TUN-528: Move cloudflared into a separate repo

vendor/github.com/coreos/go-systemd/sdjournal/functions.go

@@ -0,0 +1,66 @@
+// Copyright 2015 RedHat, Inc.
+// Copyright 2015 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 sdjournal
+
+import (
+	"github.com/coreos/pkg/dlopen"
+	"sync"
+	"unsafe"
+)
+
+var (
+	// lazy initialized
+	libsystemdHandle *dlopen.LibHandle
+
+	libsystemdMutex     = &sync.Mutex{}
+	libsystemdFunctions = map[string]unsafe.Pointer{}
+	libsystemdNames     = []string{
+		// systemd < 209
+		"libsystemd-journal.so.0",
+		"libsystemd-journal.so",
+
+		// systemd >= 209 merged libsystemd-journal into libsystemd proper
+		"libsystemd.so.0",
+		"libsystemd.so",
+	}
+)
+
+func getFunction(name string) (unsafe.Pointer, error) {
+	libsystemdMutex.Lock()
+	defer libsystemdMutex.Unlock()
+
+	if libsystemdHandle == nil {
+		h, err := dlopen.GetHandle(libsystemdNames)
+		if err != nil {
+			return nil, err
+		}
+
+		libsystemdHandle = h
+	}
+
+	f, ok := libsystemdFunctions[name]
+	if !ok {
+		var err error
+		f, err = libsystemdHandle.GetSymbolPointer(name)
+		if err != nil {
+			return nil, err
+		}
+
+		libsystemdFunctions[name] = f
+	}
+
+	return f, nil
+}

vendor/github.com/coreos/go-systemd/sdjournal/functions_test.go

@@ -0,0 +1,36 @@
+// Copyright 2015 RedHat, Inc.
+// Copyright 2015 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 sdjournal
+
+import "testing"
+
+func TestGetFunction(t *testing.T) {
+	f, err := getFunction("sd_journal_open")
+
+	if err != nil {
+		t.Errorf("Error getting an existing function: %s", err)
+	}
+
+	if f == nil {
+		t.Error("Got nil function pointer")
+	}
+
+	_, err = getFunction("non_existent_function")
+
+	if err == nil {
+		t.Error("Expected to get an error, got nil")
+	}
+}

vendor/github.com/coreos/go-systemd/sdjournal/journal_test.go

@@ -0,0 +1,508 @@
+// Copyright 2015 RedHat, Inc.
+// Copyright 2015 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 sdjournal
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"math/rand"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/coreos/go-systemd/journal"
+)
+
+func TestJournalFollow(t *testing.T) {
+	r, err := NewJournalReader(JournalReaderConfig{
+		Since: time.Duration(-15) * time.Second,
+		Matches: []Match{
+			{
+				Field: SD_JOURNAL_FIELD_SYSTEMD_UNIT,
+				Value: "NetworkManager.service",
+			},
+		},
+	})
+
+	if err != nil {
+		t.Fatalf("Error opening journal: %s", err)
+	}
+
+	if r == nil {
+		t.Fatal("Got a nil reader")
+	}
+
+	defer r.Close()
+
+	// start writing some test entries
+	done := make(chan struct{}, 1)
+	errCh := make(chan error, 1)
+	defer close(done)
+	go func() {
+		for {
+			select {
+			case <-done:
+				return
+			default:
+				if perr := journal.Print(journal.PriInfo, "test message %s", time.Now()); err != nil {
+					errCh <- perr
+					return
+				}
+
+				time.Sleep(time.Second)
+			}
+		}
+	}()
+
+	// and follow the reader synchronously
+	timeout := time.Duration(5) * time.Second
+	if err = r.Follow(time.After(timeout), os.Stdout); err != ErrExpired {
+		t.Fatalf("Error during follow: %s", err)
+	}
+
+	select {
+	case err := <-errCh:
+		t.Fatalf("Error writing to journal: %s", err)
+	default:
+	}
+}
+
+func TestJournalWait(t *testing.T) {
+	id := time.Now().String()
+	j, err := NewJournal()
+	if err != nil {
+		t.Fatalf("Error opening journal: %s", err)
+	}
+	if err := j.AddMatch("TEST=TestJournalWait " + id); err != nil {
+		t.Fatalf("Error adding match: %s", err)
+	}
+	if err := j.SeekTail(); err != nil {
+		t.Fatalf("Error seeking to tail: %s", err)
+	}
+	if _, err := j.Next(); err != nil {
+		t.Fatalf("Error retrieving next entry: %s", err)
+	}
+
+	var t1, t2 time.Time
+	for ret := -1; ret != SD_JOURNAL_NOP; {
+		// Wait() might return for reasons other than timeout.
