main.py

# pylint: disable=protected-access
"""Main module of kytos/mef_eline Kytos Network Application.

NApp to provision circuits from user request.
"""
from threading import Lock

from flask import jsonify, request
from werkzeug.exceptions import (BadRequest, Conflict, Forbidden,
                                 MethodNotAllowed, NotFound,
                                 UnsupportedMediaType)

from kytos.core import KytosNApp, log, rest
from kytos.core.events import KytosEvent
from kytos.core.helpers import listen_to
from kytos.core.interface import TAG, UNI
from kytos.core.link import Link
from napps.kytos.mef_eline import settings
from napps.kytos.mef_eline.exceptions import InvalidPath
from napps.kytos.mef_eline.models import EVC, DynamicPathManager, Path
from napps.kytos.mef_eline.scheduler import CircuitSchedule, Scheduler
from napps.kytos.mef_eline.storehouse import StoreHouse
from napps.kytos.mef_eline.utils import emit_event, load_spec, validate


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

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

    spec = load_spec()

    def setup(self):
        """Replace the '__init__' method for the KytosNApp subclass.

        The setup method is automatically called by the controller when your
        application is loaded.

        So, if you have any setup routine, insert it here.
        """
        # object used to scheduler circuit events
        self.sched = Scheduler()

        # object to save and load circuits
        self.storehouse = StoreHouse(self.controller)

        # set the controller that will manager the dynamic paths
        DynamicPathManager.set_controller(self.controller)

        # dictionary of EVCs created. It acts as a circuit buffer.
        # Every create/update/delete must be synced to storehouse.
        self.circuits = {}

        self._lock = Lock()

        self.execute_as_loop(settings.DEPLOY_EVCS_INTERVAL)
        self.execution_rounds = 0
        self.load_all_evcs()

    def execute(self):
        """Execute once when the napp is running."""
        if self._lock.locked():
            return
        log.debug("Starting consistency routine")
        with self._lock:
            self.execute_consistency()
        log.debug("Finished consistency routine")

    def execute_consistency(self):
        """Execute consistency routine."""
        self.execution_rounds += 1
        stored_circuits = self.storehouse.get_data().copy()
        for circuit in tuple(self.circuits.values()):
            stored_circuits.pop(circuit.id, None)
            if (
                circuit.is_enabled()
                and not circuit.is_active()
                and not circuit.lock.locked()
            ):
                if circuit.check_traces():
                    log.info(f"{circuit} enabled but inactive - activating")
                    with circuit.lock:
                        circuit.activate()
                        circuit.sync()
                else:
                    if self.execution_rounds > settings.WAIT_FOR_OLD_PATH:
                        log.info(f"{circuit} enabled but inactive - redeploy")
                        with circuit.lock:
                            circuit.deploy()
        for circuit_id in stored_circuits:
            log.info(f"EVC found in storehouse but unloaded {circuit_id}")
            self._load_evc(stored_circuits[circuit_id])

    def shutdown(self):
        """Execute when your napp is unloaded.

        If you have some cleanup procedure, insert it here.
        """

    @rest("/v2/evc/", methods=["GET"])
    def list_circuits(self):
        """Endpoint to return circuits stored.

        If archived is set to True return all circuits, else only the ones
        not archived.
        """
        log.debug("list_circuits /v2/evc")
        archived = request.args.get("archived", False)
        circuits = self.storehouse.get_data()
        if not circuits:
            return jsonify({}), 200
        if archived:
            return jsonify(circuits), 200
        return (
            jsonify(
                {
                    circuit_id: circuit
                    for circuit_id, circuit in circuits.items()
                    if not circuit.get("archived", False)
                }
            ),
            200,
        )

    @rest("/v2/evc/<circuit_id>", methods=["GET"])
    def get_circuit(self, circuit_id):
        """Endpoint to return a circuit based on id."""
        log.debug("get_circuit /v2/evc/%s", circuit_id)
        circuits = self.storehouse.get_data()

        try:
            result = circuits[circuit_id]
        except KeyError:
            result = f"circuit_id {circuit_id} not found"
            log.debug("get_circuit result %s %s", result, 404)
            raise NotFound(result) from KeyError
        status = 200
        log.debug("get_circuit result %s %s", result, status)
        return jsonify(result), status

    @rest("/v2/evc/", methods=["POST"])
    @validate(spec)
    def create_circuit(self, data):
        """Try to create a new circuit.

