python-maas-provisioningserver 1.5.4+bzr2294-0ubuntu1.2 / usr / lib / python2.7 / dist-packages / provisioningserver / config.py

# Copyright 2012-2014 Canonical Ltd.  This software is licensed under the
# GNU Affero General Public License version 3 (see the file LICENSE).

"""MAAS Provisioning Configuration.

Configuration for most elements of a Cluster Controller can be obtained
through this module's `Config` and `BootConfig` classes.  At the time of
writing the exceptions are the Celery worker's configuration, as well as the
`CLUSTER_UUID` and `MAAS_URL` environment variables
(see `provisioningserver.cluster_config`).

It's pretty simple. Typical usage is::

  >>> config = Config.load_from_cache()
  {...}

This reads in a configuration file from `Config.DEFAULT_FILENAME` (see a note
about that later). The configuration file is parsed as YAML, and a plain `dict`
is returned with configuration nested within it. The configuration is validated
at load time using `formencode`. The policy for validation is laid out in this
module; see the various `formencode.Schema` subclasses.

All configuration is optional, and a sensible default is provided in every
instance. When adding or changing settings bear this policy in mind, and also
that the defaults should be geared towards a system in production, and not a
development environment. The defaults can be obtained by calling
`Config.get_defaults()`.

An alternative to `Config.load_from_cache()` is `Config.load()`, which loads
and validates a configuration file while bypassing the cache.  See `Config` for
other useful functions.

`Config.DEFAULT_FILENAME` is a class property, so does not need to be
referenced via an instance of `Config`. It refers to the
``MAAS_PROVISIONING_SETTINGS`` environment variable in the first instance, but
has a sensible default too. You can write to this property and it will update
the environment so that child processes will also use the same configuration
filename. To revert to the default - i.e. erase the environment variable - you
can `del Config.DEFAULT_FILENAME`.

When testing, see `provisioningserver.testing.config.ConfigFixture` to
temporarily use a different configuration.

"""

from __future__ import (
    absolute_import,
    print_function,
    unicode_literals,
    )

str = None

__metaclass__ = type
__all__ = [
    "BootConfig",
    "Config",
    "ConfigBase",
    "ConfigMeta",
    ]

from copy import deepcopy
from getpass import getuser
from os import environ
import os.path
from shutil import copyfile
from threading import RLock

from formencode import (
    ForEach,
    Schema,
    )
from formencode.declarative import DeclarativeMeta
from formencode.validators import (
    Bool,
    Int,
    RequireIfPresent,
    Set,
    String,
    )
from provisioningserver.utils import atomic_write
import yaml


class ConfigOops(Schema):
    """Configuration validator for OOPS options."""

    if_key_missing = None

    directory = String(if_missing=b"")
    reporter = String(if_missing=b"")

    chained_validators = (
        RequireIfPresent("reporter", present="directory"),
        )


class ConfigBroker(Schema):
    """Configuration validator for message broker options."""

    if_key_missing = None

    host = String(if_missing=b"localhost")
    port = Int(min=1, max=65535, if_missing=5673)
    username = String(if_missing=getuser())
    password = String(if_missing=b"test")
    vhost = String(if_missing="/")


class ConfigTFTP(Schema):
    """Configuration validator for the TFTP service."""

    if_key_missing = None

    # Obsolete: old TFTP root directory.  This is retained for the purpose of
    # deriving new, Simplestreams-based import configuration from previously
    # imported boot images.
    # The last time this is needed is for upgrading an older cluster
    # controller to the Ubuntu 14.04 version of MAAS.  After installation of
    # the 14.04 version, this setting is never used.
    root = String(if_missing="/var/lib/maas/tftp")

    # TFTP root directory, managed by the Simplestreams-based import script.
    # Equates to $storage/current.  The import script maintains "current" as a
    # symlink pointing to the most recent images.
    resource_root = String(
        if_missing="/var/lib/maas/boot-resources/current/")

    port = Int(min=1, max=65535, if_missing=69)
    generator = String(if_missing=b"http://localhost/MAAS/api/1.0/pxeconfig/")


class ConfigLegacyEphemeral(Schema):
    """Legacy `eephemeral` section in `pserv.yaml` prior to MAAS 1.5.

    This has been replaced with boot-source selection in `bootresources.yaml`.
    It is still accepted in `pserv.yaml`, but not used.
    """
    if_key_missing = None
    images_directory = String(if_missing=None)
    releases = Set(if_missing=None)


class ConfigLegacyBoot(Schema):
    """Legacy `boot` section in `pserv.yaml` prior to MAAS 1.5.

