Issue #79: Refactor config loading to use flag sets

* support cmdline, env vars and properties
* support env vars with and without a FABIO_ prefix
* support loading properties from URL
* support consul agent on https

Inspired by PR #63 from @doublerebel

config/config.go

@@ -6,7 +6,7 @@ type Config struct {
 	Proxy    Proxy
 	Registry Registry
 	Listen   []Listen
-	Metrics  []Metrics
+	Metrics  Metrics
 	UI       UI
 	Runtime  Runtime
 }
@@ -35,10 +35,13 @@ type Proxy struct {
 	DialTimeout           time.Duration
 	ResponseHeaderTimeout time.Duration
 	KeepAliveTimeout      time.Duration
+	ReadTimeout           time.Duration
+	WriteTimeout          time.Duration
 	LocalIP               string
 	ClientIPHeader        string
 	TLSHeader             string
 	TLSHeaderValue        string
+	ListenerAddr          string
 }
 
 type Runtime struct {
@@ -47,10 +50,10 @@ type Runtime struct {
 }
 
 type Metrics struct {
-	Target   string
-	Prefix   string
-	Interval time.Duration
-	Addr     string
+	Target       string
+	Prefix       string
+	Interval     time.Duration
+	GraphiteAddr string
 }
 
 type Registry struct {
@@ -70,6 +73,7 @@ type File struct {
 
 type Consul struct {
 	Addr          string
+	Scheme        string
 	Token         string
 	KVPath        string
 	TagPrefix     string

config/default.go

@@ -7,16 +7,18 @@ import (
 
 var Default = &Config{
 	Proxy: Proxy{
-		MaxConn:     10000,
-		Strategy:    "rnd",
-		Matcher:     "prefix",
-		DialTimeout: 30 * time.Second,
-		LocalIP:     LocalIPString(),
+		MaxConn:      10000,
+		Strategy:     "rnd",
+		Matcher:      "prefix",
+		DialTimeout:  30 * time.Second,
+		LocalIP:      LocalIPString(),
+		ListenerAddr: ":9999",
 	},
 	Registry: Registry{
 		Backend: "consul",
 		Consul: Consul{
 			Addr:          "localhost:8500",
+			Scheme:        "http",
 			KVPath:        "/fabio/config",
 			TagPrefix:     "urlprefix-",
 			ServiceAddr:   ":9998",
@@ -25,11 +27,6 @@ var Default = &Config{
 			CheckTimeout:  3 * time.Second,
 		},
 	},
-	Listen: []Listen{
-		{
-			Addr: ":9999",
-		},
-	},
 	Runtime: Runtime{
 		GOGC:       800,
 		GOMAXPROCS: runtime.NumCPU(),
@@ -38,12 +35,8 @@ var Default = &Config{
 		Addr:  ":9998",
 		Color: "light-green",
 	},
-	Metrics: []Metrics{
-		{
-			Target:   "",
-			Prefix:   "default",
-			Addr:     "",
-			Interval: 30 * time.Second,
-		},
+	Metrics: Metrics{
+		Prefix:   "default",
+		Interval: 30 * time.Second,
 	},
 }

config/flagset.go

@@ -0,0 +1,79 @@
+package config
+
+import (
+	"flag"
+	"strings"
+
+	"github.com/magiconair/properties"
+)
+
+type FlagSet struct {
+	flag.FlagSet
+	set map[string]bool
+}
+
+func NewFlagSet(name string, errorHandling flag.ErrorHandling) *FlagSet {
+	fs := &FlagSet{set: make(map[string]bool)}
+	fs.Init(name, errorHandling)
+	return fs
+}
+
+// IsSet returns true if a variable was set via any mechanism.
+func (f *FlagSet) IsSet(name string) bool {
+	return f.set[name]
+}
+
+// ParseFlags parses command line arguments and provides fallback
+// values from environment variables and config file values.
+// Environment variables are case-insensitive and can have either
+// of the provided prefixes.
+func (f *FlagSet) ParseFlags(args, environ, prefixes []string, p *properties.Properties) error {
+	if err := f.Parse(args); err != nil {
+		return err
+	}
+
+	if len(prefixes) == 0 {
+		prefixes = []string{""}
+	}
+
+	// parse environment in case-insensitive way
+	env := map[string]string{}
+	for _, e := range environ {
+		p := strings.Split(e, "=")
+		env[strings.ToUpper(p[0])] = p[1]
+	}
+
+	// determine all values that were set via cmdline
+	f.Visit(func(fl *flag.Flag) {
+		f.set[fl.Name] = true
+	})
+
+	// lookup the rest via environ and properties
+	f.VisitAll(func(fl *flag.Flag) {
+		// skip if already set
+		if f.set[fl.Name] {
+			return
+		}
+
+		// check environment variables
+		for _, pfx := range prefixes {
+			name := strings.ToUpper(pfx + strings.Replace(fl.Name, ".", "_", -1))
+			if val, ok := env[name]; ok {
+				f.set[fl.Name] = true
+				f.Set(fl.Name, val)
+				return
+			}
+		}
+
+		// check properties
+		if p == nil {
+			return
+		}
+		if val, ok := p.Get(fl.Name); ok {
+			f.set[fl.Name] = true
+			f.Set(fl.Name, val)
+			return
+		}
+	})
+	return nil
+}

config/flagset_test.go

@@ -0,0 +1,62 @@
+package config
+
+import (
+	"flag"
+	"testing"
+
+	"github.com/magiconair/properties"
+)
+
+func TestParseFlags(t *testing.T) {
+	props := func(s string) *properties.Properties {
+		return properties.MustLoadString(s)
+	}
+
+	tests := []struct {
+		desc   string
+		args   []string
+		env    []string
+		prefix []string
+		props  string
+		v      string
+	}{
+		{
+			desc:  "cmdline should win",
+			args:  []string{"-v", "cmdline"},
+			env:   []string{"v=env"},
+			props: "v=props",
+			v:     "cmdline",
+		},
+		{
+			desc:  "env should win",
+			env:   []string{"v=env"},
+			props: "v=props",
+			v:     "env",
+		},
+		{
+			desc:   "env with prefix should win",
+			env:    []string{"v=env", "p_v=prefix"},
+			prefix: []string{"p_"},
+			props:  "v=props",
+			v:      "prefix",
+		},
+		{
+			desc:  "props should win",
+			props: "v=props",
+			v:     "props",
+		},
+	}
+
+	for i, tt := range tests {
+		var v string
+		f := NewFlagSet("test", flag.ExitOnError)
+		f.StringVar(&v, "v", "default", "")
+		err := f.ParseFlags(tt.args, tt.env, tt.prefix, props(tt.props))
+		if err != nil {
+			t.Errorf("%d -%s: got %v want nil", i, tt.desc, err)
+		}
+		if got, want := v, tt.v; got != want {
+			t.Errorf("%d - %s: got %q want %q", i, tt.desc, got, want)
+		}
+	}
+}