xds: Implement channel caching utility for GrpcService channels for ext_authz and ext_proc

[sauravzg]

Child PR of #12492

Split this from some other PR way down the chain and modified it to be not ext authz specific.

• This is currently a thread safe trivial implementation of caching based on (target, channel_creds)
• This is intended to be instantiated per Filter and not be used as some sort of a shared channel pool
• On a config change that requires creating new channels, this may perform 2 blocking operations before returning
• Creation of the channel and this happens within a lock
• shutdown of old channel if present

This should probably be okay, since this happens in the control path changes but has the potential of hammering dataplane throughtput temporarily during updates due to channel creation within the lock.

[kannanjgithub]

Minor changes requested.

[Copilot]

Pull request overview

Adds internal xDS utilities to parse Envoy GrpcService/ext_authz configuration into immutable Java config objects, introduces bootstrap parsing for allowed_grpc_services, and provides a simple per-filter ManagedChannel caching utility keyed by (target, channel_creds).

Changes:

• Add GrpcServiceConfig model + GrpcServiceConfigParser (channel creds, access-token call creds, initial metadata, timeout) and related header validation/value utilities.
• Add ext_authz config model/parser plus shared header-mutation rules model/parser and matcher parsing for fractional percents.
• Add AllowedGrpcServices bootstrap parsing + CachedChannelManager for per-filter channel reuse.

Reviewed changes

Copilot reviewed 31 out of 31 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
xds/src/main/java/io/grpc/xds/internal/headermutations/HeaderMutationRulesParser.java	Parses Envoy HeaderMutationRules into an internal config.
xds/src/main/java/io/grpc/xds/internal/headermutations/HeaderMutationRulesConfig.java	Immutable config representation for header mutation rules.
xds/src/main/java/io/grpc/xds/internal/grpcservice/HeaderValueValidationUtils.java	Validates header key/value constraints for initial metadata.
xds/src/main/java/io/grpc/xds/internal/grpcservice/HeaderValue.java	Immutable internal header key/value representation (string vs raw bytes).
xds/src/main/java/io/grpc/xds/internal/grpcservice/GrpcServiceXdsContextProvider.java	Provides per-target context for trusted/untrusted control plane decisions.
xds/src/main/java/io/grpc/xds/internal/grpcservice/GrpcServiceXdsContext.java	AutoValue context object used during GrpcService parsing.
xds/src/main/java/io/grpc/xds/internal/grpcservice/GrpcServiceParseException.java	Parse exception for GrpcService config parsing.
xds/src/main/java/io/grpc/xds/internal/grpcservice/GrpcServiceConfigParser.java	Parses Envoy GrpcService/GoogleGrpc, validates metadata/timeout, builds creds.
xds/src/main/java/io/grpc/xds/internal/grpcservice/GrpcServiceConfig.java	Immutable GrpcService config model.
xds/src/main/java/io/grpc/xds/internal/grpcservice/ConfiguredChannelCredentials.java	Bundles ChannelCredentials with comparable credential config.
xds/src/main/java/io/grpc/xds/internal/grpcservice/ChannelCredsConfig.java	Interface for credential config identity/equality.
xds/src/main/java/io/grpc/xds/internal/grpcservice/CachedChannelManager.java	Per-filter cache for ManagedChannel keyed by target + creds config.
xds/src/main/java/io/grpc/xds/internal/grpcservice/AllowedGrpcServices.java	Container for parsed allowed_grpc_services entries.
xds/src/main/java/io/grpc/xds/internal/grpcservice/AllowedGrpcService.java	Single allowed service entry (override creds/call creds).
xds/src/main/java/io/grpc/xds/internal/extauthz/ExtAuthzParseException.java	Parse exception for ext_authz parsing.
xds/src/main/java/io/grpc/xds/internal/extauthz/ExtAuthzConfigParser.java	Parses Envoy ExtAuthz into an internal config model.
xds/src/main/java/io/grpc/xds/internal/extauthz/ExtAuthzConfig.java	Immutable ext_authz config model.
xds/src/main/java/io/grpc/xds/internal/MatcherParser.java	Adds parsing for Envoy FractionalPercent to internal matcher type.
xds/src/main/java/io/grpc/xds/client/BootstrapperImpl.java	Wires bootstrap parsing hook for allowed_grpc_services.
xds/src/main/java/io/grpc/xds/client/Bootstrapper.java	Adds allowedGrpcServices() field to bootstrap info (opaque type).
xds/src/main/java/io/grpc/xds/GrpcBootstrapperImpl.java	Implements allowed_grpc_services parsing and wraps channel creds with config identity.
xds/src/test/java/io/grpc/xds/internal/headermutations/HeaderMutationRulesParserTest.java	Tests parsing of header mutation rules and invalid regex behavior.
xds/src/test/java/io/grpc/xds/internal/headermutations/HeaderMutationRulesConfigTest.java	Tests builder defaults and field setting for header mutation config.
xds/src/test/java/io/grpc/xds/internal/grpcservice/HeaderValueValidationUtilsTest.java	Tests header ignore/validation behavior (key + value/raw length rules).
xds/src/test/java/io/grpc/xds/internal/grpcservice/HeaderValueTest.java	Tests HeaderValue creation for string vs raw values.
xds/src/test/java/io/grpc/xds/internal/grpcservice/GrpcServiceXdsContextTestUtil.java	Provides dummy GrpcServiceXdsContextProvider for parser tests.
xds/src/test/java/io/grpc/xds/internal/grpcservice/GrpcServiceConfigParserTest.java	Tests GrpcService parsing, creds selection, untrusted override behavior, timeout, call-creds security gating.
xds/src/test/java/io/grpc/xds/internal/grpcservice/CachedChannelManagerTest.java	Tests channel caching and shutdown behavior on config changes/close.
xds/src/test/java/io/grpc/xds/internal/extauthz/ExtAuthzConfigParserTest.java	Tests ext_authz parsing including header mutation rules and matchers.
xds/src/test/java/io/grpc/xds/internal/MatcherParserTest.java	Tests parsing of string matchers and fractional percent denominators.
xds/src/test/java/io/grpc/xds/GrpcBootstrapperImplTest.java	Adds tests for parsing bootstrap allowed_grpc_services.

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[kannanjgithub]

The review by Co-pilot seems to have all valid points. Please fix them.

[sauravzg]

@kannanjgithub All copilot comments have either been addressed in #12492 or #12690

[sauravzg]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces support for the ext_authz (External Authorization) filter and the allowed_grpc_services field in the xDS bootstrap. It includes new parsers for ExtAuthz and GrpcService protos, internal configuration models for header mutations and matchers, and a CachedChannelManager to manage the lifecycle of gRPC channels used by the authorization service. Feedback was provided regarding the synchronization strategy in CachedChannelManager, suggesting that creating ManagedChannel instances outside of the synchronized block could prevent potential performance bottlenecks during configuration updates.