rearrange some code

agent/app/agent.go

@@ -1101,7 +1101,7 @@ func (agent *ecsAgent) startACSSession(
 // Minimum docker version supported is 1.9.0, maps to api version 1.21
 // see https://docs.docker.com/develop/sdk/#api-version-matrix
 func (agent *ecsAgent) verifyRequiredDockerVersion() (int, bool) {
-	supportedVersions := dockerapi.SupportedVersionsExtended(agent.dockerClient)
+	supportedVersions := dockerclient.SupportedVersionsExtended(agent.dockerClient.SupportedVersions)
 	if len(supportedVersions) == 0 {
 		seelog.Critical("Could not get supported docker versions.")
 		return exitcodes.ExitError, false

agent/app/agent_capability.go

@@ -22,7 +22,6 @@ import (
 
 	"github.com/aws/amazon-ecs-agent/agent/config"
 	"github.com/aws/amazon-ecs-agent/agent/dockerclient"
-	"github.com/aws/amazon-ecs-agent/agent/dockerclient/dockerapi"
 	dm "github.com/aws/amazon-ecs-agent/agent/engine/daemonmanager"
 	"github.com/aws/amazon-ecs-agent/ecs-agent/api/ecs/model/ecs"
 	"github.com/aws/amazon-ecs-agent/ecs-agent/logger"
@@ -208,13 +207,8 @@ func (agent *ecsAgent) capabilities() ([]*ecs.Attribute, error) {
 
 	supportedVersions := make(map[dockerclient.DockerVersion]bool)
 	// Determine API versions to report as supported via com.amazonaws.ecs.capability.docker-remote-api.X.XX capabilities
-	// We advertise all known versions here rather than "supported" versions. The reason for this is that ECS backend
-	// adds required capabilities to some features at the minimum supported version. If this is less than our Minimum
-	// supported version (currently 1.24), then the capability will not match.
-	// In other words, here we advertise supporting docker api versions that this agent may not actually support, for the
-	// sake of task definition required attributes.
-	// TODO edit this comment ^
-	for _, version := range dockerapi.SupportedVersionsExtended(agent.dockerClient) {
+	// and for determining which features we support that depend on specific docker API versions
+	for _, version := range dockerclient.SupportedVersionsExtended(agent.dockerClient.SupportedVersions) {
 		capabilities = appendNameOnlyAttribute(capabilities, capabilityPrefix+"docker-remote-api."+string(version))
 		supportedVersions[version] = true
 	}

agent/dockerclient/versions.go

@@ -81,6 +81,29 @@ func (d DockerVersion) Compare(rhs DockerVersion) int {
 	return 1
 }
 
+// SupportedVersionsExtended
+func SupportedVersionsExtended(supportedVersionsFn func() []DockerVersion) []DockerVersion {
+	supportedAPIVersions := supportedVersionsFn()
+	cmp := MinDockerAPIVersion.Compare(Version_1_24)
+
+	if cmp == 1 || cmp == 0 {
+		extendedAPIVersions := []DockerVersion{}
+		knownAPIVersions := GetKnownAPIVersions()
+		for _, knownAPIVersion := range knownAPIVersions {
+			if knownAPIVersion.Compare(MinDockerAPIVersion) < 0 {
+				extendedAPIVersions = append(extendedAPIVersions, knownAPIVersion)
+			}
+		}
+		supportedAPIVersions = append(extendedAPIVersions, supportedAPIVersions...)
+	}
+
+	logger.Debug("Extended supported versions", logger.Fields{
+		"supportedVersions": supportedAPIVersions,
+	})
+	return supportedAPIVersions
+}
+
+// SetMinDockerAPIVersion
 func SetMinDockerAPIVersion(v DockerVersion) {
 	MinDockerAPIVersionMu.Lock()
 	defer MinDockerAPIVersionMu.Unlock()