journald logger: fix race condition

libpod/container_log_linux.go

@@ -6,14 +6,12 @@ package libpod
 import (
 	"context"
 	"fmt"
-	"io"
-	"math"
 	"strings"
 	"time"
 
-	"github.com/containers/podman/v3/libpod/define"
+	"github.com/containers/podman/v3/libpod/events"
 	"github.com/containers/podman/v3/libpod/logs"
-	journal "github.com/coreos/go-systemd/v22/sdjournal"
+	"github.com/coreos/go-systemd/v22/sdjournal"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 )
@@ -24,122 +22,187 @@ const (
 
 	// journaldLogErr is the journald priority signifying stderr
 	journaldLogErr = "3"
-
-	// bufLen is the length of the buffer to read from a k8s-file
-	// formatted log line
-	// let's set it as 2k just to be safe if k8s-file format ever changes
-	bufLen = 16384
 )
 
 func (c *Container) readFromJournal(ctx context.Context, options *logs.LogOptions, logChannel chan *logs.LogLine) error {
-	var config journal.JournalReaderConfig
-	if options.Tail < 0 {
-		config.NumFromTail = 0
-	} else if options.Tail == 0 {
-		config.NumFromTail = math.MaxUint64
-	} else {
-		config.NumFromTail = uint64(options.Tail)
+	journal, err := sdjournal.NewJournal()
+	if err != nil {
+		return err
 	}
-	if options.Multi {
-		config.Formatter = journalFormatterWithID
-	} else {
-		config.Formatter = journalFormatter
-	}
-	defaultTime := time.Time{}
-	if options.Since != defaultTime {
-		// coreos/go-systemd/sdjournal doesn't correctly handle requests for data in the future
-		// return nothing instead of falsely printing
-		if time.Now().Before(options.Since) {
-			return nil
-		}
-		// coreos/go-systemd/sdjournal expects a negative time.Duration for times in the past
-		config.Since = -time.Since(options.Since)
+	// While logs are written to the `logChannel`, we inspect each event
+	// and stop once the container has died.  Having logs and events in one
+	// stream prevents a race condition that we faced in #10323.
+
+	// Add the filters for events.
+	match := sdjournal.Match{Field: "SYSLOG_IDENTIFIER", Value: "podman"}
+	if err := journal.AddMatch(match.String()); err != nil {
+		return errors.Wrapf(err, "adding filter to journald logger: %v", match)
+	}
+	match = sdjournal.Match{Field: "PODMAN_ID", Value: c.ID()}
+	if err := journal.AddMatch(match.String()); err != nil {
+		return errors.Wrapf(err, "adding filter to journald logger: %v", match)
 	}
-	config.Matches = append(config.Matches, journal.Match{
-		Field: "CONTAINER_ID_FULL",
-		Value: c.ID(),
-	})
-	options.WaitGroup.Add(1)
 
-	r, err := journal.NewJournalReader(config)
-	if err != nil {
+	// Add the filter for logs.  Note the disjunction so that we match
+	// either the events or the logs.
+	if err := journal.AddDisjunction(); err != nil {
+		return errors.Wrap(err, "adding filter disjunction to journald logger")
+	}
+	match = sdjournal.Match{Field: "CONTAINER_ID_FULL", Value: c.ID()}
+	if err := journal.AddMatch(match.String()); err != nil {
+		return errors.Wrapf(err, "adding filter to journald logger: %v", match)
+	}
+
+	if err := journal.SeekHead(); err != nil {
 		return err
 	}
-	if r == nil {
-		return errors.Errorf("journal reader creation failed")
+	// API requires Next() immediately after SeekHead().
+	if _, err := journal.Next(); err != nil {
+		return errors.Wrap(err, "initial journal cursor")
 	}
-	if options.Tail == math.MaxInt64 {
-		r.Rewind()
+
+	// API requires a next|prev before getting a cursor.
+	if _, err := journal.Previous(); err != nil {
+		return errors.Wrap(err, "initial journal cursor")
 	}
-	state, err := c.State()
-	if err != nil {
-		return err
+
+	// Note that the initial cursor may not yet be ready, so we'll do an
+	// exponential backoff.
+	var cursor string
+	var cursorError error
+	for i := 1; i <= 3; i++ {
+		cursor, cursorError = journal.GetCursor()
+		if err != nil {
+			continue
+		}
+		time.Sleep(time.Duration(i*100) * time.Millisecond)
+		break
+	}
+	if cursorError != nil {
+		return errors.Wrap(cursorError, "inital journal cursor")
+	}
+
+	// We need the container's events in the same journal to guarantee
+	// consistency, see #10323.
+	if options.Follow && c.runtime.config.Engine.EventsLogger != "journald" {
+		return errors.Errorf("using --follow with the journald --log-driver but without the journald --events-backend (%s) is not supported", c.runtime.config.Engine.EventsLogger)
 	}
 