+		// For example the first call initializes stuff and returns immediately.
+		t1 = time.Now()
+		ret = j.Wait(time.Millisecond * 300)
+		t2 = time.Now()
+	}
+	duration := t2.Sub(t1)
+
+	if duration > time.Millisecond*325 || duration < time.Millisecond*300 {
+		t.Errorf("Wait did not wait 300ms. Actually waited %s", duration.String())
+	}
+
+	journal.Send("test message", journal.PriInfo, map[string]string{"TEST": "TestJournalWait " + id})
+	for ret := -1; ret != SD_JOURNAL_APPEND; {
+		t1 = time.Now()
+		ret = j.Wait(time.Millisecond * 300)
+		t2 = time.Now()
+	}
+	duration = t2.Sub(t1)
+
+	if duration >= time.Millisecond*300 {
+		t.Errorf("Wait took longer than 300ms. Actual duration %s", duration.String())
+	}
+}
+
+func TestJournalGetUsage(t *testing.T) {
+	j, err := NewJournal()
+
+	if err != nil {
+		t.Fatalf("Error opening journal: %s", err)
+	}
+
+	if j == nil {
+		t.Fatal("Got a nil journal")
+	}
+
+	defer j.Close()
+
+	_, err = j.GetUsage()
+
+	if err != nil {
+		t.Fatalf("Error getting journal size: %s", err)
+	}
+}
+
+func TestJournalCursorGetSeekAndTest(t *testing.T) {
+	j, err := NewJournal()
+	if err != nil {
+		t.Fatalf("Error opening journal: %s", err)
+	}
+
+	if j == nil {
+		t.Fatal("Got a nil journal")
+	}
+
+	defer j.Close()
+
+	err = journal.Print(journal.PriInfo, "test message for cursor %s", time.Now())
+	if err != nil {
+		t.Fatalf("Error writing to journal: %s", err)
+	}
+
+	if err = waitAndNext(j); err != nil {
+		t.Fatalf(err.Error())
+	}
+
+	c, err := j.GetCursor()
+	if err != nil {
+		t.Fatalf("Error getting cursor from journal: %s", err)
+	}
+
+	err = j.SeekCursor(c)
+	if err != nil {
+		t.Fatalf("Error seeking cursor to journal: %s", err)
+	}
+
+	if err = waitAndNext(j); err != nil {
+		t.Fatalf(err.Error())
+	}
+
+	err = j.TestCursor(c)
+	if err != nil {
+		t.Fatalf("Error testing cursor to journal: %s", err)
+	}
+
+	err = journal.Print(journal.PriInfo, "second message %s", time.Now())
+	if err != nil {
+		t.Fatalf("Error writing to journal: %s", err)
+	}
+
+	if err = waitAndNext(j); err != nil {
+		t.Fatalf(err.Error())
+	}
+
+	err = j.TestCursor(c)
+	if err != ErrNoTestCursor {
+		t.Fatalf("Error, TestCursor should fail because current cursor has moved from the previous obtained cursor")
+	}
+}
+
+func TestNewJournalFromDir(t *testing.T) {
+	// test for error handling
+	dir := "/ClearlyNonExistingPath/"
+	j, err := NewJournalFromDir(dir)
+	if err == nil {
+		defer j.Close()
+		t.Fatalf("Error expected when opening dummy path (%s)", dir)
+	}
+	// test for main code path
+	dir, err = ioutil.TempDir("", "go-systemd-test")
+	if err != nil {
+		t.Fatalf("Error creating tempdir: %s", err)
+	}
+	defer os.RemoveAll(dir)
+	j, err = NewJournalFromDir(dir)
+	if err != nil {
+		t.Fatalf("Error opening journal: %s", err)
+	}
+	if j == nil {
+		t.Fatal("Got a nil journal")
+	}
+	j.Close()
+}
+
