kytos-ng / topology

main.py

"""Main module of kytos/topology Kytos Network Application.

Manage the network topology
"""
# pylint: disable=wrong-import-order
import pathlib
import time
from collections import defaultdict
from datetime import timezone
from threading import Lock
from typing import List, Optional

import httpx
import tenacity
from tenacity import (retry_if_exception_type, stop_after_attempt,
                      wait_combine, wait_fixed, wait_random)

from kytos.core import KytosEvent, KytosNApp, log, rest
from kytos.core.common import EntityStatus, GenericEntity
from kytos.core.exceptions import (KytosInvalidTagRanges,
                                   KytosLinkCreationError, KytosTagError)
from kytos.core.helpers import listen_to, load_spec, now, validate_openapi
from kytos.core.interface import Interface
from kytos.core.link import Link
from kytos.core.rest_api import (HTTPException, JSONResponse, Request,
                                 content_type_json_or_415, get_json_or_400)
from kytos.core.retry import before_sleep
from kytos.core.switch import Switch
from kytos.core.tag_ranges import get_tag_ranges
from napps.kytos.topology import settings

from .controllers import TopoController
from .exceptions import RestoreError
from .models import Topology

DEFAULT_LINK_UP_TIMER = 10


class Main(KytosNApp):  # pylint: disable=too-many-public-methods
    """Main class of kytos/topology NApp.

    This class is the entry point for this napp.
    """

    spec = load_spec(pathlib.Path(__file__).parent / "openapi.yml")

    def setup(self):
        """Initialize the NApp's links list."""
        self.links: dict[str, Link] = {}
        self.intf_available_tags = {}
        self.link_up_timer = getattr(settings, 'LINK_UP_TIMER',
                                     DEFAULT_LINK_UP_TIMER)

        self._links_lock = Lock()
        # to keep track of potential unorded scheduled interface events
        self._intfs_lock = defaultdict(Lock)
        self._intfs_updated_at = {}
        self._intfs_tags_updated_at = {}
        self.link_up = set()
        self.link_status_lock = Lock()
        self._switch_lock = defaultdict(Lock)
        self.topo_controller = self.get_topo_controller()

        # Track when we last received a link up, that resulted in
        # activating a deactivated link.
        self.link_status_change = defaultdict[str, dict](dict)
        Link.register_status_func(f"{self.napp_id}_link_up_timer",
                                  self.link_status_hook_link_up_timer)
        self.topo_controller.bootstrap_indexes()
        self.load_topology()

    @staticmethod
    def get_topo_controller() -> TopoController:
        """Get TopoController."""
        return TopoController()

    def execute(self):
        """Execute once when the napp is running."""
        pass

    def shutdown(self):
        """Do nothing."""
        log.info('NApp kytos/topology shutting down.')

    def _get_metadata(self, request: Request) -> dict:
        """Return a JSON with metadata."""
        content_type_json_or_415(request)
        metadata = get_json_or_400(request, self.controller.loop)
        if not isinstance(metadata, dict):
            raise HTTPException(400, "Invalid metadata value: {metadata}")
        return metadata

    def _get_link_or_create(self, endpoint_a, endpoint_b):
        """Get an existing link or create a new one.

        Returns:
            Tuple(Link, bool): Link and a boolean whether it has been created.
        """
        new_link = Link(endpoint_a, endpoint_b)

        if new_link.id in self.links:
            return (self.links[new_link.id], False)

        self.links[new_link.id] = new_link
        return (new_link, True)

    def _get_switches_dict(self):
        """Return a dictionary with the known switches."""
        switches = {'switches': {}}
        for idx, switch in enumerate(self.controller.switches.copy().values()):
            switch_data = switch.as_dict()
            if not all(key in switch_data['metadata']
                       for key in ('lat', 'lng')):
                # Switches are initialized somewhere in the ocean
                switch_data['metadata']['lat'] = str(0.0)
                switch_data['metadata']['lng'] = str(-30.0+idx*10.0)
            switches['switches'][switch.id] = switch_data
        return switches

    def _get_links_dict(self):
        """Return a dictionary with the known links."""
        return {'links': {link.id: link.as_dict() for link in
                          self.links.copy().values()}}

    def _get_topology_dict(self):
        """Return a dictionary with the known topology."""
        return {'topology': {**self._get_switches_dict(),
                             **self._get_links_dict()}}

    def _get_topology(self):
        """Return an object representing the topology."""
        return Topology(self.controller.switches.copy(), self.links.copy())

    def _get_link_from_interface(self, interface: Interface):
        """Return the link of the interface, or None if it does not exist."""
        for link in list(self.links.values()):
            if interface in (link.endpoint_a, link.endpoint_b):
                return link
        return None

    def _load_link(self, link_att):
        endpoint_a = link_att['endpoint_a']['id']
        endpoint_b = link_att['endpoint_b']['id']
        link_str = link_att['id']
        log.info(f"Loading link: {link_str}")
        interface_a = self.controller.get_interface_by_id(endpoint_a)
        interface_b = self.controller.get_interface_by_id(endpoint_b)

        error = f"Fail to load endpoints for link {link_str}. "
        if not interface_a:
            raise RestoreError(f"{error}, endpoint_a {endpoint_a} not found")
        if not interface_b:
            raise RestoreError(f"{error}, endpoint_b {endpoint_b} not found")

        with self._links_lock:
            link, _ = self._get_link_or_create(interface_a, interface_b)

        if link_att['enabled']:
            link.enable()
        else:
            link.disable()

        link.extend_metadata(link_att["metadata"])
        interface_a.update_link(link)
        interface_b.update_link(link)
        interface_a.nni = True
        interface_b.nni = True

    def _load_switch(self, switch_id, switch_att):
        log.info(f'Loading switch dpid: {switch_id}')
        switch = self.controller.get_switch_or_create(switch_id)
        if switch_att['enabled']:
            switch.enable()
        else:
            switch.disable()
        switch.description['manufacturer'] = switch_att.get('manufacturer', '')
        switch.description['hardware'] = switch_att.get('hardware', '')
        switch.description['software'] = switch_att.get('software')
        switch.description['serial'] = switch_att.get('serial', '')
        switch.description['data_path'] = switch_att.get('data_path', '')
        switch.extend_metadata(switch_att["metadata"])

