seekbuf: add Bytes method.

- Support suppressing console output.
- DefaultDebugOptions sets the correct tag now.
- FatalError(error, string) calls log.Fatal(message, err) if err != nil.

LICENSE

@@ -11,3 +11,34 @@ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 
+
+
+=======================================================================
+The backoff package (written during my time at Cloudflare) is released
+under the following license:
+
+Copyright (c) 2016 CloudFlare Inc.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+Redistributions of source code must retain the above copyright notice,
+this list of conditions and the following disclaimer.
+
+Redistributions in binary form must reproduce the above copyright notice,
+this list of conditions and the following disclaimer in the documentation
+and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+

README.md

@@ -12,6 +12,7 @@ Contents:
 
     ahash/          Provides hashes from string algorithm specifiers.
     assert/         Error handling, assertion-style.
+    backoff/        Implementation of an intelligent backoff strategy.
     cmd/
         atping/     Automated TCP ping, meant for putting in cronjobs.
         certchain/  Display the certificate chain from a
@@ -27,6 +28,7 @@ Contents:
         cruntar/    Untar an archive with hard links, copying instead of
                     linking.
         csrpubdump/ Dump the public key from an X.509 certificate request.
+        data_sync/  Sync the user's homedir to external storage.
         diskimg/    Write a disk image to a device.
         eig/        EEPROM image generator.
         fragment/   Print a fragment of a file.

backoff/LICENSE

@@ -0,0 +1,24 @@
+Copyright (c) 2016 CloudFlare Inc.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+Redistributions of source code must retain the above copyright notice,
+this list of conditions and the following disclaimer.
+
+Redistributions in binary form must reproduce the above copyright notice,
+this list of conditions and the following disclaimer in the documentation
+and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

backoff/README.md

@@ -0,0 +1,83 @@
+# backoff
+## Go implementation of "Exponential Backoff And Jitter"
+
+This package implements the backoff strategy described in the AWS
+Architecture Blog article
+["Exponential Backoff And Jitter"](http://www.awsarchitectureblog.com/2015/03/backoff.html). Essentially,
+the backoff has an interval `time.Duration`; the *n<sup>th</sup>* call
+to backoff will return an a `time.Duration` that is *2 <sup>n</sup> *
+interval*. If jitter is enabled (which is the default behaviour), the
+duration is a random value between 0 and *2 <sup>n</sup> * interval*.
+The backoff is configured with a maximum duration that will not be
+exceeded; e.g., by default, the longest duration returned is
+`backoff.DefaultMaxDuration`.
+
+## Usage
+
+A `Backoff` is initialised with a call to `New`. Using zero values
+causes it to use `DefaultMaxDuration` and `DefaultInterval` as the
+maximum duration and interval.
+
+```
+package something
+
+import "github.com/cloudflare/backoff"
+
+func retryable() {
+        b := backoff.New(0, 0)
+        for {
+                err := someOperation()
+                if err == nil {
+                    break
+                }
+
+                log.Printf("error in someOperation: %v", err)
+                <-time.After(b.Duration())
+        }
+
+        log.Printf("succeeded after %d tries", b.Tries()+1)
+        b.Reset()
+}
+```
+
+It can also be used to rate limit code that should retry infinitely, but which does not
+use `Backoff` itself.
+
+```
+package something
+
+import (
+    "time"
+
+    "github.com/cloudflare/backoff"
+)
+
+func retryable() {
+        b := backoff.New(0, 0)
+        b.SetDecay(30 * time.Second)
+
+        for {
+                // b will reset if someOperation returns later than
+                // the last call to b.Duration() + 30s.
+                err := someOperation()
+                if err == nil {
+                    break
+                }
+
+                log.Printf("error in someOperation: %v", err)
+                <-time.After(b.Duration())
+        }
+}
+```
+
+## Tunables
+
+* `NewWithoutJitter` creates a Backoff that doesn't use jitter.
+
+The default behaviour is controlled by two variables:
+
+* `DefaultInterval` sets the base interval for backoffs created with
+  the zero `time.Duration` value in the `Interval` field.
+* `DefaultMaxDuration` sets the maximum duration for backoffs created
+  with the zero `time.Duration` value in the `MaxDuration` field.
+

