build.models.path

Complexity

Total Complexity

53

Size/Duplication

Total Lines	239
Duplicated Lines	0 %

Test Coverage

Coverage

94.53%

Importance

Changes

0

15 Methods

Rating	Name	Duplication	Size	Complexity
A	Path.is_affected_by_link()	0	5	2
A	Path.__eq__()	0	5	3
A	Path.make_vlans_available()	0	5	2
A	Path.choose_vlans()	0	5	2
A	Path.link_affected_by_interface()	0	8	4
A	DynamicPathManager.get_best_path()	0	7	2
A	DynamicPathManager.get_best_paths()	0	5	2
B	Path.status()	0	30	7
A	DynamicPathManager.create_path()	0	17	5
A	DynamicPathManager.set_controller()	0	4	1
C	DynamicPathManager.get_disjoint_paths()	0	65	9
C	Path.is_valid()	0	21	10
A	DynamicPathManager.get_paths()	0	21	2
A	Path.as_dict()	0	3	1
A	DynamicPathManager._clear_path()	0	4	1

"""Classes related to paths"""
import requests

from kytos.core import log
from kytos.core.common import EntityStatus, GenericEntity
from kytos.core.link import Link
from napps.kytos.mef_eline import settings
from napps.kytos.mef_eline.exceptions import InvalidPath


class Path(list, GenericEntity):
    """Class to represent a Path."""

    def __eq__(self, other=None):
        """Compare paths."""
        if not other or not isinstance(other, Path):
            return False
        return super().__eq__(other)

    def is_affected_by_link(self, link=None):
        """Verify if the current path is affected by link."""
        if not link:
            return False
        return link in self

    def link_affected_by_interface(self, interface=None):
        """Return the link using this interface, if any, or None otherwise."""
        if not interface:
            return None
        for link in self:
            if interface in (link.endpoint_a, link.endpoint_b):
                return link
        return None

    def choose_vlans(self):
        """Choose the VLANs to be used for the circuit."""
        for link in self:
            tag = link.get_next_available_tag()
            link.add_metadata("s_vlan", tag)

    def make_vlans_available(self):
        """Make the VLANs used in a path available when undeployed."""
        for link in self:
            link.make_tag_available(link.get_metadata("s_vlan"))
            link.remove_metadata("s_vlan")

    def is_valid(self, switch_a, switch_z, is_scheduled=False):
        """Check if this is a valid path."""
        if not self:
            return True
        previous = switch_a
        for link in self:
            if link.endpoint_a.switch != previous:
                raise InvalidPath(
                    f"{link.endpoint_a} switch is different" f" from previous."
                )
            if is_scheduled is False and (
                link.endpoint_a.link is None
                or link.endpoint_a.link != link
                or link.endpoint_b.link is None
                or link.endpoint_b.link != link
            ):
                raise InvalidPath(f"Link {link} is not available.")
            previous = link.endpoint_b.switch
        if previous == switch_z:
            return True
        raise InvalidPath("Last endpoint is different from uni_z")

    @property
    def status(self):
        """Check for the  status of a path.

        If any link in this path is down, the path is considered down.
        """
        if not self:
            return EntityStatus.DISABLED

        endpoint = f"{settings.TOPOLOGY_URL}/links"
        api_reply = requests.get(endpoint)
        if api_reply.status_code != getattr(requests.codes, "ok"):
            log.error(
                "Failed to get links at %s. Returned %s",
                endpoint,
                api_reply.status_code,
            )
            return None
        links = api_reply.json()["links"]
        return_status = EntityStatus.UP
        for path_link in self:
            try:
                link = links[path_link.id]
            except KeyError:
                return EntityStatus.DISABLED
            if link["enabled"] is False:
                return EntityStatus.DISABLED
            if link["active"] is False:
                return_status = EntityStatus.DOWN
        return return_status

    def as_dict(self):
        """Return list comprehension of links as_dict."""
        return [link.as_dict() for link in self if link]


class DynamicPathManager:
    """Class to handle and create paths."""

    controller = None

    @classmethod
    def set_controller(cls, controller=None):
        """Set the controller to discovery news paths."""
        cls.controller = controller

