synapse-old/synapse/config/_base.py

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# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2017-2018 New Vector Ltd
# Copyright 2019 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import argparse
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import errno
import logging
import os
import re
from collections import OrderedDict
from enum import Enum, auto
from hashlib import sha256
from textwrap import dedent
from typing import (
Any,
ClassVar,
Dict,
Iterable,
Iterator,
List,
MutableMapping,
Optional,
Tuple,
Type,
TypeVar,
Union,
)
import attr
import jinja2
import pkg_resources
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import yaml
from synapse.types import StrSequence
from synapse.util.templates import _create_mxc_to_http_filter, _format_ts_filter
logger = logging.getLogger(__name__)
class ConfigError(Exception):
"""Represents a problem parsing the configuration
Args:
msg: A textual description of the error.
path: Where appropriate, an indication of where in the configuration
the problem lies.
"""
def __init__(self, msg: str, path: Optional[StrSequence] = None):
self.msg = msg
self.path = path
def format_config_error(e: ConfigError) -> Iterator[str]:
"""
Formats a config error neatly
The idea is to format the immediate error, plus the "causes" of those errors,
hopefully in a way that makes sense to the user. For example:
Error in configuration at 'oidc_config.user_mapping_provider.config.display_name_template':
Failed to parse config for module 'JinjaOidcMappingProvider':
invalid jinja template:
unexpected end of template, expected 'end of print statement'.
Args:
e: the error to be formatted
Returns: An iterator which yields string fragments to be formatted
"""
yield "Error in configuration"
if e.path:
yield " at '%s'" % (".".join(e.path),)
yield ":\n %s" % (e.msg,)
parent_e = e.__cause__
indent = 1
while parent_e:
indent += 1
yield ":\n%s%s" % (" " * indent, str(parent_e))
parent_e = parent_e.__cause__
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# We split these messages out to allow packages to override with package
# specific instructions.
MISSING_REPORT_STATS_CONFIG_INSTRUCTIONS = """\
Please opt in or out of reporting homeserver usage statistics, by setting
the `report_stats` key in your config file to either True or False.
"""
MISSING_REPORT_STATS_SPIEL = """\
We would really appreciate it if you could help our project out by reporting
homeserver usage statistics from your homeserver. Your homeserver's server name,
along with very basic aggregate data (e.g. number of users) will be reported. But
it helps us to track the growth of the Matrix community, and helps us to make Matrix
a success, as well as to convince other networks that they should peer with us.
Thank you.
"""
MISSING_SERVER_NAME = """\
Missing mandatory `server_name` config option.
"""
CONFIG_FILE_HEADER = """\
# Configuration file for Synapse.
#
# This is a YAML file: see [1] for a quick introduction. Note in particular
# that *indentation is important*: all the elements of a list or dictionary
# should have the same indentation.
#
# [1] https://docs.ansible.com/ansible/latest/reference_appendices/YAMLSyntax.html
#
# For more information on how to configure Synapse, including a complete accounting of
# each option, go to docs/usage/configuration/config_documentation.md or
# https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html
"""
def path_exists(file_path: str) -> bool:
"""Check if a file exists
Unlike os.path.exists, this throws an exception if there is an error
checking if the file exists (for example, if there is a perms error on
the parent dir).
Returns:
True if the file exists; False if not.
"""
try:
os.stat(file_path)
return True
except OSError as e:
if e.errno != errno.ENOENT:
raise e
return False
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class Config:
"""
A configuration section, containing configuration keys and values.
Attributes:
section: The section title of this config object, such as
"tls" or "logger". This is used to refer to it on the root
logger (for example, `config.tls.some_option`). Must be
defined in subclasses.
"""
section: ClassVar[str]
def __init__(self, root_config: "RootConfig" = None):
self.root = root_config
# Get the path to the default Synapse template directory
self.default_template_dir = pkg_resources.resource_filename(
"synapse", "res/templates"
)
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@staticmethod
def parse_size(value: Union[str, int]) -> int:
"""Interpret `value` as a number of bytes.
