logs: stream corrosion logs with 'uc machine logs corrosion' from container instead of journal (fixes #392)

internal/cli/logs/formatter.go

@@ -129,7 +129,7 @@ func (f *Formatter) PrintEntry(entry api.ServiceLogEntry) {
 	output.WriteString(f.formatMachine(entry.Metadata.MachineName))
 	output.WriteString(" ")
 
-	// Service/container_id or service name for a systemd service.
+	// Service/container_id or service name for a system service.
 	output.WriteString(f.formatService(entry.Metadata.ServiceName, entry.Metadata.ContainerID, entry.Metadata.Hook))
 	output.WriteString(" ")
 
@@ -160,7 +160,7 @@ func (f *Formatter) printError(entry api.ServiceLogEntry) {
 			stringid.TruncateID(entry.Metadata.ContainerID),
 			entry.Metadata.MachineName)
 	} else {
-		msg = fmt.Sprintf("WARNING: log stream from systemd service '%s' on machine '%s'",
+		msg = fmt.Sprintf("WARNING: log stream from system service '%s' on machine '%s'",
 			entry.Metadata.ServiceName,
 			entry.Metadata.MachineName)
 	}

internal/journal/journal.go

@@ -10,31 +10,11 @@ import (
 	"github.com/psviderski/uncloud/pkg/api"
 )
 
-const (
-	UnitUncloud   = "uncloud"
-	UnitDocker    = "docker"
-	UnitCorrosion = "uncloud-corrosion"
-)
-
-func ValidUnit(unit string) bool {
-	switch unit {
-	case UnitUncloud:
-	case UnitDocker:
-	case UnitCorrosion:
-	default:
-		return false
-	}
-	return true
-}
-
 const journalctl = "journalctl"
 
 var commandContext = exec.CommandContext // allow override for test
 
 func logs(ctx context.Context, unit string, opts api.ServiceLogsOptions) (io.ReadCloser, func() error, error) {
-	if !ValidUnit(unit) {
-		return nil, nil, fmt.Errorf("journal logs: invalid unit: %s", unit)
-	}
 	args := []string{"-u", unit, "--no-hostname"}
 	args = append(args, "-n")
 	if opts.Tail > -1 {

internal/journal/logs.go

@@ -3,7 +3,6 @@ package journal
 import (
 	"bytes"
 	"context"
-	"fmt"
 	"slices"
 	"strconv"
 	"time"
@@ -13,10 +12,6 @@ import (
 
 // Logs streams logs from a service and returns entries via a channel.
 func Logs(ctx context.Context, unit string, opts api.ServiceLogsOptions) (<-chan api.LogEntry, error) {
-	if !ValidUnit(unit) {
-		return nil, fmt.Errorf("journal logs: invalid unit: %s", unit)
-	}
-
 	reader, wait, err := logs(ctx, unit, opts)
 	if err != nil {
 		return nil, err

internal/machine/corroservice/docker.go

@@ -17,8 +17,12 @@ import (
 	"github.com/psviderski/uncloud/pkg/api"
 )
 
-// Image is the Corrosion image pinned to the uncloudd version.
-const Image = "ghcr.io/unlabs-dev/corrosion:2026.6.15"
+const (
+	// Image is the Corrosion image pinned to the uncloudd version.
+	Image = "ghcr.io/unlabs-dev/corrosion:2026.6.15"
+	// ContainerName is the name of the managed Corrosion container.
+	ContainerName = "uncloud-corrosion"
+)
 
 type DockerService struct {
 	Client *client.Client

internal/machine/docker/service.go

@@ -170,7 +170,9 @@ func (s *Service) ListImages(ctx context.Context, opts image.ListOptions) (Image
 
 // ContainerLogs streams logs from a container and returns demultiplexed entries via a channel.
 // The channel is closed when streaming completes or context is cancelled.
-func (s *Service) ContainerLogs(ctx context.Context, containerID string, opts api.ServiceLogsOptions) (<-chan api.LogEntry, error) {
+func (s *Service) ContainerLogs(
+	ctx context.Context, containerID string, opts api.ServiceLogsOptions,
+) (<-chan api.LogEntry, error) {
 	dockerOpts := container.LogsOptions{
 		ShowStdout: true,
 		ShowStderr: true,

internal/machine/machine.go

@@ -13,6 +13,7 @@ import (
 	"path/filepath"
 	"slices"
 	"strconv"
+	"strings"
 	"sync"
 	"time"
 
@@ -139,7 +140,7 @@ func (c *Config) SetDefaults() (*Config, error) {
 		cfg.CorrosionService = &corroservice.DockerService{
 			Client:  cfg.DockerClient,
 			Image:   corroservice.Image,
-			Name:    "uncloud-corrosion",
+			Name:    corroservice.ContainerName,
 			DataDir: cfg.CorrosionDataDir,
 			RunDir:  cfg.CorrosionRunDir,
 			User:    fmt.Sprintf("%d:%d", uid, gid),
@@ -1217,7 +1218,7 @@ func (m *Machine) InspectService(
 // logsHeartbeatInterval is the interval at which heartbeat entries are sent when there are no logs to stream.
 const logsHeartbeatInterval = 200 * time.Millisecond
 
-// MachineLogs streams logs from a systemd service.
+// MachineLogs streams logs from a system service.
 func (m *Machine) MachineLogs(
 	req *pb.LogsRequest, stream grpc.ServerStreamingServer[pb.LogEntry],
 ) error {
@@ -1231,16 +1232,31 @@ func (m *Machine) MachineLogs(
 		Until:  req.Until,
 	}
 
-	logsCh, err := journal.Logs(ctx, req.Id, opts)
+	var logsCh <-chan api.LogEntry
+	var err error
+	log := slog.With("stream_id", fmt.Sprintf("%p", stream)[2:])
+	switch req.Id {
+	case api.SystemServiceUncloud, api.SystemServiceDocker:
+		// These run as systemd units whose names match the service name.
+		logsCh, err = journal.Logs(ctx, req.Id, opts)
+		log = log.With("unit", req.Id)
+	case api.SystemServiceCorrosion:
+		// Corrosion runs as a daemon-managed container, not a systemd unit, so read its logs
+		// from the container, the same way `uc logs` does for service containers.
+		logsCh, err = m.dockerService.ContainerLogs(ctx, corroservice.ContainerName, opts)
+		log = log.With("container", corroservice.ContainerName)
+	default:
+		return status.Errorf(codes.InvalidArgument, "unsupported system service %q; supported services: %s",
+			req.Id, strings.Join(api.SystemServices, ", "))
+	}
 	if err != nil {
 		if errdefs.IsNotFound(err) {
 			return status.Error(codes.NotFound, err.Error())
 		}
-		return status.Errorf(codes.Internal, "get journal logs: %v", err)
+		return status.Errorf(codes.Internal, "get logs: %v", err)
 	}
 
-	log := slog.With("unit", req.Id, "stream_id", fmt.Sprintf("%p", stream)[2:])
-	log.Debug("Starting systemd service logs streaming.",
+	log.Debug("Starting system service logs streaming.",
 		"follow", req.Follow, "tail", req.Tail, "since", req.Since, "until", req.Until)
 
 	// Heartbeats are needed only when following logs to let the client know when there are no new log entries