backoff/backoff.go

@@ -0,0 +1,197 @@
+// Package backoff contains an implementation of an intelligent backoff
+// strategy. It is based on the approach in the AWS architecture blog
+// article titled "Exponential Backoff And Jitter", which is found at
+// http://www.awsarchitectureblog.com/2015/03/backoff.html.
+//
+// Essentially, the backoff has an interval `time.Duration`; the nth
+// call to backoff will return a `time.Duration` that is 2^n *
+// interval. If jitter is enabled (which is the default behaviour),
+// the duration is a random value between 0 and 2^n * interval.  The
+// backoff is configured with a maximum duration that will not be
+// exceeded.
+//
+// The `New` function will attempt to use the system's cryptographic
+// random number generator to seed a Go math/rand random number
+// source. If this fails, the package will panic on startup.
+package backoff
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	"io"
+	"math"
+	mrand "math/rand"
+	"sync"
+	"time"
+)
+
+var prngMu sync.Mutex
+var prng *mrand.Rand
+
+// DefaultInterval is used when a Backoff is initialised with a
+// zero-value Interval.
+var DefaultInterval = 5 * time.Minute
+
+// DefaultMaxDuration is maximum amount of time that the backoff will
+// delay for.
+var DefaultMaxDuration = 6 * time.Hour
+
+// A Backoff contains the information needed to intelligently backoff
+// and retry operations using an exponential backoff algorithm. It should
+// be initialised with a call to `New`.
+//
+// Only use a Backoff from a single goroutine, it is not safe for concurrent
+// access.
+type Backoff struct {
+	// maxDuration is the largest possible duration that can be
+	// returned from a call to Duration.
+	maxDuration time.Duration
+
+	// interval controls the time step for backing off.
+	interval time.Duration
+
+	// noJitter controls whether to use the "Full Jitter"
+	// improvement to attempt to smooth out spikes in a high
+	// contention scenario. If noJitter is set to true, no
+	// jitter will be introduced.
+	noJitter bool
+
+	// decay controls the decay of n. If it is non-zero, n is
+	// reset if more than the last backoff + decay has elapsed since
+	// the last try.
+	decay time.Duration
+
+	n       uint64
+	lastTry time.Time
+}
+
+// New creates a new backoff with the specified max duration and
+// interval. Zero values may be used to use the default values.
+//
+// Panics if either max or interval is negative.
+func New(max time.Duration, interval time.Duration) *Backoff {
+	if max < 0 || interval < 0 {
+		panic("backoff: max or interval is negative")
+	}
+
+	b := &Backoff{
+		maxDuration: max,
+		interval:    interval,
+	}
+	b.setup()
+	return b
+}
+
+// NewWithoutJitter works similarly to New, except that the created
+// Backoff will not use jitter.
+func NewWithoutJitter(max time.Duration, interval time.Duration) *Backoff {
+	b := New(max, interval)
+	b.noJitter = true
+	return b
+}
+
+func init() {
+	var buf [8]byte
+	var n int64
+
+	_, err := io.ReadFull(rand.Reader, buf[:])
+	if err != nil {
+		panic(err.Error())
+	}
+
+	n = int64(binary.LittleEndian.Uint64(buf[:]))
+
+	src := mrand.NewSource(n)
+	prng = mrand.New(src)
+}
+
+func (b *Backoff) setup() {
+	if b.interval == 0 {
+		b.interval = DefaultInterval
+	}
+
+	if b.maxDuration == 0 {
+		b.maxDuration = DefaultMaxDuration
+	}
+}
+
+// Duration returns a time.Duration appropriate for the backoff,
+// incrementing the attempt counter.
+func (b *Backoff) Duration() time.Duration {
+	b.setup()
+
+	b.decayN()
+
+	t := b.duration(b.n)
+
+	if b.n < math.MaxUint64 {
+		b.n++
+	}
+
+	if !b.noJitter {
+		prngMu.Lock()
+		t = time.Duration(prng.Int63n(int64(t)))
+		prngMu.Unlock()
+	}
+
+	return t
+}
+
+// requires b to be locked.
+func (b *Backoff) duration(n uint64) (t time.Duration) {
+	// Saturate pow
+	pow := time.Duration(math.MaxInt64)
+	if n < 63 {
+		pow = 1 << n
+	}
+
+	t = b.interval * pow
+	if t/pow != b.interval || t > b.maxDuration {
+		t = b.maxDuration
+	}
+
+	return
+}
+
+// Reset resets the attempt counter of a backoff.
+//
+// It should be called when the rate-limited action succeeds.
+func (b *Backoff) Reset() {
+	b.lastTry = time.Time{}
+	b.n = 0
+}
+
+// SetDecay sets the duration after which the try counter will be reset.
+// Panics if decay is smaller than 0.
+//
+// The decay only kicks in if at least the last backoff + decay has elapsed
+// since the last try.
+func (b *Backoff) SetDecay(decay time.Duration) {
+	if decay < 0 {
+		panic("backoff: decay < 0")
+	}
+
+	b.decay = decay
+}
+
+// requires b to be locked
+func (b *Backoff) decayN() {
+	if b.decay == 0 {
+		return
+	}
+
+	if b.lastTry.IsZero() {
+		b.lastTry = time.Now()
+		return
+	}
+
+	lastDuration := b.duration(b.n - 1)
+	decayed := time.Since(b.lastTry) > lastDuration+b.decay
+	b.lastTry = time.Now()
+
+	if !decayed {
+		return
+	}
+
+	b.n = 0
+}

