selfprivacy-rest-api/selfprivacy_api/backup/__init__.py

"""
This module contains the controller class for backups.
"""
from datetime import datetime, timedelta, timezone
import time
import os
from os import statvfs
from typing import Callable, List, Optional

from selfprivacy_api.utils import ReadUserData, WriteUserData

from selfprivacy_api.services import (
    get_service_by_id,
    get_all_services,
)
from selfprivacy_api.services.service import (
    Service,
    ServiceStatus,
    StoppedService,
)

from selfprivacy_api.jobs import Jobs, JobStatus, Job

from selfprivacy_api.graphql.queries.providers import (
    BackupProvider as BackupProviderEnum,
)
from selfprivacy_api.graphql.common_types.backup import (
    RestoreStrategy,
    BackupReason,
    AutobackupQuotas,
)


from selfprivacy_api.models.backup.snapshot import Snapshot

from selfprivacy_api.backup.providers.provider import AbstractBackupProvider
from selfprivacy_api.backup.providers import get_provider
from selfprivacy_api.backup.storage import Storage
from selfprivacy_api.backup.jobs import (
    get_backup_job,
    get_backup_fail,
    add_backup_job,
    get_restore_job,
    add_restore_job,
)

DEFAULT_JSON_PROVIDER = {
    "provider": "BACKBLAZE",
    "accountId": "",
    "accountKey": "",
    "bucket": "",
}

BACKUP_PROVIDER_ENVS = {
    "kind": "BACKUP_KIND",
    "login": "BACKUP_LOGIN",
    "key": "BACKUP_KEY",
    "location": "BACKUP_LOCATION",
}

AUTOBACKUP_JOB_EXPIRATION_SECONDS = 60 * 60  # one hour


class NotDeadError(AssertionError):
    """
    This error is raised when we try to back up a service that is not dead yet.
    """

    def __init__(self, service: Service):
        self.service_name = service.get_id()
        super().__init__()

    def __str__(self):
        return f"""
        Service {self.service_name} should be either stopped or dead from
        an error before we back up.
        Normally, this error is unreachable because we do try ensure this.
        Apparently, not this time.
        """


class RotationBucket:
    """
    Bucket object used for rotation.
    Has the following mutable fields:
    - the counter, int
    - the lambda function which takes datetime and the int and returns the int
    - the last, int
    """

    def __init__(self, counter: int, last: int, rotation_lambda):
        self.counter: int = counter
        self.last: int = last
        self.rotation_lambda: Callable[[datetime, int], int] = rotation_lambda

    def __str__(self) -> str:
        return f"Bucket(counter={self.counter}, last={self.last})"


class Backups:
    """A stateless controller class for backups"""

    # Providers

    @staticmethod
    def provider() -> AbstractBackupProvider:
        """
        Returns the current backup storage provider.
        """
        return Backups._lookup_provider()

    @staticmethod
    def set_provider(
        kind: BackupProviderEnum,
        login: str,
        key: str,
        location: str,
        repo_id: str = "",
    ) -> None:
        """
        Sets the new configuration of the backup storage provider.

        In case of `BackupProviderEnum.BACKBLAZE`, the `login` is the key ID,
        the `key` is the key itself, and the `location` is the bucket name and
        the `repo_id` is the bucket ID.
        """
        provider: AbstractBackupProvider = Backups._construct_provider(
            kind,
            login,
            key,
            location,
            repo_id,
        )
        Storage.store_provider(provider)

    @staticmethod
    def reset(reset_json=True) -> None:
        """
        Deletes all the data about the backup storage provider.
        """
        Storage.reset()
        if reset_json:
            try:
                Backups._reset_provider_json()
            except FileNotFoundError:
                # if there is no userdata file, we do not need to reset it
                pass

    @staticmethod
    def _lookup_provider() -> AbstractBackupProvider:
        redis_provider = Backups._load_provider_redis()
        if redis_provider is not None:
            return redis_provider

        try:
            json_provider = Backups._load_provider_json()
        except FileNotFoundError:
            json_provider = None

        if json_provider is not None:
            Storage.store_provider(json_provider)
            return json_provider

        none_provider = Backups._construct_provider(
            BackupProviderEnum.NONE, login="", key="", location=""
        )
        Storage.store_provider(none_provider)
        return none_provider

