improve performance on the critical path.

@tonyyyycui tonyyyycui changed the title Add HedgeSettings and integrate with publisher for token operations feat(pubsub): add HedgeSettings and integrate with Publisher Jul 13, 2026
@tonyyyycui tonyyyycui changed the title feat(pubsub): add HedgeSettings and integrate with Publisher feat(pubsub): implement HedgeSettings and integrate with Publisher Jul 13, 2026

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At a higher level, I think the full implementation should be one PR (instead of the , given any submitted changes become public. It would be unexpected for customers to be able to set HedgingSettings without anything actually happening, so the final PR should have everything needed for the implementation included.

*
* @return the hedging delay.
*/
public Duration getHedgeDelay() {

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nit: Does this method need to be public? I think leaving it without an access modifier (i.e., making it package-private) should be sufficient.

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I've removed it for now, but I think it would also make sense if the user could see what they see the hedge delay is set to since it's a configurable field. Leaving this conversation unresolved.

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Thought more on this and I actually think having this public makes sense and matches what we do for SubscriberShutdownSettings. All of the getters for HedgingSettings can be public.

@tonyyyycui tonyyyycui changed the title feat(pubsub): implement HedgeSettings and integrate with Publisher feat(pubsub): implement publish hedging to reduce tail latency Jul 20, 2026
*
* @return the hedging delay.
*/
public Duration getHedgeDelay() {

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Thought more on this and I actually think having this public makes sense and matches what we do for SubscriberShutdownSettings. All of the getters for HedgingSettings can be public.

}

if (runningAttempts.isEmpty() || !isRetryable) {
if (done.compareAndSet(false, true)) {

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I believe the lock added in CancellationSharer prevents this race condition.

@tonyyyycui
tonyyyycui merged commit b302615 into googleapis:main Sep 14, 2026
210 checks passed
blakeli0 pushed a commit that referenced this pull request Sep 23, 2026
🤖 I have created a release *beep* *boop*
---


<details><summary>1.92.0</summary>

##
[1.92.0](v1.91.0...v1.92.0)
(2026-09-23)


### Features

* **bigquery-jdbc:** add `EnableTimestampPicos` connection property and
its plumbing
([#14284](#14284))
([b4aa5ac](b4aa5ac))
* **bigquery-jdbc:** implement picosecond temporal math and formatting
engine
([#14286](#14286))
([2a9612a](2a9612a))
* **bigquery-jdbc:** support picosecond in REST JSON path and nested
types
([#14334](#14334))
([15ffe4a](15ffe4a))
* **bigquery-jdbc:** support picosecond in `PreparedStatement`
parameters and batching
([#14373](#14373))
([c1aac66](c1aac66))
* **bigquery-jdbc:** support picosecond timestamp in `ResultSetMetaData`
and `DatabaseMetaData`
([#14358](#14358))
([43acdd3](43acdd3))
* **bigquery-jdbc:** support picosecond timestamps in Arrow Storage Read
API and nested types
([#14332](#14332))
([b5d9aca](b5d9aca))
* **bigquery-jdbc:** support qualified project delimiter in
`DefaultDataset` property
([#14240](#14240))
([6e8d6c8](6e8d6c8))
* **bigquery:** accelerate row-based query() with Arrow wire format
([#14405](#14405))
([8d12a8f](8d12a8f))
* **bigquery:** add ArrowDeserializer helper utility
([#13943](#13943))
([d9a298b](d9a298b))
* **bigquery:** add ArrowQueryPageFetcher for Arrow query result
pagination
([#14404](#14404))
([615409f](615409f))
* **bigquery:** add ArrowQueryResult and ArrowQueryResultImpl for Arrow
result streaming
([#13944](#13944))
([a62fdf8](a62fdf8))
* **bigquery:** add Storage Read API slow-path fallback for row-based
query()
([#14409](#14409))
([26e568a](26e568a))
* **bigquery:** add zero-copy queryArrow API for Arrow VectorSchemaRoot
streaming
([#14402](#14402))
([b44ffe8](b44ffe8))
* **bigquery:** make BigQuery AutoCloseable with default no-op close
method
([#14434](#14434))
([00bf3de](00bf3de))
* **firestore:** add support for BSON types
([#13189](#13189))
([8a123d9](8a123d9))
* **gax:** add ApiCallContext and request-level settings overloads to
ResumableUploadCallable
([#14251](#14251))
([e8cbd42](e8cbd42))
* **gax:** add globalTimeout settings field to
ResumableUploadCallSettings
([#14253](#14253))
([438cda6](438cda6))
* **gax:** add resumable upload error classification and retry algorithm
([#14419](#14419))
([b70396d](b70396d))
* **gax:** add ResumableUploadCallable creation to Callables and
HttpJsonCallableFactory
([#14242](#14242))
([7de24de](7de24de))
* **gax:** implement baseline Callable and Future for resumable uploads
([#14241](#14241))
([5a54db9](5a54db9))
* **generator:** add model flag and allowlist parser for resumable
upload RPCs
([#14317](#14317))
([acc1856](acc1856))
* **generator:** emit resumable upload client surface
([#14319](#14319))
([a9fed00](a9fed00))
* **generator:** emit resumable upload settings and HttpJson upload stub
([#14321](#14321))
([c122474](c122474))
* **generator:** enable resumable upload generation for showcase
([#14325](#14325))
([f9ebd79](f9ebd79))
* **generator:** switch resumable upload specialized stubs to package
private
([#14471](#14471))
([0d4e875](0d4e875))
* **generator:** wire transport stub delegation to resumable upload
stubs
([#14322](#14322))
([cc4b980](cc4b980))
* **google/cloud/backupdr/v1beta:** add backupdr
([#14410](#14410))
([a4a47da](a4a47da))
* **google/cloud/networkservices/v1beta1:** add networkservices
([#14407](#14407))
([21c4955](21c4955))
* **pubsub:** add publish telemetry headers for publish attempt
observability
([#14338](#14338))
([c167ab8](c167ab8))
* **pubsub:** implement publish hedging to reduce tail latency
([#13735](#13735))
([b302615](b302615))
* **spanner:** Support dynamic TLS certificate and key rotation for
Spanner Omni
([#14456](#14456))
([ffc745c](ffc745c))
* **storage/control:** add delete folder recursive sample
([#13642](#13642))
([f4b1b46](f4b1b46))
* **storage/control:** add delete folder recursive sample
([#14397](#14397))
([2c01d55](2c01d55))