        for iface_id, iface_att in switch_att.get('interfaces', {}).items():
            log.info(f'Loading interface iface_id={iface_id}')
            interface = switch.update_or_create_interface(
                            port_no=iface_att['port_number'],
                            name=iface_att['name'],
                            address=iface_att.get('mac', None),
                            speed=iface_att.get('speed', None))
            if iface_att['enabled']:
                interface.enable()
            else:
                interface.disable()
            interface.lldp = iface_att['lldp']
            interface.extend_metadata(iface_att["metadata"])
            interface.deactivate()
            name = 'kytos/topology.port.created'
            event = KytosEvent(name=name, content={
                                              'switch': switch_id,
                                              'port': interface.port_number,
                                              'port_description': {
                                                  'alias': interface.name,
                                                  'mac': interface.address,
                                                  'state': interface.state
                                                  }
                                              })
            self.controller.buffers.app.put(event, timeout=1)

        intf_ids = [v["id"] for v in switch_att.get("interfaces", {}).values()]
        intf_details = self.topo_controller.get_interfaces_details(intf_ids)
        with self._links_lock:
            self.load_interfaces_tags_values(switch, intf_details)

    # pylint: disable=attribute-defined-outside-init
    def load_topology(self):
        """Load network topology from DB."""
        topology = self.topo_controller.get_topology()
        switches = topology["topology"]["switches"]
        links = topology["topology"]["links"]

        failed_switches = {}
        log.debug(f"_load_network_status switches={switches}")
        for switch_id, switch_att in switches.items():
            try:
                self._load_switch(switch_id, switch_att)
            except (KeyError, AttributeError, TypeError) as err:
                failed_switches[switch_id] = err
                log.error(f'Error loading switch: {err}')

        failed_links = {}
        log.debug(f"_load_network_status links={links}")
        for link_id, link_att in links.items():
            try:
                self._load_link(link_att)
            except (KeyError, AttributeError, TypeError) as err:
                failed_links[link_id] = err
                log.error(f'Error loading link {link_id}: {err}')

        name = 'kytos/topology.topology_loaded'
        event = KytosEvent(
            name=name,
            content={
                'topology': self._get_topology(),
                'failed_switches': failed_switches,
                'failed_links': failed_links
            })
        self.controller.buffers.app.put(event, timeout=1)

    @rest('v3/')
    def get_topology(self, _request: Request) -> JSONResponse:
        """Return the latest known topology.

        This topology is updated when there are network events.
        """
        return JSONResponse(self._get_topology_dict())

    # Switch related methods
    @rest('v3/switches')
    def get_switches(self, _request: Request) -> JSONResponse:
        """Return a json with all the switches in the topology."""
        return JSONResponse(self._get_switches_dict())

    @rest('v3/switches/{dpid}/enable', methods=['POST'])
    def enable_switch(self, request: Request) -> JSONResponse:
        """Administratively enable a switch in the topology."""
        dpid = request.path_params["dpid"]
        try:
            switch = self.controller.switches[dpid]
            self.topo_controller.enable_switch(dpid)
            switch.enable()
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        self.notify_topology_update()
        self.notify_switch_enabled(dpid)
        self.notify_switch_links_status(switch, "link enabled")
        return JSONResponse("Operation successful", status_code=201)

    @rest('v3/switches/{dpid}/disable', methods=['POST'])
    def disable_switch(self, request: Request) -> JSONResponse:
        """Administratively disable a switch in the topology."""
        dpid = request.path_params["dpid"]
        try:
            switch = self.controller.switches[dpid]
            link_ids = set()
            for _, interface in switch.interfaces.copy().items():
                if (interface.link and interface.link.is_enabled()):
                    link_ids.add(interface.link.id)
                    interface.link.disable()
                    self.notify_link_enabled_state(interface.link, "disabled")
            self.topo_controller.bulk_disable_links(link_ids)
            self.topo_controller.disable_switch(dpid)
            switch.disable()
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        self.notify_topology_update()
        self.notify_switch_disabled(dpid)
        self.notify_switch_links_status(switch, "link disabled")
        return JSONResponse("Operation successful", status_code=201)

    @rest('v3/switches/{dpid}', methods=['DELETE'])
    def delete_switch(self, request: Request) -> JSONResponse:
        """Delete a switch.

        Requirements:
            - There should not be installed flows related to switch.
            - The switch should be disabled.
            - All tags from switch interfaces should be available.
            - The switch should not have links.
        """
        dpid = request.path_params["dpid"]
        try:
            switch: Switch = self.controller.switches[dpid]
            with self._switch_lock[dpid]:
                if switch.status != EntityStatus.DISABLED:
                    raise HTTPException(
                        409, detail="Switch should be disabled."
                    )
                for intf_id, interface in switch.interfaces.copy().items():
                    if not interface.all_tags_available():
                        detail = f"Interface {intf_id} vlans are being used."\
                                 " Delete any service using vlans."
                        raise HTTPException(409, detail=detail)
                with self._links_lock:
                    for link_id, link in self.links.items():
                        if (dpid in
                                (link.endpoint_a.switch.dpid,
                                 link.endpoint_b.switch.dpid)):
                            raise HTTPException(
                                409, detail=f"Switch should not have links. "
                                            f"Link found {link_id}."
                            )
                try:
                    flows = self.get_flows_by_switch(dpid)
                except tenacity.RetryError as err:
                    detail = "Error while getting flows: "\
                             f"{err.last_attempt.exception()}."
                    raise HTTPException(409, detail=detail)
                if flows:
                    raise HTTPException(409, detail="Switch has flows. Verify"
                                                    " if a switch is used.")
                switch = self.controller.switches.pop(dpid)
                self.topo_controller.delete_switch_data(dpid)
        except KeyError:
            raise HTTPException(404, detail="Switch not found.")
        name = 'kytos/topology.switch.deleted'
        event = KytosEvent(name=name, content={'switch': switch})
        self.controller.buffers.app.put(event)
        self.notify_topology_update()
        return JSONResponse("Operation successful")

    @rest('v3/switches/{dpid}/metadata')
    def get_switch_metadata(self, request: Request) -> JSONResponse:
        """Get metadata from a switch."""
        dpid = request.path_params["dpid"]
        try:
            metadata = self.controller.switches[dpid].metadata
            return JSONResponse({"metadata": metadata})
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