    @staticmethod
    def set_provider_from_envs():
        for env in BACKUP_PROVIDER_ENVS.values():
            if env not in os.environ.keys():
                raise ValueError(
                    f"Cannot set backup provider from envs, there is no {env} set"
                )

        kind_str = os.environ[BACKUP_PROVIDER_ENVS["kind"]]
        kind_enum = BackupProviderEnum[kind_str]
        provider = Backups._construct_provider(
            kind=kind_enum,
            login=os.environ[BACKUP_PROVIDER_ENVS["login"]],
            key=os.environ[BACKUP_PROVIDER_ENVS["key"]],
            location=os.environ[BACKUP_PROVIDER_ENVS["location"]],
        )
        Storage.store_provider(provider)

    @staticmethod
    def _construct_provider(
        kind: BackupProviderEnum,
        login: str,
        key: str,
        location: str,
        repo_id: str = "",
    ) -> AbstractBackupProvider:
        provider_class = get_provider(kind)

        return provider_class(
            login=login,
            key=key,
            location=location,
            repo_id=repo_id,
        )

    @staticmethod
    def _load_provider_redis() -> Optional[AbstractBackupProvider]:
        provider_model = Storage.load_provider()
        if provider_model is None:
            return None
        return Backups._construct_provider(
            BackupProviderEnum[provider_model.kind],
            provider_model.login,
            provider_model.key,
            provider_model.location,
            provider_model.repo_id,
        )

    @staticmethod
    def _load_provider_json() -> Optional[AbstractBackupProvider]:
        with ReadUserData() as user_data:
            provider_dict = {
                "provider": "",
                "accountId": "",
                "accountKey": "",
                "bucket": "",
            }

            if "backup" not in user_data.keys():
                if "backblaze" in user_data.keys():
                    provider_dict.update(user_data["backblaze"])
                    provider_dict["provider"] = "BACKBLAZE"
                return None
            else:
                provider_dict.update(user_data["backup"])

            if provider_dict == DEFAULT_JSON_PROVIDER:
                return None
            try:
                return Backups._construct_provider(
                    kind=BackupProviderEnum[provider_dict["provider"]],
                    login=provider_dict["accountId"],
                    key=provider_dict["accountKey"],
                    location=provider_dict["bucket"],
                )
            except KeyError:
                return None

    @staticmethod
    def _reset_provider_json() -> None:
        with WriteUserData() as user_data:
            if "backblaze" in user_data.keys():
                del user_data["backblaze"]

            user_data["backup"] = DEFAULT_JSON_PROVIDER

    # Init

    @staticmethod
    def init_repo() -> None:
        """
        Initializes the backup repository. This is required once per repo.
        """
        Backups.provider().backupper.init()
        Storage.mark_as_init()

    @staticmethod
    def erase_repo() -> None:
        """
        Completely empties the remote
        """
        Backups.provider().backupper.erase_repo()
        Storage.mark_as_uninitted()

    @staticmethod
    def is_initted() -> bool:
        """
        Returns whether the backup repository is initialized or not.
        If it is not initialized, we cannot back up and probably should
        call `init_repo` first.
        """
        if Storage.has_init_mark():
            return True

        initted = Backups.provider().backupper.is_initted()
        if initted:
            Storage.mark_as_init()
            return True

        return False

    # Backup

    @staticmethod
    def back_up(
        service: Service, reason: BackupReason = BackupReason.EXPLICIT
    ) -> Snapshot:
        """The top-level function to back up a service
        If it fails for any reason at all, it should both mark job as
        errored and re-raise an error"""

        job = get_backup_job(service)
        if job is None:
            job = add_backup_job(service)
        Jobs.update(job, status=JobStatus.RUNNING)

        try:
            if service.can_be_backed_up() is False:
                raise ValueError("cannot backup a non-backuppable service")
            folders = service.get_folders()
            service_name = service.get_id()
            service.pre_backup()
            snapshot = Backups.provider().backupper.start_backup(
                folders,
                service_name,
                reason=reason,
            )

            Backups._store_last_snapshot(service_name, snapshot)
            if reason == BackupReason.AUTO:
                Backups._prune_auto_snaps(service)
            service.post_restore()
        except Exception as error:
            Jobs.update(job, status=JobStatus.ERROR, status_text=str(error))
            raise error

        Jobs.update(job, status=JobStatus.FINISHED)
        if reason in [BackupReason.AUTO, BackupReason.PRE_RESTORE]:
            Jobs.set_expiration(job, AUTOBACKUP_JOB_EXPIRATION_SECONDS)
        return snapshot

    @staticmethod
    def _auto_snaps(service):
        return [
            snap
            for snap in Backups.get_snapshots(service)
            if snap.reason == BackupReason.AUTO
        ]

