feat: make grpc-gcp default enabled #4239

rahul2393 · 2025-11-20T18:47:03Z

This PR enables the gRPC-GCP channel pool extension by default for Cloud Spanner Java client.

What's Changing for Customers

Before this change

gRPC-GCP extension was disabled by default
Default number of channels: 4
Channel pooling was handled by GAX

After this change

gRPC-GCP extension is enabled by default
Default number of channels: 8
Channel pooling is handled by gRPC-GCP extension

Benefits of gRPC-GCP

Improved resilience: When a network connection fails on a particular channel, operations can be automatically retried on a different gRPC channel
Better channel management: gRPC-GCP provides more sophisticated channel affinity and load balancing

How to Disable gRPC-GCP (Switch Back to GAX Channel Pool)

If you need to disable gRPC-GCP and use the previous GAX channel pooling behavior, use the disableGrpcGcpExtension() method:

SpannerOptions options = SpannerOptions.newBuilder()
    .setProjectId("my-project")
    .disableGrpcGcpExtension()
    .build();

When disabled, the default number of channels reverts to 4 (the previous default).

When You Might Want to Disable gRPC-GCP

Maintaining previous behavior: If you want to keep the exact same behavior as before this change (GAX channel pool with 4 default channels).
Troubleshooting: If you experience any unexpected behavior, disabling gRPC-GCP can help isolate whether the issue is related to the channel pooling mechanism.

gemini-code-assist · 2025-11-20T18:47:37Z

Summary of Changes

Hello @rahul2393, 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 transitions the grpc-gcp extension in the Spanner client library to be enabled by default. This change simplifies the client's internal logic by removing a configuration flag and its conditional code paths, ensuring that all users benefit from the performance and reliability improvements offered by gRPC-GCP without requiring manual activation.

Highlights

Default gRPC-GCP Enablement: The grpc-gcp extension is now enabled by default, removing the need for explicit configuration to activate it.
Code Simplification: The grpcGcpExtensionEnabled boolean field and all associated conditional logic have been removed from SpannerOptions and GapicSpannerRpc, streamlining the codebase.
Consistent Channel Management: Channel affinity and the number of channels are now consistently managed under the assumption that gRPC-GCP is always active, simplifying channel configuration.

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Code Review

This pull request makes the grpc-gcp extension enabled by default, which is a good simplification. The changes correctly remove the feature flag and update the related logic. My review includes a few suggestions to improve API clarity and test naming following these changes:

API Clarity: The methods enableGrpcGcpExtension and disableGrpcGcpExtension are now misleading or no-ops. I've suggested addressing this to avoid confusion.
Test Naming: Some test method names have become outdated due to the changes. I've pointed these out with suggestions for new names that better reflect their current purpose.

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java

google-cloud-spanner/src/test/java/com/google/cloud/spanner/SpannerOptionsTest.java

sakthivelmanii · 2025-11-21T01:06:16Z

@rahul2393 as a first step, can you please enable it by default without removing the option? If needed, customer can disable it.

olavloite · 2025-12-12T15:37:25Z

google-cloud-spanner-bom/pom.xml

        <artifactId>proto-google-cloud-spanner-admin-database-v1</artifactId>
        <version>6.104.0</version><!-- {x-version-update:proto-google-cloud-spanner-admin-database-v1:current} -->
      </dependency>
+      <dependency>


I find this a bit surprising. I would rather have expected this to only be a dependency of com.google.cloud:google-cloud-spanner (so only the actual hand-written client library).

olavloite · 2025-12-12T15:38:14Z

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AbstractReadContext.java

+            this.incrementXGoogRequestIdAttempt();
+            Map<SpannerRpc.Option, ?> txChannelHint = getTransactionChannelHint();
+            if (txChannelHint != null && txChannelHint.get(Option.CHANNEL_HINT) != null) {
+              long channelHint = Option.CHANNEL_HINT.getLong(txChannelHint);
+              this.xGoogRequestId.setChannelId(channelHint);
+            } else {
+              this.xGoogRequestId.setChannelId(session.getChannel());
+            }


