Add probe cobra command (istio#97)

* Add probe cobra command

mixer, galley and security(istio_ca) have `probe` sub-command and
their codes are duplicated.

This patch adds probe cobra command to be commonly used.

* Fix review comments:

* Add the func Validate() to produce proper error.
* Add the Example.
* Add the LongDesc to understand the option more easily.
* Add the comment for CobraCommand for probe.
* Add copyright banner

* Fix typo

probe/cobra.go

@@ -0,0 +1,62 @@
+// Copyright 2020 Istio Authors
+//
+// 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 probe
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+var (
+	probeLongDesc = `Check the liveness or readiness of a locally-running server
+
+Check if the target file is older than the interval. The locally-running server updates the last modified time
+(you need to enable it on server side), so probe command compares it with current time.`
+
+	probeExample = `
+  # Check if the target file '/health' is older than interval of 4 seconds
+  probe --probe-path=/health --interval=4s`
+)
+
+// CobraCommand returns a command used to probe liveness or readiness of a locally-running server
+// by checking the last modified time of target file.
+func CobraCommand() *cobra.Command {
+	var probeOptions Options
+
+	prb := &cobra.Command{
+		Use:     "probe",
+		Short:   "Check the liveness or readiness of a locally-running server",
+		Long:    probeLongDesc,
+		Args:    cobra.ExactArgs(0),
+		Example: probeExample,
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			if err := probeOptions.Validate(); err != nil {
+				return err
+			}
+			if err := NewFileClient(&probeOptions).GetStatus(); err != nil {
+				return fmt.Errorf("fail on inspecting path %s: %v", probeOptions.Path, err)
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "OK")
+			return nil
+		},
+	}
+	prb.PersistentFlags().StringVar(&probeOptions.Path, "probe-path", "",
+		"Path of the file for checking the last modified time.")
+	prb.PersistentFlags().DurationVar(&probeOptions.UpdateInterval, "interval", 0,
+		"Duration used for checking the target file's last modified time.")
+
+	return prb
+}

probe/cobra_test.go

@@ -0,0 +1,66 @@
+// Copyright 2020 Istio Authors
+
+// 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 probe
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestOpts(t *testing.T) {
+	fp, err := ioutil.TempFile(os.TempDir(), t.Name())
+	if err != nil {
+		t.Fatalf("failed to create temp file")
+	}
+	cases := []struct {
+		args       string
+		expectFail bool
+	}{
+		{
+			"probe",
+			true,
+		},
+		{
+			"extra-args",
+			true,
+		},
+		{
+			fmt.Sprintf("--probe-path=%s.invalid --interval=1s", fp.Name()),
+			true,
+		},
+		{
+			fmt.Sprintf("--probe-path=%s --interval=1s", fp.Name()),
+			false,
+		},
+	}
+
+	for _, v := range cases {
+		t.Run(v.args, func(t *testing.T) {
+			cmd := CobraCommand()
+			cmd.SetArgs(strings.Split(v.args, " "))
+			err := cmd.Execute()
+
+			if !v.expectFail && err != nil {
+				t.Errorf("Got %v, expecting success", err)
+			}
+			if v.expectFail && err == nil {
+				t.Errorf("Expected failure, got success")
+			}
+		})
+	}
+}

probe/option.go

@@ -14,7 +14,10 @@
 
 package probe
 
-import "time"
+import (
+	"fmt"
+	"time"
+)
 
 // Options customizes the parameters of a probe.
 type Options struct {
@@ -30,3 +33,17 @@ type Options struct {
 func (o *Options) IsValid() bool {
 	return o != nil && o.Path != "" && o.UpdateInterval > 0*time.Second
 }
+
+// Validate returns true if some values are filled into the options.
+func (o *Options) Validate() error {
+	if o == nil {
+		return fmt.Errorf("option is empty")
+	}
+	if o.Path == "" {
+		return fmt.Errorf("probe-path must be specified")
+	}
+	if o.UpdateInterval <= 0*time.Second {
+		return fmt.Errorf("interval must be greater than zero")
+	}
+	return nil
+}

probe/option_test.go

@@ -24,20 +24,35 @@ func TestOption(t *testing.T) {
 	if o.IsValid() {
 		t.Error("nil should not be valid")
 	}
+	if err := o.Validate(); err == nil {
+		t.Errorf("nil should produce an error")
+	}
 	o = &Options{}
 	if o.IsValid() {
 		t.Errorf("Empty option %+v should not be valid", o)
 	}
+	if err := o.Validate(); err == nil {
+		t.Errorf("Empty option %+v should produce an error", o)
+	}
 	o.Path = "foo"
 	if o.IsValid() {
 		t.Errorf("%+v should not be valid since interval is missing", o)
 	}
+	if err := o.Validate(); err == nil {
+		t.Errorf("%+v should produce an error since interval is missing", o)
+	}
 	o.UpdateInterval = time.Second
 	if !o.IsValid() {
 		t.Errorf("%+v should be valid", o)
 	}
+	if err := o.Validate(); err != nil {
+		t.Errorf("%+v should be no error but got %v", o, err)
+	}
 	o.Path = ""
 	if o.IsValid() {
 		t.Errorf("%+v should not be valid since path is missing", o)
 	}
+	if err := o.Validate(); err == nil {
+		t.Errorf("%+v should produce an error since path is missing", o)
+	}
 }