backoff/backoff_test.go

@@ -0,0 +1,175 @@
+package backoff
+
+import (
+	"fmt"
+	"math"
+	"testing"
+	"time"
+)
+
+// If given New with 0's and no jitter, ensure that certain invariants are met:
+//
+//   - the default max duration and interval should be used
+//   - noJitter should be true
+//   - the RNG should not be initialised
+//   - the first duration should be equal to the default interval
+func TestDefaults(t *testing.T) {
+	b := NewWithoutJitter(0, 0)
+
+	if b.maxDuration != DefaultMaxDuration {
+		t.Fatalf("expected new backoff to use the default max duration (%s), but have %s", DefaultMaxDuration, b.maxDuration)
+	}
+
+	if b.interval != DefaultInterval {
+		t.Fatalf("exepcted new backoff to use the default interval (%s), but have %s", DefaultInterval, b.interval)
+	}
+
+	if b.noJitter != true {
+		t.Fatal("backoff should have been initialised without jitter")
+	}
+
+	dur := b.Duration()
+	if dur != DefaultInterval {
+		t.Fatalf("expected first duration to be %s, have %s", DefaultInterval, dur)
+	}
+}
+
+// Given a zero-value initialised Backoff, it should be transparently
+// setup.
+func TestSetup(t *testing.T) {
+	b := new(Backoff)
+	dur := b.Duration()
+	if dur < 0 || dur > (5*time.Minute) {
+		t.Fatalf("want duration between 0 and 5 minutes, have %s", dur)
+	}
+}
+
+// Ensure that tries incremenets as expected.
+func TestTries(t *testing.T) {
+	b := NewWithoutJitter(5, 1)
+
+	for i := uint64(0); i < 3; i++ {
+		if b.n != i {
+			t.Fatalf("want tries=%d, have tries=%d", i, b.n)
+		}
+
+		pow := 1 << i
+		expected := time.Duration(pow)
+		dur := b.Duration()
+		if dur != expected {
+			t.Fatalf("want duration=%d, have duration=%d at i=%d", expected, dur, i)
+		}
+	}
+
+	for i := uint(3); i < 5; i++ {
+		dur := b.Duration()
+		if dur != 5 {
+			t.Fatalf("want duration=5, have %d at i=%d", dur, i)
+		}
+	}
+}
+
+// Ensure that a call to Reset will actually reset the Backoff.
+func TestReset(t *testing.T) {
+	const iter = 10
+	b := New(1000, 1)
+	for i := 0; i < iter; i++ {
+		_ = b.Duration()
+	}
+
+	if b.n != iter {
+		t.Fatalf("expected tries=%d, have tries=%d", iter, b.n)
+	}
+
+	b.Reset()
+	if b.n != 0 {
+		t.Fatalf("expected tries=0 after reset, have tries=%d", b.n)
+	}
+}
+
+const decay = 5 * time.Millisecond
+const max = 10 * time.Millisecond
+const interval = time.Millisecond
+
+func TestDecay(t *testing.T) {
+	const iter = 10
+
+	b := NewWithoutJitter(max, 1)
+	b.SetDecay(decay)
+
+	var backoff time.Duration
+	for i := 0; i < iter; i++ {
+		backoff = b.Duration()
+	}
+
+	if b.n != iter {
+		t.Fatalf("expected tries=%d, have tries=%d", iter, b.n)
+	}
+
+	// Don't decay below backoff
+	b.lastTry = time.Now().Add(-backoff + 1)
+	backoff = b.Duration()
+	if b.n != iter+1 {
+		t.Fatalf("expected tries=%d, have tries=%d", iter+1, b.n)
+	}
+
+	// Reset after backoff + decay
+	b.lastTry = time.Now().Add(-backoff - decay)
+	b.Duration()
+	if b.n != 1 {
+		t.Fatalf("expected tries=%d, have tries=%d", 1, b.n)
+	}
+}
+
+// Ensure that decay works even if the retry counter is saturated.
+func TestDecaySaturation(t *testing.T) {
+	b := NewWithoutJitter(1<<2, 1)
+	b.SetDecay(decay)
+
+	var duration time.Duration
+	for i := 0; i <= 2; i++ {
+		duration = b.Duration()
+	}
+
+	if duration != 1<<2 {
+		t.Fatalf("expected duration=%v, have duration=%v", 1<<2, duration)
+	}
+
+	b.lastTry = time.Now().Add(-duration - decay)
+	b.n = math.MaxUint64
+
+	duration = b.Duration()
+	if duration != 1 {
+		t.Errorf("expected duration=%v, have duration=%v", 1, duration)
+	}
+}
+
+func ExampleBackoff_SetDecay() {
+	b := NewWithoutJitter(max, interval)
+	b.SetDecay(decay)
+
+	// try 0
+	fmt.Println(b.Duration())
+
+	// try 1
+	fmt.Println(b.Duration())
+
+	// try 2
+	duration := b.Duration()
+	fmt.Println(duration)
+
+	// try 3, below decay
+	time.Sleep(duration)
+	duration = b.Duration()
+	fmt.Println(duration)
+
+	// try 4, resets
+	time.Sleep(duration + decay)
+	fmt.Println(b.Duration())
+
+	// Output: 1ms
+	// 2ms
+	// 4ms
+	// 8ms
+	// 1ms
+}