    @staticmethod
    def _prune_snaps_with_quotas(snapshots: List[Snapshot]) -> List[Snapshot]:
        # Function broken out for testability
        # Sorting newest first
        sorted_snaps = sorted(snapshots, key=lambda s: s.created_at, reverse=True)
        quotas: AutobackupQuotas = Backups.autobackup_quotas()

        buckets: list[RotationBucket] = [
            RotationBucket(
                quotas.last,  # type: ignore
                -1,
                lambda _, index: index,
            ),
            RotationBucket(
                quotas.daily,  # type: ignore
                -1,
                lambda date, _: date.year * 10000 + date.month * 100 + date.day,
            ),
            RotationBucket(
                quotas.weekly,  # type: ignore
                -1,
                lambda date, _: date.year * 100 + date.isocalendar()[1],
            ),
            RotationBucket(
                quotas.monthly,  # type: ignore
                -1,
                lambda date, _: date.year * 100 + date.month,
            ),
            RotationBucket(
                quotas.yearly,  # type: ignore
                -1,
                lambda date, _: date.year,
            ),
        ]

        new_snaplist: List[Snapshot] = []
        for i, snap in enumerate(sorted_snaps):
            keep_snap = False
            for bucket in buckets:
                if (bucket.counter > 0) or (bucket.counter == -1):
                    val = bucket.rotation_lambda(snap.created_at, i)
                    if (val != bucket.last) or (i == len(sorted_snaps) - 1):
                        bucket.last = val
                        if bucket.counter > 0:
                            bucket.counter -= 1
                        if not keep_snap:
                            new_snaplist.append(snap)
                        keep_snap = True

        return new_snaplist

    @staticmethod
    def _prune_auto_snaps(service) -> None:
        # Not very testable by itself, so most testing is going on Backups._prune_snaps_with_quotas
        # We can still test total limits and, say, daily limits

        auto_snaps = Backups._auto_snaps(service)
        new_snaplist = Backups._prune_snaps_with_quotas(auto_snaps)

        # TODO: Can be optimized since there is forgetting of an array in one restic op
        # but most of the time this will be only one snap to forget.
        for snap in auto_snaps:
            if snap not in new_snaplist:
                Backups.forget_snapshot(snap)

    @staticmethod
    def _standardize_quotas(i: int) -> int:
        if i <= -1:
            i = -1
        return i

    @staticmethod
    def autobackup_quotas() -> AutobackupQuotas:
        """0 means do not keep, -1 means unlimited"""

        return Storage.autobackup_quotas()

    @staticmethod
    def set_autobackup_quotas(quotas: AutobackupQuotas) -> None:
        """0 means do not keep, -1 means unlimited"""

        Storage.set_autobackup_quotas(
            AutobackupQuotas(
                last=Backups._standardize_quotas(quotas.last),  # type: ignore
                daily=Backups._standardize_quotas(quotas.daily),  # type: ignore
                weekly=Backups._standardize_quotas(quotas.weekly),  # type: ignore
                monthly=Backups._standardize_quotas(quotas.monthly),  # type: ignore
                yearly=Backups._standardize_quotas(quotas.yearly),  # type: ignore
            )
        )

        for service in get_all_services():
            Backups._prune_auto_snaps(service)

    # Restoring

    @staticmethod
    def _ensure_queued_restore_job(service, snapshot) -> Job:
        job = get_restore_job(service)
        if job is None:
            job = add_restore_job(snapshot)

        Jobs.update(job, status=JobStatus.CREATED)
        return job

    @staticmethod
    def _inplace_restore(
        service: Service,
        snapshot: Snapshot,
        job: Job,
    ) -> None:
        Jobs.update(
            job, status=JobStatus.CREATED, status_text="Waiting for pre-restore backup"
        )
        failsafe_snapshot = Backups.back_up(service, BackupReason.PRE_RESTORE)

        Jobs.update(
            job, status=JobStatus.RUNNING, status_text=f"Restoring from {snapshot.id}"
        )
        try:
            Backups._restore_service_from_snapshot(
                service,
                snapshot.id,
                verify=False,
            )
        except Exception as error:
            Jobs.update(
                job,
                status=JobStatus.ERROR,
                status_text=f"Restore failed with {str(error)}, reverting to {failsafe_snapshot.id}",
            )
            Backups._restore_service_from_snapshot(
                service, failsafe_snapshot.id, verify=False
            )
            Jobs.update(
                job,
                status=JobStatus.ERROR,
                status_text=f"Restore failed with {str(error)}, reverted to {failsafe_snapshot.id}",
            )
            raise error