### Bug Fixes

* **auth:** restore transportFactory upon deserialization in
InternalAwsSecurityCredentialsSupplier
([#14340](#14340))
([beea42f](beea42f))
* **bigquery-jdbc:** ensure row ordering in PCNT IT
([#14330](#14330))
([a16f048](a16f048))
* **bigquery-jdbc:** fix htapi fallback due to permission logic
([#14418](#14418))
([21e6dc8](21e6dc8))
* **bigquery-jdbc:** fix Timestamp assertions
([#14290](#14290))
([533ba14](533ba14))
* **bigquery-jdbc:** handle null parameters in Storage Write API bulk
inserts
([#14270](#14270))
([dd2c41a](dd2c41a)),
refs
[#14066](#14066)
* **bigquery-jdbc:** handle SQL NULLs in ResultSet primitive getters
([#14383](#14383))
([8e464fe](8e464fe)),
refs
[#14371](#14371)
* **bigquery:** default Arrow pagination stream location to US instead
of global
([#14458](#14458))
([2775eb1](2775eb1))
* **bigquery:** preserve page token and paginate correctly in Arrow
query when maxResults is set
([#14469](#14469))
([f5601f4](f5601f4))
* **bigquery:** use first page row count for Arrow query pagination
offset
([#14466](#14466))
([9d10dd0](9d10dd0))
* **bigtable:** don't notify config listeners while holding the manager
lock
([#14294](#14294))
([4426ccd](4426ccd))
* **bigtable:** fall back to classic path when per-RPC CallCredentials
are set on session path
([#14477](#14477))
([57bacb0](57bacb0))
* **bigtable:** fix abnormal session closures and scale-up in session
pool
([#14431](#14431))
([6361ecd](6361ecd))
* **biqguery:** fix undeclared QueryParameter wiring in QueryStatistics
([#14401](#14401))
([64cf1d3](64cf1d3))
* **bom:** restore google-cloud-spanner-jdbc to libraries-bom
([#14362](#14362))
([bc7be5e](bc7be5e)),
refs
[#14347](#14347)
* **spanner:** honor maxAttempts and totalTimeout in streaming resume
loop
([#14370](#14370))
([305f47d](305f47d))
* **spanner:** only set snapshot isolation read timestamp for SI or
optimistic txns in CloudClientExecutor
([#14346](#14346))
([54c0d0f](54c0d0f))
* **spanner:** prevent statement cancellation race in
AbstractBaseUnitOfWork
([#14283](#14283))
([d9a8eef](d9a8eef))
* **spanner:** re-enable ITInstanceAdminTest on cloud-devel and
cloud-staging
([#14281](#14281))
([89a8268](89a8268))


### Performance Improvements

* **spanner:** stop re-parsing the request id on every RPC
([#14353](#14353))
([46108f4](46108f4))


### Documentation

* Add a Http/Json Post-Quantum Cryptography Guide
([#13963](#13963))
([fcc65b0](fcc65b0))
* **bigquery:** add QueryArrow code sample and document JDK 17+ JVM
requirements
([#14437](#14437))
([bd363f6](bd363f6))
</details>

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

---------

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
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5 participants