app.py

"""
The binderhub application
"""
import asyncio
import ipaddress
import json
import logging
import os
import re
import secrets
import warnings
from binascii import a2b_hex
from concurrent.futures import ThreadPoolExecutor
from glob import glob
from urllib.parse import urlparse

import kubernetes.client
import kubernetes.config
import tornado.ioloop
import tornado.log
import tornado.options
import tornado.web
from jinja2 import ChoiceLoader, Environment, FileSystemLoader, PrefixLoader
from jupyterhub.services.auth import HubOAuthCallbackHandler
from jupyterhub.traitlets import Callable
from tornado.httpclient import AsyncHTTPClient
from tornado.httpserver import HTTPServer
from tornado.log import app_log
from traitlets import (
    Bool,
    Bytes,
    Dict,
    Integer,
    TraitError,
    Type,
    Unicode,
    Union,
    default,
    observe,
    validate,
)
from traitlets.config import Application

from .base import AboutHandler, Custom404, VersionHandler
from .build import BuildExecutor, KubernetesBuildExecutor, KubernetesCleaner
from .builder import BuildHandler
from .config import ConfigHandler
from .events import EventLog
from .health import HealthHandler, KubernetesHealthHandler
from .launcher import Launcher
from .log import log_request
from .main import LegacyRedirectHandler, MainHandler, ParameterizedMainHandler
from .metrics import MetricsHandler
from .quota import KubernetesLaunchQuota, LaunchQuota
from .ratelimit import RateLimiter
from .registry import DockerRegistry
from .repoproviders import (
    DataverseProvider,
    FigshareProvider,
    GistRepoProvider,
    GitHubRepoProvider,
    GitLabRepoProvider,
    GitRepoProvider,
    HydroshareProvider,
    RepoProvider,
    ZenodoProvider,
)
from .utils import ByteSpecification, url_path_join

HERE = os.path.dirname(os.path.abspath(__file__))


class BinderHub(Application):
    """An Application for starting a builder."""

    @default("log_level")
    def _log_level(self):
        return logging.INFO

    aliases = {
        "log-level": "Application.log_level",
        "f": "BinderHub.config_file",
        "config": "BinderHub.config_file",
        "port": "BinderHub.port",
    }

    flags = {
        "debug": (
            {"BinderHub": {"debug": True}},
            "Enable debug HTTP serving & debug logging",
        )
    }

    config_file = Unicode(
        "binderhub_config.py",
        help="""
        Config file to load.

        If a relative path is provided, it is taken relative to current directory
        """,
        config=True,
    )

    google_analytics_code = Unicode(
        None,
        allow_none=True,
        help="""
        The Google Analytics code to use on the main page.

        Note that we'll respect Do Not Track settings, despite the fact that GA does not.
        We will not load the GA scripts on browsers with DNT enabled.
        """,
        config=True,
    )

    google_analytics_domain = Unicode(
        "auto",
        help="""
        The Google Analytics domain to use on the main page.

        By default this is set to 'auto', which sets it up for current domain and all
        subdomains. This can be set to a more restrictive domain here for better privacy
        """,
        config=True,
    )

    about_message = Unicode(
        "",
        help="""
        Additional message to display on the about page.

        Will be directly inserted into the about page's source so you can use
        raw HTML.
        """,
        config=True,
    )

    banner_message = Unicode(
        "",
        help="""
        Message to display in a banner on all pages.

        The value will be inserted "as is" into a HTML <div> element
        with grey background, located at the top of the BinderHub pages. Raw
        HTML is supported.
        """,
        config=True,
    )

    extra_footer_scripts = Dict(
        {},
        help="""
        Extra bits of JavaScript that should be loaded in footer of each page.

        Only the values are set up as scripts. Keys are used only
        for sorting.

