enable child channel plugins by AgraVator · Pull Request #12578 · grpc/grpc-java

AgraVator · 2025-12-22T08:41:33Z

AgraVator · 2025-12-23T05:16:44Z

+  ObjectPool<XdsClient> getOrCreate(
+      String target, BootstrapInfo bootstrapInfo, MetricRecorder metricRecorder,
+      ManagedChannel parentChannel);
+


Should this be a generic object instead of ManagedChannel ?

AgraVator · 2025-12-29T14:31:26Z

    return new XdsServerWrapper("0.0.0.0:" + port, delegate, xdsServingStatusListener,
-            filterChainSelectorManager, xdsClientPoolFactory, bootstrapOverride, filterRegistry);
+            filterChainSelectorManager, xdsClientPoolFactory, bootstrapOverride, filterRegistry,
+        this.childChannelConfigurer);


Why does this not pass the builder object ?

ejona86

I know there will be changes based on the gRFC discussion, but here are some things I noticed.

…ServerConfigurer

ejona86 · 2026-06-03T20:23:15Z

-  @Internal
-  protected T addMetricSink(MetricSink metricSink) {
+  public T addMetricSink(MetricSink metricSink) {


What's happening here? Why will this no longer be internal? Even if we were going to make it public, we wouldn't have it go immediately stable; it'd be experimental first.

When an application or test implements ChannelConfigurator, it receives a reference to the child channel's ManagedChannelBuilder.
If addMetricSink were protected (or package-private), then class implementations of ChannelConfigurator outside of the io.grpc package (such as user applications or test suites like FakeControlPlaneXdsIntegrationTest.java) would not be able to call builder.addMetricSink(sink) to register their metric sinks.

What is the problem with that? What new thing do they need to do because of ChannelConfigurator? If addMetricSink() being hidden was a problem, wouldn't that be a pre-existing problem?

GrpcOpenTelemetry.configureChannelBuilder() still works fine with ChannelConfigurator, and it calls addMetricSink() on the user's behalf.

ejona86 · 2026-06-03T20:42:15Z

  // NamedFilterConfig.filterStateKey -> filter_instance.
  private final HashMap<String, Filter> activeFiltersDefaultChain = new HashMap<>();

+  private ChannelConfigurator channelConfigurator = new ChannelConfigurator() {};


We really want this field to be final. I see there is some difficulty with the constructors here, but we should handle that with another constructor that has both ScheduledExecutorService and ChannelConfigurator.

(And we should really clean this up by using ObjectPool/SharedResourcePool/FixedObjectPool to get rid of sharedTimeService. But that is pre-existing.)

I've sent out #12841 to clean that up. Obviously the two PRs will conflict. I'm fine with waiting until this goes in and handling the conflicts. If you want it to go in first to clean up this PR, just tell me.

Rereviewing.

ejona86

This needs some more work, but I'm comfortable with Kannan reviewing it after the changes from these comments come in (no need to wait for me).

ejona86 · 2026-06-15T22:27:34Z

+   * Sets a configurator that will be applied to all internal child channels created by this
+   * channel.
+   *
+   * <p>This allows injecting configuration (like credentials, interceptors, or flow control)


Remove "credentials", it doesn't do that and shouldn't be used for that. And with the text about strongly discouraging casting it to specific implementation types, flow control isn't possible to configure either.

ejona86 · 2026-06-15T22:29:02Z

+       *
+       * @since 1.83.0
+       */
+      public Builder setChildChannelConfigurator(ChannelConfigurator channelConfigurator) {


getChildChannelConfigurator() is @Internal but this isn't. Seems weird to have them be different.

ejona86 · 2026-06-15T22:29:38Z

  }

  private NameResolver.Args createArgs() {
+    ChannelConfigurator channelConfigurator = builder -> { };


Delete this, now that NameResolver.Args fills in the same default noop?

ejona86 · 2026-06-15T22:35:23Z

    return new XdsClientResult(SharedXdsClientPoolProvider.getDefaultProvider()
-        .getOrCreate(target, bootstrapInfo, metricRecorder, transportCallCredentials));
+        .getOrCreate(target, bootstrapInfo, metricRecorder, transportCallCredentials,
+            null));


Looks like we need to add another override for the additional parameter, for use in GoogleCloudToProdNameResolver.

ejona86 · 2026-06-15T22:38:10Z

+        if (hasMetrics) {
+          break;
+        }
+        Thread.sleep(100);


What is this for?

ejona86 · 2026-06-15T22:40:03Z

+ * xDS + OpenTelemetry E2E integration test using a fake control plane.
+ */
+@RunWith(Parameterized.class)
+public class FakeControlPlaneXdsOtelIntegrationTest {


This test doesn't seem to do anything special. It isn't actually checking that xds client metrics are propagating. If you disable xds in this test, it will still pass, because it is using the generic grpc.client. prefix, which the RPC itself satisfies.

ejona86 · 2026-06-15T22:40:40Z

+      }
+      assertThat(hasMetrics).isTrue();
+    } finally {
+      channel.shutdownNow();


Use GrpcCleanupRule instead of try-finally+shutdown.