If an integer is provided it is treated as bytes and is unchanged.
String byte sizes can have a suffix of 'K', `M`, `G` or `T`,
representing kibibytes, mebibytes, gibibytes and tebibytes respectively.
No suffix is understood as a plain byte count.
Raises:
TypeError, if given something other than an integer or a string
ValueError: if given a string not of the form described above.
"""
if type(value) is int: # noqa: E721
return value
elif isinstance(value, str):
sizes = {"K": 1024, "M": 1024 * 1024, "G": 1024**3, "T": 1024**4}
size = 1
suffix = value[-1]
if suffix in sizes:
value = value[:-1]
size = sizes[suffix]
return int(value) * size
else:
raise TypeError(f"Bad byte size {value!r}")
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@staticmethod
def parse_duration(value: Union[str, int]) -> int:
"""Convert a duration as a string or integer to a number of milliseconds.
If an integer is provided it is treated as milliseconds and is unchanged.
String durations can have a suffix of 's', 'm', 'h', 'd', 'w', or 'y'.
No suffix is treated as milliseconds.
Args:
value: The duration to parse.
Returns:
The number of milliseconds in the duration.
Raises:
TypeError, if given something other than an integer or a string
ValueError: if given a string not of the form described above.
"""
if type(value) is int: # noqa: E721
return value
elif isinstance(value, str):
second = 1000
minute = 60 * second
hour = 60 * minute
day = 24 * hour
week = 7 * day
year = 365 * day
sizes = {
"s": second,
"m": minute,
"h": hour,
"d": day,
"w": week,
"y": year,
}
size = 1
suffix = value[-1]
if suffix in sizes:
value = value[:-1]
size = sizes[suffix]
return int(value) * size
else:
raise TypeError(f"Bad duration {value!r}")
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@staticmethod
def abspath(file_path: str) -> str:
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return os.path.abspath(file_path) if file_path else file_path
@classmethod
def path_exists(cls, file_path: str) -> bool:
return path_exists(file_path)
@classmethod
def check_file(cls, file_path: Optional[str], config_name: str) -> str:
if file_path is None:
raise ConfigError("Missing config for %s." % (config_name,))
try:
os.stat(file_path)
except OSError as e:
raise ConfigError(
"Error accessing file '%s' (config for %s): %s"
% (file_path, config_name, e.strerror)
)
return cls.abspath(file_path)
@classmethod
def ensure_directory(cls, dir_path: str) -> str:
dir_path = cls.abspath(dir_path)
os.makedirs(dir_path, exist_ok=True)
if not os.path.isdir(dir_path):
raise ConfigError("%s is not a directory" % (dir_path,))
return dir_path
@classmethod
def read_file(cls, file_path: Any, config_name: str) -> str:
"""Deprecated: call read_file directly"""
return read_file(file_path, (config_name,))
def read_template(self, filename: str) -> jinja2.Template:
"""Load a template file from disk.
This function will attempt to load the given template from the default Synapse
template directory.
Files read are treated as Jinja templates. The templates is not rendered yet
and has autoescape enabled.
Args:
filename: A template filename to read.
Raises:
ConfigError: if the file's path is incorrect or otherwise cannot be read.
Returns:
A jinja2 template.
"""
return self.read_templates([filename])[0]
def read_templates(
self,
filenames: List[str],
custom_template_directories: Optional[Iterable[str]] = None,
) -> List[jinja2.Template]:
"""Load a list of template files from disk using the given variables.
This function will attempt to load the given templates from the default Synapse
template directory. If `custom_template_directories` is supplied, any directory
in this list is tried (in the order they appear in the list) before trying
Synapse's default directory.
Files read are treated as Jinja templates. The templates are not rendered yet
and have autoescape enabled.
