feat: add ability to increase the max parallelism when deploying a given process type

plugins/app-json/.gitignore

@@ -6,3 +6,4 @@
 /subcommands/*
 /triggers
 /triggers/*
+/app-json-process-deploy-parallelism

plugins/app-json/Makefile

@@ -1,5 +1,5 @@
 SUBCOMMANDS = subcommands/report subcommands/set
-TRIGGERS = triggers/install triggers/post-delete triggers/post-deploy triggers/pre-deploy triggers/report
+TRIGGERS = triggers/app-json-process-deploy-parallelism triggers/install triggers/post-delete triggers/post-deploy triggers/pre-deploy triggers/report
 BUILD = commands subcommands triggers
 PLUGIN_NAME = app-json
 

plugins/app-json/appjson.go

@@ -39,7 +39,8 @@ type CronCommand struct {
 
 // Formation is a struct that represents the scale for a process from an app.json file
 type Formation struct {
-	Quantity int `json:"quantity"`
+	Quantity    *int `json:"quantity"`
+	MaxParallel *int `json:"max_parallel"`
 }
 
 // GetAppjsonDirectory returns the directory containing a given app's extracted app.json file

plugins/app-json/functions.go

@@ -500,7 +500,9 @@ func setScale(appName string, image string) error {
 	clearExisting := false
 	args := []string{appName, strconv.FormatBool(skipDeploy), strconv.FormatBool(clearExisting)}
 	for processType, formation := range appJSON.Formation {
-		args = append(args, fmt.Sprintf("%s=%d", processType, formation.Quantity))
+		if formation.Quantity != nil {
+			args = append(args, fmt.Sprintf("%s=%d", processType, *formation.Quantity))
+		}
 	}
 
 	if len(args) == 3 {
@@ -567,7 +569,7 @@ func injectDokkuScale(appName string, image string) error {
 		}
 
 		appJSON.Formation[processType] = Formation{
-			Quantity: quantity,
+			Quantity: &quantity,
 		}
 	}
 

plugins/app-json/src/triggers/triggers.go

@@ -18,6 +18,10 @@ func main() {
 
 	var err error
 	switch trigger {
+	case "app-json-process-deploy-parallelism":
+		appName := flag.Arg(0)
+		processType := flag.Arg(1)
+		err = appjson.TriggerAppJSONProcessDeployParallelism(appName, processType)
 	case "install":
 		err = appjson.TriggerInstall()
 	case "post-delete":

plugins/app-json/triggers.go

@@ -8,6 +8,32 @@ import (
 	"github.com/dokku/dokku/plugins/common"
 )
 
+// TriggerAppJSONProcessDeployParallelism returns the max number of processes to deploy in parallel
+func TriggerAppJSONProcessDeployParallelism(appName string, processType string) error {
+	appJSON, err := getAppJSON(appName)
+	if err != nil {
+		return err
+	}
+
+	parallelism := 1
+	for procType, formation := range appJSON.Formation {
+		if procType != processType {
+			continue
+		}
+
+		if formation.MaxParallel == nil {
+			continue
+		}
+
+		if *formation.MaxParallel > 0 {
+			parallelism = *formation.MaxParallel
+		}
+	}
+
+	fmt.Println(parallelism)
+	return nil
+}
+
 // TriggerInstall initializes app restart policies
 func TriggerInstall() error {
 	if err := common.PropertySetup("app-json"); err != nil {