Set Load Balancer internal/external per process instead of per applic…

…ation

Introduces EMPIRE_X_EXPOSURE which needs to be either `internal` or `internet-facing` (kept AWS terminology here).

If that environment variable is not set, we fallback to the default selection via application (where you use `domain-add`).

Fixes remind101#1076

.gitignore

@@ -4,3 +4,5 @@ build
 *.dump
 *.key
 *.cert
+\#*\#
+.\#*

scheduler/cloudformation/template.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"reflect"
 	"regexp"
 	"sort"
@@ -36,6 +37,20 @@ const (
 	applicationLoadBalancer = "alb"
 )
 
+const (
+	schemeInternal = "internal"
+	schemeExternal = "internet-facing"
+
+	defaultConnectionDrainingTimeout int64 = 30
+	defaultCNAMETTL                        = 60
+
+	runTaskFunction = "RunTaskFunction"
+
+	appEnvironment = "AppEnvironment"
+
+	restartLabel = "cloudformation.restart-key"
+)
+
 // Returns the type of load balancer that should be used (ELB/ALB).
 func loadBalancerType(app *twelvefactor.Manifest, process *twelvefactor.Process) string {
 	check := []string{
@@ -54,6 +69,20 @@ func loadBalancerType(app *twelvefactor.Manifest, process *twelvefactor.Process)
 	return classicLoadBalancer
 }
 
+func schemeExposure(app *twelvefactor.Manifest, process *twelvefactor.Process) string {
+	env := twelvefactor.Env(app, process)
+	if v, ok := env["EMPIRE_X_EXPOSURE"]; ok {
+		if v == schemeExternal {
+			return v
+		}
+	}
+	// For backwards compatibility we check the application setting via process
+	if process.Exposure.External {
+		return schemeExternal
+	}
+	return schemeInternal
+}
+
 // Returns the name of the CloudFormation resource that should be used to create
 // custom task definitions.
 func taskDefinitionResourceType(app *twelvefactor.Manifest) string {
@@ -89,20 +118,6 @@ func taskRoleArn(app *twelvefactor.Manifest) *string {
 	return nil
 }
 
-const (
-	schemeInternal = "internal"
-	schemeExternal = "internet-facing"
-
-	defaultConnectionDrainingTimeout int64 = 30
-	defaultCNAMETTL                        = 60
-
-	runTaskFunction = "RunTaskFunction"
-
-	appEnvironment = "AppEnvironment"
-
-	restartLabel = "cloudformation.restart-key"
-)
-
 // This implements the Template interface to create a suitable CloudFormation
 // template for an Empire app.
 type EmpireTemplate struct {
@@ -400,12 +415,12 @@ func (t *EmpireTemplate) addService(tmpl *troposphere.Template, app *twelvefacto
 	var serviceDependencies []string
 	loadBalancers := []map[string]interface{}{}
 	if p.Exposure != nil {
-		scheme := schemeInternal
 		sg := t.InternalSecurityGroupID
 		subnets := t.InternalSubnetIDs
 
-		if p.Exposure.External {
-			scheme = schemeExternal
+		scheme := schemeExposure(app, p)
+
+		if scheme == schemeExternal {
 			sg = t.ExternalSecurityGroupID
 			subnets = t.ExternalSubnetIDs
 		}