    @rest('v3/switches/{dpid}/metadata', methods=['POST'])
    def add_switch_metadata(self, request: Request) -> JSONResponse:
        """Add metadata to a switch."""
        dpid = request.path_params["dpid"]
        metadata = self._get_metadata(request)
        try:
            switch = self.controller.switches[dpid]
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        self.topo_controller.add_switch_metadata(dpid, metadata)
        switch.extend_metadata(metadata)
        self.notify_metadata_changes(switch, 'added')
        return JSONResponse("Operation successful", status_code=201)

    @rest('v3/switches/{dpid}/metadata/{key}', methods=['DELETE'])
    def delete_switch_metadata(self, request: Request) -> JSONResponse:
        """Delete metadata from a switch."""
        dpid = request.path_params["dpid"]
        key = request.path_params["key"]
        try:
            switch = self.controller.switches[dpid]
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        try:
            _ = switch.metadata[key]
        except KeyError:
            raise HTTPException(404, "Metadata not found")

        self.topo_controller.delete_switch_metadata_key(dpid, key)
        switch.remove_metadata(key)
        self.notify_metadata_changes(switch, 'removed')
        return JSONResponse("Operation successful")

    # Interface related methods
    @rest('v3/interfaces')
    def get_interfaces(self, _request: Request) -> JSONResponse:
        """Return a json with all the interfaces in the topology."""
        interfaces = {}
        switches = self._get_switches_dict()
        for switch in switches['switches'].values():
            for interface_id, interface in switch['interfaces'].items():
                interfaces[interface_id] = interface

        return JSONResponse({'interfaces': interfaces})

    @rest('v3/interfaces/switch/{dpid}/enable', methods=['POST'])
    @rest('v3/interfaces/{interface_enable_id}/enable', methods=['POST'])
    def enable_interface(self, request: Request) -> JSONResponse:
        """Administratively enable interfaces in the topology."""
        interface_enable_id = request.path_params.get("interface_enable_id")
        dpid = request.path_params.get("dpid")
        if dpid is None:
            dpid = ":".join(interface_enable_id.split(":")[:-1])
        try:
            switch = self.controller.switches[dpid]
            if not switch.is_enabled():
                raise HTTPException(409, detail="Enable Switch first")
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        if interface_enable_id:
            interface_number = int(interface_enable_id.split(":")[-1])

            try:
                interface = switch.interfaces[interface_number]
                self.topo_controller.enable_interface(interface.id)
                interface.enable()
                self.notify_interface_link_status(interface, "link enabled")
            except KeyError:
                msg = f"Switch {dpid} interface {interface_number} not found"
                raise HTTPException(404, detail=msg)
        else:
            for interface in switch.interfaces.copy().values():
                interface.enable()
                self.notify_interface_link_status(interface, "link enabled")
            self.topo_controller.upsert_switch(switch.id, switch.as_dict())
        self.notify_topology_update()
        return JSONResponse("Operation successful")

    @rest('v3/interfaces/switch/{dpid}/disable', methods=['POST'])
    @rest('v3/interfaces/{interface_disable_id}/disable', methods=['POST'])
    def disable_interface(self, request: Request) -> JSONResponse:
        """Administratively disable interfaces in the topology."""
        interface_disable_id = request.path_params.get("interface_disable_id")
        dpid = request.path_params.get("dpid")
        if dpid is None:
            dpid = ":".join(interface_disable_id.split(":")[:-1])
        try:
            switch = self.controller.switches[dpid]
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        if interface_disable_id:
            interface_number = int(interface_disable_id.split(":")[-1])

            try:
                interface = switch.interfaces[interface_number]
                self.topo_controller.disable_interface(interface.id)
                if interface.link and interface.link.is_enabled():
                    self.topo_controller.disable_link(interface.link.id)
                    interface.link.disable()
                    self.notify_link_enabled_state(interface.link, "disabled")
                interface.disable()
                self.notify_interface_link_status(interface, "link disabled")
            except KeyError:
                msg = f"Switch {dpid} interface {interface_number} not found"
                raise HTTPException(404, detail=msg)
        else:
            link_ids = set()
            for interface in switch.interfaces.copy().values():
                if interface.link and interface.link.is_enabled():
                    link_ids.add(interface.link.id)
                    interface.link.disable()
                    self.notify_link_enabled_state(interface.link, "disabled")
                interface.disable()
                self.notify_interface_link_status(interface, "link disabled")
            self.topo_controller.bulk_disable_links(link_ids)
            self.topo_controller.upsert_switch(switch.id, switch.as_dict())
        self.notify_topology_update()
        return JSONResponse("Operation successful")

    @rest('v3/interfaces/{interface_id}/metadata')
    def get_interface_metadata(self, request: Request) -> JSONResponse:
        """Get metadata from an interface."""
        interface_id = request.path_params["interface_id"]
        switch_id = ":".join(interface_id.split(":")[:-1])
        interface_number = int(interface_id.split(":")[-1])
        try:
            switch = self.controller.switches[switch_id]
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        try:
            interface = switch.interfaces[interface_number]
        except KeyError:
            raise HTTPException(404, detail="Interface not found")

        return JSONResponse({"metadata": interface.metadata})

    @rest('v3/interfaces/{interface_id}/metadata', methods=['POST'])
    def add_interface_metadata(self, request: Request) -> JSONResponse:
        """Add metadata to an interface."""
        interface_id = request.path_params["interface_id"]
        metadata = self._get_metadata(request)
        switch_id = ":".join(interface_id.split(":")[:-1])
        interface_number = int(interface_id.split(":")[-1])
        try:
            switch = self.controller.switches[switch_id]
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        try:
            interface = switch.interfaces[interface_number]
            self.topo_controller.add_interface_metadata(interface.id, metadata)
        except KeyError:
            raise HTTPException(404, detail="Interface not found")

        interface.extend_metadata(metadata)
        self.notify_metadata_changes(interface, 'added')
        return JSONResponse("Operation successful", status_code=201)

    @rest('v3/interfaces/{interface_id}/metadata/{key}', methods=['DELETE'])
    def delete_interface_metadata(self, request: Request) -> JSONResponse:
        """Delete metadata from an interface."""
        interface_id = request.path_params["interface_id"]
        key = request.path_params["key"]
        switch_id = ":".join(interface_id.split(":")[:-1])
        try:
            interface_number = int(interface_id.split(":")[-1])
        except ValueError:
            detail = f"Invalid interface_id {interface_id}"
            raise HTTPException(400, detail=detail)

        try:
            switch = self.controller.switches[switch_id]
        except KeyError:
            raise HTTPException(404, detail="Switch not found")

        try:
            interface = switch.interfaces[interface_number]
        except KeyError:
            raise HTTPException(404, detail="Interface not found")

        try:
            _ = interface.metadata[key]
        except KeyError:
            raise HTTPException(404, detail="Metadata not found")

        self.topo_controller.delete_interface_metadata_key(interface.id, key)
        interface.remove_metadata(key)
        self.notify_metadata_changes(interface, 'removed')
        return JSONResponse("Operation successful")