Args:
filenames: A list of template filenames to read.
custom_template_directories: A list of directory to try to look for the
templates before using the default Synapse template directory instead.
Raises:
ConfigError: if the file's path is incorrect or otherwise cannot be read.
Returns:
A list of jinja2 templates.
"""
search_directories = []
# The loader will first look in the custom template directories (if specified)
# for the given filename. If it doesn't find it, it will use the default
# template dir instead.
if custom_template_directories is not None:
for custom_template_directory in custom_template_directories:
# Check that the given template directory exists
if not self.path_exists(custom_template_directory):
raise ConfigError(
"Configured template directory does not exist: %s"
% (custom_template_directory,)
)
# Search the custom template directory as well
search_directories.append(custom_template_directory)
# Append the default directory at the end of the list so Jinja can fallback on it
# if a template is missing from any custom directory.
search_directories.append(self.default_template_dir)
# TODO: switch to synapse.util.templates.build_jinja_env
loader = jinja2.FileSystemLoader(search_directories)
env = jinja2.Environment(
loader=loader,
autoescape=jinja2.select_autoescape(),
)
# Update the environment with our custom filters
env.filters.update(
{
"format_ts": _format_ts_filter,
"mxc_to_http": _create_mxc_to_http_filter(
self.root.server.public_baseurl
),
}
)
# Load the templates
return [env.get_template(filename) for filename in filenames]
TRootConfig = TypeVar("TRootConfig", bound="RootConfig")
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class RootConfig:
"""
Holder of an application's configuration.
What configuration this object holds is defined by `config_classes`, a list
of Config classes that will be instantiated and given the contents of a
configuration file to read. They can then be accessed on this class by their
section name, defined in the Config or dynamically set to be the name of the
class, lower-cased and with "Config" removed.
"""
config_classes: List[Type[Config]] = []
def __init__(self, config_files: StrSequence = ()):
# Capture absolute paths here, so we can reload config after we daemonize.
self.config_files = [os.path.abspath(path) for path in config_files]
for config_class in self.config_classes:
if config_class.section is None:
raise ValueError("%r requires a section name" % (config_class,))
try:
conf = config_class(self)
except Exception as e:
raise Exception("Failed making %s: %r" % (config_class.section, e))
setattr(self, config_class.section, conf)
def invoke_all(
self, func_name: str, *args: Any, **kwargs: Any
) -> MutableMapping[str, Any]:
"""
Invoke a function on all instantiated config objects this RootConfig is
configured to use.
Args:
func_name: Name of function to invoke
*args
**kwargs
Returns:
ordered dictionary of config section name and the result of the
function from it.
"""
res = OrderedDict()
for config_class in self.config_classes:
config = getattr(self, config_class.section)
if hasattr(config, func_name):
res[config_class.section] = getattr(config, func_name)(*args, **kwargs)
return res
@classmethod
def invoke_all_static(cls, func_name: str, *args: Any, **kwargs: any) -> None:
"""
Invoke a static function on config objects this RootConfig is
configured to use.
Args:
func_name: Name of function to invoke
*args
**kwargs
Returns:
ordered dictionary of config section name and the result of the
function from it.
"""
for config in cls.config_classes:
if hasattr(config, func_name):
getattr(config, func_name)(*args, **kwargs)
def generate_config(
self,
config_dir_path: str,
data_dir_path: str,
server_name: str,
generate_secrets: bool = False,
report_stats: Optional[bool] = None,
open_private_ports: bool = False,
listeners: Optional[List[dict]] = None,
tls_certificate_path: Optional[str] = None,
tls_private_key_path: Optional[str] = None,
) -> str:
"""
Build a default configuration file
This is used when the user explicitly asks us to generate a config file
(eg with --generate-config).
