xds bootstrap: support config content in env variable

xds/internal/client/bootstrap/bootstrap.go

@@ -96,6 +96,29 @@ type xdsServer struct {
 	ServerFeatures []string       `json:"server_features"`
 }
 
+func bootstrapConfigFromEnvVariable() ([]byte, error) {
+	fName := env.BootstrapFileName
+	fContent := env.BootstrapFileContent
+
+	// Bootstrap file name has higher priority than bootstrap content.
+	if fName != "" {
+		// If file name is set
+		// - If file not found (or other errors), fail
+		// - Otherwise, use the content.
+		//
+		// Note that even if the content is invalid, we don't failover to the
+		// file content env variable.
+		logger.Debugf("xds: using bootstrap file with name %q", fName)
+		return bootstrapFileReadFunc(fName)
+	}
+
+	if fContent != "" {
+		return []byte(fContent), nil
+	}
+
+	return nil, fmt.Errorf("none of the bootstrap environment variables (%q or %q) defined", env.BootstrapFileNameEnv, env.BootstrapFileContentEnv)
+}
+
 // NewConfig returns a new instance of Config initialized by reading the
 // bootstrap file found at ${GRPC_XDS_BOOTSTRAP}.
 //
@@ -136,21 +159,15 @@ type xdsServer struct {
 func NewConfig() (*Config, error) {
 	config := &Config{}
 
-	fName := env.BootstrapFileName
-	if fName == "" {
-		return nil, fmt.Errorf("xds: Environment variable %q not defined", "GRPC_XDS_BOOTSTRAP")
-	}
-	logger.Infof("Got bootstrap file location %q", fName)
-
-	data, err := bootstrapFileReadFunc(fName)
+	data, err := bootstrapConfigFromEnvVariable()
 	if err != nil {
-		return nil, fmt.Errorf("xds: Failed to read bootstrap file %s with error %v", fName, err)
+		return nil, fmt.Errorf("xds: Failed to read bootstrap config: %v", err)
 	}
 	logger.Debugf("Bootstrap content: %s", data)
 
 	var jsonData map[string]json.RawMessage
 	if err := json.Unmarshal(data, &jsonData); err != nil {
-		return nil, fmt.Errorf("xds: Failed to parse file %s (content %v) with error: %v", fName, string(data), err)
+		return nil, fmt.Errorf("xds: Failed to parse bootstrap config: %v", err)
 	}
 
 	serverSupportsV3 := false

xds/internal/client/bootstrap/bootstrap_test.go

@@ -264,20 +264,67 @@ func (c *Config) compare(want *Config) error {
 	return nil
 }
 
+func fileReadFromFileMap(bootstrapFileMap map[string]string, name string) ([]byte, error) {
+	if b, ok := bootstrapFileMap[name]; ok {
+		return []byte(b), nil
+	}
+	return nil, os.ErrNotExist
+}
+
 func setupBootstrapOverride(bootstrapFileMap map[string]string) func() {
 	oldFileReadFunc := bootstrapFileReadFunc
-	bootstrapFileReadFunc = func(name string) ([]byte, error) {
-		if b, ok := bootstrapFileMap[name]; ok {
-			return []byte(b), nil
-		}
-		return nil, os.ErrNotExist
+	bootstrapFileReadFunc = func(filename string) ([]byte, error) {
+		return fileReadFromFileMap(bootstrapFileMap, filename)
 	}
 	return func() { bootstrapFileReadFunc = oldFileReadFunc }
 }
 
 // TODO: enable leak check for this package when
 // https://github.com/googleapis/google-cloud-go/issues/2417 is fixed.
 