+func setupJournalRoundtrip() (*Journal, map[string]string, error) {
+	j, err := NewJournal()
+	if err != nil {
+		return nil, nil, fmt.Errorf("Error opening journal: %s", err)
+	}
+
+	if j == nil {
+		return nil, nil, fmt.Errorf("Got a nil journal")
+	}
+
+	j.FlushMatches()
+
+	matchField := "TESTJOURNALENTRY"
+	matchValue := fmt.Sprintf("%d", time.Now().UnixNano())
+	m := Match{Field: matchField, Value: matchValue}
+	err = j.AddMatch(m.String())
+	if err != nil {
+		return nil, nil, fmt.Errorf("Error adding matches to journal: %s", err)
+	}
+
+	msg := fmt.Sprintf("test journal get entry message %s", time.Now())
+	data := map[string]string{matchField: matchValue}
+	err = journal.Send(msg, journal.PriInfo, data)
+	if err != nil {
+		return nil, nil, fmt.Errorf("Error writing to journal: %s", err)
+	}
+
+	time.Sleep(time.Duration(1) * time.Second)
+
+	n, err := j.Next()
+	if err != nil {
+		return nil, nil, fmt.Errorf("Error reading from journal: %s", err)
+	}
+
+	if n == 0 {
+		return nil, nil, fmt.Errorf("Error reading from journal: %s", io.EOF)
+	}
+
+	data["MESSAGE"] = msg
+
+	return j, data, nil
+}
+
+func TestJournalGetData(t *testing.T) {
+	j, wantEntry, err := setupJournalRoundtrip()
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+
+	defer j.Close()
+
+	for k, v := range wantEntry {
+		data := fmt.Sprintf("%s=%s", k, v)
+
+		dataStr, err := j.GetData(k)
+		if err != nil {
+			t.Fatalf("GetData() error: %v", err)
+		}
+
+		if dataStr != data {
+			t.Fatalf("Invalid data for \"%s\": got %s, want %s", k, dataStr, data)
+		}
+
+		dataBytes, err := j.GetDataBytes(k)
+		if err != nil {
+			t.Fatalf("GetDataBytes() error: %v", err)
+		}
+
+		if string(dataBytes) != data {
+			t.Fatalf("Invalid data bytes for \"%s\": got %s, want %s", k, string(dataBytes), data)
+		}
+
+		valStr, err := j.GetDataValue(k)
+		if err != nil {
+			t.Fatalf("GetDataValue() error: %v", err)
+		}
+
+		if valStr != v {
+			t.Fatalf("Invalid data value for \"%s\": got %s, want %s", k, valStr, v)
+		}
+
+		valBytes, err := j.GetDataValueBytes(k)
+		if err != nil {
+			t.Fatalf("GetDataValueBytes() error: %v", err)
+		}
+
+		if string(valBytes) != v {
+			t.Fatalf("Invalid data value bytes for \"%s\": got %s, want %s", k, string(valBytes), v)
+		}
+	}
+}
+
+func TestJournalGetEntry(t *testing.T) {
+	j, wantEntry, err := setupJournalRoundtrip()
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+
+	defer j.Close()
+
+	entry, err := j.GetEntry()
+	if err != nil {
+		t.Fatalf("Error getting the entry to journal: %s", err)
+	}
+
+	for k, wantV := range wantEntry {
+		gotV := entry.Fields[k]
+		if gotV != wantV {
+			t.Fatalf("Bad result for entry.Fields[\"%s\"]: got %s, want %s", k, gotV, wantV)
+		}
+	}
+}
+
+// Check for incorrect read into small buffers,
+// see https://github.com/coreos/go-systemd/issues/172
+func TestJournalReaderSmallReadBuffer(t *testing.T) {
+	// Write a long entry ...