Args:
config_dir_path: The path where the config files are kept. Used to
create filenames for things like the log config and the signing key.
data_dir_path: The path where the data files are kept. Used to create
filenames for things like the database and media store.
server_name: The server name. Used to initialise the server_name
config param, but also used in the names of some of the config files.
generate_secrets: True if we should generate new secrets for things
like the macaroon_secret_key. If False, these parameters will be left
unset.
report_stats: Initial setting for the report_stats setting.
If None, report_stats will be left unset.
open_private_ports: True to leave private ports (such as the non-TLS
HTTP listener) open to the internet.
listeners: A list of descriptions of the listeners synapse should
start with each of which specifies a port (int), a list of
resources (list(str)), tls (bool) and type (str). For example:
[{
"port": 8448,
"resources": [{"names": ["federation"]}],
"tls": True,
"type": "http",
},
{
"port": 443,
"resources": [{"names": ["client"]}],
"tls": False,
"type": "http",
}],
tls_certificate_path: The path to the tls certificate.
tls_private_key_path: The path to the tls private key.
Returns:
The yaml config file
"""
conf = CONFIG_FILE_HEADER + "\n".join(
dedent(conf)
for conf in self.invoke_all(
"generate_config_section",
config_dir_path=config_dir_path,
data_dir_path=data_dir_path,
server_name=server_name,
generate_secrets=generate_secrets,
report_stats=report_stats,
open_private_ports=open_private_ports,
listeners=listeners,
tls_certificate_path=tls_certificate_path,
tls_private_key_path=tls_private_key_path,
).values()
)
conf = re.sub("\n{2,}", "\n", conf)
return conf
@classmethod
def load_config(
cls: Type[TRootConfig], description: str, argv: List[str]
) -> TRootConfig:
"""Parse the commandline and config files
Doesn't support config-file-generation: used by the worker apps.
Returns:
Config object.
"""
config_parser = argparse.ArgumentParser(description=description)
cls.add_arguments_to_parser(config_parser)
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obj, _ = cls.load_config_with_parser(config_parser, argv)
return obj
@classmethod
def add_arguments_to_parser(cls, config_parser: argparse.ArgumentParser) -> None:
"""Adds all the config flags to an ArgumentParser.
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Doesn't support config-file-generation: used by the worker apps.
Used for workers where we want to add extra flags/subcommands.
Args:
config_parser: App description
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"""
config_parser.add_argument(
"-c",
"--config-path",
action="append",
metavar="CONFIG_FILE",
help="Specify config file. Can be given multiple times and"
" may specify directories containing *.yaml files.",
)
config_parser.add_argument(
"--keys-directory",
metavar="DIRECTORY",
help="Where files such as certs and signing keys are stored when"
" their location is not given explicitly in the config."
" Defaults to the directory containing the last config file",
)
cls.invoke_all_static("add_arguments", config_parser)
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@classmethod
def load_config_with_parser(
cls: Type[TRootConfig], parser: argparse.ArgumentParser, argv: List[str]
) -> Tuple[TRootConfig, argparse.Namespace]:
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"""Parse the commandline and config files with the given parser
Doesn't support config-file-generation: used by the worker apps.
Used for workers where we want to add extra flags/subcommands.
Args:
parser
argv
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Returns:
Returns the parsed config object and the parsed argparse.Namespace
object from parser.parse_args(..)`
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"""
config_args = parser.parse_args(argv)
config_files = find_config_files(search_paths=config_args.config_path)
obj = cls(config_files)
if not config_files:
parser.error("Must supply a config file.")
if config_args.keys_directory:
config_dir_path = config_args.keys_directory
else:
config_dir_path = os.path.dirname(config_files[-1])
config_dir_path = os.path.abspath(config_dir_path)
data_dir_path = os.getcwd()
config_dict = read_config_files(config_files)
obj.parse_config_dict(
config_dict, config_dir_path=config_dir_path, data_dir_path=data_dir_path
)
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obj.invoke_all("read_arguments", config_args)
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return obj, config_args
@classmethod
def load_or_generate_config(
cls: Type[TRootConfig], description: str, argv: List[str]
) -> Optional[TRootConfig]:
"""Parse the commandline and config files
Supports generation of config files, so is used for the main homeserver app.