    @staticmethod
    def restore_snapshot(
        snapshot: Snapshot, strategy=RestoreStrategy.DOWNLOAD_VERIFY_OVERWRITE
    ) -> None:
        """Restores a snapshot to its original service using the given strategy"""
        service = get_service_by_id(snapshot.service_name)
        if service is None:
            raise ValueError(
                f"snapshot has a nonexistent service: {snapshot.service_name}"
            )
        job = Backups._ensure_queued_restore_job(service, snapshot)

        try:
            Backups._assert_restorable(snapshot)
            Jobs.update(
                job, status=JobStatus.RUNNING, status_text="Stopping the service"
            )
            with StoppedService(service):
                Backups.assert_dead(service)
                if strategy == RestoreStrategy.INPLACE:
                    Backups._inplace_restore(service, snapshot, job)
                else:  # verify_before_download is our default
                    Jobs.update(
                        job,
                        status=JobStatus.RUNNING,
                        status_text=f"Restoring from {snapshot.id}",
                    )
                    Backups._restore_service_from_snapshot(
                        service, snapshot.id, verify=True
                    )

                service.post_restore()
                Jobs.update(
                    job,
                    status=JobStatus.RUNNING,
                    progress=90,
                    status_text="Restarting the service",
                )

        except Exception as error:
            Jobs.update(job, status=JobStatus.ERROR, status_text=str(error))
            raise error

        Jobs.update(job, status=JobStatus.FINISHED)

    @staticmethod
    def _assert_restorable(
        snapshot: Snapshot, strategy=RestoreStrategy.DOWNLOAD_VERIFY_OVERWRITE
    ) -> None:
        service = get_service_by_id(snapshot.service_name)
        if service is None:
            raise ValueError(
                f"snapshot has a nonexistent service: {snapshot.service_name}"
            )

        restored_snap_size = Backups.snapshot_restored_size(snapshot.id)

        if strategy == RestoreStrategy.DOWNLOAD_VERIFY_OVERWRITE:
            needed_space = restored_snap_size
        elif strategy == RestoreStrategy.INPLACE:
            needed_space = restored_snap_size - service.get_storage_usage()
        else:
            raise NotImplementedError(
                """
            We do not know if there is enough space for restoration because
            there is some novel restore strategy used!
            This is a developer's fault, open an issue please
            """
            )
        available_space = Backups.space_usable_for_service(service)
        if needed_space > available_space:
            raise ValueError(
                f"we only have {available_space} bytes "
                f"but snapshot needs {needed_space}"
            )

    @staticmethod
    def _restore_service_from_snapshot(
        service: Service,
        snapshot_id: str,
        verify=True,
    ) -> None:
        folders = service.get_folders()

        Backups.provider().backupper.restore_from_backup(
            snapshot_id,
            folders,
            verify=verify,
        )

    # Snapshots

    @staticmethod
    def get_snapshots(service: Service) -> List[Snapshot]:
        """Returns all snapshots for a given service"""
        snapshots = Backups.get_all_snapshots()
        service_id = service.get_id()
        return list(
            filter(
                lambda snap: snap.service_name == service_id,
                snapshots,
            )
        )

    @staticmethod
    def get_all_snapshots() -> List[Snapshot]:
        """Returns all snapshots"""
        cached_snapshots = Storage.get_cached_snapshots()
        if cached_snapshots:
            return cached_snapshots
        # TODO: the oldest snapshots will get expired faster than the new ones.
        # How to detect that the end is missing?

        Backups.force_snapshot_cache_reload()
        return Storage.get_cached_snapshots()

    @staticmethod
    def get_snapshot_by_id(snapshot_id: str) -> Optional[Snapshot]:
        """Returns a backup snapshot by its id"""
        snap = Storage.get_cached_snapshot_by_id(snapshot_id)
        if snap is not None:
            return snap

        # Possibly our cache entry got invalidated, let's try one more time
        Backups.force_snapshot_cache_reload()
        snap = Storage.get_cached_snapshot_by_id(snapshot_id)

        return snap

    @staticmethod
    def forget_snapshot(snapshot: Snapshot) -> None:
        """Deletes a snapshot from the repo and from cache"""
        Backups.provider().backupper.forget_snapshot(snapshot.id)
        Storage.delete_cached_snapshot(snapshot)

    @staticmethod
    def forget_all_snapshots():
        """deliberately erase all snapshots we made"""
        # there is no dedicated optimized command for this,
        # but maybe we can have a multi-erase
        for snapshot in Backups.get_all_snapshots():
            Backups.forget_snapshot(snapshot)

    @staticmethod
    def force_snapshot_cache_reload() -> None:
        """
        Forces a reload of the snapshot cache.