cmd/data_sync/README

@@ -0,0 +1,32 @@
+data_sync
+
+This is a tool I wrote primarily to sync my home directory to a backup
+drive plugged into my laptop. This system is provisioned by Ansible,
+and the goal is to be able to just copy my home directory back in the
+event of a failure without having lost a great deal of work or to wait
+for ansible to finish installing the right backup software. Specifically,
+I use a Framework laptop with the 1TB storage module, encrypted with
+LUKS, and run this twice daily (timed to correspond with my commute,
+though that's not really necessary). It started off as a shell script,
+then I decided to just write it as a program.
+
+Usage: data_sync [-d path] [-l level] [-m path] [-nqsv]
+                                  [-t path]
+        -d path         path to sync source directory
+                        (default "~")
+        -l level        log level to output (default "INFO"). Valid log
+                        levels are DEBUG, INFO, NOTICE, WARNING, ERR,
+                        CRIT, ALERT, EMERG. The default is INFO.
+        -m path         path to sync mount directory
+                        (default "/media/$USER/$(hostname -s)_data")
+        -n              dry-run mode: only check paths and print files to
+                        exclude
+        -q              suppress console output
+        -s              suppress syslog output
+        -t path         path to sync target directory
+                        (default "/media/$USER/$(hostname -s)_data/$USER")
+        -v              verbose rsync output
+
+data_sync rsyncs the tree at the sync source directory (-d) to the sync target
+directory (-t); it checks the mount directory (-m) exists; the sync target
+target directory must exist on the mount directory.