Returns:
Config object, or None if --generate-config or --generate-keys was set
"""
parser = argparse.ArgumentParser(description=description)
parser.add_argument(
"-c",
"--config-path",
action="append",
metavar="CONFIG_FILE",
help="Specify config file. Can be given multiple times and"
" may specify directories containing *.yaml files.",
)
# we nest the mutually-exclusive group inside another group so that the help
# text shows them in their own group.
generate_mode_group = parser.add_argument_group(
"Config generation mode",
)
generate_mode_exclusive = generate_mode_group.add_mutually_exclusive_group()
generate_mode_exclusive.add_argument(
# hidden option to make the type and default work
"--generate-mode",
help=argparse.SUPPRESS,
type=_ConfigGenerateMode,
default=_ConfigGenerateMode.GENERATE_MISSING_AND_RUN,
)
generate_mode_exclusive.add_argument(
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"--generate-config",
help="Generate a config file, then exit.",
action="store_const",
const=_ConfigGenerateMode.GENERATE_EVERYTHING_AND_EXIT,
dest="generate_mode",
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)
generate_mode_exclusive.add_argument(
"--generate-missing-configs",
"--generate-keys",
help="Generate any missing additional config files, then exit.",
action="store_const",
const=_ConfigGenerateMode.GENERATE_MISSING_AND_EXIT,
dest="generate_mode",
)
generate_mode_exclusive.add_argument(
"--generate-missing-and-run",
help="Generate any missing additional config files, then run. This is the "
"default behaviour.",
action="store_const",
const=_ConfigGenerateMode.GENERATE_MISSING_AND_RUN,
dest="generate_mode",
)
generate_group = parser.add_argument_group("Details for --generate-config")
generate_group.add_argument(
"-H", "--server-name", help="The server name to generate a config file for."
)
generate_group.add_argument(
"--report-stats",
action="store",
help="Whether the generated config reports homeserver usage statistics.",
choices=["yes", "no"],
)
generate_group.add_argument(
"--config-directory",
"--keys-directory",
metavar="DIRECTORY",
help=(
"Specify where additional config files such as signing keys and log"
" config should be stored. Defaults to the same directory as the last"
" config file."
),
)
generate_group.add_argument(
"--data-directory",
metavar="DIRECTORY",
help=(
"Specify where data such as the media store and database file should be"
" stored. Defaults to the current working directory."
),
)
generate_group.add_argument(
"--open-private-ports",
action="store_true",
help=(
"Leave private ports (such as the non-TLS HTTP listener) open to the"
" internet. Do not use this unless you know what you are doing."
),
)
cls.invoke_all_static("add_arguments", parser)
config_args = parser.parse_args(argv)
config_files = find_config_files(search_paths=config_args.config_path)
if not config_files:
parser.error(
"Must supply a config file.\nA config file can be automatically"
' generated using "--generate-config -H SERVER_NAME'
' -c CONFIG-FILE"'
)
if config_args.config_directory:
config_dir_path = config_args.config_directory
else:
config_dir_path = os.path.dirname(config_files[-1])
config_dir_path = os.path.abspath(config_dir_path)
data_dir_path = os.getcwd()
obj = cls(config_files)
if (
config_args.generate_mode
== _ConfigGenerateMode.GENERATE_EVERYTHING_AND_EXIT
):
if config_args.report_stats is None:
parser.error(
"Please specify either --report-stats=yes or --report-stats=no\n\n"
+ MISSING_REPORT_STATS_SPIEL
)
(config_path,) = config_files
if not path_exists(config_path):
print("Generating config file %s" % (config_path,))
if config_args.data_directory:
data_dir_path = config_args.data_directory
else:
data_dir_path = os.getcwd()
data_dir_path = os.path.abspath(data_dir_path)
server_name = config_args.server_name
if not server_name:
raise ConfigError(
"Must specify a server_name to a generate config for."