        Firstly, for EVPL: E-Line NApp verifies if UNI_A's requested C-VID and
        UNI_Z's requested C-VID are available from the interfaces' pools. This
        is checked when creating the UNI object.

        Then, E-Line NApp requests a primary and a backup path to the
        Pathfinder NApp using the attributes primary_links and backup_links
        submitted via REST

        # For each link composing paths in #3:
        #  - E-Line NApp requests a S-VID available from the link VLAN pool.
        #  - Using the S-VID obtained, generate abstract flow entries to be
        #    sent to FlowManager

        Push abstract flow entries to FlowManager and FlowManager pushes
        OpenFlow entries to datapaths

        E-Line NApp generates an event to notify all Kytos NApps of a new EVC
        creation

        Finnaly, notify user of the status of its request.
        """
        # Try to create the circuit object
        log.debug("create_circuit /v2/evc/")

        try:
            evc = self._evc_from_dict(data)
        except ValueError as exception:
            log.debug("create_circuit result %s %s", exception, 400)
            raise BadRequest(str(exception)) from BadRequest

        if evc.primary_path:
            try:
                evc.primary_path.is_valid(
                    evc.uni_a.interface.switch,
                    evc.uni_z.interface.switch,
                    bool(evc.circuit_scheduler),
                )
            except InvalidPath as exception:
                raise BadRequest(
                    f"primary_path is not valid: {exception}"
                ) from exception
        if evc.backup_path:
            try:
                evc.backup_path.is_valid(
                    evc.uni_a.interface.switch,
                    evc.uni_z.interface.switch,
                    bool(evc.circuit_scheduler),
                )
            except InvalidPath as exception:
                raise BadRequest(
                    f"backup_path is not valid: {exception}"
                ) from exception

        # verify duplicated evc
        if self._is_duplicated_evc(evc):
            result = "The EVC already exists."
            log.debug("create_circuit result %s %s", result, 409)
            raise Conflict(result)

        if (
            not evc.primary_path
            and evc.dynamic_backup_path is False
            and evc.uni_a.interface.switch != evc.uni_z.interface.switch
        ):
            result = "The EVC must have a primary path or allow dynamic paths."
            log.debug("create_circuit result %s %s", result, 400)
            raise BadRequest(result)

        # store circuit in dictionary
        self.circuits[evc.id] = evc

        # save circuit
        self.storehouse.save_evc(evc)

        # Schedule the circuit deploy
        self.sched.add(evc)

        # Circuit has no schedule, deploy now
        if not evc.circuit_scheduler:
            with evc.lock:
                evc.deploy()

        # Notify users
        event = KytosEvent(
            name="kytos.mef_eline.created", content=evc.as_dict()
        )
        self.controller.buffers.app.put(event)

        result = {"circuit_id": evc.id}
        status = 201
        log.debug("create_circuit result %s %s", result, status)
        emit_event(self.controller, "created", evc_id=evc.id)
        return jsonify(result), status

    @rest("/v2/evc/<circuit_id>", methods=["PATCH"])
    def update(self, circuit_id):
        """Update a circuit based on payload.

        The EVC required attributes (name, uni_a, uni_z) can't be updated.
        """
        log.debug("update /v2/evc/%s", circuit_id)
        try:
            evc = self.circuits[circuit_id]
        except KeyError:
            result = f"circuit_id {circuit_id} not found"
            log.debug("update result %s %s", result, 404)
            raise NotFound(result) from NotFound

        if evc.archived:
            result = "Can't update archived EVC"
            log.debug("update result %s %s", result, 405)
            raise MethodNotAllowed(["GET"], result)

        try:
            data = request.get_json()
        except BadRequest:
            result = "The request body is not a well-formed JSON."
            log.debug("update result %s %s", result, 400)
            raise BadRequest(result) from BadRequest
        if data is None:
            result = "The request body mimetype is not application/json."
            log.debug("update result %s %s", result, 415)
            raise UnsupportedMediaType(result) from UnsupportedMediaType

        try:
            enable, redeploy = evc.update(
                **self._evc_dict_with_instances(data)
            )
        except ValueError as exception:
            log.error(exception)
            log.debug("update result %s %s", exception, 400)
            raise BadRequest(str(exception)) from BadRequest

        if evc.is_active():
            if enable is False:  # disable if active
                with evc.lock:
                    evc.remove()
            elif redeploy is not None:  # redeploy if active
                with evc.lock:
                    evc.remove()
                    evc.deploy()
        else:
            if enable is True:  # enable if inactive
                with evc.lock:
                    evc.deploy()
        result = {evc.id: evc.as_dict()}
        status = 200

        log.debug("update result %s %s", result, status)
        emit_event(self.controller, "updated", evc_id=evc.id, data=data)
        return jsonify(result), status

    @rest("/v2/evc/<circuit_id>", methods=["DELETE"])
    def delete_circuit(self, circuit_id):
        """Remove a circuit.

