logging: new mode -l passthrough

it allows to pass the current std streams down to the container.

conmon support: https://github.com/containers/conmon/pull/289

[NO TESTS NEEDED] it needs a new conmon.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

libpod/container_api.go

@@ -229,6 +229,10 @@ func (c *Container) Kill(signal uint) error {
 // This function returns when the attach finishes. It does not hold the lock for
 // the duration of its runtime, only using it at the beginning to verify state.
 func (c *Container) Attach(streams *define.AttachStreams, keys string, resize <-chan define.TerminalSize) error {
+	switch c.LogDriver() {
+	case define.PassthroughLogging:
+		return errors.Wrapf(define.ErrNoLogs, "this container is using the 'passthrough' log driver, cannot attach")
+	}
 	if !c.batched {
 		c.lock.Lock()
 		if err := c.syncContainer(); err != nil {

libpod/container_log.go

@@ -18,7 +18,7 @@ import (
 var logDrivers []string
 
 func init() {
-	logDrivers = append(logDrivers, define.KubernetesLogging, define.NoLogging)
+	logDrivers = append(logDrivers, define.KubernetesLogging, define.NoLogging, define.PassthroughLogging)
 }
 
 // Log is a runtime function that can read one or more container logs.
@@ -34,6 +34,8 @@ func (r *Runtime) Log(ctx context.Context, containers []*Container, options *log
 // ReadLog reads a containers log based on the input options and returns log lines over a channel.
 func (c *Container) ReadLog(ctx context.Context, options *logs.LogOptions, logChannel chan *logs.LogLine) error {
 	switch c.LogDriver() {
+	case define.PassthroughLogging:
+		return errors.Wrapf(define.ErrNoLogs, "this container is using the 'passthrough' log driver, cannot read logs")
 	case define.NoLogging:
 		return errors.Wrapf(define.ErrNoLogs, "this container is using the 'none' log driver, cannot read logs")
 	case define.JournaldLogging:

libpod/define/config.go

@@ -78,6 +78,9 @@ const JSONLogging = "json-file"
 // NoLogging is the string conmon expects when specifying to use no log driver whatsoever
 const NoLogging = "none"
 
+// PassthroughLogging is the string conmon expects when specifying to use the passthrough driver
+const PassthroughLogging = "passthrough"
+
 // Strings used for --sdnotify option to podman
 const (
 	SdNotifyModeContainer = "container"

libpod/oci_attach_linux.go

@@ -40,7 +40,9 @@ func openUnixSocket(path string) (*net.UnixConn, error) {
 // Does not check if state is appropriate
 // started is only required if startContainer is true
 func (c *Container) attach(streams *define.AttachStreams, keys string, resize <-chan define.TerminalSize, startContainer bool, started chan bool, attachRdy chan<- bool) error {
-	if !streams.AttachOutput && !streams.AttachError && !streams.AttachInput {
+	passthrough := c.LogDriver() == define.PassthroughLogging
+
+	if !streams.AttachOutput && !streams.AttachError && !streams.AttachInput && !passthrough {
 		return errors.Wrapf(define.ErrInvalidArg, "must provide at least one stream to attach to")
 	}
 	if startContainer && started == nil {
@@ -52,24 +54,27 @@ func (c *Container) attach(streams *define.AttachStreams, keys string, resize <-
 		return err
 	}
 
-	logrus.Debugf("Attaching to container %s", c.ID())
+	var conn *net.UnixConn
+	if !passthrough {
+		logrus.Debugf("Attaching to container %s", c.ID())
 
-	registerResizeFunc(resize, c.bundlePath())
+		registerResizeFunc(resize, c.bundlePath())
 
-	attachSock, err := c.AttachSocketPath()
-	if err != nil {
-		return err
-	}
-
-	conn, err := openUnixSocket(attachSock)
-	if err != nil {
-		return errors.Wrapf(err, "failed to connect to container's attach socket: %v", attachSock)
-	}
-	defer func() {
-		if err := conn.Close(); err != nil {
-			logrus.Errorf("Unable to close socket: %q", err)
+		attachSock, err := c.AttachSocketPath()
+		if err != nil {
+			return err
 		}
-	}()
+
+		conn, err = openUnixSocket(attachSock)
+		if err != nil {
+			return errors.Wrapf(err, "failed to connect to container's attach socket: %v", attachSock)
+		}
+		defer func() {
+			if err := conn.Close(); err != nil {
+				logrus.Errorf("unable to close socket: %q", err)
+			}
+		}()
+	}
 
 	// If starting was requested, start the container and notify when that's
 	// done.
@@ -80,6 +85,10 @@ func (c *Container) attach(streams *define.AttachStreams, keys string, resize <-
 		started <- true
 	}
 
+	if passthrough {
+		return nil
+	}
+
 	receiveStdoutError, stdinDone := setupStdioChannels(streams, conn, detachKeys)
 	if attachRdy != nil {
 		attachRdy <- true

libpod/oci_conmon_linux.go

@@ -1288,6 +1288,8 @@ func (r *ConmonOCIRuntime) sharedConmonArgs(ctr *Container, cuuid, bundlePath, p
 		logDriverArg = define.JournaldLogging
 	case define.NoLogging:
 		logDriverArg = define.NoLogging
+	case define.PassthroughLogging:
+		logDriverArg = define.PassthroughLogging
 	case define.JSONLogging:
 		fallthrough
 	//lint:ignore ST1015 the default case has to be here

libpod/options.go

@@ -1114,7 +1114,7 @@ func WithLogDriver(driver string) CtrCreateOption {
 		switch driver {
 		case "":
 			return errors.Wrapf(define.ErrInvalidArg, "log driver must be set")
-		case define.JournaldLogging, define.KubernetesLogging, define.JSONLogging, define.NoLogging:
+		case define.JournaldLogging, define.KubernetesLogging, define.JSONLogging, define.NoLogging, define.PassthroughLogging:
 			break
 		default:
 			return errors.Wrapf(define.ErrInvalidArg, "invalid log driver")

libpod/runtime_ctr.go

@@ -473,7 +473,7 @@ func (r *Runtime) setupContainer(ctx context.Context, ctr *Container) (_ *Contai
 	}
 
 	switch ctr.config.LogDriver {
-	case define.NoLogging:
+	case define.NoLogging, define.PassthroughLogging:
 		break
 	case define.JournaldLogging:
 		ctr.initializeJournal(ctx)