unified matcher and CEL by shivaspeaks · Pull Request #5 · shivaspeaks/grpc-java

shivaspeaks · 2026-01-27T19:13:45Z

Implements gRFC 106: xDS Unified Matcher and CEL Integration

https://github.com/sergiitk/grfc-proposal/blob/a106-xds-unified-matcher-and-cel/A106-xds-unified-matcher-and-cel.md

gemini-code-assist · 2026-01-27T19:15:01Z

Summary of Changes

Hello @shivaspeaks, 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 introduces CEL-based matching capabilities to gRPC's xDS implementation, enabling more sophisticated traffic routing and management. It includes new classes for CEL compilation, evaluation, and string extraction, along with enhancements to existing string matching logic. The changes also incorporate necessary dependency updates and code reorganization to support the new functionality.

Highlights

CEL Integration: Introduces Common Expression Language (CEL) for advanced matching capabilities in gRPC xDS, allowing for more flexible and dynamic traffic management.
String Matching Enhancement: Extends the StringMatcher to support case-insensitive contains matching, improving the versatility of string-based routing.
Dependency Updates: Adds CEL runtime and compiler dependencies, and protobuf exclusions to avoid conflicts.
Code Reorganization: Introduces new classes for CEL matching and string extraction, and refactors existing matcher logic to accommodate CEL expressions.

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gemini-code-assist

Code Review

This pull request introduces the xDS Unified Matcher and CEL integration, aligning with gRFC 106. The implementation provides a flexible and powerful mechanism for request matching using CEL expressions and various input types. The code is well-structured, includes necessary dependency updates, and incorporates important features like recursion depth checks and keepMatching semantics. The accompanying test cases demonstrate good coverage of the new functionality.

xds/src/main/java/io/grpc/xds/internal/matcher/CelMatcher.java

xds/src/main/java/io/grpc/xds/internal/matcher/CelStringExtractor.java

xds/src/main/java/io/grpc/xds/internal/matcher/GrpcCelEnvironment.java

xds/src/main/java/io/grpc/xds/internal/matcher/HeadersWrapper.java

xds/src/main/java/io/grpc/xds/internal/matcher/MatchResult.java

xds/src/main/java/io/grpc/xds/internal/matcher/UnifiedMatcher.java

xds/src/test/java/io/grpc/xds/internal/matcher/CelEnvironmentTest.java

xds/src/test/java/io/grpc/xds/internal/matcher/CelStringExtractorTest.java

xds/src/test/java/io/grpc/xds/internal/matcher/UnifiedMatcherTest.java

xds/build.gradle

shivaspeaks · 2026-01-28T09:39:54Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces a new xDS matching framework with support for Common Expression Language (CEL) based matching and string extraction. Key changes include adding cel-runtime and cel-compiler dependencies, new classes like CelMatcher, CelStringExtractor, GrpcCelEnvironment, HeadersWrapper, and a hierarchy of UnifiedMatcher components (MatcherList, MatcherTree, PredicateEvaluator, OnMatch, MatchResult, MatchInput). The MatcherParser and Matchers classes were updated to support an ignoreCase option for string contains matching. Build configurations were adjusted for CEL dependencies and shading. Review comments noted significant code duplication between CelMatcher and CelStringExtractor that should be refactored into a shared helper, and a typo in the OnMatch class where isSpecifed should be isSpecified.