        First, the flows are removed from the switches, and then the EVC is
        disabled.
        """
        log.debug("delete_circuit /v2/evc/%s", circuit_id)
        try:
            evc = self.circuits[circuit_id]
        except KeyError:
            result = f"circuit_id {circuit_id} not found"
            log.debug("delete_circuit result %s %s", result, 404)
            raise NotFound(result) from NotFound

        if evc.archived:
            result = f"Circuit {circuit_id} already removed"
            log.debug("delete_circuit result %s %s", result, 404)
            raise NotFound(result) from NotFound

        log.info("Removing %s", evc)
        with evc.lock:
            evc.remove_current_flows()
            evc.deactivate()
            evc.disable()
            self.sched.remove(evc)
            evc.archive()
            evc.sync()
        log.info("EVC removed. %s", evc)
        result = {"response": f"Circuit {circuit_id} removed"}
        status = 200

        log.debug("delete_circuit result %s %s", result, status)
        emit_event(self.controller, "deleted", evc_id=evc.id)
        return jsonify(result), status

    @rest("v2/evc/<circuit_id>/metadata", methods=["GET"])
    def get_metadata(self, circuit_id):
        """Get metadata from an EVC."""
        try:
            return (
                jsonify({"metadata": self.circuits[circuit_id].metadata}),
                200,
            )
        except KeyError as error:
            raise NotFound(f"circuit_id {circuit_id} not found.") from error

    @rest("v2/evc/<circuit_id>/metadata", methods=["POST"])
    def add_metadata(self, circuit_id):
        """Add metadata to an EVC."""
        try:
            metadata = request.get_json()
            content_type = request.content_type
        except BadRequest as error:
            result = "The request body is not a well-formed JSON."
            raise BadRequest(result) from error
        if content_type is None:
            result = "The request body is empty."
            raise BadRequest(result)
        if metadata is None:
            if content_type != "application/json":
                result = (
                    "The content type must be application/json "
                    f"(received {content_type})."
                )
            else:
                result = "Metadata is empty."
            raise UnsupportedMediaType(result)

        try:
            evc = self.circuits[circuit_id]
        except KeyError as error:
            raise NotFound(f"circuit_id {circuit_id} not found.") from error

        evc.extend_metadata(metadata)
        evc.sync()
        return jsonify("Operation successful"), 201

    @rest("v2/evc/<circuit_id>/metadata/<key>", methods=["DELETE"])
    def delete_metadata(self, circuit_id, key):
        """Delete metadata from an EVC."""
        try:
            evc = self.circuits[circuit_id]
        except KeyError as error:
            raise NotFound(f"circuit_id {circuit_id} not found.") from error

        evc.remove_metadata(key)
        evc.sync()
        return jsonify("Operation successful"), 200

    @rest("/v2/evc/<circuit_id>/redeploy", methods=["PATCH"])
    def redeploy(self, circuit_id):
        """Endpoint to force the redeployment of an EVC."""
        log.debug("redeploy /v2/evc/%s/redeploy", circuit_id)
        try:
            evc = self.circuits[circuit_id]
        except KeyError:
            result = f"circuit_id {circuit_id} not found"
            raise NotFound(result) from NotFound
        if evc.is_enabled():
            with evc.lock:
                evc.remove_current_flows()
                evc.deploy()
            result = {"response": f"Circuit {circuit_id} redeploy received."}
            status = 202
        else:
            result = {"response": f"Circuit {circuit_id} is disabled."}
            status = 409

        return jsonify(result), status

    @rest("/v2/evc/schedule", methods=["GET"])
    def list_schedules(self):
        """Endpoint to return all schedules stored for all circuits.