+// This function overrides the bootstrap file NAME env variable, to test the
+// code that reads file with the given fileName.
+func testNewConfigWithFileNameEnv(t *testing.T, fileName string, wantError bool, wantConfig *Config) {
+	origBootstrapFileName := env.BootstrapFileName
+	env.BootstrapFileName = fileName
+	defer func() { env.BootstrapFileName = origBootstrapFileName }()
+
+	c, err := NewConfig()
+	if (err != nil) != wantError {
+		t.Fatalf("NewConfig() returned error %v, wantError: %v", err, wantError)
+	}
+	if wantError {
+		return
+	}
+	if err := c.compare(wantConfig); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// This function overrides the bootstrap file CONTENT env variable, to test the
+// code that uses the content from env directly.
+func testNewConfigWithFileContentEnv(t *testing.T, fileName string, wantError bool, wantConfig *Config) {
+	b, err := bootstrapFileReadFunc(fileName)
+	if err != nil {
+		// If file reading failed, skip this test.
+		return
+	}
+	origBootstrapContent := env.BootstrapFileContent
+	env.BootstrapFileContent = string(b)
+	defer func() { env.BootstrapFileContent = origBootstrapContent }()
+
+	c, err := NewConfig()
+	if (err != nil) != wantError {
+		t.Fatalf("NewConfig() returned error %v, wantError: %v", err, wantError)
+	}
+	if wantError {
+		return
+	}
+	if err := c.compare(wantConfig); err != nil {
+		t.Fatal(err)
+	}
+}
+
 // TestNewConfigV2ProtoFailure exercises the functionality in NewConfig with
 // different bootstrap file contents which are expected to fail.
 func TestNewConfigV2ProtoFailure(t *testing.T) {
@@ -338,13 +385,8 @@ func TestNewConfigV2ProtoFailure(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			origBootstrapFileName := env.BootstrapFileName
-			env.BootstrapFileName = test.name
-			defer func() { env.BootstrapFileName = origBootstrapFileName }()
-
-			if _, err := NewConfig(); err == nil {
-				t.Fatalf("NewConfig() returned nil error, expected to fail")
-			}
+			testNewConfigWithFileNameEnv(t, test.name, true, nil)
+			testNewConfigWithFileContentEnv(t, test.name, true, nil)
 		})
 	}
 }
@@ -382,17 +424,8 @@ func TestNewConfigV2ProtoSuccess(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			origBootstrapFileName := env.BootstrapFileName
-			env.BootstrapFileName = test.name
-			defer func() { env.BootstrapFileName = origBootstrapFileName }()
-
-			c, err := NewConfig()
-			if err != nil {
-				t.Fatalf("NewConfig() failed: %v", err)
-			}
-			if err := c.compare(test.wantConfig); err != nil {
-				t.Fatal(err)
-			}
+			testNewConfigWithFileNameEnv(t, test.name, false, test.wantConfig)
+			testNewConfigWithFileContentEnv(t, test.name, false, test.wantConfig)
 		})
 	}
 }
@@ -419,17 +452,8 @@ func TestNewConfigV3SupportNotEnabledOnClient(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			origBootstrapFileName := env.BootstrapFileName
-			env.BootstrapFileName = test.name
-			defer func() { env.BootstrapFileName = origBootstrapFileName }()
-
-			c, err := NewConfig()
-			if err != nil {
-				t.Fatalf("NewConfig() failed: %v", err)
-			}
-			if err := c.compare(test.wantConfig); err != nil {
-				t.Fatal(err)
-			}
+			testNewConfigWithFileNameEnv(t, test.name, false, test.wantConfig)
+			testNewConfigWithFileContentEnv(t, test.name, false, test.wantConfig)
 		})
 	}
 }
@@ -456,31 +480,66 @@ func TestNewConfigV3SupportEnabledOnClient(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			origBootstrapFileName := env.BootstrapFileName
-			env.BootstrapFileName = test.name
-			defer func() { env.BootstrapFileName = origBootstrapFileName }()
-
-			c, err := NewConfig()
-			if err != nil {
-				t.Fatalf("NewConfig() failed: %v", err)
-			}
-			if err := c.compare(test.wantConfig); err != nil {
-				t.Fatal(err)
-			}
+			testNewConfigWithFileNameEnv(t, test.name, false, test.wantConfig)
+			testNewConfigWithFileContentEnv(t, test.name, false, test.wantConfig)
 		})
 	}
 }
 
-// TestNewConfigBootstrapFileEnvNotSet tests the case where the bootstrap file
+// TestNewConfigBootstrapEnvPriority tests that the two env variables are read in correct priority
+//
+// the case where the bootstrap file
 // environment variable is not set.
-func TestNewConfigBootstrapFileEnvNotSet(t *testing.T) {
+func TestNewConfigBootstrapEnvPriority(t *testing.T) {
+	origV3Support := env.V3Support
+	env.V3Support = true
+	defer func() { env.V3Support = origV3Support }()
+
+	oldFileReadFunc := bootstrapFileReadFunc
+	bootstrapFileReadFunc = func(filename string) ([]byte, error) {
+		return fileReadFromFileMap(v2BootstrapFileMap, filename)
+	}
+	defer func() { bootstrapFileReadFunc = oldFileReadFunc }()
+
+	goodFileName1 := "goodBootstrap"
+	goodConfig1 := nonNilCredsConfigV2
+
+	goodFileName2 := "serverSupportsV3"
+	goodFileContent2 := v3BootstrapFileMap[goodFileName2]
+	goodConfig2 := nonNilCredsConfigV3
+
 	origBootstrapFileName := env.BootstrapFileName
 	env.BootstrapFileName = ""
 	defer func() { env.BootstrapFileName = origBootstrapFileName }()
 