        Omit the <script> tag. This should be primarily used for
        analytics code.
        """,
        config=True,
    )

    base_url = Unicode("/", help="The base URL of the entire application", config=True)

    @validate("base_url")
    def _valid_base_url(self, proposal):
        if not proposal.value.startswith("/"):
            proposal.value = "/" + proposal.value
        if not proposal.value.endswith("/"):
            proposal.value = proposal.value + "/"
        return proposal.value

    badge_base_url = Union(
        trait_types=[Unicode(), Callable()],
        help="""
        Base URL to use when generating launch badges.
        Can also be a function that is passed the current handler and returns
        the badge base URL, or "" for the default.

        For example, you could get the badge_base_url from a custom HTTP
        header, the Referer header, or from a request parameter
        """,
        config=True,
    )

    @default("badge_base_url")
    def _badge_base_url_default(self):
        return ""

    @validate("badge_base_url")
    def _valid_badge_base_url(self, proposal):
        if callable(proposal.value):
            return proposal.value
        # add a trailing slash only when a value is set
        if proposal.value and not proposal.value.endswith("/"):
            proposal.value = proposal.value + "/"
        return proposal.value

    cors_allow_origin = Unicode(
        "",
        help="""
        Origins that can access the BinderHub API.

        Sets the Access-Control-Allow-Origin header in the spawned
        notebooks. Set to '*' to allow any origin to access spawned
        notebook servers.

        See also BinderSpawner.cors_allow_origin in the binderhub spawner
        mixin for setting this property on the spawned notebooks.
        """,
        config=True,
    )

    auth_enabled = Bool(
        False,
        help="""If JupyterHub authentication enabled,
        require user to login (don't create temporary users during launch) and
        start the new server for the logged in user.""",
        config=True,
    )

    port = Integer(
        8585,
        help="""
        Port for the builder to listen on.
        """,
        config=True,
    )

    appendix = Unicode(
        help="""
        DEPRECATED: Use c.BuildExecutor.appendix

        Appendix to pass to repo2docker

        A multi-line string of Docker directives to run.
        Since the build context cannot be affected,
        ADD will typically not be useful.

        This should be a Python string template.
        It will be formatted with at least the following names available:

        - binder_url: the shareable URL for the current image
          (e.g. for sharing links to the current Binder)
        - repo_url: the repository URL used to build the image
        """,
        config=True,
    )

    sticky_builds = Bool(
        False,
        help="""
        DEPRECATED: Use c.KubernetesBuildExecutor.sticky_builds

        Attempt to assign builds for the same repository to the same node.

        In order to speed up re-builds of a repository all its builds will
        be assigned to the same node in the cluster.

        Note: This feature only works if you also enable docker-in-docker support.
        """,
        config=True,
    )

    use_registry = Bool(
        True,
        help="""
        Set to true to push images to a registry & check for images in registry.

        Set to false to use only local docker images. Useful when running
        in a single node.
        """,
        config=True,
    )

    build_class = Type(
        KubernetesBuildExecutor,
        klass=BuildExecutor,
        help="""
        The class used to build repo2docker images.

        Must inherit from binderhub.build.BuildExecutor
        """,
        config=True,
    )

    build_cleaner_class = Type(
        KubernetesCleaner,
        allow_none=True,
        help="""
        The class used to cleanup builders.
        """,
        config=True,
    )

    registry_class = Type(
        DockerRegistry,
        help="""
        The class used to Query a Docker registry.

        Must inherit from binderhub.registry.DockerRegistry
        """,
        config=True,
    )

    health_handler_class = Type(
        HealthHandler,
        help="The Tornado /health handler class",
        config=True,
    )

    @default("health_handler_class")
    def _default_health_handler_class(self):
        if issubclass(self.build_class, KubernetesBuildExecutor):
            return KubernetesHealthHandler
        return HealthHandler

    per_repo_quota = Integer(
        0,
        help="""
        Maximum number of concurrent users running from a given repo.

        Limits the amount of Binder that can be consumed by a single repo.

