fixed issues in zebra config service, updated config services to start and validate different modes appropriately, added service dependency startup for config services

daemon/core/configservice/dependencies.py

@@ -0,0 +1,97 @@
+import logging
+from typing import TYPE_CHECKING, Dict, List
+
+if TYPE_CHECKING:
+    from core.configservice.base import ConfigService
+
+
+class ConfigServiceDependencies:
+    """
+    Can generate boot paths for services, based on their dependencies. Will validate
+    that all services will be booted and that all dependencies exist within the services provided.
+    """
+
+    def __init__(self, services: Dict[str, "ConfigService"]) -> None:
+        # helpers to check validity
+        self.dependents = {}
+        self.booted = set()
+        self.node_services = {}
+        for service in services.values():
+            self.node_services[service.name] = service
+            for dependency in service.dependencies:
+                dependents = self.dependents.setdefault(dependency, set())
+                dependents.add(service.name)
+
+        # used to find paths
+        self.path = []
+        self.visited = set()
+        self.visiting = set()
+
+    def boot_paths(self) -> List[List["ConfigService"]]:
+        paths = []
+        for name in self.node_services:
+            service = self.node_services[name]
+            if service.name in self.booted:
+                logging.debug(
+                    "skipping service that will already be booted: %s", service.name
+                )
+                continue
+
+            path = self._start(service)
+            if path:
+                paths.append(path)
+
+        if self.booted != set(self.node_services):
+            raise ValueError(
+                "failure to boot all services: %s != %s"
+                % (self.booted, self.node_services.keys())
+            )
+
+        return paths
+
+    def _reset(self) -> None:
+        self.path = []
+        self.visited.clear()
+        self.visiting.clear()
+
+    def _start(self, service: "ConfigService") -> List["ConfigService"]:
+        logging.debug("starting service dependency check: %s", service.name)
+        self._reset()
+        return self._visit(service)
+
+    def _visit(self, current_service: "ConfigService") -> List["ConfigService"]:
+        logging.debug("visiting service(%s): %s", current_service.name, self.path)
+        self.visited.add(current_service.name)
+        self.visiting.add(current_service.name)
+
+        # dive down
+        for service_name in current_service.dependencies:
+            if service_name not in self.node_services:
+                raise ValueError(
+                    "required dependency was not included in node services: %s"
+                    % service_name
+                )
+
+            if service_name in self.visiting:
+                raise ValueError(
+                    "cyclic dependency at service(%s): %s"
+                    % (current_service.name, service_name)
+                )
+
+            if service_name not in self.visited:
+                service = self.node_services[service_name]
+                self._visit(service)
+
+        # add service when bottom is found
+        logging.debug("adding service to boot path: %s", current_service.name)
+        self.booted.add(current_service.name)
+        self.path.append(current_service)
+        self.visiting.remove(current_service.name)
+
+        # rise back up
+        for service_name in self.dependents.get(current_service.name, []):
+            if service_name not in self.visited:
+                service = self.node_services[service_name]
+                self._visit(service)
+
+        return self.path