    @rest('v3/interfaces/{interface_id}/tag_ranges', methods=['POST'])
    @validate_openapi(spec)
    def set_tag_range(self, request: Request) -> JSONResponse:
        """Set tag range"""
        content_type_json_or_415(request)
        content = get_json_or_400(request, self.controller.loop)
        tag_type = content.get("tag_type")
        try:
            ranges = get_tag_ranges(content["tag_ranges"])
        except KytosInvalidTagRanges as err:
            raise HTTPException(400, detail=str(err))
        interface_id = request.path_params["interface_id"]
        interface = self.controller.get_interface_by_id(interface_id)
        if not interface:
            raise HTTPException(404, detail="Interface not found")
        try:
            interface.set_tag_ranges(ranges, tag_type)
            self.handle_on_interface_tags(interface)
        except KytosTagError as err:
            raise HTTPException(400, detail=str(err))
        return JSONResponse("Operation Successful", status_code=200)

    @rest('v3/interfaces/{interface_id}/tag_ranges', methods=['DELETE'])
    @validate_openapi(spec)
    def delete_tag_range(self, request: Request) -> JSONResponse:
        """Set tag_range from tag_type to default value [1, 4095]"""
        interface_id = request.path_params["interface_id"]
        params = request.query_params
        tag_type = params.get("tag_type", 'vlan')
        interface = self.controller.get_interface_by_id(interface_id)
        if not interface:
            raise HTTPException(404, detail="Interface not found")
        try:
            interface.remove_tag_ranges(tag_type)
            self.handle_on_interface_tags(interface)
        except KytosTagError as err:
            raise HTTPException(400, detail=str(err))
        return JSONResponse("Operation Successful", status_code=200)

    @rest('v3/interfaces/{interface_id}/special_tags', methods=['POST'])
    @validate_openapi(spec)
    def set_special_tags(self, request: Request) -> JSONResponse:
        """Set special_tags"""
        content_type_json_or_415(request)
        content = get_json_or_400(request, self.controller.loop)
        tag_type = content.get("tag_type")
        special_tags = content["special_tags"]
        interface_id = request.path_params["interface_id"]
        interface = self.controller.get_interface_by_id(interface_id)
        if not interface:
            raise HTTPException(404, detail="Interface not found")
        try:
            interface.set_special_tags(tag_type, special_tags)
            self.handle_on_interface_tags(interface)
        except KytosTagError as err:
            raise HTTPException(400, detail=str(err))
        return JSONResponse("Operation Successful", status_code=200)

    @rest('v3/interfaces/tag_ranges', methods=['GET'])
    @validate_openapi(spec)
    def get_all_tag_ranges(self, _: Request) -> JSONResponse:
        """Get all tag_ranges, available_tags, special_tags
         and special_available_tags from interfaces"""
        result = {}
        for switch in self.controller.switches.copy().values():
            for interface in switch.interfaces.copy().values():
                result[interface.id] = {
                    "available_tags": interface.available_tags,
                    "tag_ranges": interface.tag_ranges,
                    "special_tags": interface.special_tags,
                    "special_available_tags": interface.special_available_tags
                }
        return JSONResponse(result, status_code=200)

    @rest('v3/interfaces/{interface_id}/tag_ranges', methods=['GET'])
    @validate_openapi(spec)
    def get_tag_ranges_by_intf(self, request: Request) -> JSONResponse:
        """Get tag_ranges, available_tags, special_tags
         and special_available_tags from an interface"""
        interface_id = request.path_params["interface_id"]
        interface = self.controller.get_interface_by_id(interface_id)
        if not interface:
            raise HTTPException(404, detail="Interface not found")
        result = {
            interface_id: {
                "available_tags": interface.available_tags,
                "tag_ranges": interface.tag_ranges,
                "special_tags": interface.special_tags,
                "special_available_tags": interface.special_available_tags
            }
        }
        return JSONResponse(result, status_code=200)

    # Link related methods
    @rest('v3/links')
    def get_links(self, _request: Request) -> JSONResponse:
        """Return a json with all the links in the topology.

        Links are connections between interfaces.
        """
        return JSONResponse(self._get_links_dict())

    @rest('v3/links/{link_id}/enable', methods=['POST'])
    def enable_link(self, request: Request) -> JSONResponse:
        """Administratively enable a link in the topology."""
        link_id = request.path_params["link_id"]
        try:
            with self._links_lock:
                link = self.links[link_id]
                if not link.endpoint_a.is_enabled():
                    detail = f"{link.endpoint_a.id} needs enabling."
                    raise HTTPException(409, detail=detail)
                if not link.endpoint_b.is_enabled():
                    detail = f"{link.endpoint_b.id} needs enabling."
                    raise HTTPException(409, detail=detail)
                if not link.is_enabled():
                    self.topo_controller.enable_link(link.id)
                    link.enable()
                    self.notify_link_enabled_state(link, "enabled")
        except KeyError:
            raise HTTPException(404, detail="Link not found")
        self.notify_link_status_change(
            self.links[link_id],
            reason='link enabled'
        )
        self.notify_topology_update()
        return JSONResponse("Operation successful", status_code=201)

    @rest('v3/links/{link_id}/disable', methods=['POST'])
    def disable_link(self, request: Request) -> JSONResponse:
        """Administratively disable a link in the topology."""
        link_id = request.path_params["link_id"]
        try:
            with self._links_lock:
                link = self.links[link_id]
                if link.is_enabled():
                    self.topo_controller.disable_link(link.id)
                    link.disable()
                    self.notify_link_enabled_state(link, "disabled")
        except KeyError:
            raise HTTPException(404, detail="Link not found")
        self.notify_link_status_change(
            self.links[link_id],
            reason='link disabled'
        )
        self.notify_topology_update()
        return JSONResponse("Operation successful", status_code=201)

    def notify_link_enabled_state(self, link: Link, action: str):
        """Send a KytosEvent whether a link status (enabled/disabled)
         has changed its status."""
        name = f'kytos/topology.link.{action}'
        content = {'link': link}
        event = KytosEvent(name=name, content=content)
        self.controller.buffers.app.put(event)

