internal/envconfig: add convenience boolFromEnv to improve readability (#5887)

internal/envconfig/envconfig.go

@@ -25,18 +25,12 @@ import (
 	"strings"
 )
 
-const (
-	prefix                  = "GRPC_GO_"
-	txtErrIgnoreStr         = prefix + "IGNORE_TXT_ERRORS"
-	advertiseCompressorsStr = prefix + "ADVERTISE_COMPRESSORS"
-)
-
 var (
 	// TXTErrIgnore is set if TXT errors should be ignored ("GRPC_GO_IGNORE_TXT_ERRORS" is not "false").
-	TXTErrIgnore = !strings.EqualFold(os.Getenv(txtErrIgnoreStr), "false")
+	TXTErrIgnore = boolFromEnv("GRPC_GO_IGNORE_TXT_ERRORS", true)
 	// AdvertiseCompressors is set if registered compressor should be advertised
 	// ("GRPC_GO_ADVERTISE_COMPRESSORS" is not "false").
-	AdvertiseCompressors = !strings.EqualFold(os.Getenv(advertiseCompressorsStr), "false")
+	AdvertiseCompressors = boolFromEnv("GRPC_GO_ADVERTISE_COMPRESSORS", true)
 	// RingHashCap indicates the maximum ring size which defaults to 4096
 	// entries but may be overridden by setting the environment variable
 	// "GRPC_RING_HASH_CAP".  This does not override the default bounds
@@ -44,6 +38,15 @@ var (
 	RingHashCap = uint64FromEnv("GRPC_RING_HASH_CAP", 4096, 1, 8*1024*1024)
 )
 
+func boolFromEnv(envVar string, def bool) bool {
+	if def {
+		// The default is true; return true unless the variable is "false".
+		return !strings.EqualFold(os.Getenv(envVar), "false")
+	}
+	// The default is false; return false unless the variable is "true".
+	return strings.EqualFold(os.Getenv(envVar), "true")
+}
+
 func uint64FromEnv(envVar string, def, min, max uint64) uint64 {
 	v, err := strconv.ParseUint(os.Getenv(envVar), 10, 64)
 	if err != nil {

internal/envconfig/envconfig_test.go

@@ -34,7 +34,6 @@ func Test(t *testing.T) {
 }
 
 func (s) TestUint64FromEnv(t *testing.T) {
-
 	var testCases = []struct {
 		name          string
 		val           string
@@ -72,3 +71,33 @@ func (s) TestUint64FromEnv(t *testing.T) {
 		})
 	}
 }
+
+func (s) TestBoolFromEnv(t *testing.T) {
+	var testCases = []struct {
+		val  string
+		def  bool
+		want bool
+	}{
+		{val: "", def: true, want: true},
+		{val: "", def: false, want: false},
+		{val: "true", def: true, want: true},
+		{val: "true", def: false, want: true},
+		{val: "false", def: true, want: false},
+		{val: "false", def: false, want: false},
+		{val: "asdf", def: true, want: true},
+		{val: "asdf", def: false, want: false},
+	}
+	for _, tc := range testCases {
+		t.Run("", func(t *testing.T) {
+			const testVar = "testvar"
+			if tc.val == "" {
+				os.Unsetenv(testVar)
+			} else {
+				os.Setenv(testVar, tc.val)
+			}
+			if got := boolFromEnv(testVar, tc.def); got != tc.want {
+				t.Errorf("boolFromEnv(%q(=%q), %v) = %v; want %v", testVar, tc.val, tc.def, got, tc.want)
+			}
+		})
+	}
+}

internal/envconfig/xds.go

@@ -20,7 +20,6 @@ package envconfig
 
 import (
 	"os"
-	"strings"
 )
 
 const (
@@ -36,16 +35,6 @@ const (
 	//
 	// When both bootstrap FileName and FileContent are set, FileName is used.
 	XDSBootstrapFileContentEnv = "GRPC_XDS_BOOTSTRAP_CONFIG"
-
-	ringHashSupportEnv           = "GRPC_XDS_EXPERIMENTAL_ENABLE_RING_HASH"
-	clientSideSecuritySupportEnv = "GRPC_XDS_EXPERIMENTAL_SECURITY_SUPPORT"
-	aggregateAndDNSSupportEnv    = "GRPC_XDS_EXPERIMENTAL_ENABLE_AGGREGATE_AND_LOGICAL_DNS_CLUSTER"
-	rbacSupportEnv               = "GRPC_XDS_EXPERIMENTAL_RBAC"
-	outlierDetectionSupportEnv   = "GRPC_EXPERIMENTAL_ENABLE_OUTLIER_DETECTION"
-	federationEnv                = "GRPC_EXPERIMENTAL_XDS_FEDERATION"
-	rlsInXDSEnv                  = "GRPC_EXPERIMENTAL_XDS_RLS_LB"
-
-	c2pResolverTestOnlyTrafficDirectorURIEnv = "GRPC_TEST_ONLY_GOOGLE_C2P_RESOLVER_TRAFFIC_DIRECTOR_URI"
 )
 