        Return a JSON with the following template:
        [{"schedule_id": <schedule_id>,
         "circuit_id": <circuit_id>,
         "schedule": <schedule object>}]
        """
        log.debug("list_schedules /v2/evc/schedule")
        circuits = self.storehouse.get_data().values()
        if not circuits:
            result = {}
            status = 200
            return jsonify(result), status

        result = []
        status = 200
        for circuit in circuits:
            circuit_scheduler = circuit.get("circuit_scheduler")
            if circuit_scheduler:
                for scheduler in circuit_scheduler:
                    value = {
                        "schedule_id": scheduler.get("id"),
                        "circuit_id": circuit.get("id"),
                        "schedule": scheduler,
                    }
                    result.append(value)

        log.debug("list_schedules result %s %s", result, status)
        return jsonify(result), status

    @rest("/v2/evc/schedule/", methods=["POST"])
    def create_schedule(self):
        """
        Create a new schedule for a given circuit.

        This service do no check if there are conflicts with another schedule.
        Payload example:
            {
              "circuit_id":"aa:bb:cc",
              "schedule": {
                "date": "2019-08-07T14:52:10.967Z",
                "interval": "string",
                "frequency": "1 * * * *",
                "action": "create"
              }
            }
        """
        log.debug("create_schedule /v2/evc/schedule/")

        json_data = self._json_from_request("create_schedule")
        try:
            circuit_id = json_data["circuit_id"]
        except TypeError:
            result = "The payload should have a dictionary."
            log.debug("create_schedule result %s %s", result, 400)
            raise BadRequest(result) from BadRequest
        except KeyError:
            result = "Missing circuit_id."
            log.debug("create_schedule result %s %s", result, 400)
            raise BadRequest(result) from BadRequest

        try:
            schedule_data = json_data["schedule"]
        except KeyError:
            result = "Missing schedule data."
            log.debug("create_schedule result %s %s", result, 400)
            raise BadRequest(result) from BadRequest

        # Get EVC from circuits buffer
        circuits = self._get_circuits_buffer()

        # get the circuit
        evc = circuits.get(circuit_id)

        # get the circuit
        if not evc:
            result = f"circuit_id {circuit_id} not found"
            log.debug("create_schedule result %s %s", result, 404)
            raise NotFound(result) from NotFound
        # Can not modify circuits deleted and archived
        if evc.archived:
            result = f"Circuit {circuit_id} is archived. Update is forbidden."
            log.debug("create_schedule result %s %s", result, 403)
            raise Forbidden(result) from Forbidden

        # new schedule from dict
        new_schedule = CircuitSchedule.from_dict(schedule_data)

        # If there is no schedule, create the list
        if not evc.circuit_scheduler:
            evc.circuit_scheduler = []

        # Add the new schedule
        evc.circuit_scheduler.append(new_schedule)

        # Add schedule job
        self.sched.add_circuit_job(evc, new_schedule)

        # save circuit to storehouse
        evc.sync()

        result = new_schedule.as_dict()
        status = 201

        log.debug("create_schedule result %s %s", result, status)
        return jsonify(result), status

    @rest("/v2/evc/schedule/<schedule_id>", methods=["PATCH"])
    def update_schedule(self, schedule_id):
        """Update a schedule.

        Change all attributes from the given schedule from a EVC circuit.
        The schedule ID is preserved as default.
        Payload example:
            {
              "date": "2019-08-07T14:52:10.967Z",
              "interval": "string",
              "frequency": "1 * * *",
              "action": "create"
            }
        """
        log.debug("update_schedule /v2/evc/schedule/%s", schedule_id)

        # Try to find a circuit schedule
        evc, found_schedule = self._find_evc_by_schedule_id(schedule_id)

        # Can not modify circuits deleted and archived
        if not found_schedule:
            result = f"schedule_id {schedule_id} not found"
            log.debug("update_schedule result %s %s", result, 404)
            raise NotFound(result) from NotFound
        if evc.archived:
            result = f"Circuit {evc.id} is archived. Update is forbidden."
            log.debug("update_schedule result %s %s", result, 403)
            raise Forbidden(result) from Forbidden

        data = self._json_from_request("update_schedule")

        new_schedule = CircuitSchedule.from_dict(data)
        new_schedule.id = found_schedule.id
        # Remove the old schedule
        evc.circuit_scheduler.remove(found_schedule)
        # Append the modified schedule
        evc.circuit_scheduler.append(new_schedule)

        # Cancel all schedule jobs
        self.sched.cancel_job(found_schedule.id)
        # Add the new circuit schedule
        self.sched.add_circuit_job(evc, new_schedule)
        # Save EVC to the storehouse
        evc.sync()

        result = new_schedule.as_dict()
        status = 200

        log.debug("update_schedule result %s %s", result, status)
        return jsonify(result), status

    @rest("/v2/evc/schedule/<schedule_id>", methods=["DELETE"])
    def delete_schedule(self, schedule_id):
        """Remove a circuit schedule.

