Support use of environment variables to configure the client

cmdline/remotecmd/client.go

@@ -44,7 +44,7 @@ type ReaderGetter interface {
 
 // Make a single API request to a named endpoint, handling directory lookup and failover automatically.
 func CallRemote(endpoint, method string, query *url.Values, body ReaderGetter) (*http.Response, error) {
-	if err := shared.InitConfig(); err != nil {
+	if err := shared.InitClientConfig(); err != nil {
 		return nil, err
 	}
 	if shared.CurrentConfig.Remote == nil {
@@ -121,7 +121,7 @@ func buildRequest(base, endpoint, method, encoding string, query *url.Values, bo
 
 // Build TLS config based on client configuration
 func makeTLSConfig() (*tls.Config, error) {
-	err := shared.InitConfig()
+	err := shared.InitClientConfig()
 	if err != nil {
 		return nil, err
 	}

cmdline/shared/util.go

@@ -26,26 +26,53 @@ import (
 )
 
 func InitConfig() error {
+	return initConfig(false)
+}
+
+func InitClientConfig() error {
+	return initConfig(true)
+}
+
+func initConfig(client bool) error {
 	if CurrentConfig != nil {
 		return nil
 	}
 	dlog.SetLevel(ArgDebug)
 	usedDefault := false
 	if ArgConfig == "" {
 		ArgConfig = config.DefaultConfig()
-		if ArgConfig == "" {
-			return errors.New("--config not specified")
-		}
 		usedDefault = true
 	}
-	config, err := config.ReadFile(ArgConfig)
+	if client && usedDefault {
+		cfg, err := config.FromEnvironment()
+		if err != nil {
+			return err
+		} else if cfg != nil {
+			CurrentConfig = cfg
+			return nil
+		}
+	}
+	if ArgConfig == "" {
+		return errors.New("--config not specified")
+	}
+	cfg, err := config.ReadFile(ArgConfig)
 	if err != nil {
 		if os.IsNotExist(err) && usedDefault {
+			if client {
+				// try to use environment
+				cfg, err = config.FromEnvironment()
+				if err != nil {
+					return err
+				} else if cfg != nil {
+					CurrentConfig = cfg
+					return nil
+				}
+			}
 			return fmt.Errorf("--config not specified and default config at %s does not exist", ArgConfig)
 		}
 		return err
 	}
-	CurrentConfig = config
+	CurrentConfig = cfg
 	return nil
 }
 

config/env.go

@@ -0,0 +1,47 @@
+//
+// Copyright (c) SAS Institute Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package config
+
+import (
+	"errors"
+	"os"
+)
+
+// FromEnvironment tries to build a client-only config from environment variables. If none are set then returns nil.
+func FromEnvironment() (*Config, error) {
+	remoteURL := os.Getenv("RELIC_URL")
+	if remoteURL == "" {
+		return nil, nil
+	}
+	clientCert := os.Getenv("RELIC_CLIENT_CERT")
+	clientKey := os.Getenv("RELIC_CLIENT_KEY")
+	if clientCert == "" {
+		return nil, errors.New("RELIC_CLIENT_CERT must be set when RELIC_URL is set")
+	}
+	if clientKey == "" {
+		clientKey = clientCert
+	}
+	cfg := &Config{
+		Remote: &RemoteConfig{
+			DirectoryURL: remoteURL,
+			KeyFile:      clientKey,
+			CertFile:     clientCert,
+			CaCert:       os.Getenv("RELIC_CACERT"),
+		},
+	}
+	return cfg, cfg.Normalize("<env>")
+}