Support external URL for FaaS functions

gateway/types/readconfig.go

@@ -0,0 +1,77 @@
+package types
+
+import (
+	"log"
+	"net/url"
+	"os"
+	"strconv"
+	"time"
+)
+
+// OsEnv implements interface to wrap os.Getenv
+type OsEnv struct {
+}
+
+// Getenv wraps os.Getenv
+func (OsEnv) Getenv(key string) string {
+	return os.Getenv(key)
+}
+
+// HasEnv provides interface for os.Getenv
+type HasEnv interface {
+	Getenv(key string) string
+}
+
+// ReadConfig constitutes config from env variables
+type ReadConfig struct {
+}
+
+func parseBoolValue(val string) bool {
+	if val == "true" {
+		return true
+	}
+	return false
+}
+
+func parseIntValue(val string, fallback int) int {
+	if len(val) > 0 {
+		parsedVal, parseErr := strconv.Atoi(val)
+		if parseErr == nil && parsedVal >= 0 {
+			return parsedVal
+		}
+	}
+	return fallback
+}
+
+// Read fetches config from environmental variables.
+func (ReadConfig) Read(hasEnv HasEnv) GatewayConfig {
+	cfg := GatewayConfig{}
+
+	readTimeout := parseIntValue(hasEnv.Getenv("read_timeout"), 8)
+	writeTimeout := parseIntValue(hasEnv.Getenv("write_timeout"), 8)
+
+	cfg.ReadTimeout = time.Duration(readTimeout) * time.Second
+	cfg.WriteTimeout = time.Duration(writeTimeout) * time.Second
+
+	if len(hasEnv.Getenv("functions_provider_url")) > 0 {
+		var err error
+		cfg.FunctionsProviderURL, err = url.Parse(hasEnv.Getenv("functions_provider_url"))
+		if err != nil {
+			log.Fatal("If functions_provider_url is provided, then it should be a valid URL.", err)
+		}
+	}
+
+	return cfg
+}
+
+// GatewayConfig for the process.
+type GatewayConfig struct {
+	ReadTimeout          time.Duration
+	WriteTimeout         time.Duration
+	FunctionsProviderURL *url.URL
+}
+
+// UseExternalProvider decide whether to bypass built-in Docker Swarm engine
+func (g *GatewayConfig) UseExternalProvider() bool {
+	return g.FunctionsProviderURL != nil
+}