    @rest('v3/links/{link_id}/metadata')
    def get_link_metadata(self, request: Request) -> JSONResponse:
        """Get metadata from a link."""
        link_id = request.path_params["link_id"]
        try:
            return JSONResponse({"metadata": self.links[link_id].metadata})
        except KeyError:
            raise HTTPException(404, detail="Link not found")

    @rest('v3/links/{link_id}/metadata', methods=['POST'])
    def add_link_metadata(self, request: Request) -> JSONResponse:
        """Add metadata to a link."""
        link_id = request.path_params["link_id"]
        metadata = self._get_metadata(request)
        try:
            link = self.links[link_id]
        except KeyError:
            raise HTTPException(404, detail="Link not found")

        self.topo_controller.add_link_metadata(link_id, metadata)
        link.extend_metadata(metadata)
        self.notify_metadata_changes(link, 'added')
        self.notify_topology_update()
        return JSONResponse("Operation successful", status_code=201)

    @rest('v3/links/{link_id}/metadata/{key}', methods=['DELETE'])
    def delete_link_metadata(self, request: Request) -> JSONResponse:
        """Delete metadata from a link."""
        link_id = request.path_params["link_id"]
        key = request.path_params["key"]
        try:
            link = self.links[link_id]
        except KeyError:
            raise HTTPException(404, detail="Link not found")

        try:
            _ = link.metadata[key]
        except KeyError:
            raise HTTPException(404, detail="Metadata not found")

        self.topo_controller.delete_link_metadata_key(link.id, key)
        link.remove_metadata(key)
        self.notify_metadata_changes(link, 'removed')
        self.notify_topology_update()
        return JSONResponse("Operation successful")

    @rest('v3/links/{link_id}', methods=['DELETE'])
    def delete_link(self, request: Request) -> JSONResponse:
        """Delete a disabled link from topology.
         It won't work for link with other statuses.
        """
        link_id = request.path_params["link_id"]
        try:
            with self._links_lock:
                link = self.links[link_id]
                if link.status != EntityStatus.DISABLED:
                    raise HTTPException(409, detail="Link is not disabled.")
                if link.endpoint_a.link and link == link.endpoint_a.link:
                    switch = link.endpoint_a.switch
                    link.endpoint_a.link = None
                    link.endpoint_a.nni = False
                    self.topo_controller.upsert_switch(
                        switch.id, switch.as_dict()
                    )
                if link.endpoint_b.link and link == link.endpoint_b.link:
                    switch = link.endpoint_b.switch
                    link.endpoint_b.link = None
                    link.endpoint_b.nni = False
                    self.topo_controller.upsert_switch(
                        switch.id, switch.as_dict()
                    )
                self.topo_controller.delete_link(link_id)
                link = self.links.pop(link_id)
        except KeyError:
            raise HTTPException(404, detail="Link not found.")
        self.notify_topology_update()
        name = 'kytos/topology.link.deleted'
        event = KytosEvent(name=name, content={'link': link})
        self.controller.buffers.app.put(event)
        return JSONResponse("Operation successful")

    @rest('v3/interfaces/{intf_id}', methods=['DELETE'])
    def delete_interface(self, request: Request) -> JSONResponse:
        """Delete an interface only if it is not used."""
        intf_id = request.path_params.get("intf_id")
        intf_split = intf_id.split(":")
        switch_id = ":".join(intf_split[:-1])
        try:
            intf_port = int(intf_split[-1])
        except ValueError:
            raise HTTPException(400, detail="Invalid interface id.")
        try:
            switch = self.controller.switches[switch_id]
        except KeyError:
            raise HTTPException(404, detail="Switch not found.")
        try:
            interface = switch.interfaces[intf_port]
        except KeyError:
            raise HTTPException(404, detail="Interface not found.")

        usage = self.get_intf_usage(interface)
        if usage:
            raise HTTPException(409, detail=f"Interface could not be "
                                            f"deleted. Reason: {usage}")
        self._delete_interface(interface)
        return JSONResponse("Operation Successful", status_code=200)

    @listen_to(
        "kytos/.*.liveness.(up|down|disabled)",
        pool="dynamic_single"
    )
    def on_link_liveness(self, event) -> None:
        """Handle link liveness up|down|disabled event."""
        with self._links_lock:
            liveness_status = event.name.split(".")[-1]
            if liveness_status == "disabled":
                interfaces = event.content["interfaces"]
                self.handle_link_liveness_disabled(interfaces)
            elif liveness_status in ("up", "down"):
                link = Link(event.content["interface_a"],
                            event.content["interface_b"])
                try:
                    link = self.links[link.id]
                except KeyError:
                    log.error(f"Link id {link.id} not found, {link}")
                    return
                self.handle_link_liveness_status(self.links[link.id],
                                                 liveness_status)

    def handle_link_liveness_status(self, link, liveness_status) -> None:
        """Handle link liveness."""
        metadata = {"liveness_status": liveness_status}
        log.info(f"Link liveness {liveness_status}: {link}")
        link.extend_metadata(metadata)
        self.notify_topology_update()
        if link.status == EntityStatus.UP and liveness_status == "up":
            self.notify_link_status_change(link, reason="liveness_up")
        if link.status == EntityStatus.DOWN and liveness_status == "down":
            self.notify_link_status_change(link, reason="liveness_down")

    def get_links_from_interfaces(self, interfaces) -> dict:
        """Get links from interfaces."""
        links_found = {}
        for interface in interfaces:
            for link in list(self.links.values()):
                if any((
                    interface.id == link.endpoint_a.id,
                    interface.id == link.endpoint_b.id,
                )):
                    links_found[link.id] = link
        return links_found

    def handle_link_liveness_disabled(self, interfaces) -> None:
        """Handle link liveness disabled."""
        log.info(f"Link liveness disabled interfaces: {interfaces}")

        key = "liveness_status"
        links = self.get_links_from_interfaces(interfaces)
        for link in links.values():
            link.remove_metadata(key)
        self.notify_topology_update()
        for link in links.values():
            self.notify_link_status_change(link, reason="liveness_disabled")

    @listen_to("kytos/core.interface_tags")
    def on_interface_tags(self, event):
        """Handle on_interface_tags."""
        interface = event.content['interface']
        with self._intfs_lock[interface.id]:
            if (
                interface.id in self._intfs_tags_updated_at
                and self._intfs_tags_updated_at[interface.id] > event.timestamp
            ):
                return
            self._intfs_tags_updated_at[interface.id] = event.timestamp
            self.handle_on_interface_tags(interface)

    def handle_on_interface_tags(self, interface):
        """Update interface details"""
        intf_id = interface.id
        self.topo_controller.upsert_interface_details(
            intf_id, interface.available_tags, interface.tag_ranges,
            interface.special_available_tags,
            interface.special_tags
        )

    @listen_to('.*.switch.(new|reconnected)')
    def on_new_switch(self, event):
        """Create a new Device on the Topology.

