Add new org.osbuild.tuned stage for setting active TuneD profile

Add a new stage for setting active TuneD profile. The stage checks the
value of chosen TuneD profile(s) with the list of available TuneD
profiles installed in the filesystem root. If any of the chosen profiles
does not exist, the stage raises an exception.

Add unit tests for the new stage.

Fix #792

Signed-off-by: Tomas Hozza <thozza@redhat.com>

stages/org.osbuild.tuned

@@ -0,0 +1,105 @@
+#!/usr/bin/python3
+"""
+Sets active TuneD profile.
+
+The stage calls sets active TuneD profile to 'profiles' as if one called
+'tuned-adm profile <profile>'. In the most usual case, only one active profile
+is set. However in case multiple profiles are provided, then TuneD tries to
+merge all profiles into active configuration. In case of conflicting values,
+the value from the latest profile is used.
+"""
+
+
+import os
+import sys
+
+import osbuild.api
+
+
+SCHEMA = """
+"additionalProperties": false,
+"required": ["profiles"],
+"description": "Manually set TuneD profile.",
+"properties": {
+  "profiles": {
+    "type": "array",
+    "description": "TuneD profile to activate. If multiple profiles are provided, TuneD will try to merge them.",
+    "minItems": 1,
+    "items": {
+      "type": "string"
+    }
+  }
+}
+"""
+
+
+class TunedProfilesDB:
+    """
+    Class for loading available TuneD profiles from the given filesystem tree
+    and checking if a profile with particular name exists.
+    """
+    def __init__(self, tree):
+        self._available_profiles = self._load_available_profiles(tree)
+
+    @staticmethod
+    def _load_available_profiles(tree):
+        """
+        Loads available TuneD profiles.
+
+        TuneD determines available profile names by listing all directories
+        in 'profile_directories' with "tuned.conf" file inside them. Profile names
+        are names of the directories.
+        """
+        available_profiles = set()
+
+        # Directories, from which TuneD loads profile definitions
+        profile_directories = [
+            "/usr/lib/tuned",
+            "/etc/tuned"
+        ]
+        profile_config_file = "tuned.conf"
+
+        for path in profile_directories:
+            for dir_entry in os.scandir(f"{tree}{path}"):
+                if dir_entry.is_dir() and os.path.isfile(f"{tree}{path}/{dir_entry.name}/{profile_config_file}"):
+                    available_profiles.add(dir_entry.name)
+
+        return available_profiles
+
+    def check_profile_exists(self, profile):
+        """
+        Checks whether a profile with the given name exists.
+        """
+        if profile in self._available_profiles:
+            return True
+        return False
+
+
+def main(tree, options):
+    # File which holds the name of the active profile
+    active_profile_file = "/etc/tuned/active_profile"
+    # File which tells TuneD whether the active profile was set manually or automatically
+    profile_mode_file = "/etc/tuned/profile_mode"
+
+    profiles = options["profiles"]
+    profiles_db = TunedProfilesDB(tree)
+
+    for profile in profiles:
+        if not profiles_db.check_profile_exists(profile):
+            raise ValueError(f"TuneD profile '{profile}' does not exist")
+
+    # Set the active profile
+    with open(f"{tree}{active_profile_file}", "w") as f:
+        f.write(" ".join(profiles) + "\n")
+
+    # Mode needs to be set to "manual" if set explicitly
+    with open(f"{tree}{profile_mode_file}", "w") as f:
+        f.write("manual\n")
+
+    return 0
+
+
+if __name__ == '__main__':
+    args = osbuild.api.arguments()
+    r = main(args["tree"], args["options"])
+    sys.exit(r)