        0 (default) means no quotas.
        """,
        config=True,
    )

    pod_quota = Integer(
        None,
        help="""
        DEPRECATED: Use c.LaunchQuota.total_quota

        The number of concurrent pods this hub has been designed to support.

        This quota is used as an indication for how much above or below the
        design capacity a hub is running.

        Attempts to launch new pods once the quota has been reached will fail.

        The default corresponds to no quota, 0 means the hub can't accept pods
        (maybe because it is in maintenance mode), and any positive integer
        sets the quota.
        """,
        allow_none=True,
        config=True,
    )

    @observe("pod_quota")
    def _pod_quota_deprecated(self, change):
        self.log.warning(
            "BinderHub.pod_quota is deprecated, use LaunchQuota.total_quota"
        )
        self.config.LaunchQuota.total_quota = change.new

    per_repo_quota_higher = Integer(
        0,
        help="""
        Maximum number of concurrent users running from a higher-quota repo.

        Limits the amount of Binder that can be consumed by a single repo. This
        quota is a second limit for repos with special status. See the
        `high_quota_specs` parameter of RepoProvider classes for usage.

        0 (default) means no quotas.
        """,
        config=True,
    )

    launch_quota_class = Type(
        klass=LaunchQuota,
        default_value=KubernetesLaunchQuota,
        help="""
        The class used to check quotas for launched servers.

        Must inherit from binderhub.quota.LaunchQuota
        """,
        config=True,
    )

    log_tail_lines = Integer(
        100,
        help="""
        DEPRECATED: Use c.KubernetesBuildExecutor.log_tail_lines

        Limit number of log lines to show when connecting to an already running build.
        """,
        config=True,
    )

    push_secret = Unicode(
        "binder-build-docker-config",
        allow_none=True,
        help="""
        DEPRECATED: Use c.BuildExecutor.push_secret

        A kubernetes secret object that provides credentials for pushing built images.
        """,
        config=True,
    )

    image_prefix = Unicode(
        "",
        help="""
        Prefix for all built docker images.

        If you are pushing to gcr.io, this would start with:
            gcr.io/<your-project-name>/

        Set according to whatever registry you are pushing to.

        Defaults to "", which is probably not what you want :)
        """,
        config=True,
    )

    build_memory_request = ByteSpecification(
        0,
        help="""
        DEPRECATED: Use c.KubernetesBuildExecutor.memory_request

        Amount of memory to request when scheduling a build

        0 reserves no memory.

        This is used as the request for the pod that is spawned to do the building,
        even though the pod itself will not be using that much memory
        since the docker building is happening outside the pod.
        However, it makes kubernetes aware of the resources being used,
        and lets it schedule more intelligently.
        """,
        config=True,
    )
    build_memory_limit = ByteSpecification(
        0,
        help="""
        DEPRECATED: Use c.BuildExecutor.memory_limit

        Max amount of memory allocated for each image build process.

        0 sets no limit.

        This is applied to the docker build itself via repo2docker,
        though it is also applied to our pod that submits the build,
        even though that pod will rarely consume much memory.
        Still, it makes it easier to see the resource limits in place via kubernetes.
        """,
        config=True,
    )

    debug = Bool(
        False,
        help="""
        Turn on debugging.
        """,
        config=True,
    )

    build_docker_host = Unicode(
        "/var/run/docker.sock",
        config=True,
        help="""
        DEPRECATED: Use c.KubernetesBuildExecutor.docker_host

        The docker URL repo2docker should use to build the images.