+	delim := "%%%%%%"
+	longEntry := strings.Repeat("a", 256)
+	matchField := "TESTJOURNALREADERSMALLBUF"
+	matchValue := fmt.Sprintf("%d", time.Now().UnixNano())
+	r, err := NewJournalReader(JournalReaderConfig{
+		Since: time.Duration(-15) * time.Second,
+		Matches: []Match{
+			{
+				Field: matchField,
+				Value: matchValue,
+			},
+		},
+	})
+	if err != nil {
+		t.Fatalf("Error opening journal: %s", err)
+	}
+	if r == nil {
+		t.Fatal("Got a nil reader")
+	}
+	defer r.Close()
+
+	want := fmt.Sprintf("%slongentry %s%s", delim, longEntry, delim)
+	err = journal.Send(want, journal.PriInfo, map[string]string{matchField: matchValue})
+	if err != nil {
+		t.Fatal("Error writing to journal", err)
+	}
+	time.Sleep(time.Second)
+
+	// ... and try to read it back piece by piece via a small buffer
+	finalBuff := new(bytes.Buffer)
+	var e error
+	for c := -1; c != 0 && e == nil; {
+		smallBuf := make([]byte, 5)
+		c, e = r.Read(smallBuf)
+		if c > len(smallBuf) {
+			t.Fatalf("Got unexpected read length: %d vs %d", c, len(smallBuf))
+		}
+		_, _ = finalBuff.Write(smallBuf)
+	}
+	b := finalBuff.String()
+	got := strings.Split(b, delim)
+	if len(got) != 3 {
+		t.Fatalf("Got unexpected entry %s", b)
+	}
+	if got[1] != strings.Trim(want, delim) {
+		t.Fatalf("Got unexpected message %s", got[1])
+	}
+}
+
+func TestJournalGetUniqueValues(t *testing.T) {
+	j, err := NewJournal()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer j.Close()
+
+	uniqueString := generateRandomField(20)
+	testEntries := []string{"A", "B", "C", "D"}
+	for _, v := range testEntries {
+		err = journal.Send("TEST: "+uniqueString, journal.PriInfo, map[string]string{uniqueString: v})
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// TODO: add proper `waitOnMatch` function which should wait for journal entry with filter to commit.
+	time.Sleep(time.Millisecond * 500)
+
+	values, err := j.GetUniqueValues(uniqueString)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(values) != len(testEntries) {
+		t.Fatalf("Expect %d entries. Got %d", len(testEntries), len(values))
+	}
+
+	if !contains(values, "A") || !contains(values, "B") || !contains(values, "C") || !contains(values, "D") {
+		t.Fatalf("Expect 4 values for %s field: A,B,C,D. Got %s", uniqueString, values)
+	}
+}
+
+func TestJournalGetCatalog(t *testing.T) {
+	want := []string{
+		"Subject: ",
+		"Defined-By: systemd",
+		"Support: ",
+	}
+	j, err := NewJournal()
+	if err != nil {
+		t.Fatalf("Error opening journal: %s", err)
+	}
+
+	if j == nil {
+		t.Fatal("Got a nil journal")
+	}
+
+	defer j.Close()
+
+	if err = j.SeekHead(); err != nil {
+		t.Fatalf("Seek to head failed: %s", err)
+	}
+
+	matchField := SD_JOURNAL_FIELD_SYSTEMD_UNIT
+	m := Match{Field: matchField, Value: "systemd-journald.service"}
+	if err = j.AddMatch(m.String()); err != nil {
+		t.Fatalf("Error adding matches to journal: %s", err)
+	}
+
+	if err = waitAndNext(j); err != nil {
+		t.Fatalf(err.Error())
+	}
+
+	catalog, err := j.GetCatalog()
+
+	if err != nil {
+		t.Fatalf("Failed to retrieve catalog entry: %s", err)
+	}
+
+	for _, w := range want {
+		if !strings.Contains(catalog, w) {
+			t.Fatalf("Failed to find \"%s\" in \n%s", w, catalog)
+		}
+	}
+}
+
+func contains(s []string, v string) bool {
+	for _, entry := range s {
+		if entry == v {
+			return true
+		}
+	}
+	return false
+}
+
+func generateRandomField(n int) string {
+	letters := []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
+	s := make([]rune, n)
+	rand.Seed(time.Now().UnixNano())
+	for i := range s {
+		s[i] = letters[rand.Intn(len(letters))]
+	}
+	return string(s)
+}
+
+func waitAndNext(j *Journal) error {
+	r := j.Wait(time.Duration(1) * time.Second)
+	if r < 0 {
+		return errors.New("Error waiting to journal")
+	}
+
+	n, err := j.Next()
+	if err != nil {
+		return fmt.Errorf("Error reading to journal: %s", err)
+	}
+
+	if n == 0 {
+		return fmt.Errorf("Error reading to journal: %s", io.EOF)
+	}
+
+	return nil
+}

vendor/github.com/coreos/go-systemd/sdjournal/read.go

@@ -0,0 +1,272 @@
+// Copyright 2015 RedHat, Inc.
