From 10ab91179be6fa462ebe27d58f447353640110a7 Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Mon, 9 Oct 2017 20:29:01 -0700
Subject: [PATCH] Use SSH to list most recent snapshot age.

---
 zfs_replication_exporter.go | 146 ++++++++++++++++++++----------------
 1 file changed, 83 insertions(+), 63 deletions(-)

diff --git a/zfs_replication_exporter.go b/zfs_replication_exporter.go
index f535463..325d0fa 100644
--- a/zfs_replication_exporter.go
+++ b/zfs_replication_exporter.go
@@ -1,18 +1,19 @@
 package main
 
 import (
+	"bufio"
+	"bytes"
 	"flag"
 	"fmt"
-	"io"
-	"log"
+	"io/ioutil"
 	"os"
-	"strings"
+	"path/filepath"
+	"regexp"
 	"time"
 
-	"golang.org/x/crypto/ssh"
+	"github.com/golang/glog"
 
-	"xinu.tv/thumbnailer/auth"
-	"xinu.tv/thumbnailer/scp"
+	"golang.org/x/crypto/ssh"
 )
 
 var (
@@ -20,51 +21,54 @@ var (
 	user = flag.String("user", os.Getenv("USER"), "ssh user")
 )
 
-func checkFatal(err error) {
-	if err != nil {
-		log.Fatal(err)
-	}
-}
+// Example: @auto-20171001.1400-2w
+var (
+	snapshotPattern = regexp.MustCompile(`^([^@]+)@auto-(\d{8}\.\d{4})-\d+[mwy]$`)
+	snapshotFormat  = "20060102.1504"
+)
 
-func progress(w io.Writer, r io.Reader, size int64) error {
-	const (
-		chunkSize = 1 << 10
-		width     = 50
-	)
-	var err error
-	total, bLast := int64(0), int64(0)
-	tLast := time.Now()
-	defer fmt.Println()
-	for {
-		var n int64
-		n, err = io.CopyN(w, r, chunkSize)
-		total += n
-		bLast += n
-		if time.Since(tLast) > (300 * time.Millisecond) {
-			kbps := float64(bLast) / time.Since(tLast).Seconds() / 1024
-			frac := int(total * width / size)
-			fmt.Printf("\rDownloaded: %s>%s| %.2f Kb/s", strings.Repeat("=", frac),
-				strings.Repeat(" ", width-frac), kbps)
-			tLast = time.Now()
-			bLast = 0
-		}
+func newPublicKey() ([]ssh.AuthMethod, error) {
+	var signers []ssh.AuthMethod
 
+	for _, path := range []string{
+		filepath.Join(os.Getenv("HOME"), ".ssh", "id_dsa"),
+		filepath.Join(os.Getenv("HOME"), ".ssh", "id_rsa"),
+	} {
+
+		// A public key may be used to authenticate against the remote
+		// server by using an unencrypted PEM-encoded private key file.
+		//
+		// If you have an encrypted private key, the crypto/x509 package
+		// can be used to decrypt it.
+		key, err := ioutil.ReadFile(path)
 		if err != nil {
-			break
+			if os.IsNotExist(err) {
+				continue
+			}
+			return nil, fmt.Errorf("unable to read private key %q: %v", path, err)
 		}
-	}
-	if err == io.EOF {
-		return nil
-	}
-	return err
-}
 
-var sink, _ = os.Create(os.DevNull)
+		// Create the Signer for this private key.
+		signer, err := ssh.ParsePrivateKey(key)
+		if err != nil {
+			return nil, fmt.Errorf("unable to parse private key %q: %v", path, err)
+		}
+		signers = append(signers, ssh.PublicKeys(signer))
+	}
+	if len(signers) == 0 {
+		return nil, fmt.Errorf("no public keys configured")
+	}
+	return signers, nil
+}
 
 func main() {
 	flag.Parse()
-	ams, err := auth.NewPublicKey()
-	checkFatal(err)
+	defer glog.Flush()
+
+	ams, err := newPublicKey()
+	if err != nil {
+		glog.Exitf("Error fetching public keys: %v", err)
+	}
 
 	// An SSH client is represented with a ClientConn.
 	//
@@ -77,27 +81,43 @@ func main() {
 		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
 	}
 	client, err := ssh.Dial("tcp", *host, config)
-	checkFatal(err)
+	if err != nil {
+		glog.Exitf("Error dialing %q: %v", *host, err)
+	}
 
-	for _, fn := range flag.Args() {
-		log.Println("Fetching", fn)
-		// Each ClientConn can support multiple interactive sessions,
-		// represented by a Session.
-		session, err := client.NewSession()
-		checkFatal(err)
-
-		f, err := scp.ScpFrom(session, fn)
-		if err != nil {
-			log.Println(err)
-			continue
+	// Each ClientConn can support multiple interactive sessions,
+	// represented by a Session.
+	s, err := client.NewSession()
+	if err != nil {
+		glog.Exitf("Error creating new session: %v", err)
+	}
+	cmd := "/sbin/zfs list -t snapshot -H -o name -s name"
+	b, err := s.CombinedOutput(cmd)
+	if err != nil {
+		glog.Exitf("Error running %q: %v", cmd, err)
+	}
+	scanner := bufio.NewScanner(bytes.NewReader(b))
+	snapshotAges := map[string]time.Time{}
+	for scanner.Scan() {
+		l := scanner.Text()
+		m := snapshotPattern.FindStringSubmatch(l)
+		if len(m) == 3 {
+			snapshot := m[1]
+			t, err := time.Parse(snapshotFormat, m[2])
+			if err != nil {
+				glog.Errorf("Malformed time in snapshot %q: %v", m[2], err)
+				continue
+			}
+			snapshotTime := snapshotAges[snapshot]
+			if snapshotTime.Before(t) {
+				snapshotAges[snapshot] = t
+			}
 		}
-
-		log.Println(f.Name, f.Perm, f.Size)
-
-		err = progress(sink, f, f.Size)
-		checkFatal(err)
-
-		checkFatal(f.Close())
-		checkFatal(session.Close())
+	}
+	if err := scanner.Err(); err != nil {
+		glog.Exitf("Failed to scan response: %v", err)
+	}
+	for snapshot, snapshotTime := range snapshotAges {
+		fmt.Println(snapshot, snapshotTime, time.Since(snapshotTime))
 	}
 }