        Remove the Schedule from EVC.
        Remove the Schedule from cron job.
        Save the EVC to the Storehouse.
        """
        log.debug("delete_schedule /v2/evc/schedule/%s", schedule_id)
        evc, found_schedule = self._find_evc_by_schedule_id(schedule_id)

        # Can not modify circuits deleted and archived
        if not found_schedule:
            result = f"schedule_id {schedule_id} not found"
            log.debug("delete_schedule result %s %s", result, 404)
            raise NotFound(result)

        if evc.archived:
            result = f"Circuit {evc.id} is archived. Update is forbidden."
            log.debug("delete_schedule result %s %s", result, 403)
            raise Forbidden(result)

        # Remove the old schedule
        evc.circuit_scheduler.remove(found_schedule)

        # Cancel all schedule jobs
        self.sched.cancel_job(found_schedule.id)
        # Save EVC to the storehouse
        evc.sync()

        result = "Schedule removed"
        status = 200

        log.debug("delete_schedule result %s %s", result, status)
        return jsonify(result), status

    def _is_duplicated_evc(self, evc):
        """Verify if the circuit given is duplicated with the stored evcs.

        Args:
            evc (EVC): circuit to be analysed.

        Returns:
            boolean: True if the circuit is duplicated, otherwise False.

        """
        for circuit in tuple(self.circuits.values()):
            if not circuit.archived and circuit.shares_uni(evc):
                return True
        return False

    @listen_to("kytos/topology.link_up")
    def on_link_up(self, event):
        """Change circuit when link is up or end_maintenance."""
        self.handle_link_up(event)

    def handle_link_up(self, event):
        """Change circuit when link is up or end_maintenance."""
        log.debug("Event handle_link_up %s", event)
        for evc in self.circuits.values():
            if evc.is_enabled() and not evc.archived:
                with evc.lock:
                    evc.handle_link_up(event.content["link"])

    @listen_to("kytos/topology.link_down")
    def on_link_down(self, event):
        """Change circuit when link is down or under_mantenance."""
        self.handle_link_down(event)

    def handle_link_down(self, event):
        """Change circuit when link is down or under_mantenance."""
        log.debug("Event handle_link_down %s", event)
        for evc in self.circuits.values():
            with evc.lock:
                if evc.is_affected_by_link(event.content["link"]):
                    log.debug(f"Handling evc {evc.id} on link down")
                    if evc.handle_link_down():
                        emit_event(
                            self.controller,
                            "redeployed_link_down",
                            evc_id=evc.id,
                        )
                    else:
                        emit_event(
                            self.controller,
                            "error_redeploy_link_down",
                            evc_id=evc.id,
                        )

    def load_all_evcs(self):
        """Try to load all EVCs on startup."""
        for circuit_id, circuit in self.storehouse.get_data().items():
            if circuit_id not in self.circuits:
                self._load_evc(circuit)

    def _load_evc(self, circuit_dict):
        """Load one EVC from storehouse to memory."""
        try:
            evc = self._evc_from_dict(circuit_dict)
        except ValueError as exception:
            log.error(
                f'Could not load EVC {circuit_dict["id"]} '
                f"because {exception}"
            )
            return None

        if evc.archived:
            return None
        evc.deactivate()
        evc.sync()
        self.circuits.setdefault(evc.id, evc)
        self.sched.add(evc)
        return evc

    @listen_to("kytos/flow_manager.flow.error")
    def on_flow_mod_error(self, event):
        """Handle flow mod errors related to an EVC."""
        self.handle_flow_mod_error(event)

    def handle_flow_mod_error(self, event):
        """Handle flow mod errors related to an EVC."""
        flow = event.content["flow"]
        command = event.content.get("error_command")
        if command != "add":
            return
        evc = self.circuits.get(EVC.get_id_from_cookie(flow.cookie))
        if evc:
            evc.remove_current_flows()

    def _evc_dict_with_instances(self, evc_dict):
        """Convert some dict values to instance of EVC classes.