+// Copyright 2015 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 sdjournal
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	// ErrExpired gets returned when the Follow function runs into the
+	// specified timeout.
+	ErrExpired = errors.New("Timeout expired")
+)
+
+// JournalReaderConfig represents options to drive the behavior of a JournalReader.
+type JournalReaderConfig struct {
+	// The Since, NumFromTail and Cursor options are mutually exclusive and
+	// determine where the reading begins within the journal. The order in which
+	// options are written is exactly the order of precedence.
+	Since       time.Duration // start relative to a Duration from now
+	NumFromTail uint64        // start relative to the tail
+	Cursor      string        // start relative to the cursor
+
+	// Show only journal entries whose fields match the supplied values. If
+	// the array is empty, entries will not be filtered.
+	Matches []Match
+
+	// If not empty, the journal instance will point to a journal residing
+	// in this directory. The supplied path may be relative or absolute.
+	Path string
+
+	// If not nil, Formatter will be used to translate the resulting entries
+	// into strings. If not set, the default format (timestamp and message field)
+	// will be used. If Formatter returns an error, Read will stop and return the error.
+	Formatter func(entry *JournalEntry) (string, error)
+}
+
+// JournalReader is an io.ReadCloser which provides a simple interface for iterating through the
+// systemd journal. A JournalReader is not safe for concurrent use by multiple goroutines.
+type JournalReader struct {
+	journal   *Journal
+	msgReader *strings.Reader
+	formatter func(entry *JournalEntry) (string, error)
+}
+
+// NewJournalReader creates a new JournalReader with configuration options that are similar to the
+// systemd journalctl tool's iteration and filtering features.
+func NewJournalReader(config JournalReaderConfig) (*JournalReader, error) {
+	// use simpleMessageFormatter as default formatter.
+	if config.Formatter == nil {
+		config.Formatter = simpleMessageFormatter
+	}
+
+	r := &JournalReader{
+		formatter: config.Formatter,
+	}
+
+	// Open the journal
+	var err error
+	if config.Path != "" {
+		r.journal, err = NewJournalFromDir(config.Path)
+	} else {
+		r.journal, err = NewJournal()
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	// Add any supplied matches
+	for _, m := range config.Matches {
+		if err = r.journal.AddMatch(m.String()); err != nil {
+			return nil, err
+		}
+	}
+
+	// Set the start position based on options
+	if config.Since != 0 {
+		// Start based on a relative time
+		start := time.Now().Add(config.Since)
+		if err := r.journal.SeekRealtimeUsec(uint64(start.UnixNano() / 1000)); err != nil {
+			return nil, err
+		}
+	} else if config.NumFromTail != 0 {
+		// Start based on a number of lines before the tail
+		if err := r.journal.SeekTail(); err != nil {
+			return nil, err
+		}
+
+		// Move the read pointer into position near the tail. Go one further than
+		// the option so that the initial cursor advancement positions us at the
+		// correct starting point.
+		skip, err := r.journal.PreviousSkip(config.NumFromTail + 1)
+		if err != nil {
+			return nil, err
+		}
+		// If we skipped fewer lines than expected, we have reached journal start.
+		// Thus, we seek to head so that next invocation can read the first line.
+		if skip != config.NumFromTail+1 {
+			if err := r.journal.SeekHead(); err != nil {
+				return nil, err
+			}
+		}
+	} else if config.Cursor != "" {
+		// Start based on a custom cursor
+		if err := r.journal.SeekCursor(config.Cursor); err != nil {
+			return nil, err
+		}
+	}
+
+	return r, nil
+}
+
+// Read reads entries from the journal. Read follows the Reader interface so
+// it must be able to read a specific amount of bytes. Journald on the other
+// hand only allows us to read full entries of arbitrary size (without byte
+// granularity). JournalReader is therefore internally buffering entries that
+// don't fit in the read buffer. Callers should keep calling until 0 and/or an
+// error is returned.