gemini-code-assist · 2026-01-28T09:43:30Z

xds/src/main/java/io/grpc/xds/internal/matcher/CelMatcher.java

+public final class CelMatcher {
+
+  private static final CelOptions CEL_OPTIONS = CelOptions.newBuilder()
+      .enableComprehension(false)
+      .enableStringConversion(false)
+      .enableStringConcatenation(false)
+      .enableListConcatenation(false)
+      .maxRegexProgramSize(100)
+      .build();
+
+  private static final CelCompiler COMPILER = CelCompilerFactory.standardCelCompilerBuilder()
+      .addVar("request", SimpleType.DYN)
+      .setOptions(CEL_OPTIONS)
+      .build();
+
+  private static final CelRuntime RUNTIME = CelRuntimeFactory.standardCelRuntimeBuilder()
+      .setOptions(CEL_OPTIONS)
+      .build();
+
+  private final CelRuntime.Program program;
+
+  private CelMatcher(CelRuntime.Program program) {
+    this.program = program;
+  }
+
+  /**
+   * Compiles the AST into a CelMatcher.
+   */
+  public static CelMatcher compile(CelAbstractSyntaxTree ast) 
+      throws CelValidationException, CelEvaluationException {
+    if (ast.getResultType() != SimpleType.BOOL) {
+      throw new IllegalArgumentException(
+          "CEL expression must evaluate to boolean, got: " + ast.getResultType());
+    }
+    checkAllowedVariables(ast);
+    CelRuntime.Program program = RUNTIME.createProgram(ast);
+    return new CelMatcher(program);
+  }
+
+  /**
+   * Compiles the CEL expression string into a CelMatcher.
+   */
+  @VisibleForTesting
+  public static CelMatcher compile(String expression)
+      throws CelValidationException, CelEvaluationException {
+    CelAbstractSyntaxTree ast = COMPILER.compile(expression).getAst();
+    return compile(ast);
+  }
+
+  /**
+   * Evaluates the CEL expression against the input activation.
+   */
+  public boolean match(Object input) throws CelEvaluationException {
+    Object result;
+    if (input instanceof dev.cel.runtime.CelVariableResolver) {
+      result = program.eval((dev.cel.runtime.CelVariableResolver) input);
+    } else if (input instanceof java.util.Map) {
+      @SuppressWarnings("unchecked")
+      java.util.Map<String, ?> mapInput = (java.util.Map<String, ?>) input;
+      result = program.eval(mapInput);
+    } else {
+      throw new CelEvaluationException(
+          "Unsupported input type for CEL evaluation: " + input.getClass().getName());
+    }
+    // Validated to be boolean during compile check ideally, or we cast safely
+    if (result instanceof Boolean) {
+      return (Boolean) result;
+    }
+    throw new CelEvaluationException(
+        "CEL expression must evaluate to boolean, got: " + result.getClass().getName());
+  }
+
+  private static void checkAllowedVariables(CelAbstractSyntaxTree ast) {
+    // Basic validation to ensure only supported variables (request) are used.
+    // This iterates over the reference map generated by the type checker.
+    for (java.util.Map.Entry<Long, dev.cel.common.ast.CelReference> entry : 
+        ast.getReferenceMap().entrySet()) {
+      dev.cel.common.ast.CelReference ref = entry.getValue();
+      // If overload_id is empty, it's a variable reference or type name.
+      // We only support "request".
+      if (ref.value() == null && ref.overloadIds().isEmpty()) {
+        if (!"request".equals(ref.name())) {
+          throw new IllegalArgumentException(
+              "CEL expression references unknown variable: " + ref.name());
+        }
+      }
+    }
+  }
+}


There is significant code duplication between CelMatcher and CelStringExtractor. Both classes define identical CEL_OPTIONS, COMPILER, and RUNTIME static fields, and have an identical checkAllowedVariables method. The overall structure and logic for compilation and evaluation are also very similar.

To improve maintainability and reduce redundancy, consider refactoring the common code into a shared helper class, for example CelHelper. This helper could contain the static CEL components and the checkAllowedVariables method. CelMatcher and CelStringExtractor would then use this helper, keeping only their specific logic.

gemini-code-assist · 2026-01-28T09:43:30Z

xds/src/main/java/io/grpc/xds/internal/matcher/OnMatch.java

+final class OnMatch {
+  @Nullable private final UnifiedMatcher nestedMatcher;
+  @Nullable private final TypedExtensionConfig action;
+  private final boolean isSpecifed;


There is a typo in the variable name isSpecifed. It should be isSpecified. Please correct this typo and its usages within the class to improve code clarity and maintainability.

Suggested change

private final boolean isSpecifed;

private final boolean isSpecified;

gemini-code-assist bot reviewed Jan 27, 2026

View reviewed changes

shivaspeaks force-pushed the a106 branch 4 times, most recently from d493aa6 to 3bc58f7 Compare January 28, 2026 08:13

gemini-code-assist bot reviewed Jan 28, 2026

View reviewed changes

shivaspeaks force-pushed the a106 branch 2 times, most recently from 90c750a to 4f0d41a Compare February 2, 2026 06:42

unified matcher and CEL

880878b

shivaspeaks force-pushed the a106 branch from 4f0d41a to 880878b Compare February 3, 2026 09:39

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unified matcher and CEL#5

unified matcher and CEL#5
shivaspeaks wants to merge 1 commit intomasterfrom
a106

shivaspeaks commented Jan 27, 2026 •

edited

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	private final boolean isSpecifed;
	private final boolean isSpecified;

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shivaspeaks commented Jan 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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shivaspeaks commented Jan 27, 2026 •

edited

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