-	if options.Follow && state == define.ContainerStateRunning {
-		go func() {
-			done := make(chan bool)
-			until := make(chan time.Time)
-			go func() {
-				select {
-				case <-ctx.Done():
-					until <- time.Time{}
-				case <-done:
-					// nothing to do anymore
+	options.WaitGroup.Add(1)
+	go func() {
+		defer func() {
+			options.WaitGroup.Done()
+			if err := journal.Close(); err != nil {
+				logrus.Errorf("Unable to close journal: %v", err)
+			}
+		}()
+
+		afterTimeStamp := false        // needed for options.Since
+		tailQueue := []*logs.LogLine{} // needed for options.Tail
+		doTail := options.Tail > 0
+		for {
+			select {
+			case <-ctx.Done():
+				// Remote client may have closed/lost the connection.
+				return
+			default:
+				// Fallthrough
+			}
+
+			if _, err := journal.Next(); err != nil {
+				logrus.Errorf("Failed to move journal cursor to next entry: %v", err)
+				return
+			}
+			latestCursor, err := journal.GetCursor()
+			if err != nil {
+				logrus.Errorf("Failed to get journal cursor: %v", err)
+				return
+			}
+
+			// Hit the end of the journal.
+			if cursor == latestCursor {
+				if doTail {
+					// Flush *once* we hit the end of the journal.
+					startIndex := int64(len(tailQueue)-1) - options.Tail
+					if startIndex < 0 {
+						startIndex = 0
+					}
+					for i := startIndex; i < int64(len(tailQueue)); i++ {
+						logChannel <- tailQueue[i]
+					}
+					tailQueue = nil
+					doTail = false
+				}
+				// Unless we follow, quit.
+				if !options.Follow {
+					return
 				}
-			}()
-			go func() {
-				// FIXME (#10323): we are facing a terrible
-				// race condition here. At the time the
-				// container dies and `c.Wait()` has returned,
-				// we may not have received all journald logs.
-				// So far there is no other way than waiting
-				// for a second.  Ultimately, `r.Follow` is
-				// racy and we may have to implement our custom
-				// logic here.
-				c.Wait(ctx)
-				time.Sleep(time.Second)
-				until <- time.Time{}
-			}()
-			follower := journaldFollowBuffer{logChannel, options.Multi}
-			err := r.Follow(until, follower)
+				// Sleep until something's happening on the journal.
+				journal.Wait(sdjournal.IndefiniteWait)
+				continue
+			}
+			cursor = latestCursor
+
+			entry, err := journal.GetEntry()
 			if err != nil {
-				logrus.Debugf(err.Error())
+				logrus.Errorf("Failed to get journal entry: %v", err)
+				return
 			}
-			r.Close()
-			options.WaitGroup.Done()
-			done <- true
-			return
-		}()
-		return nil
-	}
 