 var (
@@ -64,38 +53,40 @@ var (
 	// XDSRingHash indicates whether ring hash support is enabled, which can be
 	// disabled by setting the environment variable
 	// "GRPC_XDS_EXPERIMENTAL_ENABLE_RING_HASH" to "false".
-	XDSRingHash = !strings.EqualFold(os.Getenv(ringHashSupportEnv), "false")
+	XDSRingHash = boolFromEnv("GRPC_XDS_EXPERIMENTAL_ENABLE_RING_HASH", true)
 	// XDSClientSideSecurity is used to control processing of security
 	// configuration on the client-side.
 	//
 	// Note that there is no env var protection for the server-side because we
 	// have a brand new API on the server-side and users explicitly need to use
 	// the new API to get security integration on the server.
-	XDSClientSideSecurity = !strings.EqualFold(os.Getenv(clientSideSecuritySupportEnv), "false")
+	XDSClientSideSecurity = boolFromEnv("GRPC_XDS_EXPERIMENTAL_SECURITY_SUPPORT", true)
 	// XDSAggregateAndDNS indicates whether processing of aggregated cluster
 	// and DNS cluster is enabled, which can be enabled by setting the
 	// environment variable
 	// "GRPC_XDS_EXPERIMENTAL_ENABLE_AGGREGATE_AND_LOGICAL_DNS_CLUSTER" to
 	// "true".
-	XDSAggregateAndDNS = !strings.EqualFold(os.Getenv(aggregateAndDNSSupportEnv), "false")
+	XDSAggregateAndDNS = boolFromEnv("GRPC_XDS_EXPERIMENTAL_ENABLE_AGGREGATE_AND_LOGICAL_DNS_CLUSTER", true)
 
 	// XDSRBAC indicates whether xDS configured RBAC HTTP Filter is enabled,
 	// which can be disabled by setting the environment variable
 	// "GRPC_XDS_EXPERIMENTAL_RBAC" to "false".
-	XDSRBAC = !strings.EqualFold(os.Getenv(rbacSupportEnv), "false")
+	XDSRBAC = boolFromEnv("GRPC_XDS_EXPERIMENTAL_RBAC", true)
 	// XDSOutlierDetection indicates whether outlier detection support is
 	// enabled, which can be disabled by setting the environment variable
 	// "GRPC_EXPERIMENTAL_ENABLE_OUTLIER_DETECTION" to "false".
-	XDSOutlierDetection = !strings.EqualFold(os.Getenv(outlierDetectionSupportEnv), "false")
-	// XDSFederation indicates whether federation support is enabled.
-	XDSFederation = strings.EqualFold(os.Getenv(federationEnv), "true")
+	XDSOutlierDetection = boolFromEnv("GRPC_EXPERIMENTAL_ENABLE_OUTLIER_DETECTION", true)
+	// XDSFederation indicates whether federation support is enabled, which can
+	// be enabled by setting the environment variable
+	// "GRPC_EXPERIMENTAL_XDS_FEDERATION" to "true".
+	XDSFederation = boolFromEnv("GRPC_EXPERIMENTAL_XDS_FEDERATION", false)
 
 	// XDSRLS indicates whether processing of Cluster Specifier plugins and
 	// support for the RLS CLuster Specifier is enabled, which can be enabled by
 	// setting the environment variable "GRPC_EXPERIMENTAL_XDS_RLS_LB" to
 	// "true".
-	XDSRLS = strings.EqualFold(os.Getenv(rlsInXDSEnv), "true")
+	XDSRLS = boolFromEnv("GRPC_EXPERIMENTAL_XDS_RLS_LB", false)
 
 	// C2PResolverTestOnlyTrafficDirectorURI is the TD URI for testing.
-	C2PResolverTestOnlyTrafficDirectorURI = os.Getenv(c2pResolverTestOnlyTrafficDirectorURIEnv)
+	C2PResolverTestOnlyTrafficDirectorURI = os.Getenv("GRPC_TEST_ONLY_GOOGLE_C2P_RESOLVER_TRAFFIC_DIRECTOR_URI")
 )