[m3query] Allow for optional override config file.

src/cmd/services/m3coordinator/main/main.go

@@ -26,17 +26,17 @@ import (
 	"os"
 
 	"github.com/m3db/m3/src/query/server"
+	xconfig "github.com/m3db/m3/src/x/config"
 	"github.com/m3db/m3/src/x/etcd"
 )
 
-var (
-	configFile = flag.String("f", "", "configuration file")
-)
+var configFiles xconfig.FlagStringSlice
 
 func main() {
+	flag.Var(&configFiles, "f", "configuration file(s)")
 	flag.Parse()
 
-	if len(*configFile) == 0 {
+	if len(configFiles) == 0 || len(configFiles[0]) == 0 {
 		flag.Usage()
 		os.Exit(1)
 	}
@@ -45,6 +45,6 @@ func main() {
 	etcd.SetGlobals()
 
 	server.Run(server.RunOptions{
-		ConfigFile: *configFile,
+		ConfigFiles: configFiles,
 	})
 }

src/cmd/services/m3query/main/main.go

@@ -26,17 +26,17 @@ import (
 	"os"
 
 	"github.com/m3db/m3/src/query/server"
+	xconfig "github.com/m3db/m3/src/x/config"
 	"github.com/m3db/m3/src/x/etcd"
 )
 
-var (
-	configFile = flag.String("f", "", "configuration file")
-)
+var configFiles xconfig.FlagStringSlice
 
 func main() {
+	flag.Var(&configFiles, "f", "configuration file(s)")
 	flag.Parse()
 
-	if len(*configFile) == 0 {
+	if len(configFiles) == 0 || len(configFiles[0]) == 0 {
 		flag.Usage()
 		os.Exit(1)
 	}
@@ -45,6 +45,6 @@ func main() {
 	etcd.SetGlobals()
 
 	server.Run(server.RunOptions{
-		ConfigFile: *configFile,
+		ConfigFiles: configFiles,
 	})
 }

src/query/server/server.go

@@ -97,8 +97,8 @@ type cleanupFn func() error
 // RunOptions provides options for running the server
 // with backwards compatibility if only solely adding fields.
 type RunOptions struct {
-	// ConfigFile is the config file to use.
-	ConfigFile string
+	// ConfigFiles is the array of config files to use. All files of the array get merged together.
+	ConfigFiles []string
 
 	// Config is an alternate way to provide configuration and will be used
 	// instead of parsing ConfigFile if ConfigFile is not specified.
@@ -127,12 +127,12 @@ func Run(runOpts RunOptions) {
 	rand.Seed(time.Now().UnixNano())
 
 	var cfg config.Configuration
-	if runOpts.ConfigFile != "" {
-		if err := xconfig.LoadFile(&cfg, runOpts.ConfigFile, xconfig.Options{}); err != nil {
-			fmt.Fprintf(os.Stderr, "unable to load %s: %v", runOpts.ConfigFile, err)
+	if len(runOpts.ConfigFiles) > 0 {
+		if err := xconfig.LoadFiles(&cfg, runOpts.ConfigFiles, xconfig.Options{}); err != nil {
+			fmt.Fprintf(os.Stderr, "unable to load %s: %v", runOpts.ConfigFiles, err)
 			os.Exit(1)
 		}
-		fmt.Fprintf(os.Stdout, "using %s config file: %v", serviceName, runOpts.ConfigFile)
+		fmt.Fprintf(os.Stdout, "using %s config files: %v", serviceName, runOpts.ConfigFiles)
 	} else {
 		cfg = runOpts.Config
 	}

src/x/config/example_test.go

@@ -21,6 +21,7 @@
 package config_test
 
 import (
+	"flag"
 	"fmt"
 	"log"
 
