docker:send GPU instance config only when GPUs are present

Author: sharanyad

ecs-init/docker/docker.go

@@ -253,6 +253,11 @@ func (c *Client) LoadEnvVars() map[string]string {
 envVariables := make(map[string]string)
 // merge in instance-specific environment variables
 for envKey, envValue := range c.loadCustomInstanceEnvVars() {
+if envKey == config.GPUSupportEnvVar && envValue == "true" {
+if !nvidiaGPUDevicesPresent() {
+continue
+}
+}
 envVariables[envKey] = envValue
 }
 

ecs-init/docker/docker_test.go

@@ -482,6 +482,13 @@ func TestGetInstanceConfig(t *testing.T) {
 defer mockCtrl.Finish()
 
 envFile := "\nECS_ENABLE_GPU_SUPPORT=true\n"
+defer func() {
+MatchFilePatternForGPU = FilePatternMatchForGPU
+}()
+MatchFilePatternForGPU = func(pattern string) ([]string, error) {
+// GPU device present
+return []string{"/dev/nvidia0"}, nil
+}
 
 mockFS := NewMockfileSystem(mockCtrl)
 
@@ -500,6 +507,38 @@ func TestGetInstanceConfig(t *testing.T) {
 expectKey("ECS_ENABLE_GPU_SUPPORT=true", envVariables, t)
 }
 
+func TestGetNonGPUInstanceConfig(t *testing.T) {
+mockCtrl := gomock.NewController(t)
+defer mockCtrl.Finish()
+
+envFile := "\nECS_ENABLE_GPU_SUPPORT=true\n"
+defer func() {
+MatchFilePatternForGPU = FilePatternMatchForGPU
+}()
+MatchFilePatternForGPU = func(pattern string) ([]string, error) {
+// matches is nil
+return nil, nil
+}
+
+mockFS := NewMockfileSystem(mockCtrl)
+
+mockFS.EXPECT().ReadFile(config.InstanceConfigFile()).Return([]byte(envFile), nil)
+mockFS.EXPECT().ReadFile(config.AgentConfigFile()).Return(nil, errors.New("not found"))
+
+client := &Client{
+fs: mockFS,
+}
+cfg := client.getContainerConfig()
+
+envVariables := make(map[string]struct{})
+for _, envVar := range cfg.Env {
+envVariables[envVar] = struct{}{}
+}
+if _, ok := envVariables["ECS_ENABLE_GPU_SUPPORT=true"]; ok {
+t.Errorf("Expected ECS_ENABLE_GPU_SUPPORT=true to be not present")
+}
+}
+
 func TestGetConfigOverrides(t *testing.T) {
 mockCtrl := gomock.NewController(t)
 defer mockCtrl.Finish()