update check active

agent/app/core/installer.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import time
-from pathlib import Path
+from pathlib import Path, PurePosixPath
 
 from app.core.command_runner import CommandError, CommandRunner
 
@@ -125,6 +125,38 @@ class AptInstaller(DebInstaller):
             env=APT_NONINTERACTIVE_ENV,
         )
 
+    def discover_service_units(self, package_name: str) -> list[str]:
+        """Return concrete systemd service units shipped by an installed package.
+
+        The package name is already constrained by the Agent APT allowlist.  It is
+        still passed as a single argv item and no shell expansion is performed.
+        Template units are omitted because they cannot be meaningfully checked
+        without an instance name.
+        """
+        try:
+            result = self.command_runner.run(
+                ["dpkg-query", "-L", package_name],
+                timeout=30,
+                log_output=False,
+            )
+        except CommandError:
+            return []
+
+        service_names: set[str] = set()
+        for raw_path in result.stdout.splitlines():
+            path = raw_path.strip()
+            if not path.endswith(".service"):
+                continue
+            if "/systemd/system/" not in path:
+                continue
+
+            service_name = PurePosixPath(path).name
+            if "@" in service_name:
+                continue
+            service_names.add(service_name)
+
+        return sorted(service_names)
+
     def wait_for_postgresql(
         self,
         attempts: int = 6,
@@ -141,3 +173,10 @@ class AptInstaller(DebInstaller):
                     time.sleep(delay_seconds)
 
         raise RuntimeError("PostgreSQL did not become ready after installation") from last_error
+
+    def is_postgresql_ready(self) -> bool:
+        try:
+            self.command_runner.run(["pg_isready", "--timeout=5"], timeout=10)
+            return True
+        except Exception:
+            return False