refactor: Clean up internals of the logstreams

internal/mtail/read_pipe_integration_unix_test.go

@@ -17,7 +17,7 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-func TestReadFromPipe(t *testing.T) {
+func TestReadFromFifo(t *testing.T) {
 	testutil.SkipIfShort(t)
 	tmpDir := testutil.TestTempDir(t)
 

internal/mtail/testing.go

@@ -63,7 +63,12 @@ func TestMakeServer(tb testing.TB, patternWakers int, streamWakers int, options
 		tb:     tb,
 		cancel: cancel,
 	}
-	ts.streamWaker, ts.AwakenLogStreams = waker.NewTest(ctx, streamWakers, "streams")
+	if streamWakers == 0 {
+		ts.streamWaker = waker.NewTestAlways()
+		ts.AwakenLogStreams = func(int, int) {}
+	} else {
+		ts.streamWaker, ts.AwakenLogStreams = waker.NewTest(ctx, streamWakers, "streams")
+	}
 	ts.patternWaker, ts.AwakenPatternPollers = waker.NewTest(ctx, patternWakers, "patterns")
 	options = append(options,
 		LogstreamPollWaker(ts.streamWaker),

internal/tailer/logstream/base.go

@@ -0,0 +1,24 @@
+// Copyright 2024 Google Inc. All Rights Reserved.
+// This file is available under the Apache license.
+
+package logstream
+
+import (
+	"time"
+
+	"github.com/google/mtail/internal/logline"
+)
+
+type streamBase struct {
+	sourcename string // human readable name of the logstream source
+
+	lines chan *logline.LogLine // outbound channel for lines
+
+	staleTimer *time.Timer // Expire the stream if no read in 24h.
+}
+
+// Lines returns the output log line channel for this stream.  The stream is
+// completed when this channel closes.
+func (s *streamBase) Lines() <-chan *logline.LogLine {
+	return s.lines
+}

internal/tailer/logstream/cancel.go

@@ -11,10 +11,14 @@ import (
 	"github.com/golang/glog"
 )
 
+// ReadDeadliner has a SetReadDeadline function to be used for interrupting reads.
 type ReadDeadliner interface {
 	SetReadDeadline(t time.Time) error
 }
 
+// SetReadDeadlineOnDone waits for the context to be done, and then sets an
+// immediate read deadline on the flie descriptor `d`.  This causes any blocked
+// reads on that descriptor to return with an i/o timeout error.
 func SetReadDeadlineOnDone(ctx context.Context, d ReadDeadliner) {
 	go func() {
 		<-ctx.Done()
@@ -25,7 +29,11 @@ func SetReadDeadlineOnDone(ctx context.Context, d ReadDeadliner) {
 	}()
 }
 
-func IsEndOrCancel(err error) bool {
+// IsExitableError returns true if a stream should exit because of this error.
+func IsExitableError(err error) bool {
+	if err == nil {
+		return false
+	}
 	if errors.Is(err, io.EOF) {
 		return true
 	}

internal/tailer/logstream/decode.go

@@ -17,7 +17,7 @@ import (
 var logLines = expvar.NewMap("log_lines_total")
 
 // decodeAndSend transforms the byte array `b` into unicode in `partial`, sending to the llp as each newline is decoded.
-func decodeAndSend(ctx context.Context, lines chan<- *logline.LogLine, pathname string, n int, b []byte, partial *bytes.Buffer) int {
+func (s *streamBase) decodeAndSend(ctx context.Context, n int, b []byte, partial *bytes.Buffer) int {
 	var (
 		r     rune
 		width int
@@ -50,7 +50,7 @@ func decodeAndSend(ctx context.Context, lines chan<- *logline.LogLine, pathname
 		case r == '\r':
 			// nom
 		case r == '\n':
-			sendLine(ctx, pathname, partial, lines)
+			s.sendLine(ctx, partial)
 		default:
 			partial.WriteRune(r)
 		}
@@ -60,9 +60,9 @@ func decodeAndSend(ctx context.Context, lines chan<- *logline.LogLine, pathname
 	return count
 }
 