" Pass -H server.name."
)
config_str = obj.generate_config(
config_dir_path=config_dir_path,
data_dir_path=data_dir_path,
server_name=server_name,
report_stats=(config_args.report_stats == "yes"),
generate_secrets=True,
open_private_ports=config_args.open_private_ports,
)
os.makedirs(config_dir_path, exist_ok=True)
with open(config_path, "w") as config_file:
config_file.write(config_str)
config_file.write("\n\n# vim:ft=yaml")
config_dict = yaml.safe_load(config_str)
obj.generate_missing_files(config_dict, config_dir_path)
print(
(
"A config file has been generated in %r for server name"
" %r. Please review this file and customise it"
" to your needs."
)
% (config_path, server_name)
)
return
else:
print(
(
"Config file %r already exists. Generating any missing config"
" files."
)
% (config_path,)
)
config_dict = read_config_files(config_files)
obj.generate_missing_files(config_dict, config_dir_path)
if config_args.generate_mode in (
_ConfigGenerateMode.GENERATE_EVERYTHING_AND_EXIT,
_ConfigGenerateMode.GENERATE_MISSING_AND_EXIT,
):
return None
obj.parse_config_dict(
config_dict, config_dir_path=config_dir_path, data_dir_path=data_dir_path
)
obj.invoke_all("read_arguments", config_args)
return obj
def parse_config_dict(
self, config_dict: Dict[str, Any], config_dir_path: str, data_dir_path: str
) -> None:
"""Read the information from the config dict into this Config object.
Args:
config_dict: Configuration data, as read from the yaml
config_dir_path: The path where the config files are kept. Used to
create filenames for things like the log config and the signing key.
data_dir_path: The path where the data files are kept. Used to create
filenames for things like the database and media store.
"""
self.invoke_all(
"read_config",
config_dict,
config_dir_path=config_dir_path,
data_dir_path=data_dir_path,
)
def generate_missing_files(
self, config_dict: Dict[str, Any], config_dir_path: str
) -> None:
self.invoke_all("generate_files", config_dict, config_dir_path)
def reload_config_section(self, section_name: str) -> Config:
"""Reconstruct the given config section, leaving all others unchanged.
This works in three steps:
1. Create a new instance of the relevant `Config` subclass.
2. Call `read_config` on that instance to parse the new config.
3. Replace the existing config instance with the new one.
:raises ValueError: if the given `section` does not exist.
:raises ConfigError: for any other problems reloading config.
:returns: the previous config object, which no longer has a reference to this
RootConfig.
"""
existing_config: Optional[Config] = getattr(self, section_name, None)
if existing_config is None:
raise ValueError(f"Unknown config section '{section_name}'")
logger.info("Reloading config section '%s'", section_name)
new_config_data = read_config_files(self.config_files)
new_config = type(existing_config)(self)
new_config.read_config(new_config_data)
setattr(self, section_name, new_config)
existing_config.root = None
return existing_config
def read_config_files(config_files: Iterable[str]) -> Dict[str, Any]:
"""Read the config files into a dict
Args:
config_files: A list of the config files to read
Returns:
The configuration dictionary.
"""
specified_config = {}
for config_file in config_files:
with open(config_file) as file_stream:
yaml_config = yaml.safe_load(file_stream)
if not isinstance(yaml_config, dict):
err = "File %r is empty or doesn't parse into a key-value map. IGNORING."
print(err % (config_file,))
continue
specified_config.update(yaml_config)
if "server_name" not in specified_config:
raise ConfigError(MISSING_SERVER_NAME)
if "report_stats" not in specified_config:
raise ConfigError(
MISSING_REPORT_STATS_CONFIG_INSTRUCTIONS + "\n" + MISSING_REPORT_STATS_SPIEL
)
return specified_config
def find_config_files(search_paths: List[str]) -> List[str]:
"""Finds config files using a list of search paths. If a path is a file
then that file path is added to the list. If a search path is a directory
then all the "*.yaml" files in that directory are added to the list in
sorted order.