    @staticmethod
    def get_paths(circuit, max_paths=2, **kwargs):
        """Get a valid path for the circuit from the Pathfinder."""
        endpoint = settings.PATHFINDER_URL
        request_data = {
            "source": circuit.uni_a.interface.id,
            "destination": circuit.uni_z.interface.id,
            "spf_max_paths": max_paths,
        }
        request_data.update(kwargs)
        api_reply = requests.post(endpoint, json=request_data)

        if api_reply.status_code != getattr(requests.codes, "ok"):
            log.error(
                "Failed to get paths at %s. Returned %s",
                endpoint,
                api_reply.status_code,
            )
            return None
        reply_data = api_reply.json()
        return reply_data.get("paths")

    @staticmethod
    def _clear_path(path):
        """Remove switches from a path, returning only interfaces."""
        return [endpoint for endpoint in path if len(endpoint) > 23]

    @classmethod
    def get_best_path(cls, circuit):
        """Return the best path available for a circuit, if exists."""
        paths = cls.get_paths(circuit)
        if paths:
            return cls.create_path(cls.get_paths(circuit)[0]["hops"])
        return None

    @classmethod
    def get_best_paths(cls, circuit, **kwargs):
        """Return the best paths available for a circuit, if they exist."""
        for path in cls.get_paths(circuit, **kwargs):
            yield cls.create_path(path["hops"])

    @classmethod
    def get_disjoint_paths(
        cls, circuit, unwanted_path, cutoff=settings.DISJOINT_PATH_CUTOFF
    ):
        """Computes the maximum disjoint paths from the unwanted_path for a EVC

        Maximum disjoint paths from the unwanted_path are the paths from the
        source node to the target node that share the minimum number os links
        contained in unwanted_path. In other words, unwanted_path is the path
        we want to avoid: we want the maximum possible disjoint path from it.
        The disjointness of a path in regards to unwanted_path is calculated
        by the complementary percentage of shared links between them. As an
        example, if the unwanted_path has 3 links, a given path P1 has 1 link
        shared with unwanted_path, and a given path P2 has 2 links shared with
        unwanted_path, then the disjointness of P1 is 0.67 and the disjointness
        of P2 is 0.33. In this example, P1 is preferable over P2 because it
        offers a better disjoint path. When two paths have the same
        disjointness they are ordered by 'cost' attributed as returned from
        Pathfinder. When the disjointness of a path is equal to 0 (i.e., it
        shares all the links with unwanted_path), that particular path is not
        considered a candidate.

        Parameters:
        -----------

        circuit : EVC
            The EVC providing source node (uni_a) and target node (uni_z)

        unwanted_path : Path
            The Path which we want to avoid.

        cutoff: int
            Maximum number of paths to consider when calculating the disjoint
            paths (number of paths to request from pathfinder)

        Returns:
        --------
        paths : generator
            Generator of unwanted_path disjoint paths. If unwanted_path is
            not provided or empty, we return an empty list.
        """
        unwanted_links = [
            (link.endpoint_a.id, link.endpoint_b.id) for link in unwanted_path
        ]
        if not unwanted_links:
            return None

        paths = cls.get_paths(circuit, max_paths=cutoff,
                              **circuit.secondary_constraints)
        for path in paths:
            head = path["hops"][:-1]
            tail = path["hops"][1:]
            shared_edges = 0
            for (endpoint_a, endpoint_b) in unwanted_links:
                if ((endpoint_a, endpoint_b) in zip(head, tail)) or (
                    (endpoint_b, endpoint_a) in zip(head, tail)
                ):
                    shared_edges += 1
            path["disjointness"] = 1 - shared_edges / len(unwanted_links)
        paths = sorted(paths, key=lambda x: (-x['disjointness'], x['cost']))
        for path in paths:
            if path["disjointness"] == 0:
                continue
            yield cls.create_path(path["hops"])
        return None

    @classmethod
    def create_path(cls, path):
        """Return the path containing only the interfaces."""
        new_path = Path()
        clean_path = cls._clear_path(path)

        if len(clean_path) % 2:
            return None

        for link in zip(clean_path[1:-1:2], clean_path[2::2]):
            interface_a = cls.controller.get_interface_by_id(link[0])
            interface_b = cls.controller.get_interface_by_id(link[1])
            if interface_a is None or interface_b is None:
                return None
            new_path.append(Link(interface_a, interface_b))

        return new_path