Do not share container log driver for exec

When the container uses journald logging, we don't want to
automatically use the same driver for its exec sessions. If we do
we will pollute the journal (particularly in the case of
healthchecks) with large amounts of undesired logs. Instead,
force exec sessions logs to file for now; we can add a log-driver
flag later (we'll probably want to add a `podman logs` command
that reads exec session logs at the same time).

As part of this, add support for the new 'none' logs driver in
Conmon. It will be the default log driver for exec sessions, and
can be optionally selected for containers.

Great thanks to Joe Gooch (mrwizard@dok.org) for adding support
to Conmon for a null log driver, and wiring it in here.

Fixes #6555

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 13 insertions, 4 deletions

diff --git a/libpod/container_log.go b/libpod/container_log.go
index 39c395fe6..ac4720cfb 100644
--- a/libpod/container_log.go
+++ b/libpod/container_log.go
@@ -22,12 +22,21 @@ func (r *Runtime) Log(containers []*Container, options *logs.LogOptions, logChan
 
 // ReadLog reads a containers log based on the input options and returns loglines over a channel.
 func (c *Container) ReadLog(options *logs.LogOptions, logChannel chan *logs.LogLine) error {
-	// TODO Skip sending logs until journald logs can be read
-	// TODO make this not a magic string
-	if c.LogDriver() == define.JournaldLogging {
+	switch c.LogDriver() {
+	case define.NoLogging:
+		return errors.Wrapf(define.ErrNoLogs, "this container is using the 'none' log driver, cannot read logs")
+	case define.JournaldLogging:
+		// TODO Skip sending logs until journald logs can be read
 		return c.readFromJournal(options, logChannel)
+	case define.JSONLogging:
+		// TODO provide a separate implementation of this when Conmon
+		// has support.
+		fallthrough
+	case define.KubernetesLogging, "":
+		return c.readFromLogFile(options, logChannel)
+	default:
+		return errors.Wrapf(define.ErrInternal, "unrecognized log driver %q, cannot read logs", c.LogDriver())
 	}
-	return c.readFromLogFile(options, logChannel)
 }
 
 func (c *Container) readFromLogFile(options *logs.LogOptions, logChannel chan *logs.LogLine) error {