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perf(spanner): only create sessions if multiplexed sessions are disabled#13477

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olavloite merged 2 commits intomainfrom
spanner-only-create-sessions-if-needed
Dec 15, 2025
Merged

perf(spanner): only create sessions if multiplexed sessions are disabled#13477
olavloite merged 2 commits intomainfrom
spanner-only-create-sessions-if-needed

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@olavloite olavloite commented Dec 15, 2025

Only create regular sessions if multiplexed sessions have not been enabled for all operations. If multiplexed sessions have been enabled for all operations, and the application has not set a custom number of minimum number of sessions, then the session pool will no longer create a default of 100 regular sessions. These then also do not need to be maintained by the pool.

This change will cause the session pool to contain 0 session by default. The session pool will only be initialized with a non-zero number of sessions if any of the following is true:

  1. MinOpened has been set to a non-default value (meaning: MinOpened != 100)
  2. Multiplexed sessions have been disabled for at least one type of operation.

Only create regular sessions if multiplexed sessions have not been enabled for all
operations. If multiplexed sessions have been enabled for all operations, and the
application has not set a custom number of minimum number of sessions, then the
session pool will no longer create a default of 100 regular sessions. These then
also do not need to be maintained by the pool.
@olavloite olavloite requested review from a team December 15, 2025 09:35
@olavloite olavloite requested a review from a team as a code owner December 15, 2025 09:35
@product-auto-label product-auto-label bot added the api: spanner Issues related to the Spanner API. label Dec 15, 2025
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Summary of Changes

Hello @olavloite, I'm Gemini Code Assist1! 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 implements a performance enhancement for the Spanner client by optimizing session pool initialization. It intelligently prevents the creation of a default set of regular sessions when multiplexed sessions are fully active and the application hasn't explicitly configured a minimum session count, thereby reducing resource overhead and improving efficiency.

Highlights

  • Performance Optimization: The session pool will no longer create a default of 100 regular sessions if multiplexed sessions are fully enabled for all operations and the application has not specified a custom minimum number of sessions. This reduces unnecessary resource allocation and maintenance.
  • Test Case Refinement: Updated a test case to dynamically adjust the expected session count based on the configured MinOpened value, and modified the MinOpened and MaxOpened settings in a test client configuration for better test coverage.
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@olavloite olavloite requested a review from rahul2393 December 15, 2025 09:36
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Code Review

This pull request introduces a performance optimization to prevent the creation of regular sessions when multiplexed sessions are enabled for all operations and the default minimum session count hasn't been customized. The logic is sound and the accompanying test changes improve robustness by removing hardcoded values. I have one suggestion to improve the readability of the new conditional logic in spanner/client.go.

rahul2393
rahul2393 previously approved these changes Dec 15, 2025
@olavloite olavloite force-pushed the spanner-only-create-sessions-if-needed branch from 8f8b238 to 70c9de6 Compare December 15, 2025 10:17
@olavloite olavloite added the kokoro:force-run Add this label to force Kokoro to re-run the tests. label Dec 15, 2025
@kokoro-team kokoro-team removed the kokoro:force-run Add this label to force Kokoro to re-run the tests. label Dec 15, 2025
@olavloite olavloite merged commit e44e58f into main Dec 15, 2025
10 checks passed
@olavloite olavloite deleted the spanner-only-create-sessions-if-needed branch December 15, 2025 11:18
rahul2393 added a commit that referenced this pull request Feb 11, 2026
PR created by the Librarian CLI to initialize a release. Merging this PR
will auto trigger a release.

Librarian Version: v1.0.0
Language Image:
us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/librarian-go@sha256:19bb93e8f1f916c61b597db2bad65dc432f79baaabb210499d7d0e4ad1dffe29
<details><summary>spanner: 1.88.0</summary>

##
[1.88.0](spanner/v1.87.0...spanner/v1.88.0)
(2026-02-11)

### Features

* Adding Send and Ack Mutation Support for Cloud Spanner Queue (#13616)
([1cf600d](1cf600d6))

* include cache updates into the ResultSet response (PiperOrigin-RevId:
865546011)
([6f31019](6f310199))

* add a ClientContext field to Spanner requests (PiperOrigin-RevId:
853323071)
([80379ed](80379edb))

* add Secure Parameters to the ClientContext (PiperOrigin-RevId:
853323071)
([80379ed](80379edb))

* PGNumeric implements Scanner and Valuer (#13722)
([85bc9db](85bc9dbf))

* support struct literal (#13766)
([b4a6f4c](b4a6f4c5))

* Exposing total CPU related fields in AutoscalingConfig
(PiperOrigin-RevId: 845819318)
([db65e79](db65e792))

* add ClientContext support (#13775)
([e85d706](e85d7061))

### Bug Fixes

* disable config logging by default (#13478)
([ad19592](ad19592e))

* decode PG JSONB array to PGJsonB struct (#13602)
([d72d0f4](d72d0f45))

### Performance Improvements

* only create sessions if multiplexed sessions are disabled (#13477)
([e44e58f](e44e58f6))

### Documentation

* A comment for field `param_types` in message
`.google.spanner.v1.PartitionQueryRequest` is changed
(PiperOrigin-RevId: 865546011)
([6f31019](6f310199))

* A comment for field `transaction_tag` in message
`.google.spanner.v1.RequestOptions` is changed (PiperOrigin-RevId:
865546011)
([6f31019](6f310199))

* A comment for field `commit_timestamp` in message
`.google.spanner.v1.BatchWriteResponse` is changed (PiperOrigin-RevId:
865546011)
([6f31019](6f310199))

* A comment for field `params` in message
`.google.spanner.v1.PartitionQueryRequest` is changed
(PiperOrigin-RevId: 865546011)
([6f31019](6f310199))

* Update client side metrics and permission issues in README (#13491)
([ab56892](ab56892e))

* Update high_priority_cpu_utilization_percent in AutoscalingConfig to
be Optional and clarify its behavior when not specified
(PiperOrigin-RevId: 845819318)
([db65e79](db65e792))

</details>
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