        Handle the event of a new created switch and update the topology with
        this new device. Also notify if the switch is enabled.
        """
        self.handle_new_switch(event)

    def handle_new_switch(self, event):
        """Create a new Device on the Topology."""
        switch = event.content['switch']
        switch.activate()
        self.topo_controller.upsert_switch(switch.id, switch.as_dict())
        log.debug('Switch %s added to the Topology.', switch.id)
        self.notify_topology_update()
        if switch.is_enabled():
            self.notify_switch_enabled(switch.id)

    @listen_to('.*.connection.lost')
    def on_connection_lost(self, event):
        """Remove a Device from the topology.

        Remove the disconnected Device and every link that has one of its
        interfaces.
        """
        self.handle_connection_lost(event)

    def handle_connection_lost(self, event):
        """Remove a Device from the topology."""
        switch = event.content['source'].switch
        if switch:
            switch.deactivate()
            log.debug('Switch %s removed from the Topology.', switch.id)
            self.notify_topology_update()

    def handle_interfaces_created(self, event):
        """Update the topology based on the interfaces created."""
        interfaces = event.content["interfaces"]
        if not interfaces:
            return
        switch = interfaces[0].switch
        self.topo_controller.upsert_switch(switch.id, switch.as_dict())
        name = "kytos/topology.switch.interface.created"
        for interface in interfaces:
            event = KytosEvent(name=name, content={'interface': interface})
            self.controller.buffers.app.put(event)

    def handle_interface_created(self, event):
        """Update the topology based on an interface created event.

        It's handled as a link_up in case a switch send a
        created event again and it can be belong to a link.
        """
        interface = event.content['interface']
        if not interface.is_active():
            self.handle_interface_link_down(interface, event)
        else:
            self.handle_interface_link_up(interface, event)

    @listen_to('.*.topology.switch.interface.created')
    def on_interface_created(self, event):
        """Handle individual interface create event.

        It's handled as a link_up in case a switch send a
        created event it can belong to an existign link.
        """
        self.handle_interface_created(event)

    @listen_to('.*.switch.interfaces.created')
    def on_interfaces_created(self, event):
        """Update the topology based on a list of created interfaces."""
        self.handle_interfaces_created(event)

    def handle_interface_down(self, event):
        """Update the topology based on a Port Modify event.

        The event notifies that an interface was changed to 'down'.
        """
        interface = event.content['interface']
        with self._intfs_lock[interface.id]:
            if (
                interface.id in self._intfs_updated_at
                and self._intfs_updated_at[interface.id] > event.timestamp
            ):
                return
            self._intfs_updated_at[interface.id] = event.timestamp
            interface.deactivate()
        self.handle_interface_link_down(interface, event)

    @listen_to('.*.switch.interface.deleted')
    def on_interface_deleted(self, event):
        """Update the topology based on a Port Delete event."""
        self.handle_interface_deleted(event)

    def handle_interface_deleted(self, event):
        """Update the topology based on a Port Delete event."""
        self.handle_interface_down(event)
        interface = event.content['interface']
        usage = self.get_intf_usage(interface)
        if usage:
            log.info(f"Interface {interface.id} could not be safely removed."
                     f" Reason: {usage}")
        else:
            self._delete_interface(interface)

    def get_intf_usage(self, interface: Interface) -> Optional[str]:
        """Determines how an interface is used explained in a string,
        returns None if unused."""
        if interface.is_enabled() or interface.is_active():
            return "It is enabled or active."

        link = self._get_link_from_interface(interface)
        if link:
            return f"It has a link, {link.id}."

        flow_id = self.get_flow_id_by_intf(interface)
        if flow_id:
            return f"There is a flow installed, {flow_id}."

        return None

    def get_flow_id_by_intf(self, interface: Interface) -> str:
        """Return flow_id from first found flow used by interface."""
        flows = self.get_flows_by_switch(interface.switch.id)
        port_n = int(interface.id.split(":")[-1])
        for flow in flows:
            in_port = flow["flow"].get("match", {}).get("in_port")
            if in_port == port_n:
                return flow["flow_id"]

            instructions = flow["flow"].get("instructions", [])
            for instruction in instructions:
                if instruction["instruction_type"] == "apply_actions":
                    actions = instruction["actions"]
                    for action in actions:
                        if (action["action_type"] == "output"
                                and action.get("port") == port_n):
                            return flow["flow_id"]

            actions = flow["flow"].get("actions", [])
            for action in actions:
                if (action["action_type"] == "output"
                        and action.get("port") == port_n):
                    return flow["flow_id"]
        return None

    def _delete_interface(self, interface: Interface):
        """Delete any trace of an interface. Only use this method when
         it was confirmed that the interface is not used."""
        switch: Switch = interface.switch
        switch.remove_interface(interface)
        self.topo_controller.upsert_switch(switch.id, switch.as_dict())
        self.topo_controller.delete_interface_from_details(interface.id)

    @listen_to('.*.switch.interface.link_up')
    def on_interface_link_up(self, event):
        """Update the topology based on a Port Modify event.