cmd/data_sync/main.go

@@ -0,0 +1,230 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"git.wntrmute.dev/kyle/goutils/config"
+	"git.wntrmute.dev/kyle/goutils/fileutil"
+	"git.wntrmute.dev/kyle/goutils/log"
+)
+
+func mustHostname() string {
+	hostname, err := os.Hostname()
+	log.FatalError(err, "couldn't retrieve hostname")
+
+	if hostname == "" {
+		log.Fatal("no hostname returned")
+	}
+	return strings.Split(hostname, ".")[0]
+}
+
+var (
+	defaultDataDir   = mustHostname() + "_data"
+	defaultProgName  = defaultDataDir + "_sync"
+	defaultMountDir  = filepath.Join("/media", os.Getenv("USER"), defaultDataDir)
+	defaultSyncDir   = os.Getenv("HOME")
+	defaultTargetDir = filepath.Join(defaultMountDir, os.Getenv("USER"))
+)
+
+func usage(w io.Writer) {
+	prog := filepath.Base(os.Args[0])
+	fmt.Fprintf(w, `Usage: %s [-d path] [-l level] [-m path] [-nqsv]
+				  [-t path]
+	-d path		path to sync source directory
+			(default "%s")
+	-l level	log level to output (default "INFO"). Valid log
+			levels are DEBUG, INFO, NOTICE, WARNING, ERR,
+			CRIT, ALERT, EMERG. The default is INFO.
+	-m path		path to sync mount directory
+			(default "%s")
+	-n		dry-run mode: only check paths and print files to
+			exclude
+	-q		suppress console output
+	-s		suppress syslog output
+	-t path		path to sync target directory
+			(default "%s")
+	-v		verbose rsync output
+
+%s rsyncs the tree at the sync source directory (-d) to the sync target
+directory (-t); it checks the mount directory (-m) exists; the sync target
+target directory must exist on the mount directory.
+
+`, prog, defaultSyncDir, defaultMountDir, defaultTargetDir, prog)
+}
+
+func checkPaths(mount, target string, dryRun bool) error {
+	if !fileutil.DirectoryDoesExist(mount) {
+		return fmt.Errorf("sync dir %s isn't mounted", mount)
+	}
+
+	if !strings.HasPrefix(target, mount) {
+		return fmt.Errorf("target dir %s must exist in %s", target, mount)
+	}
+
+	if !fileutil.DirectoryDoesExist(target) {
+		if dryRun {
+			log.Infof("would mkdir %s", target)
+		} else {
+			log.Infof("mkdir %s", target)
+			if err := os.Mkdir(target, 0755); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func buildExcludes(syncDir string) ([]string, error) {
+	var excluded []string
+
+	walker := func(path string, info fs.FileInfo, err error) error {
+		if err != nil {
+			excluded = append(excluded, strings.TrimPrefix(path, syncDir))
+			if info != nil && info.IsDir() {
+				return filepath.SkipDir
+			}
+
+			return nil
+		}
+
+		if info.Mode().IsRegular() {
+			if err = fileutil.Access(path, fileutil.AccessRead); err != nil {
+				excluded = append(excluded, strings.TrimPrefix(path, syncDir))
+			}
+		}
+
+		if info.IsDir() {
+			if err = fileutil.Access(path, fileutil.AccessExec); err != nil {
+				excluded = append(excluded, strings.TrimPrefix(path, syncDir))
+			}
+		}
+
+		return nil
+	}
+
+	err := filepath.Walk(syncDir, walker)
+	return excluded, err
+}
+
+func writeExcludes(excluded []string) (string, error) {
+	if len(excluded) == 0 {
+		return "", nil
+	}
+
+	excludeFile, err := os.CreateTemp("", defaultProgName)
+	if err != nil {
+		return "", err
+	}
+
+	for _, name := range excluded {
+		fmt.Fprintln(excludeFile, name)
+	}
+
+	defer excludeFile.Close()
+	return excludeFile.Name(), nil
+}
+
+func rsync(syncDir, target, excludeFile string, verboseRsync bool) error {
+	var args []string
+
+	if excludeFile != "" {
+		args = append(args, "--exclude-from")
+		args = append(args, excludeFile)
+	}
+
+	if verboseRsync {
+		args = append(args, "--progress")
+		args = append(args, "-v")
+	}
+
+	args = append(args, []string{"-au", syncDir + "/", target + "/"}...)
+
+	path, err := exec.LookPath("rsync")
+	if err != nil {
+		return err
+	}
+
+	cmd := exec.Command(path, args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+func init() {
+	flag.Usage = func() { usage(os.Stderr) }
+}
+
+func main() {
+
+	var logLevel, mountDir, syncDir, target string
+	var dryRun, quietMode, noSyslog, verboseRsync bool
+
+	flag.StringVar(&syncDir, "d", config.GetDefault("sync_dir", defaultSyncDir),
+		"`path to sync source directory`")
+	flag.StringVar(&logLevel, "l", config.GetDefault("log_level", "INFO"),
+		"log level to output")
+	flag.StringVar(&mountDir, "m", config.GetDefault("mount_dir", defaultMountDir),
+		"`path` to sync mount directory")
+	flag.BoolVar(&dryRun, "n", false, "dry-run mode: only check paths and print files to exclude")
+	flag.BoolVar(&quietMode, "q", quietMode, "suppress console output")
+	flag.BoolVar(&noSyslog, "s", noSyslog, "suppress syslog output")
+	flag.StringVar(&target, "t", config.GetDefault("sync_target", defaultTargetDir),
+		"`path` to sync target directory")
+	flag.BoolVar(&verboseRsync, "v", false, "verbose rsync output")
+	flag.Parse()
+
+	if quietMode && noSyslog {
+		fmt.Fprintln(os.Stderr, "both console and syslog output are suppressed")
+		fmt.Fprintln(os.Stderr, "errors will NOT be reported")
+	}
+
+	logOpts := &log.Options{
+		Level:        logLevel,
+		Tag:          defaultProgName,
+		Facility:     "user",
+		WriteSyslog:  !noSyslog,
+		WriteConsole: !quietMode,
+	}
+	err := log.Setup(logOpts)
+	log.FatalError(err, "failed to set up logging")
+
+	log.Infof("checking paths: mount=%s, target=%s", mountDir, target)
+	err = checkPaths(mountDir, target, dryRun)
+	log.FatalError(err, "target dir isn't ready")
+
+	log.Infof("checking for files to exclude from %s", syncDir)
+	excluded, err := buildExcludes(syncDir)
+	log.FatalError(err, "couldn't build excludes")
+
+	if dryRun {
+		fmt.Println("excluded files:")
+		for _, path := range excluded {
+			fmt.Printf("\t%s\n", path)
+		}
+		return
+	}
+
+	excludeFile, err := writeExcludes(excluded)
+	log.FatalError(err, "couldn't write exclude file")
+	log.Infof("excluding %d files via %s", len(excluded), excludeFile)
+
+	if excludeFile != "" {
+		defer func() {
+			log.Infof("removing exclude file %s", excludeFile)
+			if err := os.Remove(excludeFile); err != nil {
+				log.Warningf("failed to remove temp file %s", excludeFile)
+			}
+		}()
+	}
+
+	err = rsync(syncDir, target, excludeFile, verboseRsync)
+	log.FatalError(err, "couldn't sync data")
+}