+	origBootstrapContent := env.BootstrapFileContent
+	env.BootstrapFileContent = ""
+	defer func() { env.BootstrapFileContent = origBootstrapContent }()
+
+	// When both env variables are empty, NewConfig should fail.
 	if _, err := NewConfig(); err == nil {
 		t.Errorf("NewConfig() returned nil error, expected to fail")
 	}
+
+	// When one of them is set, it should be used.
+	env.BootstrapFileName = goodFileName1
+	env.BootstrapFileContent = ""
+	if c, err := NewConfig(); err != nil || c.compare(goodConfig1) != nil {
+		t.Errorf("NewConfig() = %v, %v, want: %v, %v", c, err, goodConfig1, nil)
+	}
+
+	env.BootstrapFileName = ""
+	env.BootstrapFileContent = goodFileContent2
+	if c, err := NewConfig(); err != nil || c.compare(goodConfig2) != nil {
+		t.Errorf("NewConfig() = %v, %v, want: %v, %v", c, err, goodConfig1, nil)
+	}
+
+	// Set both, file name should be read.
+	env.BootstrapFileName = goodFileName1
+	env.BootstrapFileContent = goodFileContent2
+	if c, err := NewConfig(); err != nil || c.compare(goodConfig1) != nil {
+		t.Errorf("NewConfig() = %v, %v, want: %v, %v", c, err, goodConfig1, nil)
+	}
 }
 
 func init() {
@@ -686,20 +745,8 @@ func TestNewConfigWithCertificateProviders(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			origBootstrapFileName := env.BootstrapFileName
-			env.BootstrapFileName = test.name
-			defer func() { env.BootstrapFileName = origBootstrapFileName }()
-
-			c, err := NewConfig()
-			if (err != nil) != test.wantErr {
-				t.Fatalf("NewConfig() returned: %v, wantErr: %v", err, test.wantErr)
-			}
-			if test.wantErr {
-				return
-			}
-			if err := c.compare(test.wantConfig); err != nil {
-				t.Fatal(err)
-			}
+			testNewConfigWithFileNameEnv(t, test.name, test.wantErr, test.wantConfig)
+			testNewConfigWithFileContentEnv(t, test.name, test.wantErr, test.wantConfig)
 		})
 	}
 }
@@ -764,20 +811,8 @@ func TestNewConfigWithServerResourceNameID(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			origBootstrapFileName := env.BootstrapFileName
-			env.BootstrapFileName = test.name
-			defer func() { env.BootstrapFileName = origBootstrapFileName }()
-
-			c, err := NewConfig()
-			if (err != nil) != test.wantErr {
-				t.Fatalf("NewConfig() returned (%+v, %v), wantErr: %v", c, err, test.wantErr)
-			}
-			if test.wantErr {
-				return
-			}
-			if err := c.compare(test.wantConfig); err != nil {
-				t.Fatal(err)
-			}
+			testNewConfigWithFileNameEnv(t, test.name, test.wantErr, test.wantConfig)
+			testNewConfigWithFileContentEnv(t, test.name, test.wantErr, test.wantConfig)
 		})
 	}
 }

xds/internal/env/env.go

@@ -26,7 +26,18 @@ import (
 )
 
 const (
-	bootstrapFileNameEnv      = "GRPC_XDS_BOOTSTRAP"
+	// BootstrapFileNameEnv is the env variable to set bootstrap file name.
+	// Do not use this and read from env directly. Its value is read and kept in
+	// variable BootstrapFileName.
+	//
+	// When both bootstrap FileName and FileContent are set, FileName is used.
+	BootstrapFileNameEnv = "GRPC_XDS_BOOTSTRAP"
+	// BootstrapFileContentEnv is the env variable to set bootstrapp file
+	// content. Do not use this and read from env directly. Its value is read
+	// and kept in variable BootstrapFileName.
+	//
+	// When both bootstrap FileName and FileContent are set, FileName is used.
+	BootstrapFileContentEnv   = "GRPC_XDS_BOOTSTRAP_CONFIG"
 	xdsV3SupportEnv           = "GRPC_XDS_EXPERIMENTAL_V3_SUPPORT"
 	circuitBreakingSupportEnv = "GRPC_XDS_EXPERIMENTAL_CIRCUIT_BREAKING"
 	timeoutSupportEnv         = "GRPC_XDS_EXPERIMENTAL_ENABLE_TIMEOUT"
@@ -36,7 +47,15 @@ var (
 	// BootstrapFileName holds the name of the file which contains xDS bootstrap
 	// configuration. Users can specify the location of the bootstrap file by
 	// setting the environment variable "GRPC_XDS_BOOSTRAP".
-	BootstrapFileName = os.Getenv(bootstrapFileNameEnv)
+	//
+	// When both bootstrap FileName and FileContent are set, FileName is used.
+	BootstrapFileName = os.Getenv(BootstrapFileNameEnv)
+	// BootstrapFileContent holds the content of the xDS bootstrap
+	// configuration. Users can specify the bootstrap config by
+	// setting the environment variable "GRPC_XDS_BOOSTRAP_CONFIG".
+	//
+	// When both bootstrap FileName and FileContent are set, FileName is used.
+	BootstrapFileContent = os.Getenv(BootstrapFileContentEnv)
 	// V3Support indicates whether xDS v3 API support is enabled, which can be
 	// done by setting the environment variable
 	// "GRPC_XDS_EXPERIMENTAL_V3_SUPPORT" to "true".