feat(pressure reconciler): Support no planner integration

docs/changelog.md

@@ -4,6 +4,8 @@ This changelog documents user-relevant changes to the GitHub runner charm.
 
 ## 2026-03-20
 
+- The pressure reconciler is now always used, replacing the legacy reconcile mode. When no planner relation is configured, it uses `base-virtual-machines` as static pressure to maintain the configured minimum runner count.
+- HTTP server endpoints (`/runner/check`, `/runner/flush`) now use `RunnerManager` directly instead of the legacy `RunnerScaler`.
 - Set GitHub API pagination page size to 100 (up from PyGithub default of 30), reducing API calls when listing runners.
 
 ## 2026-03-18

github-runner-manager/pyproject.toml

@@ -3,7 +3,7 @@
 
 [project]
 name = "github-runner-manager"
-version = "0.15.2"
+version = "0.16.0"
 authors = [
     { name = "Canonical IS DevOps", email = "is-devops-team@canonical.com" },
 ]

github-runner-manager/src/github_runner_manager/cli.py

@@ -20,8 +20,8 @@
 from github_runner_manager.manager.pressure_reconciler import (
     PressureReconciler,
     build_pressure_reconciler,
+    build_runner_manager,
 )
-from github_runner_manager.reconcile_service import start_reconcile_service
 from github_runner_manager.thread_manager import ThreadManager
 
 version = importlib.metadata.version("github-runner-manager")
@@ -94,19 +94,12 @@ def handle_shutdown(
     default="INFO",
     help="The log level for the application.",
 )
-@click.option(
-    "--python-path",
-    type=str,
-    required=False,
-    help="The PYTHONPATH to access the github-runner-manager library.",
-)
 # The entry point for the CLI will be tested with integration test.
-def main(  # pylint: disable=too-many-arguments, too-many-positional-arguments
+def main(
     config_file: TextIO,
     host: str,
     port: int,
     debug: bool,
-    python_path: str | None,
     log_level: str,
 ) -> None:  # pragma: no cover
     """Start the reconcile service.
@@ -116,8 +109,10 @@ def main(  # pylint: disable=too-many-arguments, too-many-positional-arguments
         host: The hostname to listen on for the HTTP server
         port: The port to listen on the HTTP server.
         debug: Whether to start the application in debug mode.
-        python_path: PYTHONPATH to access the github-runner-manager library.
         log_level: The log level.
+
+    Raises:
+        ClickException: If no non-reactive combinations are configured.
     """
     logging.basicConfig(
         level=log_level,
@@ -128,30 +123,28 @@ def main(  # pylint: disable=too-many-arguments, too-many-positional-arguments
     config = ApplicationConfiguration.from_yaml_file(StringIO(config_file.read()))
     lock = Lock()
 
+    combinations = config.non_reactive_configuration.combinations
+    if not combinations:
+        raise click.ClickException("No non-reactive combinations configured.")
+    runner_manager = build_runner_manager(config, combinations[0])
+    pressure_reconciler = build_pressure_reconciler(config, runner_manager, lock)
+
     thread_manager = ThreadManager()
     http_server_args = FlaskArgs(host=host, port=port, debug=debug)
     thread_manager.add_thread(
-        target=partial(start_http_server, config, lock, http_server_args),
+        target=partial(start_http_server, runner_manager, lock, http_server_args),
         daemon=True,
     )
 
-    if config.planner_url and config.planner_token:
-        pressure_reconciler = build_pressure_reconciler(config, lock)
-        shutdown = partial(
-            handle_shutdown,
-            pressure_reconciler=pressure_reconciler,
-            thread_manager=thread_manager,
-        )
-        signal.signal(signal.SIGTERM, shutdown)
-        signal.signal(signal.SIGINT, shutdown)
-        thread_manager.add_thread(target=pressure_reconciler.start_create_loop, daemon=True)
-        thread_manager.add_thread(target=pressure_reconciler.start_reconcile_loop, daemon=True)
-    # Legacy mode is still supported for deployments without planner config.
-    else:
-        thread_manager.add_thread(
-            target=partial(start_reconcile_service, config, python_path, lock),
-            daemon=True,
-        )
+    shutdown = partial(
+        handle_shutdown,
+        pressure_reconciler=pressure_reconciler,
+        thread_manager=thread_manager,
+    )
+    signal.signal(signal.SIGTERM, shutdown)
+    signal.signal(signal.SIGINT, shutdown)
+    thread_manager.add_thread(target=pressure_reconciler.start_create_loop, daemon=True)
+    thread_manager.add_thread(target=pressure_reconciler.start_reconcile_loop, daemon=True)
 
     thread_manager.start()
     thread_manager.raise_on_error()

github-runner-manager/src/github_runner_manager/http_server.py

@@ -1,26 +1,19 @@
 #  Copyright 2026 Canonical Ltd.
 #  See LICENSE file for licensing details.
 
-"""The HTTP server for github-runner-manager.
+"""The HTTP server for github-runner-manager."""
 