    The new version of this config section lives in `bootresources.yaml`.  It
    is still accepted in `pserv.yaml`, but not used.
    """
    if_key_missing = None
    architectures = Set(if_missing=None)
    ephemeral = ConfigLegacyEphemeral


class ConfigRPC(Schema):
    """Configuration validator for the RPC service."""

    if_key_missing = None


class ConfigBootSourceSelection(Schema):
    """Configuration validator for boot source election onfiguration."""

    if_key_missing = None

    release = String(if_missing="*")
    arches = Set(if_missing=["*"])
    subarches = Set(if_missing=['*'])
    labels = Set(if_missing=['*'])


class ConfigBootSource(Schema):
    """Configuration validator for boot source configuration."""

    if_key_missing = None

    path = String(
        if_missing="http://maas.ubuntu.com/images/ephemeral-v2/releases/")
    keyring = String(
        if_missing="/usr/share/keyrings/ubuntu-cloudimage-keyring.gpg")
    selections = ForEach(
        ConfigBootSourceSelection,
        if_missing=[ConfigBootSourceSelection.to_python({})])


class ConfigBoot(Schema):
    """Configuration validator for boot configuration."""

    if_key_missing = None

    storage = String(if_missing="/var/lib/maas/boot-resources/")
    sources = ForEach(
        ConfigBootSource, if_missing=[ConfigBootSource.to_python({})])

    # Marker in the bootresources.yaml file: if True, the file has not been
    # edited yet and needs to be either configured with initial choices, or
    # rewritten based on previously downloaded boot images.
    configure_me = Bool(if_missing=False)


class ConfigBase(Schema):
    """Base configuration validator."""

    @classmethod
    def parse(cls, stream):
        """Load a YAML configuration from `stream` and validate."""
        return cls.to_python(yaml.safe_load(stream))

    @classmethod
    def load(cls, filename=None):
        """Load a YAML configuration from `filename` and validate."""
        if filename is None:
            filename = cls.DEFAULT_FILENAME
        with open(filename, "rb") as stream:
            return cls.parse(stream)

    @classmethod
    def _get_backup_name(cls, message, filename=None):
        if filename is None:
            filename = cls.DEFAULT_FILENAME
        return "%s.%s.bak" % (filename, message)

    @classmethod
    def create_backup(cls, message, filename=None):
        """Create a backup of the YAML configuration.

        The given 'message' will be used in the name of the backup file.
        """
        backup_name = cls._get_backup_name(message, filename)
        if filename is None:
            filename = cls.DEFAULT_FILENAME
        copyfile(filename, backup_name)

    @classmethod
    def save(cls, config, filename=None):
        """Save a YAML configuration to `filename`, or to the default file."""
        if filename is None:
            filename = cls.DEFAULT_FILENAME
        dump = yaml.safe_dump(config)
        atomic_write(dump, filename)

    _cache = {}
    _cache_lock = RLock()

    @classmethod
    def load_from_cache(cls, filename=None):
        """Load or return a previously loaded configuration.

        Keeps an internal cache of config files.  If the requested config file
        is not in cache, it is loaded and inserted into the cache first.

        Each call returns a distinct (deep) copy of the requested config from
        the cache, so the caller can modify its own copy without affecting what
        other call sites see.

        This is thread-safe, so is okay to use from Django, for example.
        """
        if filename is None:
            filename = cls.DEFAULT_FILENAME
        filename = os.path.abspath(filename)
        with cls._cache_lock:
            if filename not in cls._cache:
                with open(filename, "rb") as stream:
                    cls._cache[filename] = cls.parse(stream)
            return deepcopy(cls._cache[filename])

    @classmethod
    def flush_cache(cls, filename=None):
        """Evict a config file, or any cached config files, from cache."""
        with cls._cache_lock:
            if filename is None:
                cls._cache.clear()
            else:
                if filename in cls._cache:
                    del cls._cache[filename]

    @classmethod
    def field(target, *steps):
        """Obtain a field by following `steps`."""
        for step in steps:
            target = target.fields[step]
        return target

    @classmethod
    def get_defaults(cls):
        """Return the default configuration."""
        return cls.to_python({})


class ConfigMeta(DeclarativeMeta):
    """Metaclass for the root configuration schema."""

    envvar = None  # Set this in subtypes.
    default = None  # Set this in subtypes.

    def _get_default_filename(cls):
        # Avoid circular imports.
        from provisioningserver.utils import locate_config

        # Get the configuration filename from the environment. Failing that,
        # look for the configuration in its default locations.
        return environ.get(cls.envvar, locate_config(cls.default))

    def _set_default_filename(cls, filename):
        # Set the configuration filename in the environment.
        environ[cls.envvar] = filename

    def _delete_default_filename(cls):
        # Remove any setting of the configuration filename from the
        # environment.
        environ.pop(cls.envvar, None)

    DEFAULT_FILENAME = property(
        _get_default_filename, _set_default_filename,
        _delete_default_filename, doc=(
            "The default config file to load. Refers to "
            "`cls.envvar` in the environment."))


class Config(ConfigBase):
    """Configuration for the provisioning server."""

    class __metaclass__(ConfigMeta):
        envvar = "MAAS_PROVISIONING_SETTINGS"
        default = "pserv.yaml"

    if_key_missing = None

    logfile = String(if_empty=b"pserv.log", if_missing=b"pserv.log")
    oops = ConfigOops
    broker = ConfigBroker
    tftp = ConfigTFTP
    rpc = ConfigRPC
    boot = ConfigLegacyBoot


class BootConfig(ConfigBase):
    """Configuration for boot resources."""

    class __metaclass__(ConfigMeta):
        envvar = "MAAS_BOOT_RESOURCES_SETTINGS"
        default = "bootresources.yaml"

    if_key_missing = None

    boot = ConfigBoot