Merge pull request 'Add ability to use pre-existing systemd units and stop them too' (#6) from rei/systemd_default into develop

Reviewed-on: https://bics.ga/reivilibre/scone/pulls/6

scone/default/recipes/systemd.py

@@ -18,7 +18,7 @@
 from scone.default.steps.systemd_steps import (
     cook_systemd_daemon_reload,
     cook_systemd_enable,
-    cook_systemd_start,
+    cook_systemd_start, cook_systemd_stop,
 )
 from scone.head.head import Head
 from scone.head.kitchen import Kitchen, Preparation
@@ -42,15 +42,27 @@ class SystemdUnit(Recipe):
 
         unit = check_type(args.get("unit"), str)
         self.unit_name = unit if "." in unit else unit + ".service"
-        self.at = check_type(args.get("at"), str)
+        already_installed = check_type(args.get("already_installed", False), bool)
+        self.at = check_type_opt(args.get("at", None), str)
+
+        if not (already_installed or self.at):
+            # already_installed is for when the unit already exists on the system
+            # and is not created by scone.
+            raise ValueError(
+                "Must supply either already_installed = true or "
+                f"at = /path/to/{self.unit_name}"
+            )
+
         self.enabled = check_type_opt(args.get("enabled"), bool)
         self.restart_on = check_type_opt(args.get("restart_on"), list)
         self.started = check_type_opt(args.get("started"), bool)
 
     def prepare(self, preparation: Preparation, head: Head) -> None:
         super().prepare(preparation, head)
-        # TODO(potential future): preparation.provides("systemd-unit", self.unit_name)
-        preparation.needs("file", self.at)
+        if self.at:
+            # TODO(potential future): preparation.provides("systemd-unit",
+            #  self.unit_name)
+            preparation.needs("file", self.at)
 
     async def cook(self, kitchen: Kitchen) -> None:
         if self.enabled is not None or self.started is not None:
@@ -62,3 +74,5 @@ class SystemdUnit(Recipe):
         if self.started is not None:
             if self.started:
                 await cook_systemd_start(kitchen, self.unit_name)
+            else:
+                await cook_systemd_stop(kitchen, self.unit_name)

scone/default/steps/systemd_steps.py

@@ -50,3 +50,12 @@ async def cook_systemd_start(kitchen: Kitchen, unit_name: str):
 
     if result.exit_code != 0:
         raise RuntimeError(f"Failed to start {unit_name}: {result.stderr.decode()}")
+
+
+async def cook_systemd_stop(kitchen: Kitchen, unit_name: str):
+    result = await kitchen.ut1areq(
+        SimpleExec(["systemctl", "stop", unit_name], "/",), SimpleExec.Result,
+    )
+
+    if result.exit_code != 0:
+        raise RuntimeError(f"Failed to stop {unit_name}: {result.stderr.decode()}")