pkg/ntp: initial implementation

pkg/ntp/ntp.go

@@ -0,0 +1,115 @@
+// Copyright 2017 CoreOS, 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 ntp
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+var (
+	DefaultNTP    = "/usr/sbin/ntpdate"
+	DefaultServer = "time.nist.gov"
+)
+
+// DefaultSync syncs system time with NTP server.
+func DefaultSync() (string, error) {
+	return Sync(DefaultNTP, DefaultServer)
+}
+
+var inUseErr = "NTP socket is in use"
+
+// Sync syncs system time with NTP server.
+//
+//    sudo service ntp stop
+//    sudo ntpdate time.nist.gov
+//    sudo service ntp start
+//
+func Sync(ntpPath string, server string) (string, error) {
+	buf := new(bytes.Buffer)
+	err := startNTP(ntpPath, server, buf)
+	o := strings.TrimSpace(buf.String())
+	if err == nil && strings.Contains(o, "adjust time server") {
+		return o, nil
+	}
+
+	if !strings.Contains(o, inUseErr) && (err != nil && !strings.Contains(err.Error(), inUseErr)) {
+		return o, err
+	}
+
+	so, err := serviceNTP("stop")
+	if err != nil {
+		return so, err
+	}
+
+	buf.Reset()
+	err = startNTP(ntpPath, server, buf)
+	o = strings.TrimSpace(buf.String())
+	if err != nil {
+		return o, err
+	}
+
+	so, err = serviceNTP("start")
+	if err != nil {
+		return so, err
+	}
+	if so != "" {
+		o += ";" + so
+	}
+	return o, nil
+}
+
+func startNTP(ntpPath string, server string, w io.Writer) error {
+	if !exist(ntpPath) {
+		return fmt.Errorf("%q does not exist", ntpPath)
+	}
+	cmd := exec.Command("sudo", ntpPath, server)
+	cmd.Stdout = w
+	cmd.Stderr = w
+	return cmd.Run()
+}
+
+// when 'NTP socket is in use' error is returned
+func serviceNTP(command string) (string, error) {
+	buf := new(bytes.Buffer)
+	cmd := exec.Command("sudo", "service", "ntp", command)
+	cmd.Stdout = buf
+	cmd.Stderr = buf
+	err := cmd.Run()
+	return strings.TrimSpace(buf.String()), err
+}
+
+// exist returns true if the file or directory exists.
+func exist(fpath string) bool {
+	st, err := os.Stat(fpath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false
+		}
+	}
+	if st.IsDir() {
+		return true
+	}
+	if _, err := os.Stat(fpath); err != nil {
+		if os.IsNotExist(err) {
+			return false
+		}
+	}
+	return true
+}

pkg/ntp/ntp_test.go

@@ -0,0 +1,28 @@
+// Copyright 2017 CoreOS, 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 ntp
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestSync(t *testing.T) {
+	o, err := DefaultSync()
+	if err != nil {
+		t.Fatal(err)
+	}
+	fmt.Println(o)
+}