+func (r *JournalReader) Read(b []byte) (int, error) {
+	if r.msgReader == nil {
+		// Advance the journal cursor. It has to be called at least one time
+		// before reading
+		c, err := r.journal.Next()
+
+		// An unexpected error
+		if err != nil {
+			return 0, err
+		}
+
+		// EOF detection
+		if c == 0 {
+			return 0, io.EOF
+		}
+
+		entry, err := r.journal.GetEntry()
+		if err != nil {
+			return 0, err
+		}
+
+		// Build a message
+		msg, err := r.formatter(entry)
+		if err != nil {
+			return 0, err
+		}
+		r.msgReader = strings.NewReader(msg)
+	}
+
+	// Copy and return the message
+	sz, err := r.msgReader.Read(b)
+	if err == io.EOF {
+		// The current entry has been fully read. Don't propagate this
+		// EOF, so the next entry can be read at the next Read()
+		// iteration.
+		r.msgReader = nil
+		return sz, nil
+	}
+	if err != nil {
+		return sz, err
+	}
+	if r.msgReader.Len() == 0 {
+		r.msgReader = nil
+	}
+
+	return sz, nil
+}
+
+// Close closes the JournalReader's handle to the journal.
+func (r *JournalReader) Close() error {
+	return r.journal.Close()
+}
+
+// Rewind attempts to rewind the JournalReader to the first entry.
+func (r *JournalReader) Rewind() error {
+	r.msgReader = nil
+	return r.journal.SeekHead()
+}
+
+// Follow synchronously follows the JournalReader, writing each new journal entry to writer. The
+// follow will continue until a single time.Time is received on the until channel.
+func (r *JournalReader) Follow(until <-chan time.Time, writer io.Writer) error {
+
+	// Process journal entries and events. Entries are flushed until the tail or
+	// timeout is reached, and then we wait for new events or the timeout.
+	var msg = make([]byte, 64*1<<(10))
+	var waitCh = make(chan int, 1)
+	var waitGroup sync.WaitGroup
+	defer waitGroup.Wait()
+
+process:
+	for {
+		c, err := r.Read(msg)
+		if err != nil && err != io.EOF {
+			return err
+		}
+
+		select {
+		case <-until:
+			return ErrExpired
+		default:
+		}
+		if c > 0 {
+			if _, err = writer.Write(msg[:c]); err != nil {
+				return err
+			}
+			continue process
+		}
+
+		// We're at the tail, so wait for new events or time out.
+		// Holds journal events to process. Tightly bounded for now unless there's a
+		// reason to unblock the journal watch routine more quickly.
+		for {
+			waitGroup.Add(1)
+			go func() {
+				status := r.journal.Wait(100 * time.Millisecond)
+				waitCh <- status
+				waitGroup.Done()
+			}()
+
+			select {
+			case <-until:
+				return ErrExpired
+			case e := <-waitCh:
+				switch e {
+				case SD_JOURNAL_NOP:
+					// the journal did not change since the last invocation
+				case SD_JOURNAL_APPEND, SD_JOURNAL_INVALIDATE:
+					continue process
+				default:
+					if e < 0 {
+						return fmt.Errorf("received error event: %d", e)
+					}
+
+					log.Printf("received unknown event: %d\n", e)
+				}
+			}
+		}
+	}
+}
+
+// simpleMessageFormatter is the default formatter.
+// It returns a string representing the current journal entry in a simple format which
+// includes the entry timestamp and MESSAGE field.
+func simpleMessageFormatter(entry *JournalEntry) (string, error) {
+	msg, ok := entry.Fields["MESSAGE"]
+	if !ok {
+		return "", fmt.Errorf("no MESSAGE field present in journal entry")
+	}
+
+	usec := entry.RealtimeTimestamp
+	timestamp := time.Unix(0, int64(usec)*int64(time.Microsecond))
+
+	return fmt.Sprintf("%s %s\n", timestamp, msg), nil
+}