Hmm.... This is going to conflict with #4263. That PR removes most of the manual handling of Request ID.

olavloite · 2025-12-12T15:39:02Z

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java

-     * GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS to true in combination with this option, as
-     * Multiplexed sessions are not supported for gRPC-GCP.
-     */
+    /** Enables gRPC-GCP extension with the default settings. */


Suggested change

/** Enables gRPC-GCP extension with the default settings. */

/** Enables gRPC-GCP extension with the default settings. This option is enabled by default. */

olavloite · 2025-12-12T15:41:32Z

google-cloud-spanner/src/test/java/com/google/cloud/spanner/ChannelUsageTest.java

+                          if (call.getMethodDescriptor()
+                              .equals(SpannerGrpc.getBatchCreateSessionsMethod())) {


This should probably be replaced with CreateSession. It works (for now), but once the session pool is removed, this will silently be ignored, as there are no calls to BatchCreateSessions.

olavloite · 2025-12-12T15:45:29Z

pom.xml

+      <dependency>
+        <groupId>com.google.cloud</groupId>
+        <artifactId>grpc-gcp</artifactId>
+        <version>1.7.0</version>
+      </dependency>


Do we need it here? AFAICT, it is only used in the hand-written client library (in com.google.cloud:google-cloud-spanner).

nimf · 2025-12-12T20:43:14Z

Note, that, AFAIU, this will also enable grpc-gcp metrics by default (and these are many more metrics than session metrics), this can be an issue if it's shipped to the custom namespace.

rahul2393 requested review from a team as code owners November 20, 2025 18:47

product-auto-label bot added size: m Pull request size is medium. api: spanner Issues related to the googleapis/java-spanner API. labels Nov 20, 2025

gemini-code-assist bot reviewed Nov 20, 2025

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rahul2393 added do not merge Indicates a pull request not ready for merge, due to either quality or timing. and removed do not merge Indicates a pull request not ready for merge, due to either quality or timing. labels Nov 20, 2025

rahul2393 added 4 commits December 9, 2025 10:10

feat: make grpc-gcp default enabled

89df374

fix test

3498883

add logs

998c8bc

pin grpc-gcp version

c3ef0a5

rahul2393 force-pushed the default-enable-grpc-gcp branch from 4b599e1 to d2c3101 Compare December 9, 2025 04:40

fix test

75ac207

rahul2393 force-pushed the default-enable-grpc-gcp branch from 8bd7007 to 75ac207 Compare December 9, 2025 04:44

rahul2393 added 2 commits December 9, 2025 10:50

fix build

8349844

fix tests

ac8db3d

product-auto-label bot added size: l Pull request size is large. and removed size: m Pull request size is medium. labels Dec 9, 2025

fix native image tests

eaeef52

rahul2393 force-pushed the default-enable-grpc-gcp branch from cd99542 to eaeef52 Compare December 11, 2025 08:37

rahul2393 and others added 5 commits December 12, 2025 10:22

add ability to disable grpc-gcp if needed

63f0188

fix tests

0380118

Merge branch 'main' into default-enable-grpc-gcp

4cb1192

fix javadoc

bb11190

use channel hint for checking channel usage

044e1f5

olavloite reviewed Dec 12, 2025

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feat: make grpc-gcp default enabled #4239

feat: make grpc-gcp default enabled #4239

rahul2393 commented Nov 20, 2025 •

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	/** Enables gRPC-GCP extension with the default settings. */
	/** Enables gRPC-GCP extension with the default settings. This option is enabled by default. */

		if (call.getMethodDescriptor()
		.equals(SpannerGrpc.getBatchCreateSessionsMethod())) {

feat: make grpc-gcp default enabled #4239

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rahul2393 commented Nov 20, 2025 •

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