Log aws.firecracker's version since supporting -version is hard

Because the shim's flag parsing is owned by containerd's shim package,
supporting -version/-v is not straightforward. Instead the binary logs
the version.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

runtime/Makefile

@@ -22,6 +22,8 @@ DOCKER_IMAGE_TAG?=latest
 GO_CACHE_VOLUME_NAME?=gocache
 FIRECRACKER_CONTAINERD_TEST_IMAGE?=localhost/firecracker-containerd-test
 
+REVISION=$(shell git rev-parse HEAD)
+
 INTEG_TEST_SUFFIX := _Isolated
 INTEG_TESTNAMES=$(shell docker run --rm \
 	--network=none \
@@ -37,7 +39,7 @@ all: runtime
 runtime: containerd-shim-aws-firecracker
 
 containerd-shim-aws-firecracker: $(SOURCES) $(GOMOD) $(GOSUM)
-	go build -o containerd-shim-aws-firecracker $(EXTRAGOARGS)
+	go build -o containerd-shim-aws-firecracker $(EXTRAGOARGS) -ldflags "-X main.revision=$(REVISION)"
 
 install: containerd-shim-aws-firecracker
 	install -D -o root -g root -m755 -t $(INSTALLROOT)/bin containerd-shim-aws-firecracker

runtime/main.go

@@ -23,6 +23,8 @@ import (
 
 const shimID = "aws.firecracker"
 
+var revision string
+
 func init() {
 	logrus.SetFormatter(&logrus.TextFormatter{
 		TimestampFormat: log.RFC3339NanoFixed,

runtime/service.go

@@ -332,10 +332,6 @@ func (s *service) StartShim(shimCtx context.Context, containerID, containerdBina
 		// task is deleted
 		containerCount = 1
 		exitAfterAllTasksDeleted = true
-
-		log.Info("will start a single-task VM since no VMID has been provided")
-	} else {
-		log.WithField("vmID", s.vmID).Info("will start a persistent VM")
 	}
 
 	client, err := ttrpcutil.NewClient(containerdTTRPCAddress)
@@ -358,6 +354,16 @@ func (s *service) StartShim(shimCtx context.Context, containerID, containerdBina
 		}
 	}
 
+	// The shim cannot support traditional -version/-v flag because
+	// - shim.Run() will call flag.Parse(). So our main cannot call flag.Parse() before that.
+	// - -address is required and NewService() won't be called if the flag is missing.
+	// So we log the version informaion here instead
+	str := ""
+	if exitAfterAllTasksDeleted {
+		str = " The VM will be torn down after serving a single task."
+	}
+	log.WithField("vmID", s.vmID).Infof("successfully started shim (%s).%s", revision, str)
+
 	return fcShim.SocketAddress(shimCtx, s.vmID)
 }