        Currently, only paths are supported, and they are expected to be available on
        all the hosts.
        """,
    )

    @validate("build_docker_host")
    def docker_build_host_validate(self, proposal):
        parts = urlparse(proposal.value)
        if parts.scheme != "unix" or parts.netloc != "":
            raise TraitError(
                "Only unix domain sockets on same node are supported for build_docker_host"
            )
        return proposal.value

    build_docker_config = Dict(
        None,
        allow_none=True,
        help="""
        A dict which will be merged into the .docker/config.json of the build container (repo2docker)
        Here, you could for example pass proxy settings as described here:
        https://docs.docker.com/network/proxy/#configure-the-docker-client

        Note: if you provide your own push_secret, this values wont
        have an effect, as the push_secrets will overwrite
        .docker/config.json
        In this case, make sure that you include your config in your push_secret

        WARNING: The value of this parameter is managed by the binderHub Helm Chart.
        It is not managed by the BinderHub application itself.
        If you are running BinderHub in another way this parameter has no effect.
        """,
        config=True,
    )

    hub_api_token = Unicode(
        help="""API token for talking to the JupyterHub API""",
        config=True,
    )

    @default("hub_api_token")
    def _default_hub_token(self):
        return os.environ.get("JUPYTERHUB_API_TOKEN", "")

    hub_url = Unicode(
        help="""
        The base URL of the JupyterHub instance where users will run.

        e.g. https://hub.mybinder.org/
        """,
        config=True,
    )

    hub_url_local = Unicode(
        help="""
        The base URL of the JupyterHub instance for local/internal traffic

        If local/internal network connections from the BinderHub process should access
        JupyterHub using a different URL than public/external traffic set this, default
        is hub_url
        """,
        config=True,
    )

    @default("hub_url_local")
    def _default_hub_url_local(self):
        return self.hub_url

    @validate("hub_url", "hub_url_local")
    def _add_slash(self, proposal):
        """trait validator to ensure hub_url ends with a trailing slash"""
        if proposal.value is not None and not proposal.value.endswith("/"):
            return proposal.value + "/"
        return proposal.value

    build_namespace = Unicode(
        help="""
        DEPRECATED: Use c.KubernetesBuildExecutor.namespace

        Kubernetes namespace to spawn build pods in.

        Note that the push_secret must refer to a secret in this namespace.
        """,
        config=True,
    )

    @default("build_namespace")
    def _default_build_namespace(self):
        return os.environ.get("BUILD_NAMESPACE", "default")

    build_image = Unicode(
        "quay.io/jupyterhub/repo2docker:2022.10.0",
        help="""
        DEPRECATED: Use c.KubernetesBuildExecutor.build_image

        The repo2docker image to be used for doing builds
        """,
        config=True,
    )

    build_node_selector = Dict(
        {},
        config=True,
        help="""
        DEPRECATED: Use c.KubernetesBuildExecutor.node_selector

        Select the node where build pod runs on.
        """,
    )

    repo_providers = Dict(
        {
            "gh": GitHubRepoProvider,
            "gist": GistRepoProvider,
            "git": GitRepoProvider,
            "gl": GitLabRepoProvider,
            "zenodo": ZenodoProvider,
            "figshare": FigshareProvider,
            "hydroshare": HydroshareProvider,
            "dataverse": DataverseProvider,
        },
        config=True,
        help="""
        List of Repo Providers to register and try
        """,
    )

    @validate("repo_providers")
    def _validate_repo_providers(self, proposal):
        """trait validator to ensure there is at least one repo provider"""
        if not proposal.value:
            raise TraitError("Please provide at least one repo provider")

        if any(
            [
                not issubclass(provider, RepoProvider)
                for provider in proposal.value.values()
            ]
        ):
            raise TraitError(
                "Repository providers should inherit from 'binderhub.RepoProvider'"
            )

        return proposal.value

    concurrent_build_limit = Integer(
        32, config=True, help="""The number of concurrent builds to allow."""
    )
    executor_threads = Integer(
        5,
        config=True,
        help="""The number of threads to use for blocking calls

        Should generally be a small number because we don't
        care about high concurrency here, just not blocking the webserver.
        This executor is not used for long-running tasks (e.g. builds).
        """,
    )
    build_cleanup_interval = Integer(
        60,
        config=True,
        help="""Interval (in seconds) for how often stopped build pods will be deleted.""",
    )
    build_max_age = Integer(
        3600 * 4,
        config=True,
        help="""Maximum age of builds