-func sendLine(ctx context.Context, pathname string, partial *bytes.Buffer, lines chan<- *logline.LogLine) {
+func (s *streamBase) sendLine(ctx context.Context, partial *bytes.Buffer) {
 	glog.V(2).Infof("sendline")
-	logLines.Add(pathname, 1)
-	lines <- logline.New(ctx, pathname, partial.String())
+	logLines.Add(s.sourcename, 1)
+	s.lines <- logline.New(ctx, s.sourcename, partial.String())
 	partial.Reset()
 }

internal/tailer/logstream/dgramstream.go

@@ -6,6 +6,7 @@ package logstream
 import (
 	"bytes"
 	"context"
+	"fmt"
 	"net"
 	"sync"
 	"time"
@@ -16,25 +17,28 @@ import (
 )
 
 type dgramStream struct {
-	cancel context.CancelFunc
+	streamBase
 
-	lines chan *logline.LogLine
+	cancel context.CancelFunc
 
 	scheme  string // Datagram scheme, either "unixgram" or "udp".
 	address string // Given name for the underlying socket path on the filesystem or hostport.
-
-	mu           sync.RWMutex // protects following fields
-	lastReadTime time.Time    // Last time a log line was read from this named pipe
-
-	staleTimer *time.Timer // Expire the stream if no read in 24h
 }
 
 func newDgramStream(ctx context.Context, wg *sync.WaitGroup, waker waker.Waker, scheme, address string, oneShot OneShotMode) (LogStream, error) {
 	if address == "" {
 		return nil, ErrEmptySocketAddress
 	}
 	ctx, cancel := context.WithCancel(ctx)
-	ss := &dgramStream{cancel: cancel, scheme: scheme, address: address, lastReadTime: time.Now(), lines: make(chan *logline.LogLine)}
+	ss := &dgramStream{
+		cancel:  cancel,
+		scheme:  scheme,
+		address: address,
+		streamBase: streamBase{
+			sourcename: fmt.Sprintf("%s://%s", scheme, address),
+			lines:      make(chan *logline.LogLine),
+		},
+	}
 	if err := ss.stream(ctx, wg, waker, oneShot); err != nil {
 		return nil, err
 	}
@@ -50,16 +54,16 @@ func (ds *dgramStream) stream(ctx context.Context, wg *sync.WaitGroup, waker wak
 		logErrors.Add(ds.address, 1)
 		return err
 	}
-	glog.V(2).Infof("stream(%s:%s): opened new datagram socket %v", ds.scheme, ds.address, c)
+	glog.V(2).Infof("stream(%s): opened new datagram socket %v", ds.sourcename, c)
 	b := make([]byte, datagramReadBufferSize)
 	partial := bytes.NewBufferString("")
 	var total int
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
 		defer func() {
-			glog.V(2).Infof("stream(%s:%s): read total %d bytes", ds.scheme, ds.address, total)
-			glog.V(2).Infof("stream(%s:%s): closing connection", ds.scheme, ds.address)
+			glog.V(2).Infof("stream(%s): read total %d bytes", ds.sourcename, total)
+			glog.V(2).Infof("stream(%s): closing connection", ds.sourcename)
 			err := c.Close()
 			if err != nil {
 				logErrors.Add(ds.address, 1)
@@ -75,7 +79,7 @@ func (ds *dgramStream) stream(ctx context.Context, wg *sync.WaitGroup, waker wak
 
 		for {
 			n, _, err := c.ReadFrom(b)
-			glog.V(2).Infof("stream(%s:%s): read %d bytes, err is %v", ds.scheme, ds.address, n, err)
+			glog.V(2).Infof("stream(%s): read %d bytes, err is %v", ds.sourcename, n, err)
 
