podman logs k8s-file: do not reassemble partial log lines

The backend should not convert partial lines to full log lines. While
this works for most cases it cannot work when the last line is partial
since it will just be lost. The frontend logic can already display
partial lines correctly. The journald driver also works correctly since
it does not such conversion.

Fixes #14458

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

libpod/container_log.go

@@ -75,7 +75,6 @@ func (c *Container) readFromLogFile(ctx context.Context, options *logs.LogOption
 	go func() {
 		defer options.WaitGroup.Done()
 
-		var partial string
 		for line := range t.Lines {
 			select {
 			case <-ctx.Done():
@@ -89,13 +88,6 @@ func (c *Container) readFromLogFile(ctx context.Context, options *logs.LogOption
 				logrus.Errorf("Getting new log line: %v", err)
 				continue
 			}
-			if nll.Partial() {
-				partial += nll.Msg
-				continue
-			} else if !nll.Partial() && len(partial) > 0 {
-				nll.Msg = partial + nll.Msg
-				partial = ""
-			}
 			nll.CID = c.ID()
 			nll.CName = c.Name()
 			nll.ColorID = colorID

test/e2e/logs_test.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	. "github.com/containers/podman/v4/test/utils"
+	"github.com/containers/storage/pkg/stringid"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	. "github.com/onsi/gomega/gexec"
@@ -370,6 +371,26 @@ var _ = Describe("Podman logs", func() {
 			Expect(results.OutputToString()).To(Equal("stdout"))
 			Expect(results.ErrorToString()).To(Equal("stderr"))
 		})
+
+		It("podman logs partial log lines: "+log, func() {
+			skipIfJournaldInContainer()
+
+			cname := "log-test"
+			content := stringid.GenerateNonCryptoID()
+			// use printf to print no extra newline
+			logc := podmanTest.Podman([]string{"run", "--log-driver", log, "--name", cname, ALPINE, "printf", content})
+			logc.WaitWithDefaultTimeout()
+			Expect(logc).To(Exit(0))
+			// Important: do not use OutputToString(), this will remove the trailing newline from the output.
+			// However this test must make sure that there is no such extra newline.
+			Expect(string(logc.Out.Contents())).To(Equal(content))
+
+			logs := podmanTest.Podman([]string{"logs", cname})
+			logs.WaitWithDefaultTimeout()
+			Expect(logs).To(Exit(0))
+			// see comment above
+			Expect(string(logs.Out.Contents())).To(Equal(content))
+		})
 	}
 
 	It("using journald for container with container tag", func() {