dbg/BUILD.bazel

@@ -13,7 +13,7 @@ go_test(
     srcs = ["dbg_test.go"],
     embed = [":dbg"],
     deps = [
+        "//assert",
         "//testio",
-        "@com_github_stretchr_testify//require",
     ],
 )

dbg/dbg_test.go

@@ -1,12 +1,13 @@
 package dbg
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
 	"testing"
 
+	"git.wntrmute.dev/kyle/goutils/assert"
 	"git.wntrmute.dev/kyle/goutils/testio"
-	"github.com/stretchr/testify/require"
 )
 
 func TestNew(t *testing.T) {
@@ -17,16 +18,16 @@ func TestNew(t *testing.T) {
 	dbg.Print("hello")
 	dbg.Println("hello")
 	dbg.Printf("hello %s", "world")
-	require.Equal(t, 0, buf.Len())
+	assert.BoolT(t, buf.Len() == 0)
 
 	dbg.Enabled = true
 	dbg.Print("hello")              // +5
 	dbg.Println("hello")            // +6
 	dbg.Printf("hello %s", "world") // +11
-	require.Equal(t, 22, buf.Len())
+	assert.BoolT(t, buf.Len() == 22, fmt.Sprintf("buffer should be length 22 but is length %d", buf.Len()))
 