 			if ds.staleTimer != nil {
 				ds.staleTimer.Stop()
@@ -86,17 +90,17 @@ func (ds *dgramStream) stream(ctx context.Context, wg *sync.WaitGroup, waker wak
 			// equivalent to an "EOF" in connection and file oriented streams.
 			if n == 0 {
 				if oneShot {
-					glog.V(2).Infof("stream(%s:%s): exiting because zero byte read and one shot", ds.scheme, ds.address)
+					glog.V(2).Infof("stream(%s): exiting because zero byte read and one shot", ds.sourcename)
 					if partial.Len() > 0 {
-						sendLine(ctx, ds.address, partial, ds.lines)
+						ds.sendLine(ctx, partial)
 					}
 					return
 				}
 				select {
 				case <-ctx.Done():
-					glog.V(2).Infof("stream(%s:%s): exiting because zero byte read after cancellation", ds.scheme, ds.address)
+					glog.V(2).Infof("stream(%s): exiting because zero byte read after cancellation", ds.sourcename)
 					if partial.Len() > 0 {
-						sendLine(ctx, ds.address, partial, ds.lines)
+						ds.sendLine(ctx, partial)
 					}
 					return
 				default:
@@ -106,10 +110,7 @@ func (ds *dgramStream) stream(ctx context.Context, wg *sync.WaitGroup, waker wak
 			if n > 0 {
 				total += n
 				//nolint:contextcheck
-				decodeAndSend(ctx, ds.lines, ds.address, n, b[:n], partial)
-				ds.mu.Lock()
-				ds.lastReadTime = time.Now()
-				ds.mu.Unlock()
+				ds.decodeAndSend(ctx, n, b[:n], partial)
 				ds.staleTimer = time.AfterFunc(time.Hour*24, ds.cancel)
 
 				// No error implies more to read, so restart the loop.
@@ -118,16 +119,16 @@ func (ds *dgramStream) stream(ctx context.Context, wg *sync.WaitGroup, waker wak
 				}
 			}
 
-			if err != nil && IsEndOrCancel(err) {
+			if IsExitableError(err) {
 				if partial.Len() > 0 {
-					sendLine(ctx, ds.address, partial, ds.lines)
+					ds.sendLine(ctx, partial)
 				}
-				glog.V(2).Infof("stream(%s:%s): exiting, stream has error %s", ds.scheme, ds.address, err)
+				glog.V(2).Infof("stream(%s): exiting, stream has error %s", ds.sourcename, err)
 				return
 			}
 
 			// Yield and wait
-			glog.V(2).Infof("stream(%s:%s): waiting", ds.scheme, ds.address)
+			glog.V(2).Infof("stream(%s): waiting", ds.sourcename)
 			select {
 			case <-ctx.Done():
 				// Exit after next read attempt.
@@ -139,14 +140,9 @@ func (ds *dgramStream) stream(ctx context.Context, wg *sync.WaitGroup, waker wak
 				glog.V(2).Infof("stream(%s): context cancelled, exiting after next zero byte read", ds.scheme, ds.address)
 			case <-waker.Wake():
 				// sleep until next Wake()
-				glog.V(2).Infof("stream(%s:%s): Wake received", ds.scheme, ds.address)
+				glog.V(2).Infof("stream(%s): Wake received", ds.sourcename)
 			}
 		}
 	}()
 	return nil
 }
-
-// Lines implements the LogStream interface, returning the output lines channel.
-func (ds *dgramStream) Lines() <-chan *logline.LogLine {
-	return ds.lines
-}

internal/tailer/logstream/dgramstream_unix_test.go

@@ -49,7 +49,7 @@ func TestDgramStreamReadCompletedBecauseSocketClosed(t *testing.T) {
 			testutil.FatalIfErr(t, err)
 
 			expected := []*logline.LogLine{
-				{Context: context.TODO(), Filename: addr, Line: "1"},
+				{Context: context.TODO(), Filename: sockName, Line: "1"},
 			}
 			checkLineDiff := testutil.ExpectLinesReceivedNoDiff(t, expected, ds.Lines())
 
@@ -99,7 +99,7 @@ func TestDgramStreamReadCompletedBecauseCancel(t *testing.T) {
 			testutil.FatalIfErr(t, err)
 
 			expected := []*logline.LogLine{
-				{Context: context.TODO(), Filename: addr, Line: "1"},
+				{Context: context.TODO(), Filename: sockName, Line: "1"},
 			}
 			checkLineDiff := testutil.ExpectLinesReceivedNoDiff(t, expected, ds.Lines())