        The event notifies that an interface's link was changed to 'up'.
        """
        interface = event.content['interface']
        self.handle_interface_link_up(interface, event)

    def handle_interface_link_up(self, interface, event):
        """Update the topology based on a Port Modify event."""
        with self._intfs_lock[interface.id]:
            if (
                interface.id in self._intfs_updated_at
                and self._intfs_updated_at[interface.id] > event.timestamp
            ):
                return
            self._intfs_updated_at[interface.id] = event.timestamp
            self.handle_link_up(interface)

    @tenacity.retry(
        stop=stop_after_attempt(3),
        wait=wait_combine(wait_fixed(3), wait_random(min=2, max=7)),
        before_sleep=before_sleep,
        retry=retry_if_exception_type(httpx.RequestError),
    )
    def get_flows_by_switch(self, dpid: str) -> list:
        """Get installed flows by switch from flow_manager."""
        endpoint = settings.FLOW_MANAGER_URL +\
            f'/stored_flows?state=installed&dpid={dpid}'
        res = httpx.get(endpoint)
        if res.is_server_error or res.status_code in (404, 400):
            raise httpx.RequestError(res.text)
        return res.json().get(dpid, [])

    def link_status_hook_link_up_timer(
        self,
        link: Link
    ) -> Optional[EntityStatus]:
        """Link status hook link up timer."""
        tnow = time.time()
        if link.id not in self.link_status_change:
            return None
        link_status_info = self.link_status_change[link.id]
        tdelta = tnow - link_status_info['last_status_change']
        if tdelta < self.link_up_timer:
            return EntityStatus.DOWN
        return None

    def notify_link_up_if_status(self, link: Link, reason="link up") -> None:
        """Tries to notify link up and topology changes based on its status

        Currently, it needs to wait up to a timer."""
        time.sleep(self.link_up_timer)
        if link.status != EntityStatus.UP:
            return
        with self._links_lock:
            status_change_info = self.link_status_change[link.id]
            notified_at = status_change_info.get("notified_up_at")
            if (
                notified_at
                and (now() - notified_at.replace(tzinfo=timezone.utc)).seconds
                < self.link_up_timer
            ):
                return
            status_change_info["notified_up_at"] = now()
            self.notify_topology_update()
            self.notify_link_status_change(link, reason)

    def handle_link_up(self, interface: Interface):
        """Handle link up for an interface."""
        with self._links_lock:
            link = self._get_link_from_interface(interface)
            if not link:
                self.notify_topology_update()
                return
            other_interface = (
                link.endpoint_b if link.endpoint_a == interface
                else link.endpoint_a
            )
            if (
                link.id not in self.link_status_change or
                not link.is_active()
            ):
                status_change_info = self.link_status_change[link.id]
                status_change_info['last_status_change'] = time.time()
                link.activate()
            self.notify_topology_update()
            link_dependencies: list[GenericEntity] = [
                other_interface.switch,
                interface.switch,
                other_interface,
                interface,
            ]
            for dependency in link_dependencies:
                if not dependency.is_active():
                    log.info(
                        f"{link} dependency {dependency} was not active yet."
                    )
                    return
            event = KytosEvent(
                name="kytos/topology.notify_link_up_if_status",
                content={"reason": "link up", "link": link}
            )
            self.controller.buffers.app.put(event)

    @listen_to('.*.switch.interface.link_down')
    def on_interface_link_down(self, event):
        """Update the topology based on a Port Modify event.

        The event notifies that an interface's link was changed to 'down'.
        """
        interface = event.content['interface']
        self.handle_interface_link_down(interface, event)

    def handle_interface_link_down(self, interface, event):
        """Update the topology based on an interface."""
        with self._intfs_lock[interface.id]:
            if (
                interface.id in self._intfs_updated_at
                and self._intfs_updated_at[interface.id] > event.timestamp
            ):
                return
            self._intfs_updated_at[interface.id] = event.timestamp
            self.handle_link_down(interface)

    def handle_link_down(self, interface):
        """Notify a link is down."""
        with self._links_lock:
            link = self._get_link_from_interface(interface)
            if link:
                link.deactivate()
                self.notify_link_status_change(link, reason="link down")
            self.notify_topology_update()

    @listen_to('.*.interface.is.nni')
    def on_add_links(self, event):
        """Update the topology with links related to the NNI interfaces."""
        self.add_links(event)

    def add_links(self, event):
        """Update the topology with links related to the NNI interfaces."""
        interface_a = event.content['interface_a']
        interface_b = event.content['interface_b']

        try:
            with self._links_lock:
                link, created = self._get_link_or_create(interface_a,
                                                         interface_b)
                interface_a.update_link(link)
                interface_b.update_link(link)

                link.endpoint_a = interface_a
                link.endpoint_b = interface_b

                interface_a.nni = True
                interface_b.nni = True

        except KytosLinkCreationError as err:
            log.error(f'Error creating link: {err}.')
            return

        if not created:
            return

        self.notify_topology_update()
        if not link.is_active():
            return
        status_change_info = self.link_status_change[link.id]
        status_change_info['last_status_change'] = time.time()

        self.topo_controller.upsert_link(link.id, link.as_dict())
        self.notify_link_up_if_status(link, "link up")

    @listen_to('.*.of_lldp.network_status.updated')
    def on_lldp_status_updated(self, event):
        """Handle of_lldp.network_status.updated from of_lldp."""
        self.handle_lldp_status_updated(event)

    @listen_to(".*.topo_controller.upsert_switch")
    def on_topo_controller_upsert_switch(self, event) -> None:
        """Listen to topo_controller_upsert_switch."""
        self.handle_topo_controller_upsert_switch(event.content["switch"])

    def handle_topo_controller_upsert_switch(self, switch) -> Optional[dict]:
        """Handle topo_controller_upsert_switch."""
        return self.topo_controller.upsert_switch(switch.id, switch.as_dict())

    def handle_lldp_status_updated(self, event) -> None:
        """Handle .*.network_status.updated events from of_lldp."""
        content = event.content
        interface_ids = content["interface_ids"]
        switches = set()
        for interface_id in interface_ids:
            dpid = ":".join(interface_id.split(":")[:-1])
            switch = self.controller.get_switch_by_dpid(dpid)
            if switch:
                switches.add(switch)

        name = "kytos/topology.topo_controller.upsert_switch"
        for switch in switches:
            event = KytosEvent(name=name, content={"switch": switch})
            self.controller.buffers.app.put(event)

    def notify_switch_enabled(self, dpid):
        """Send an event to notify that a switch is enabled."""
        name = 'kytos/topology.switch.enabled'
        event = KytosEvent(name=name, content={'dpid': dpid})
        self.controller.buffers.app.put(event)

    def notify_switch_links_status(self, switch, reason):
        """Send an event to notify the status of a link in a switch"""
        with self._links_lock:
            for link in self.links.values():
                if switch in (link.endpoint_a.switch, link.endpoint_b.switch):
                    if reason == "link enabled":
                        name = 'kytos/topology.notify_link_up_if_status'
                        content = {'reason': reason, "link": link}
                        event = KytosEvent(name=name, content=content)
                        self.controller.buffers.app.put(event)
                    else:
                        self.notify_link_status_change(link, reason)