 	err := dbg.Close()
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 }
 
 func TestTo(t *testing.T) {
@@ -36,39 +37,38 @@ func TestTo(t *testing.T) {
 	dbg.Print("hello")
 	dbg.Println("hello")
 	dbg.Printf("hello %s", "world")
-	require.Equal(t, 0, buf.Len())
+	assert.BoolT(t, buf.Len() == 0, "debug output should be suppressed")
 
 	dbg.Enabled = true
 	dbg.Print("hello")              // +5
 	dbg.Println("hello")            // +6
 	dbg.Printf("hello %s", "world") // +11
-
+	assert.BoolT(t, buf.Len() == 22, "didn't get the expected debug output")
-	require.Equal(t, 22, buf.Len())
 
 	err := dbg.Close()
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 }
 
 func TestToFile(t *testing.T) {
 	testFile, err := ioutil.TempFile("", "dbg")
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 	err = testFile.Close()
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 
 	testFileName := testFile.Name()
 	defer os.Remove(testFileName)
 
 	dbg, err := ToFile(testFileName)
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 
 	dbg.Print("hello")
 	dbg.Println("hello")
 	dbg.Printf("hello %s", "world")
 
 	stat, err := os.Stat(testFileName)
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 
-	require.EqualValues(t, 0, stat.Size())
+	assert.BoolT(t, stat.Size() == 0, "no debug output should have been sent to the log file")
 
 	dbg.Enabled = true
 	dbg.Print("hello")              // +5
@@ -76,12 +76,12 @@ func TestToFile(t *testing.T) {
 	dbg.Printf("hello %s", "world") // +11
 
 	stat, err = os.Stat(testFileName)
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 
-	require.EqualValues(t, 22, stat.Size())
+	assert.BoolT(t, stat.Size() == 22, fmt.Sprintf("have %d bytes in the log file, expected 22", stat.Size()))
 
 	err = dbg.Close()
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 }
 
 func TestWriting(t *testing.T) {
@@ -90,31 +90,31 @@ func TestWriting(t *testing.T) {
 	dbg := To(buf)
 
 	n, err := dbg.Write(data)
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
-	require.EqualValues(t, 0, n)
+	assert.BoolT(t, n == 0, "expected nothing to be written to the buffer")
 
 	dbg.Enabled = true
 	n, err = dbg.Write(data)
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
-	require.EqualValues(t, 12, n)
+	assert.BoolT(t, n == 12, fmt.Sprintf("wrote %d bytes in the buffer, expected to write 12", n))
 
 	err = dbg.Close()
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 }
 
 func TestToFileError(t *testing.T) {
 	testFile, err := ioutil.TempFile("", "dbg")
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 	err = testFile.Chmod(0400)
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 	err = testFile.Close()
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 
 	testFileName := testFile.Name()
 
 	_, err = ToFile(testFileName)
-	require.Error(t, err)
+	assert.ErrorT(t, err)
 
 	err = os.Remove(testFileName)
-	require.NoError(t, err)
+	assert.NoErrorT(t, err)
 }

deps.bzl

@@ -221,8 +221,8 @@ def go_dependencies():
     go_repository(
         name = "com_github_stretchr_objx",
         importpath = "github.com/stretchr/objx",
-        sum = "h1:2vfRuCMp5sSVIDSqO8oNnWJq7mPa6KVP3iPIwFBuy8A=",
+        sum = "h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=",
-        version = "v0.1.1",
+        version = "v0.1.0",
     )
     go_repository(
         name = "com_github_stretchr_testify",
@@ -302,12 +302,6 @@ def go_dependencies():
         sum = "h1:bkb2NMGo3/Du52wvYj9Whth5KZfMV6d3O0Vbr3nz/UE=",
         version = "v0.0.0-20150115234039-8488cc47d90c",
     )
-    go_repository(
-        name = "org_golang_google_appengine",
-        importpath = "google.golang.org/appengine",
-        sum = "h1:lMO5rYAqUxkmaj76jAkRUvt5JZgFymx/+Q5Mzfivuhc=",
-        version = "v1.6.6",
-    )
     go_repository(
         name = "org_golang_x_crypto",
         importpath = "golang.org/x/crypto",