-The HTTP server for request to the github-runner-manager.
-"""
-
-import dataclasses
 import json
 from dataclasses import dataclass
 from threading import Lock
 
 from flask import Flask, request
 from prometheus_client import generate_latest
 
-from github_runner_manager.configuration import ApplicationConfiguration
 from github_runner_manager.errors import CloudError, LockError
-from github_runner_manager.manager.runner_manager import FlushMode
-from github_runner_manager.reconcile_service import get_runner_scaler
+from github_runner_manager.manager.runner_manager import FlushMode, RunnerManager
 
-APP_CONFIG_NAME = "app_config"
-OPENSTACK_CONFIG_NAME = "openstack_config"
+RUNNER_MANAGER_CONFIG_NAME = "runner_manager"
 
 app = Flask(__name__)
 
@@ -45,15 +38,23 @@ def check_runner() -> tuple[str, int]:
     Returns:
         Information on the runners in JSON format.
     """
-    app_config: ApplicationConfiguration = app.config[APP_CONFIG_NAME]
+    runner_manager: RunnerManager = app.config[RUNNER_MANAGER_CONFIG_NAME]
     app.logger.info("Checking runners...")
-    runner_scaler = get_runner_scaler(app_config)
     try:
-        runner_info = runner_scaler.get_runner_info()
+        runner_info = runner_manager.get_runner_info()
     except CloudError as err:
         app.logger.exception("Cloud error encountered while getting runner info")
         return (str(err), 500)
-    return (json.dumps(dataclasses.asdict(runner_info)), 200)
+
+    response = {
+        "online": runner_info.online,
+        "busy": runner_info.busy,
+        "offline": runner_info.offline,
+        "unknown": runner_info.unknown,
+        "runners": list(runner_info.runners),
+        "busy_runners": list(runner_info.busy_runners),
+    }
+    return (json.dumps(response), 200)
 
 
 @app.route("/runner/flush", methods=["POST"])
@@ -66,7 +67,7 @@ def flush_runner() -> tuple[str, int]:
     Returns:
         A empty response.
     """
-    app_config = app.config[APP_CONFIG_NAME]
+    runner_manager: RunnerManager = app.config[RUNNER_MANAGER_CONFIG_NAME]
 
     flush_busy_str = request.args.get("flush-busy")
     flush_busy = False
@@ -76,15 +77,13 @@ def flush_runner() -> tuple[str, int]:
     lock = _get_lock()
     with lock:
         app.logger.info("Flushing runners...")
-        runner_scaler = get_runner_scaler(app_config)
         app.logger.info("Flushing busy: %s", flush_busy)
         flush_mode = FlushMode.FLUSH_BUSY if flush_busy else FlushMode.FLUSH_IDLE
         try:
-            num_flushed = runner_scaler.flush(flush_mode)
+            runner_manager.flush_runners(flush_mode)
         except CloudError as err:
             app.logger.exception("Cloud error encountered while flushing runners")
             return (str(err), 500)
-        app.logger.info("Flushed %s runners", num_flushed)
     return ("", 204)
 
 
@@ -130,22 +129,22 @@ class FlaskArgs:
 
 
 def start_http_server(
-    app_config: ApplicationConfiguration,
+    runner_manager: RunnerManager,
     lock: Lock,
     flask_args: FlaskArgs,
 ) -> None:
     """Start the HTTP server for interacting with the github-runner-manager service.
 
     Args:
-        app_config: The application configuration.
+        runner_manager: The runner manager for managing runners.
         lock: The lock representing modification access to the managed set of runners.
         flask_args: The arguments for the flask HTTP server.
     """
     app.logger.info("Starting the server...")
     # The lock is passed from the caller, hence the need to update the global variable.
     global _lock  # pylint: disable=global-statement
     _lock = lock
-    app.config[APP_CONFIG_NAME] = app_config
+    app.config[RUNNER_MANAGER_CONFIG_NAME] = runner_manager
     app.run(
         host=flask_args.host,
         port=flask_args.port,

github-runner-manager/src/github_runner_manager/manager/pressure_reconciler.py

@@ -112,7 +112,7 @@ class PressureReconciler:  # pylint: disable=too-few-public-methods,too-many-ins
     def __init__(
         self,
         manager: RunnerManager,
-        planner_client: PlannerClient,
+        planner_client: PlannerClient | None,
         config: PressureReconcilerConfig,
         lock: Lock,
     ) -> None:
@@ -122,6 +122,7 @@ def __init__(
             manager: Runner manager interface for creating, cleaning up,
                 and listing runners.
             planner_client: Client used to stream pressure updates.
+                None when no planner relation is configured.
             config: Reconciler configuration.
             lock: Shared lock to serialize operations with other reconcile loops.
         """
@@ -140,6 +141,15 @@ def start_create_loop(self) -> None:
         with self._lock:
             self._runner_count = len(self._manager.get_runners())
         logger.info("Create loop: initial sync, _runner_count=%s", self._runner_count)
+        if self._planner is None:
+            self._last_pressure = self._config.min_pressure
+            logger.info(
+                "Create loop: no planner configured, using min_pressure=%s",
+                self._config.min_pressure,
+            )
+            self._handle_create_runners(self._config.min_pressure)
+            self._stop.wait()
+            return
         while not self._stop.is_set():
             try:
                 for update in self._planner.stream_pressure(self._config.flavor_name):
@@ -394,31 +404,38 @@ def _desired_total_from_pressure(self, pressure: int) -> int:
         return total
 
 
-def build_pressure_reconciler(config: ApplicationConfiguration, lock: Lock) -> PressureReconciler:
+def build_pressure_reconciler(
+    config: ApplicationConfiguration, manager: RunnerManager, lock: Lock
+) -> PressureReconciler:
     """Construct a PressureReconciler from application configuration.
 