        Builds that are still running longer than this
        will be killed.
        """,
    )

    @observe("build_max_age")
    def _build_max_age_changed(self, change):
        if self.build_cleaner_class:
            cleaner_name = self.build_cleaner_class.__name__
        else:
            cleaner_name = "CleanerName"

        if cleaner_name in self.config:
            cleaner_config = self.config[cleaner_name]
            if "max_age" in cleaner_config:
                # avoid warning about redundant deprecated config
                # which can be kept for backward-compatibility
                return

        self.log.warning(
            f"BinderHub.build_max_age is deprecated. Use `c.{cleaner_name}.max_age = {change.new}`"
        )
        self.config[cleaner_name].max_age = change.new

    build_token_check_origin = Bool(
        True,
        config=True,
        help="""Whether to validate build token origin.

        False disables the origin check.
        """,
    )

    build_token_expires_seconds = Integer(
        300,
        config=True,
        help="""Expiry (in seconds) of build tokens

        These are generally only used to authenticate a single request
        from a page, so should be short-lived.
        """,
    )

    build_token_secret = Union(
        [Unicode(), Bytes()],
        config=True,
        help="""Secret used to sign build tokens

        Lightweight validation of same-origin requests
        """,
    )

    @validate("build_token_secret")
    def _validate_build_token_secret(self, proposal):
        if isinstance(proposal.value, str):
            # allow hex string for text-only input formats
            return a2b_hex(proposal.value)
        return proposal.value

    @default("build_token_secret")
    def _default_build_token_secret(self):
        if os.environ.get("BINDERHUB_BUILD_TOKEN_SECRET"):
            return a2b_hex(os.environ["BINDERHUB_BUILD_TOKEN_SECRET"])
        app_log.warning(
            "Generating random build token secret."
            " Set BinderHub.build_token_secret to avoid this warning."
        )
        return secrets.token_bytes(32)

    # FIXME: Come up with a better name for it?
    builder_required = Bool(
        True,
        config=True,
        help="""
        If binderhub should try to continue to run without a working build infrastructure.

        Build infrastructure is kubernetes cluster + docker. This is useful for pure HTML/CSS/JS local development.
        """,
    )

    ban_networks = Dict(
        config=True,
        help="""
        Dict of networks from which requests should be rejected with 403

        Keys are CIDR notation (e.g. '1.2.3.4/32'),
        values are a label used in log / error messages.
        CIDR strings will be parsed with `ipaddress.ip_network()`.
        """,
    )

    @validate("ban_networks")
    def _cast_ban_networks(self, proposal):
        """Cast CIDR strings to IPv[4|6]Network objects"""
        networks = {}
        for cidr, message in proposal.value.items():
            networks[ipaddress.ip_network(cidr)] = message

        return networks

    ban_networks_min_prefix_len = Integer(
        1,
        help="The shortest prefix in ban_networks",
    )

    @observe("ban_networks")
    def _update_prefix_len(self, change):
        if not change.new:
            min_len = 1
        else:
            min_len = min(net.prefixlen for net in change.new)
        self.ban_networks_min_prefix_len = min_len or 1

    tornado_settings = Dict(
        config=True,
        help="""
        additional settings to pass through to tornado.

        can include things like additional headers, etc.
        """,
    )

    template_variables = Dict(
        config=True,
        help="Extra variables to supply to jinja templates when rendering.",
    )

    template_path = Unicode(
        help="Path to search for custom jinja templates, before using the default templates.",
        config=True,
    )