go.mod

@@ -7,7 +7,6 @@ require (
 	github.com/kr/text v0.2.0
 	github.com/pkg/errors v0.9.1
 	github.com/pkg/sftp v1.12.0
-	github.com/stretchr/testify v1.6.1
 	golang.org/x/crypto v0.0.0-20220314234659-1baeb1ce4c0b
 	golang.org/x/sys v0.0.0-20220412211240-33da011f77ad
 	gopkg.in/yaml.v2 v2.4.0
@@ -21,7 +20,5 @@ require (
 require (
 	github.com/kr/fs v0.1.0 // indirect
 	github.com/kr/pretty v0.1.0 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
-	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
 )

log/logger.go

@@ -14,6 +14,7 @@ import (
 type logger struct {
 	l            gsyslog.Syslogger
 	p            gsyslog.Priority
+	writeConsole bool
 }
 
 func (log *logger) printf(p gsyslog.Priority, format string, args ...interface{}) {
@@ -21,7 +22,7 @@ func (log *logger) printf(p gsyslog.Priority, format string, args ...interface{}
 		format += "\n"
 	}
 
-	if p <= log.p {
+	if p <= log.p && log.writeConsole {
 		fmt.Printf("%s [%s] ", prioritiev[p], timestamp())
 		fmt.Printf(format, args...)
 	}
@@ -32,7 +33,7 @@ func (log *logger) printf(p gsyslog.Priority, format string, args ...interface{}
 }
 
 func (log *logger) print(p gsyslog.Priority, args ...interface{}) {
-	if p <= log.p {
+	if p <= log.p && log.writeConsole {
 		fmt.Printf("%s [%s] ", prioritiev[p], timestamp())
 		fmt.Print(args...)
 	}
@@ -43,7 +44,7 @@ func (log *logger) print(p gsyslog.Priority, args ...interface{}) {
 }
 
 func (log *logger) println(p gsyslog.Priority, args ...interface{}) {
-	if p <= log.p {
+	if p <= log.p && log.writeConsole {
 		fmt.Printf("%s [%s] ", prioritiev[p], timestamp())
 		fmt.Println(args...)
 	}
@@ -102,6 +103,7 @@ type Options struct {
 	Tag          string
 	Facility     string
 	WriteSyslog  bool
+	WriteConsole bool
 }
 
 // DefaultOptions returns a sane set of defaults for syslog, using the program
@@ -117,6 +119,7 @@ func DefaultOptions(tag string, withSyslog bool) *Options {
 		Tag:          tag,
 		Facility:     "daemon",
 		WriteSyslog:  withSyslog,
+		WriteConsole: true,
 	}
 }
 
@@ -130,8 +133,10 @@ func DefaultDebugOptions(tag string, withSyslog bool) *Options {
 
 	return &Options{
 		Level:        "DEBUG",
+		Tag:          tag,
 		Facility:     "daemon",
 		WriteSyslog:  withSyslog,
+		WriteConsole: true,
 	}
 }
 
@@ -142,6 +147,7 @@ func Setup(opts *Options) error {
 	}
 
 	log.p = priority
+	log.writeConsole = opts.WriteConsole
 
 	if opts.WriteSyslog {
 		var err error
@@ -261,6 +267,17 @@ func Fatalf(format string, args ...interface{}) {
 	os.Exit(1)
 }
 
+// FatalError will only execute if err != nil. If it does,
+// it will print the message (append the error) and exit
+// the program.
+func FatalError(err error, message string) {
+	if err == nil {
+		return
+	}
+
+	Fatal(fmt.Sprintf("%s: %s", message, err))
+}
+
 // Spew will pretty print the args if the logger is set to DEBUG priority.
 func Spew(args ...interface{}) {
 	log.spew(args...)

seekbuf/seekbuf.go

@@ -55,3 +55,8 @@ func (b *Buffer) Close() error {
 func (b *Buffer) Len() int {
 	return len(b.data[b.pos:])
 }
+
+// Bytes returns the underlying bytes from the current position.
+func (b *Buffer) Bytes() []byte {
+	return b.data[b.pos:]
+}