Warn and suppress duplicate registry mirror endpoints

pkg/agent/containerd/config.go

@@ -99,6 +99,9 @@ func getHostConfigs(registry *registries.Registry, noDefaultEndpoint bool, mirro
 			}
 		}
 
+		// track which endpoints we've already seen to avoid creating duplicates
+		seenEndpoint := map[string]bool{}
+
 		// TODO: rewrites are currently copied from the mirror settings into each endpoint.
 		// In the future, we should allow for per-endpoint rewrites, instead of expecting
 		// all mirrors to have the same structure. This will require changes to the registries.yaml
@@ -107,7 +110,10 @@ func getHostConfigs(registry *registries.Registry, noDefaultEndpoint bool, mirro
 			registryName, url, override, err := normalizeEndpointAddress(endpoint, mirrorAddr)
 			if err != nil {
 				logrus.Warnf("Ignoring invalid endpoint URL %d=%s for %s: %v", i, endpoint, host, err)
+			} else if _, ok := seenEndpoint[url.String()]; ok {
+				logrus.Warnf("Skipping duplicate endpoint URL %d=%s for %s", i, endpoint, host)
 			} else {
+				seenEndpoint[url.String()] = true
 				var rewrites map[string]string
 				// Do not apply rewrites to the embedded registry endpoint
 				if url.Host != mirrorAddr {

pkg/agent/containerd/config_test.go

@@ -476,6 +476,86 @@ func Test_UnitGetHostConfigs(t *testing.T) {
 			},
 		},
 		{
+			name: "registry with mirror endpoint - duplicate endpoints",
+			args: args{
+				registryContent: `
+				  mirrors:
+						docker.io:
+							endpoint:
+								- registry.example.com
+								- registry.example.com
+				`,
+			},
+			want: HostConfigs{
+				"docker.io": templates.HostConfig{
+					Program: "k3s",
+					Default: &templates.RegistryEndpoint{
+						URL: u("https://registry-1.docker.io/v2"),
+					},
+					Endpoints: []templates.RegistryEndpoint{
+						{
+							URL: u("https://registry.example.com/v2"),
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "registry with mirror endpoint - duplicate endpoints in different formats",
+			args: args{
+				registryContent: `
+				  mirrors:
+						docker.io:
+							endpoint:
+								- registry.example.com
+								- https://registry.example.com
+								- https://registry.example.com/v2
+				`,
+			},
+			want: HostConfigs{
+				"docker.io": templates.HostConfig{
+					Program: "k3s",
+					Default: &templates.RegistryEndpoint{
+						URL: u("https://registry-1.docker.io/v2"),
+					},
+					Endpoints: []templates.RegistryEndpoint{
+						{
+							URL: u("https://registry.example.com/v2"),
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "registry with mirror endpoint - duplicate endpoints in different positions",
+			args: args{
+				registryContent: `
+				  mirrors:
+						docker.io:
+							endpoint:
+								- https://registry.example.com
+								- https://registry.example.org
+								- https://registry.example.com
+				`,
+			},
+			want: HostConfigs{
+				"docker.io": templates.HostConfig{
+					Program: "k3s",
+					Default: &templates.RegistryEndpoint{
+						URL: u("https://registry-1.docker.io/v2"),
+					},
+					Endpoints: []templates.RegistryEndpoint{
+						{
+							URL: u("https://registry.example.com/v2"),
+						},
+						{
+							URL: u("https://registry.example.org/v2"),
+						},
+					},
+				},
+			},
+		},
+		{
 			name: "registry with mirror endpoint - localhost and port only",
 			args: args{
 				registryContent: `