Args:
search_paths: A list of paths to search.
Returns:
A list of file paths.
"""
config_files = []
if search_paths:
for config_path in search_paths:
if os.path.isdir(config_path):
# We accept specifying directories as config paths, we search
# inside that directory for all files matching *.yaml, and then
# we apply them in *sorted* order.
files = []
for entry in os.listdir(config_path):
entry_path = os.path.join(config_path, entry)
if not os.path.isfile(entry_path):
err = "Found subdirectory in config directory: %r. IGNORING."
print(err % (entry_path,))
continue
if not entry.endswith(".yaml"):
err = (
"Found file in config directory that does not end in "
"'.yaml': %r. IGNORING."
)
print(err % (entry_path,))
continue
files.append(entry_path)
config_files.extend(sorted(files))
else:
config_files.append(config_path)
return config_files
@attr.s(auto_attribs=True)
class ShardedWorkerHandlingConfig:
"""Algorithm for choosing which instance is responsible for handling some
sharded work.
For example, the federation senders use this to determine which instances
handles sending stuff to a given destination (which is used as the `key`
below).
"""
instances: List[str]
def should_handle(self, instance_name: str, key: str) -> bool:
"""Whether this instance is responsible for handling the given key."""
# If no instances are defined we assume some other worker is handling
# this.
if not self.instances:
return False
return self._get_instance(key) == instance_name
def _get_instance(self, key: str) -> str:
"""Get the instance responsible for handling the given key.
Note: For federation sending and pushers the config for which instance
is sending is known only to the sender instance, so we don't expose this
method by default.
"""
if not self.instances:
raise Exception("Unknown worker")
if len(self.instances) == 1:
return self.instances[0]
# We shard by taking the hash, modulo it by the number of instances and
# then checking whether this instance matches the instance at that
# index.
#
# (Technically this introduces some bias and is not entirely uniform,
# but since the hash is so large the bias is ridiculously small).
dest_hash = sha256(key.encode("utf8")).digest()
dest_int = int.from_bytes(dest_hash, byteorder="little")
remainder = dest_int % (len(self.instances))
return self.instances[remainder]
@attr.s
class RoutableShardedWorkerHandlingConfig(ShardedWorkerHandlingConfig):
"""A version of `ShardedWorkerHandlingConfig` that is used for config
options where all instances know which instances are responsible for the
sharded work.
"""
def __attrs_post_init__(self):
# We require that `self.instances` is non-empty.
if not self.instances:
raise Exception("Got empty list of instances for shard config")
def get_instance(self, key: str) -> str:
"""Get the instance responsible for handling the given key."""
return self._get_instance(key)
def read_file(file_path: Any, config_path: Iterable[str]) -> str:
"""Check the given file exists, and read it into a string
If it does not, emit an error indicating the problem
Args:
file_path: the file to be read
config_path: where in the configuration file_path came from, so that a useful
error can be emitted if it does not exist.
Returns:
content of the file.
Raises:
ConfigError if there is a problem reading the file.
"""
if not isinstance(file_path, str):
raise ConfigError("%r is not a string", config_path)
try:
os.stat(file_path)
with open(file_path) as file_stream:
return file_stream.read()
except OSError as e:
raise ConfigError("Error accessing file %r" % (file_path,), config_path) from e
class _ConfigGenerateMode(Enum):
GENERATE_MISSING_AND_RUN = auto()
GENERATE_MISSING_AND_EXIT = auto()
GENERATE_EVERYTHING_AND_EXIT = auto()
__all__ = [
"Config",
"RootConfig",
"ShardedWorkerHandlingConfig",
"RoutableShardedWorkerHandlingConfig",
"read_file",
]