    @default("template_path")
    def _template_path_default(self):
        return os.path.join(HERE, "templates")

    extra_static_path = Unicode(
        help="Path to search for extra static files.",
        config=True,
    )

    extra_static_url_prefix = Unicode(
        "/extra_static/",
        help="Url prefix to serve extra static files.",
        config=True,
    )

    normalized_origin = Unicode(
        "",
        config=True,
        help="Origin to use when emitting events. Defaults to hostname of request when empty",
    )

    enable_api_only_mode = Bool(
        False,
        help="""
        When enabled, BinderHub will operate in an API only mode,
        without a UI, and with the only registered endpoints being:
            - /metrics
            - /versions
            - /build/([^/]+)/(.+)
            - /health
            - /_config
            - /* -> shows a 404 page
        """,
        config=True,
    )

    _build_config_deprecated_map = {
        "appendix": ("BuildExecutor", "appendix"),
        "push_secret": ("BuildExecutor", "push_secret"),
        "build_memory_limit": ("BuildExecutor", "memory_limit"),
        "sticky_builds": ("KubernetesBuildExecutor", "sticky_builds"),
        "log_tail_lines": ("KubernetesBuildExecutor", "log_tail_lines"),
        "build_memory_request": ("KubernetesBuildExecutor", "memory_request"),
        "build_docker_host": ("KubernetesBuildExecutor", "docker_host"),
        "build_namespace": ("KubernetesBuildExecutor", "namespace"),
        "build_image": ("KubernetesBuildExecutor", "build_image"),
        "build_node_selector": ("KubernetesBuildExecutor", "node_selector"),
    }

    @observe(*_build_config_deprecated_map)
    def _build_config_deprecated(self, change):
        dest_cls, dest_name = self._build_config_deprecated_map[change.name]
        self.log.warning(
            "BinderHub.%s is deprecated, use %s.%s", change.name, dest_cls, dest_name
        )
        self.config[dest_cls][dest_name] = change.new

    @staticmethod
    def add_url_prefix(prefix, handlers):
        """add a url prefix to handlers"""
        for i, tup in enumerate(handlers):
            lis = list(tup)
            lis[0] = url_path_join(prefix, tup[0])
            handlers[i] = tuple(lis)
        return handlers

    def init_pycurl(self):
        try:
            AsyncHTTPClient.configure("tornado.curl_httpclient.CurlAsyncHTTPClient")
        except ImportError as e:
            self.log.warning(
                "Could not load pycurl: %s\npycurl is recommended if you have a large number of users.",
                e,
            )
        # set max verbosity of curl_httpclient at INFO
        # because debug-logging from curl_httpclient
        # includes every full request and response
        if self.log_level < logging.INFO:
            curl_log = logging.getLogger("tornado.curl_httpclient")
            curl_log.setLevel(logging.INFO)

    def initialize(self, *args, **kwargs):
        """Load configuration settings."""
        super().initialize(*args, **kwargs)
        self.load_config_file(self.config_file)
        # hook up tornado logging
        if self.debug:
            self.log_level = logging.DEBUG
        tornado.options.options.logging = logging.getLevelName(self.log_level)
        tornado.log.enable_pretty_logging()
        self.log = tornado.log.app_log

        self.init_pycurl()

        # initialize kubernetes config
        if self.builder_required:
            try:
                kubernetes.config.load_incluster_config()
            except kubernetes.config.ConfigException:
                kubernetes.config.load_kube_config()
            self.tornado_settings[
                "kubernetes_client"
            ] = self.kube_client = kubernetes.client.CoreV1Api()