     Args:
         config: Application configuration.
+        manager: The runner manager to use for creating, cleaning up, and listing runners.
         lock: Shared lock to serialize operations with other reconcile loops.
 
     Raises:
-        ValueError: If no non-reactive combinations are configured.
+        ValueError: If planner configuration is partial (only one of URL/token set).
 
     Returns:
         A fully constructed PressureReconciler.
     """
-    combinations = config.non_reactive_configuration.combinations
-    if not combinations:
+    first = config.non_reactive_configuration.combinations[0]
+    planner_client: PlannerClient | None = None
+    has_url = bool(config.planner_url)
+    has_token = bool(config.planner_token)
+    if has_url != has_token:
         raise ValueError(
-            "Cannot build PressureReconciler: no non-reactive combinations configured."
+            "Partial planner configuration: both planner_url and planner_token must be set"
+            " or both unset."
+        )
+    if has_url and has_token:
+        planner_client = PlannerClient(
+            PlannerConfiguration(base_url=config.planner_url, token=config.planner_token)
         )
-    first = combinations[0]
-    manager = _build_runner_manager(config, first)
     return PressureReconciler(
         manager=manager,
-        planner_client=PlannerClient(
-            PlannerConfiguration(base_url=config.planner_url, token=config.planner_token)
-        ),
+        planner_client=planner_client,
         config=PressureReconcilerConfig(
             flavor_name=config.name,
             reconcile_interval=config.reconcile_interval,
@@ -429,7 +446,7 @@ def build_pressure_reconciler(config: ApplicationConfiguration, lock: Lock) -> P
     )
 
 
-def _build_runner_manager(
+def build_runner_manager(
     config: ApplicationConfiguration, combination: NonReactiveCombination
 ) -> RunnerManager:
     """Build a RunnerManager from application config and a flavor/image combination.

github-runner-manager/src/github_runner_manager/manager/runner_manager.py

@@ -1,6 +1,8 @@
 # Copyright 2026 Canonical Ltd.
 # See LICENSE file for licensing details.
 
+# RunnerInfo is duplicated in runner_scaler (legacy), will be removed in follow-up PR.
+# pylint: disable=duplicate-code
 """Module for managing the GitHub self-hosted runners hosted on cloud instances."""
 
 import copy
@@ -45,6 +47,27 @@
 IssuedMetricEventsStats = dict[Type[metric_events.Event], int]
 
 
+@dataclass(frozen=True)
+class RunnerInfo:
+    """Aggregated information on the runners.
+
+    Attributes:
+        online: The number of runners in online state.
+        busy: The number of runners in busy state.
+        offline: The number of runners in offline state.
+        unknown: The number of runners in unknown state.
+        runners: The names of the online runners.
+        busy_runners: The names of the busy runners.
+    """
+
+    online: int
+    busy: int
+    offline: int
+    unknown: int
+    runners: tuple[str, ...]
+    busy_runners: tuple[str, ...]
+
+
 class FlushMode(Enum):
     """Strategy for flushing runners.
 
@@ -263,6 +286,42 @@ def get_runners(self) -> tuple[RunnerInstance, ...]:
             for vm in vms
         )
 
+    def get_runner_info(self) -> RunnerInfo:
+        """Get aggregated information on the runners.
+
+        Returns:
+            Aggregated runner counts and names.
+        """
+        runner_list = self.get_runners()
+        online = 0
+        busy = 0
+        offline = 0
+        unknown = 0
+        online_runners: list[str] = []
+        busy_runners: list[str] = []
+        for runner in runner_list:
+            match runner.platform_state:
+                case PlatformRunnerState.BUSY:
+                    online += 1
+                    online_runners.append(runner.name)
+                    busy += 1
+                    busy_runners.append(runner.name)
+                case PlatformRunnerState.IDLE:
+                    online += 1
+                    online_runners.append(runner.name)
+                case PlatformRunnerState.OFFLINE:
+                    offline += 1
+                case _:
+                    unknown += 1
+        return RunnerInfo(
+            online=online,
+            busy=busy,
+            offline=offline,
+            unknown=unknown,
+            runners=tuple(online_runners),
+            busy_runners=tuple(busy_runners),
+        )
+
     def delete_runners(self, num: int) -> IssuedMetricEventsStats:
         """Delete up to `num` runners, preferring idle ones over busy.