        This method will convert: [UNI, Link]
        """
        data = evc_dict.copy()  # Do not modify the original dict

        for attribute, value in data.items():
            # Get multiple attributes.
            # Ex: uni_a, uni_z
            if "uni" in attribute:
                try:
                    data[attribute] = self._uni_from_dict(value)
                except ValueError:
                    result = "Error creating UNI: Invalid value"
                    raise BadRequest(result) from BadRequest

            if attribute == "circuit_scheduler":
                data[attribute] = []
                for schedule in value:
                    data[attribute].append(CircuitSchedule.from_dict(schedule))

            # Get multiple attributes.
            # Ex: primary_links,
            #     backup_links,
            #     current_links_cache,
            #     primary_links_cache,
            #     backup_links_cache
            if "links" in attribute:
                data[attribute] = [
                    self._link_from_dict(link) for link in value
                ]

            # Ex: current_path,
            #     primary_path,
            #     backup_path
            if "path" in attribute and attribute != "dynamic_backup_path":
                data[attribute] = Path(
                    [self._link_from_dict(link) for link in value]
                )

        return data

    def _evc_from_dict(self, evc_dict):
        data = self._evc_dict_with_instances(evc_dict)
        return EVC(self.controller, **data)

    def _uni_from_dict(self, uni_dict):
        """Return a UNI object from python dict."""
        if uni_dict is None:
            return False

        interface_id = uni_dict.get("interface_id")
        interface = self.controller.get_interface_by_id(interface_id)
        if interface is None:
            result = (
                "Error creating UNI:"
                + f"Could not instantiate interface {interface_id}"
            )
            raise ValueError(result) from ValueError

        tag_dict = uni_dict.get("tag", None)
        if tag_dict:
            tag = TAG.from_dict(tag_dict)
        else:
            tag = None
        uni = UNI(interface, tag)

        return uni

    def _link_from_dict(self, link_dict):
        """Return a Link object from python dict."""
        id_a = link_dict.get("endpoint_a").get("id")
        id_b = link_dict.get("endpoint_b").get("id")

        endpoint_a = self.controller.get_interface_by_id(id_a)
        endpoint_b = self.controller.get_interface_by_id(id_b)

        link = Link(endpoint_a, endpoint_b)
        if "metadata" in link_dict:
            link.extend_metadata(link_dict.get("metadata"))

        s_vlan = link.get_metadata("s_vlan")
        if s_vlan:
            tag = TAG.from_dict(s_vlan)
            if tag is False:
                error_msg = f"Could not instantiate tag from dict {s_vlan}"
                raise ValueError(error_msg)
            link.update_metadata("s_vlan", tag)
        return link

    def _find_evc_by_schedule_id(self, schedule_id):
        """
        Find an EVC and CircuitSchedule based on schedule_id.

        :param schedule_id: Schedule ID
        :return: EVC and Schedule
        """
        circuits = self._get_circuits_buffer()
        found_schedule = None
        evc = None

        # pylint: disable=unused-variable
        for c_id, circuit in circuits.items():
            for schedule in circuit.circuit_scheduler:
                if schedule.id == schedule_id:
                    found_schedule = schedule
                    evc = circuit
                    break
            if found_schedule:
                break
        return evc, found_schedule

    def _get_circuits_buffer(self):
        """
        Return the circuit buffer.

        If the buffer is empty, try to load data from storehouse.
        """
        if not self.circuits:
            # Load storehouse circuits to buffer
            circuits = self.storehouse.get_data()
            for c_id, circuit in circuits.items():
                evc = self._evc_from_dict(circuit)
                self.circuits[c_id] = evc
        return self.circuits

    @staticmethod
    def _json_from_request(caller):
        """Return a json from request.

        If it was not possible to get a json from the request, log, for debug,
        who was the caller and the error that ocurred, and raise an
        Exception.
        """
        try:
            json_data = request.get_json()
        except ValueError as exception:
            log.error(exception)
            log.debug(f"{caller} result {exception} 400")
            raise BadRequest(str(exception)) from BadRequest
        except BadRequest:
            result = "The request is not a valid JSON."
            log.debug(f"{caller} result {result} 400")
            raise BadRequest(result) from BadRequest
        if json_data is None:
            result = "Content-Type must be application/json"
            log.debug(f"{caller} result {result} 415")
            raise UnsupportedMediaType(result)
        return json_data