AgraVator added 2 commits December 22, 2025 14:09

enable child channel plugins

476e5a8

add test cases

2554a04

AgraVator requested review from ejona86 and kannanjgithub December 22, 2025 11:24

AgraVator added 2 commits December 22, 2025 17:27

remove unused field

cf4909e

correct javadoc

4905f72

AgraVator commented Dec 23, 2025

View reviewed changes

AgraVator added 2 commits December 29, 2025 17:13

plumb child channel options through xDS server

36c2927

add test case for xDS server and others

3259d67

AgraVator commented Dec 29, 2025

View reviewed changes

AgraVator mentioned this pull request Jan 5, 2026

ChildChannelConfigurer is experimental #12574

Open

kannanjgithub previously approved these changes Jan 6, 2026

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Comment thread api/src/main/java/io/grpc/ChildChannelConfigurer.java Outdated

Comment thread api/src/main/java/io/grpc/ChildChannelConfigurer.java Outdated

ejona86 reviewed Mar 4, 2026

View reviewed changes

Comment thread api/src/main/java/io/grpc/ChildChannelConfigurers.java Outdated

Comment thread api/src/main/java/io/grpc/ChildChannelConfigurers.java Outdated

Comment thread api/src/main/java/io/grpc/ManagedChannel.java Outdated

Comment thread api/src/main/java/io/grpc/Server.java Outdated

AgraVator and others added 4 commits March 14, 2026 02:04

fix: pass the configurer

eab10a9

expose APIs similar to internalConfigurator

d8398f5

Merge branch 'master' into child-channel-plugin

374cbdf

fix: refactor from ChildChannelConfigurer to ChannelConfigurer

367640e

AgraVator marked this pull request as ready for review March 18, 2026 09:04

AgraVator and others added 2 commits March 18, 2026 14:36

Merge branch 'master' into child-channel-plugin

0346e90

fix: merge conflict

3e38536

AgraVator commented May 26, 2026

View reviewed changes

Comment thread api/src/main/java/io/grpc/ChannelConfigurer.java Outdated

ejona86 reviewed May 26, 2026

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Comment thread api/src/main/java/io/grpc/MetricRecorder.java Outdated

kannanjgithub reviewed May 29, 2026

View reviewed changes

Comment thread api/src/main/java/io/grpc/ManagedChannelBuilder.java Outdated

Comment thread core/src/main/java/io/grpc/internal/ManagedChannelImplBuilder.java Outdated

AgraVator and others added 6 commits June 2, 2026 13:48

Fix: rename ChannelConfigurer to ChannelConfigurator and removes the …

d3eed7f

…ServerConfigurer

Fix: left over name changes

b9d687d

Merge branch 'master' into child-channel-plugin

f816bba

Fix: test cases

bdcb745

Fix: test cases

4cfc0c6

Fix: formatting

4ff8d40

AgraVator requested a review from kannanjgithub June 3, 2026 11:55

AgraVator requested a review from ejona86 June 3, 2026 11:55

ejona86 reviewed Jun 3, 2026

View reviewed changes

ejona86 mentioned this pull request Jun 3, 2026

xds: Use ObjectPool to manage scheduler in XdsServerWrapper #12841

Open

AgraVator added 2 commits June 8, 2026 10:25

Fix: suggested changes

b8bd9f1

Fix: bazel tests

bfa5a26

AgraVator requested a review from ejona86 June 8, 2026 06:35

Fix: formatting

03e55fd

kannanjgithub requested changes Jun 10, 2026

View reviewed changes

Comment thread api/src/main/java/io/grpc/ChannelConfigurator.java

Comment thread api/src/main/java/io/grpc/ChannelConfigurator.java

Comment thread api/src/main/java/io/grpc/ChannelConfigurator.java

Fix: suggested changes

a7a6494

AgraVator requested a review from kannanjgithub June 12, 2026 08:42

kannanjgithub approved these changes Jun 15, 2026

View reviewed changes

Fix: formatting

99a90c4

ejona86 reviewed Jun 15, 2026

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AgraVator commented Dec 22, 2025 •

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