Add and test the Listendpoint limit

Author: yigityazicilar

Sources/GRPCHealthService/HealthService+Service.swift

@@ -22,6 +22,9 @@ private import Synchronization
 extension HealthService {
   internal struct Service: Grpc_Health_V1_Health.ServiceProtocol {
     private let state = Self.State()
+    /// Defines the maximum number of resources a `List` request can return.
+    /// An `RPCError` with the code `ResourceExhaused` is thrown if this limit is exceeded.
+    private let listMaxAllowedServices = 100
   }
 }
 
@@ -49,6 +52,13 @@ extension HealthService.Service {
   ) async throws -> ServerResponse<Grpc_Health_V1_HealthListResponse> {
     let serviceStatuses = self.state.listStatuses()
 
+    guard serviceStatuses.count <= listMaxAllowedServices else {
+      throw RPCError(
+        code: .resourceExhausted,
+        message: "Server health list exceeds maximum capacity: \(listMaxAllowedServices)."
+      )
+    }
+
     var listResponse = Grpc_Health_V1_HealthListResponse()
 
     for (service, status) in serviceStatuses {

Tests/GRPCHealthServiceTests/HealthTests.swift

@@ -344,6 +344,36 @@ final class HealthTests: XCTestCase {
       XCTAssertEqual(try XCTUnwrap(response.statuses[""]?.status), .serving)
     }
   }
+
+  func testListExceedingMaxAllowedServices() async throws {
+    try await withHealthClient { (healthClient, healthProvider) in
+      let message = Grpc_Health_V1_HealthListRequest()
+      let listMaxAllowedServices = 100
+
+      for index in 1 ... listMaxAllowedServices {
+        healthProvider.updateStatus(
+          .notServing,
+          forService: ServiceDescriptor(package: "test", service: "Service\(index)")
+        )
+
+        let response = try await healthClient.list(message)
+        XCTAssertTrue(response.statuses.count == index)
+      }
+
+      healthProvider.updateStatus(.notServing, forService: ServiceDescriptor.testService)
+
+      do {
+        _ = try await healthClient.list(message)
+        XCTFail("should error")
+      } catch {
+        let resolvedError = try XCTUnwrap(
+          error as? RPCError,
+          "health client list throws unexpected error: \(error)"
+        )
+        XCTAssertEqual(resolvedError.code, .resourceExhausted)
+      }
+    }
+  }
 }
 
 @available(gRPCSwiftExtras 2.0, *)