    def notify_switch_disabled(self, dpid):
        """Send an event to notify that a switch is disabled."""
        name = 'kytos/topology.switch.disabled'
        event = KytosEvent(name=name, content={'dpid': dpid})
        self.controller.buffers.app.put(event)

    def notify_topology_update(self):
        """Send an event to notify about updates on the topology."""
        name = 'kytos/topology.updated'
        event = KytosEvent(name=name, content={'topology':
                                               self._get_topology()})
        self.controller.buffers.app.put(event)

    def notify_interface_link_status(self, interface, reason):
        """Send an event to notify the status of a link from
        an interface."""
        link = self._get_link_from_interface(interface)
        if link:
            if reason == "link enabled":
                name = 'kytos/topology.notify_link_up_if_status'
                content = {'reason': reason, "link": link}
                event = KytosEvent(name=name, content=content)
                self.controller.buffers.app.put(event)
            else:
                self.notify_link_status_change(link, reason)

    def notify_link_status_change(self, link: Link, reason='not given'):
        """Send an event to notify (up/down) from a status change on
         a link."""
        link_id = link.id
        with self.link_status_lock:
            if (
                (not link.status_reason and link.status == EntityStatus.UP)
                and link_id not in self.link_up
            ):
                log.info(f"{link} changed status {link.status}, "
                         f"reason: {reason}")
                self.link_up.add(link_id)
                event = KytosEvent(
                    name='kytos/topology.link_up',
                    content={
                        'link': link,
                        'reason': reason
                    },
                )
            elif (
                (link.status_reason or link.status != EntityStatus.UP)
                and link_id in self.link_up
            ):
                log.info(f"{link} changed status {link.status}, "
                         f"reason: {reason}")
                self.link_up.remove(link_id)
                event = KytosEvent(
                    name='kytos/topology.link_down',
                    content={
                        'link': link,
                        'reason': reason
                    },
                )
            else:
                return
        self.controller.buffers.app.put(event)

    def notify_metadata_changes(self, obj, action):
        """Send an event to notify about metadata changes."""
        if isinstance(obj, Switch):
            entity = 'switch'
            entities = 'switches'
        elif isinstance(obj, Interface):
            entity = 'interface'
            entities = 'interfaces'
        elif isinstance(obj, Link):
            entity = 'link'
            entities = 'links'
        else:
            raise ValueError(
                'Invalid object, supported: Switch, Interface, Link'
            )

        name = f'kytos/topology.{entities}.metadata.{action}'
        content = {entity: obj, 'metadata': obj.metadata.copy()}
        event = KytosEvent(name=name, content=content)
        self.controller.buffers.app.put(event)
        log.debug(f'Metadata from {obj.id} was {action}.')

    @listen_to('kytos/topology.notify_link_up_if_status')
    def on_notify_link_up_if_status(self, event):
        """Tries to notify link up and topology changes"""
        link = event.content["link"]
        reason = event.content["reason"]
        self.notify_link_up_if_status(link, reason)

    @listen_to('.*.switch.port.created')
    def on_notify_port_created(self, event):
        """Notify when a port is created."""
        self.notify_port_created(event)

    def notify_port_created(self, event):
        """Notify when a port is created."""
        name = 'kytos/topology.port.created'
        event = KytosEvent(name=name, content=event.content)
        self.controller.buffers.app.put(event)

    @staticmethod
    def load_interfaces_tags_values(switch: Switch,
                                    interfaces_details: List[dict]) -> None:
        """Load interfaces available tags (vlans)."""
        if not interfaces_details:
            return
        for interface_details in interfaces_details:
            available_tags = interface_details['available_tags']
            if not available_tags:
                continue
            log.debug(f"Interface id {interface_details['id']} loading "
                      f"{len(available_tags)} "
                      "available tags")
            port_number = int(interface_details["id"].split(":")[-1])
            interface = switch.interfaces[port_number]
            interface.set_available_tags_tag_ranges(
                available_tags,
                interface_details['tag_ranges'],
                interface_details['special_available_tags'],
                interface_details['special_tags'],
            )

    @listen_to(
        'topology.interruption.(start|end)',
        pool="dynamic_single"
    )
    def on_interruption(self, event: KytosEvent):
        """Deals with service interruptions."""
        with self._links_lock:
            _, _, interrupt_type = event.name.rpartition(".")
            if interrupt_type == "start":
                self.handle_interruption_start(event)
            elif interrupt_type == "end":
                self.handle_interruption_end(event)

    def handle_interruption_start(self, event: KytosEvent):

This code seems to be duplicated in your project.

        """Deals with the start of service interruption."""
        interrupt_type = event.content['type']
        switches = event.content.get('switches', [])
        interfaces = event.content.get('interfaces', [])
        links = event.content.get('links', [])
        log.info(
            'Received interruption start of type \'%s\' '
            'affecting switches %s, interfaces %s, links %s',
            interrupt_type,
            switches,
            interfaces,
            links
        )
        # for switch_id in switches:
        #     pass
        # for interface_id in interfaces:
        #     pass
        for link_id in links:
            link = self.links.get(link_id)
            if link is None:
                log.error(
                    "Invalid link id '%s' for interruption of type '%s;",
                    link_id,
                    interrupt_type
                )
            else:
                self.notify_link_status_change(link, interrupt_type)
        self.notify_topology_update()

    def handle_interruption_end(self, event: KytosEvent):

This code seems to be duplicated in your project.

        """Deals with the end of service interruption."""
        interrupt_type = event.content['type']
        switches = event.content.get('switches', [])
        interfaces = event.content.get('interfaces', [])
        links = event.content.get('links', [])
        log.info(
            'Received interruption end of type \'%s\' '
            'affecting switches %s, interfaces %s, links %s',
            interrupt_type,
            switches,
            interfaces,
            links
        )
        # for switch_id in switches:
        #     pass
        # for interface_id in interfaces:
        #     pass
        for link_id in links:
            link = self.links.get(link_id)
            if link is None:
                log.error(
                    "Invalid link id '%s' for interruption of type '%s;",
                    link_id,
                    interrupt_type
                )
            else:
                self.notify_link_status_change(link, interrupt_type)
        self.notify_topology_update()

    def get_latest_topology(self):
        """Get the latest topology."""
        with self._links_lock:
            return self._get_topology()