feat: skip scaled processes that are missing in the Procfile

This allows folks to deploy apps that don't have a web process without needing to scale that process down before/after the first deploy. Note that the formations key in the app.json or a manual scale of other processes will be necessary to start anything non-web.

Closes #5700

docs/development/plugin-triggers.md

@@ -1810,6 +1810,21 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 # TODO
 ```
 
+### `procfile-exists`
+
+- Description: Checks if a procfile exists for the specified app
+- Invoked by: `internally`
+- Arguments: `$APP`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+# TODO
+```
+
 ### `proxy-build-config`
 
 - Description: Builds the proxy implementation configuration for a given app

plugins/20_events/procfile-exists

@@ -0,0 +1 @@
+hook

plugins/ps/Makefile

@@ -1,5 +1,5 @@
 SUBCOMMANDS = subcommands/inspect subcommands/rebuild subcommands/report subcommands/restart subcommands/restore subcommands/retire subcommands/scale subcommands/set subcommands/start subcommands/stop
-TRIGGERS = triggers/app-restart triggers/core-post-deploy triggers/core-post-extract triggers/install triggers/post-app-clone triggers/post-app-clone-setup triggers/post-app-rename triggers/post-app-rename-setup triggers/post-create triggers/post-delete triggers/post-stop triggers/pre-deploy triggers/procfile-get-command triggers/ps-can-scale triggers/ps-current-scale triggers/ps-set-scale triggers/report
+TRIGGERS = triggers/app-restart triggers/core-post-deploy triggers/core-post-extract triggers/install triggers/post-app-clone triggers/post-app-clone-setup triggers/post-app-rename triggers/post-app-rename-setup triggers/post-create triggers/post-delete triggers/post-stop triggers/pre-deploy triggers/procfile-get-command triggers/procfile-exists triggers/ps-can-scale triggers/ps-current-scale triggers/ps-set-scale triggers/report
 BUILD = commands subcommands triggers
 PLUGIN_NAME = ps
 

plugins/ps/src/triggers/triggers.go

@@ -64,6 +64,9 @@ func main() {
 		processType := flag.Arg(1)
 		port := common.ToInt(flag.Arg(2), 5000)
 		err = ps.TriggerProcfileGetCommand(appName, processType, port)
+	case "procfile-exists":
+		appName := flag.Arg(0)
+		err = ps.TriggerProcfileExists(appName)
 	case "ps-can-scale":
 		appName := flag.Arg(0)
 		canScale := common.ToBool(flag.Arg(1))

plugins/ps/triggers.go

@@ -1,6 +1,7 @@
 package ps
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path"
@@ -259,6 +260,15 @@ func TriggerPreDeploy(appName string, imageTag string) error {
 	return nil
 }
 
+// TriggerProcfileExists checks if a procfile exists
+func TriggerProcfileExists(appName string) error {
+	if hasProcfile(appName) {
+		return nil
+	}
+
+	return errors.New("Procfile does not exist")
+}
+
 // TriggerProcfileGetCommand fetches a command from the procfile
 func TriggerProcfileGetCommand(appName string, processType string, port int) error {
 	if !hasProcfile(appName) {

plugins/scheduler-docker-local/scheduler-deploy

@@ -37,6 +37,11 @@ trigger-scheduler-docker-local-scheduler-deploy() {
 
   DOKKU_START_CMD="$(config_get "$APP" DOKKU_START_CMD || true)"
 
+  local PROCFILE_EXISTS=false
+  if plugn trigger procfile-exists "$APP" 2>/dev/null; then
+    PROCFILE_EXISTS=true
+  fi
+
   local DOKKU_WAIT_TO_RETIRE="$(plugn trigger checks-get-property "$APP" wait-to-retire)"
   export DOKKU_WAIT_TO_RETIRE
 
@@ -54,6 +59,12 @@ trigger-scheduler-docker-local-scheduler-deploy() {
       continue
     fi
 
+    local PROC_CMD=$(plugn trigger procfile-get-command "$APP" "$PROC_TYPE" "5000" 2>/dev/null || echo '')
+    if [[ "$PROCFILE_EXISTS" == true ]] && [[ "$PROC_CMD" == "" ]]; then
+      dokku_log_warn "Skipping $PROC_TYPE as it is missing from the current Procfile"
+      continue
+    fi
+
     if [[ "$PROC_TYPE" != "web" ]]; then
       echo "$PLUGIN_AVAILABLE_PATH/scheduler-docker-local/bin/scheduler-deploy-process $APP $IMAGE_SOURCE_TYPE $IMAGE $IMAGE_TAG $PROC_TYPE $PROC_COUNT" >>"$TMP_FILE"
       continue

tests/apps/python/worker.Procfile

@@ -0,0 +1 @@
+worker: python3 -u worker.py

tests/unit/scheduler-docker-local.bats

@@ -56,6 +56,24 @@ teardown() {
   assert_success
 }
 
+@test "(scheduler-docker-local) no-web" {
+  run create_app
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku ps:set $TEST_APP procfile-path worker.Procfile"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run deploy_app
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output_contains "Skipping web as it is missing from the current Procfile"
+}
+
 @test "(scheduler-docker-local) init-process" {
   run create_app
   echo "output: $output"