@@ -40,3 +41,14 @@ func ExampleLoadFile() {
 	fmt.Printf("listenAddress: %s\n", cfg.ListenAddress)
 	// Output: listenAddress: 0.0.0.0:8392
 }
+
+// The FlagStringSlice allows for multiple values when used as a flag variable.
+func ExampleFlagStringSlice() {
+	var configFiles config.FlagStringSlice
+	fs := flag.NewFlagSet("config", flag.PanicOnError)
+	fs.Var(&configFiles, "f", "config files")
+	fs.Parse([]string{"-f", "file1.yaml", "-f", "file2.yaml", "-f", "file3.yaml"})
+	fmt.Println("Config files:", configFiles)
+	// Output:
+	// Config files: [file1.yaml file2.yaml file3.yaml]
+}

src/x/config/flag.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2019 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package config
+
+import (
+	"flag"
+	"fmt"
+)
+
+var _ flag.Value = &FlagStringSlice{}
+
+// FlagStringSlice represents a slice of strings. When used as a flag variable,
+// it allows for multiple string values. For example, it can be used like this:
+// 	var configFiles FlagStringSlice
+// 	flag.Var(&configFiles, "f", "configuration file(s)")
+// Then it can be invoked like this:
+// 	./app -f file1.yaml -f file2.yaml -f valueN.yaml
+// Finally, when the flags are parsed, the variable contains all the values.
+type FlagStringSlice []string
+
+// String() returns a string implmentation of the slice.
+func (i *FlagStringSlice) String() string {
+	if i == nil {
+		return ""
+	}
+	return fmt.Sprintf("%v", ([]string)(*i))
+}
+
+// Set appends a string value to the slice.
+func (i *FlagStringSlice) Set(value string) error {
+	*i = append(*i, value)
+	return nil
+}

src/x/config/flag_test.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2019 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package config_test
+
+import (
+	"flag"
+	"testing"
+
+	"github.com/m3db/m3/src/x/config"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFlagArray(t *testing.T) {
+	tests := []struct {
+		args []string
+		name string
+		want string
+	}{
+		{
+			name: "single value",
+			args: []string{"-f", "./some/file/path/here.yaml"},
+			want: "[./some/file/path/here.yaml]",
+		},
+		{
+			name: "single empty value",
+			args: []string{"-f", ""},
+			want: "[]",
+		},
+		{
+			name: "two value",
+			args: []string{"-f", "file1.yaml", "-f", "file2.yaml"},
+			want: "[file1.yaml file2.yaml]",
+		},
+		{
+			name: "two value one of which empty",
+			args: []string{"-f", "", "-f", "file2.yaml"},
+			want: "[ file2.yaml]",
+		},
+		{
+			name: "three values",
+			args: []string{"-f", "file1.yaml", "-f", "file2.yaml", "-f", "file3.yaml"},
+			want: "[file1.yaml file2.yaml file3.yaml]",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var values config.FlagStringSlice
+			fs := flag.NewFlagSet(tt.name, flag.PanicOnError)
+			fs.Var(&values, "f", "config files")
+			err := fs.Parse(tt.args)
+			assert.NoError(t, err, "error parsing flags")
+			assert.Equal(t, tt.want, values.String(), "unexpected output")
+		})
+	}
+}
+
+func TestFlagStringSliceNilFlag(t *testing.T) {
+	var s *config.FlagStringSlice
+	assert.Equal(t, "", s.String(), "nil string slice representation")
+}
+
+func TestFlagStringSliceWithOtherFlags(t *testing.T) {
+	var values config.FlagStringSlice
+	var x string
+	fs := flag.NewFlagSet("app", flag.PanicOnError)
+	fs.StringVar(&x, "x", "", "some random var")
+	fs.Var(&values, "f", "config files")
+	fs.Parse([]string{"-f", "file1.yaml", "-x", "file2.yaml", "-f", "file3.yaml"})
+	assert.Equal(t, "[file1.yaml file3.yaml]", values.String(), "flag string slice representation")
+	assert.Equal(t, "file2.yaml", x, "x value")
+}