        # times 2 for log + build threads
        self.build_pool = ThreadPoolExecutor(self.concurrent_build_limit * 2)
        # default executor for asyncifying blocking calls (e.g. to kubernetes, docker).
        # this should not be used for long-running requests
        self.executor = ThreadPoolExecutor(self.executor_threads)

        jinja_options = dict(
            autoescape=True,
        )
        template_paths = [self.template_path]
        base_template_path = self._template_path_default()
        if base_template_path not in template_paths:
            # add base templates to the end, so they are looked up at last after custom templates
            template_paths.append(base_template_path)
        loader = ChoiceLoader(
            [
                # first load base templates with prefix
                PrefixLoader(
                    {"templates": FileSystemLoader([base_template_path])}, "/"
                ),
                # load all templates
                FileSystemLoader(template_paths),
            ]
        )
        jinja_env = Environment(loader=loader, **jinja_options)
        if self.use_registry:
            registry = self.registry_class(parent=self)
        else:
            registry = None

        self.launcher = Launcher(
            parent=self,
            hub_url=self.hub_url,
            hub_url_local=self.hub_url_local,
            hub_api_token=self.hub_api_token,
            create_user=not self.auth_enabled,
        )

        self.event_log = EventLog(parent=self)

        for schema_file in glob(os.path.join(HERE, "event-schemas", "*.json")):
            with open(schema_file) as f:
                self.event_log.register_schema(json.load(f))

        launch_quota = self.launch_quota_class(parent=self, executor=self.executor)

        # Construct a Builder so that we can extract parameters such as the
        # configuration or the version string to pass to /version and /health handlers
        example_builder = self.build_class(parent=self)
        self.tornado_settings.update(
            {
                "log_function": log_request,
                "image_prefix": self.image_prefix,
                "debug": self.debug,
                "launcher": self.launcher,
                "ban_networks": self.ban_networks,
                "ban_networks_min_prefix_len": self.ban_networks_min_prefix_len,
                "build_pool": self.build_pool,
                "build_token_check_origin": self.build_token_check_origin,
                "build_token_secret": self.build_token_secret,
                "build_token_expires_seconds": self.build_token_expires_seconds,
                "example_builder": example_builder,
                "pod_quota": self.pod_quota,
                "per_repo_quota": self.per_repo_quota,
                "per_repo_quota_higher": self.per_repo_quota_higher,
                "repo_providers": self.repo_providers,
                "launch_quota": launch_quota,
                "rate_limiter": RateLimiter(parent=self),
                "use_registry": self.use_registry,
                "build_class": self.build_class,
                "registry": registry,
                "traitlets_config": self.config,
                "traitlets_parent": self,
                "google_analytics_code": self.google_analytics_code,
                "google_analytics_domain": self.google_analytics_domain,
                "about_message": self.about_message,
                "banner_message": self.banner_message,
                "extra_footer_scripts": self.extra_footer_scripts,
                "jinja2_env": jinja_env,
                "build_docker_config": self.build_docker_config,
                "base_url": self.base_url,
                "badge_base_url": self.badge_base_url,
                "static_path": os.path.join(HERE, "static"),
                "static_url_prefix": url_path_join(self.base_url, "static/"),
                "template_variables": self.template_variables,
                "executor": self.executor,
                "auth_enabled": self.auth_enabled,
                "event_log": self.event_log,
                "normalized_origin": self.normalized_origin,
                "enable_api_only_mode": self.enable_api_only_mode,
            }
        )
        if self.auth_enabled:
            self.tornado_settings["cookie_secret"] = os.urandom(32)
        if self.cors_allow_origin:
            self.tornado_settings.setdefault("headers", {})[
                "Access-Control-Allow-Origin"
            ] = self.cors_allow_origin