-	go func() {
-		bytes := make([]byte, bufLen)
-		// /me complains about no do-while in go
-		ec, err := r.Read(bytes)
-		for ec != 0 && err == nil {
-			// because we are reusing bytes, we need to make
-			// sure the old data doesn't get into the new line
-			bytestr := string(bytes[:ec])
-			logLine, err2 := logs.NewJournaldLogLine(bytestr, options.Multi)
-			if err2 != nil {
-				logrus.Error(err2)
+			if !afterTimeStamp {
+				entryTime := time.Unix(0, int64(entry.RealtimeTimestamp)*int64(time.Microsecond))
+				if entryTime.Before(options.Since) {
+					continue
+				}
+				afterTimeStamp = true
+			}
+
+			// If we're reading an event and the container exited/died,
+			// then we're done and can return.
+			event, ok := entry.Fields["PODMAN_EVENT"]
+			if ok {
+				status, err := events.StringToStatus(event)
+				if err != nil {
+					logrus.Errorf("Failed to translate event: %v", err)
+					return
+				}
+				if status == events.Exited {
+					return
+				}
+				continue
+			}
+
+			var message string
+			var formatError error
+
+			if options.Multi {
+				message, formatError = journalFormatterWithID(entry)
+			} else {
+				message, formatError = journalFormatter(entry)
+			}
+
+			if formatError != nil {
+				logrus.Errorf("Failed to parse journald log entry: %v", err)
+				return
+			}
+
+			logLine, err := logs.NewJournaldLogLine(message, options.Multi)
+			if err != nil {
+				logrus.Errorf("Failed parse log line: %v", err)
+				return
+			}
+			if doTail {
+				tailQueue = append(tailQueue, logLine)
 				continue
 			}
 			logChannel <- logLine
-			ec, err = r.Read(bytes)
 		}
-		if err != nil && err != io.EOF {
-			logrus.Error(err)
-		}
-		r.Close()
-		options.WaitGroup.Done()
 	}()
+
 	return nil
 }
 
-func journalFormatterWithID(entry *journal.JournalEntry) (string, error) {
+func journalFormatterWithID(entry *sdjournal.JournalEntry) (string, error) {
 	output, err := formatterPrefix(entry)
 	if err != nil {
 		return "", err
@@ -162,7 +225,7 @@ func journalFormatterWithID(entry *journal.JournalEntry) (string, error) {
 	return output, nil
 }
 
-func journalFormatter(entry *journal.JournalEntry) (string, error) {
+func journalFormatter(entry *sdjournal.JournalEntry) (string, error) {
 	output, err := formatterPrefix(entry)
 	if err != nil {
 		return "", err
@@ -176,7 +239,7 @@ func journalFormatter(entry *journal.JournalEntry) (string, error) {
 	return output, nil
 }
 
-func formatterPrefix(entry *journal.JournalEntry) (string, error) {
+func formatterPrefix(entry *sdjournal.JournalEntry) (string, error) {
 	usec := entry.RealtimeTimestamp
 	tsString := time.Unix(0, int64(usec)*int64(time.Microsecond)).Format(logs.LogTimeFormat)
 	output := fmt.Sprintf("%s ", tsString)
@@ -202,7 +265,7 @@ func formatterPrefix(entry *journal.JournalEntry) (string, error) {
 	return output, nil
 }
 
-func formatterMessage(entry *journal.JournalEntry) (string, error) {
+func formatterMessage(entry *sdjournal.JournalEntry) (string, error) {
 	// Finally, append the message
 	msg, ok := entry.Fields["MESSAGE"]
 	if !ok {
@@ -211,18 +274,3 @@ func formatterMessage(entry *journal.JournalEntry) (string, error) {
 	msg = strings.TrimSuffix(msg, "\n")
 	return msg, nil
 }
-
-type journaldFollowBuffer struct {
-	logChannel chan *logs.LogLine
-	withID     bool
-}
-
-func (f journaldFollowBuffer) Write(p []byte) (int, error) {
-	bytestr := string(p)
-	logLine, err := logs.NewJournaldLogLine(bytestr, f.withID)
-	if err != nil {
-		return -1, err
-	}
-	f.logChannel <- logLine
-	return len(p), nil
-}

test/e2e/logs_test.go

@@ -163,7 +163,7 @@ var _ = Describe("Podman logs", func() {
 		})
 
 		It("podman logs on a created container should result in 0 exit code: "+log, func() {
-			session := podmanTest.Podman([]string{"create", "-t", "--name", "log", ALPINE})
+			session := podmanTest.Podman([]string{"create", "--log-driver", log, "-t", "--name", "log", ALPINE})
 			session.WaitWithDefaultTimeout()
 			Expect(session).To(Exit(0))