        This may be an expensive operation, so use it wisely.
        User pays for the API calls.
        """
        upstream_snapshots = Backups.provider().backupper.get_snapshots()
        Storage.invalidate_snapshot_storage()
        for snapshot in upstream_snapshots:
            Storage.cache_snapshot(snapshot)

    @staticmethod
    def snapshot_restored_size(snapshot_id: str) -> int:
        """Returns the size of the snapshot"""
        return Backups.provider().backupper.restored_size(
            snapshot_id,
        )

    @staticmethod
    def _store_last_snapshot(service_id: str, snapshot: Snapshot) -> None:
        """What do we do with a snapshot that is just made?"""
        # non-expiring timestamp of the last
        Storage.store_last_timestamp(service_id, snapshot)
        # expiring cache entry
        Storage.cache_snapshot(snapshot)

    # Autobackup

    @staticmethod
    def autobackup_period_minutes() -> Optional[int]:
        """None means autobackup is disabled"""
        return Storage.autobackup_period_minutes()

    @staticmethod
    def set_autobackup_period_minutes(minutes: int) -> None:
        """
        0 and negative numbers are equivalent to disable.
        Setting to a positive number may result in a backup very soon
        if some services are not backed up.
        """
        if minutes <= 0:
            Backups.disable_all_autobackup()
            return
        Storage.store_autobackup_period_minutes(minutes)

    @staticmethod
    def disable_all_autobackup() -> None:
        """
        Disables all automatic backing up,
        but does not change per-service settings
        """
        Storage.delete_backup_period()

    @staticmethod
    def is_time_to_backup(time: datetime) -> bool:
        """
        Intended as a time validator for huey cron scheduler
        of automatic backups
        """

        return Backups.services_to_back_up(time) != []

    @staticmethod
    def services_to_back_up(time: datetime) -> List[Service]:
        """Returns a list of services that should be backed up at a given time"""
        return [
            service
            for service in get_all_services()
            if Backups.is_time_to_backup_service(service, time)
        ]

    @staticmethod
    def get_last_backed_up(service: Service) -> Optional[datetime]:
        """Get a timezone-aware time of the last backup of a service"""
        return Storage.get_last_backup_time(service.get_id())

    @staticmethod
    def get_last_backup_error_time(service: Service) -> Optional[datetime]:
        """Get a timezone-aware time of the last backup of a service"""
        job = get_backup_fail(service)
        if job is not None:
            datetime_created = job.created_at
            if datetime_created.tzinfo is None:
                # assume it is in localtime
                offset = timedelta(seconds=time.localtime().tm_gmtoff)
                datetime_created = datetime_created - offset
                return datetime.combine(
                    datetime_created.date(), datetime_created.time(), timezone.utc
                )
            return datetime_created
        return None

    @staticmethod
    def is_time_to_backup_service(service: Service, time: datetime):
        """Returns True if it is time to back up a service"""
        period = Backups.autobackup_period_minutes()
        if not service.can_be_backed_up():
            return False
        if period is None:
            return False

        last_error = Backups.get_last_backup_error_time(service)

        if last_error is not None:
            if time < last_error + timedelta(seconds=AUTOBACKUP_JOB_EXPIRATION_SECONDS):
                return False

        last_backup = Backups.get_last_backed_up(service)
        if last_backup is None:
            # queue a backup immediately if there are no previous backups
            return True

        if time > last_backup + timedelta(minutes=period):
            return True

        return False

    # Helpers

    @staticmethod
    def space_usable_for_service(service: Service) -> int:
        """
        Returns the amount of space available on the volume the given
        service is located on.
        """
        folders = service.get_folders()
        if folders == []:
            raise ValueError("unallocated service", service.get_id())

        # We assume all folders of one service live at the same volume
        fs_info = statvfs(folders[0])
        usable_bytes = fs_info.f_frsize * fs_info.f_bavail
        return usable_bytes

    @staticmethod
    def set_localfile_repo(file_path: str):
        """Used by tests to set a local folder as a backup repo"""
        # pylint: disable-next=invalid-name
        ProviderClass = get_provider(BackupProviderEnum.FILE)
        provider = ProviderClass(
            login="",
            key="",
            location=file_path,
            repo_id="",
        )
        Storage.store_provider(provider)

    @staticmethod
    def assert_dead(service: Service):
        """
        Checks if a service is dead and can be safely restored from a snapshot.
        """
        if service.get_status() not in [
            ServiceStatus.INACTIVE,
            ServiceStatus.FAILED,
        ]:
            raise NotDeadError(service)