        handlers = [
            (r"/metrics", MetricsHandler),
            (r"/versions", VersionHandler),
            (r"/build/([^/]+)/(.+)", BuildHandler),
            (r"/health", self.health_handler_class, {"hub_url": self.hub_url_local}),
            (r"/_config", ConfigHandler),
        ]
        if not self.enable_api_only_mode:
            # In API only mode the endpoints in the list below
            # are unregistered as they don't make sense in a API only scenario
            handlers += [
                (r"/about", AboutHandler),
                (r"/v2/([^/]+)/(.+)", ParameterizedMainHandler),
                (r"/", MainHandler),
                (r"/repo/([^/]+)/([^/]+)(/.*)?", LegacyRedirectHandler),
                # for backward-compatible mybinder.org badge URLs
                # /assets/images/badge.svg
                (
                    r"/assets/(images/badge\.svg)",
                    tornado.web.StaticFileHandler,
                    {"path": self.tornado_settings["static_path"]},
                ),
                # /badge.svg
                (
                    r"/(badge\.svg)",
                    tornado.web.StaticFileHandler,
                    {
                        "path": os.path.join(
                            self.tornado_settings["static_path"], "images"
                        )
                    },
                ),
                # /badge_logo.svg
                (
                    r"/(badge\_logo\.svg)",
                    tornado.web.StaticFileHandler,
                    {
                        "path": os.path.join(
                            self.tornado_settings["static_path"], "images"
                        )
                    },
                ),
                # /logo_social.png
                (
                    r"/(logo\_social\.png)",
                    tornado.web.StaticFileHandler,
                    {
                        "path": os.path.join(
                            self.tornado_settings["static_path"], "images"
                        )
                    },
                ),
                # /favicon_XXX.ico
                (
                    r"/(favicon\_fail\.ico)",
                    tornado.web.StaticFileHandler,
                    {
                        "path": os.path.join(
                            self.tornado_settings["static_path"], "images"
                        )
                    },
                ),
                (
                    r"/(favicon\_success\.ico)",
                    tornado.web.StaticFileHandler,
                    {
                        "path": os.path.join(
                            self.tornado_settings["static_path"], "images"
                        )
                    },
                ),
                (
                    r"/(favicon\_building\.ico)",
                    tornado.web.StaticFileHandler,
                    {
                        "path": os.path.join(
                            self.tornado_settings["static_path"], "images"
                        )
                    },
                ),
            ]
        # This needs to be the last handler in the list, because it needs to match "everything else"
        handlers.append((r".*", Custom404))
        handlers = self.add_url_prefix(self.base_url, handlers)
        if self.extra_static_path:
            handlers.insert(
                -1,
                (
                    re.escape(
                        url_path_join(self.base_url, self.extra_static_url_prefix)
                    )
                    + r"(.*)",
                    tornado.web.StaticFileHandler,
                    {"path": self.extra_static_path},
                ),
            )
        if self.auth_enabled:
            oauth_redirect_uri = os.getenv(
                "JUPYTERHUB_OAUTH_CALLBACK_URL"
            ) or url_path_join(self.base_url, "oauth_callback")
            oauth_redirect_uri = urlparse(oauth_redirect_uri).path
            handlers.insert(
                -1, (re.escape(oauth_redirect_uri), HubOAuthCallbackHandler)
            )
        self.tornado_app = tornado.web.Application(handlers, **self.tornado_settings)

    def stop(self):
        self.http_server.stop()
        self.build_pool.shutdown()

    async def watch_build_pods(self):
        warnings.warn(
            "watch_build_pods() is deprecated, use watch_builders()", DeprecationWarning
        )
        await self.watch_builders()

    async def watch_builders(self):
        """
        Watch builders, run a cleanup function every build_cleanup_interval
        """
        while self.build_cleaner_class:
            cleaner = self.build_cleaner_class(
                kube=self.kube_client, namespace=self.build_namespace, parent=self
            )
            try:
                await asyncio.wrap_future(self.executor.submit(cleaner.cleanup))
            except Exception:
                app_log.exception("Failed to cleanup builders")
            await asyncio.sleep(self.build_cleanup_interval)

    def start(self, run_loop=True):
        self.log.info("BinderHub starting on port %i", self.port)
        self.http_server = HTTPServer(
            self.tornado_app,
            xheaders=True,
        )
        self.http_server.listen(self.port)
        if self.builder_required:
            asyncio.ensure_future(self.watch_builders())
        if run_loop:
            tornado.ioloop.IOLoop.current().start()


main = BinderHub.launch_instance

if __name__ == "__main__":
    main()