Differential D27 Diff 78 swh/storage/archiver/worker.py

Changeset View

Standalone View

swh/storage/archiver/worker.py

# Copyright (C) 2015 The Software Heritage developers		# Copyright (C) 2015 The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution		# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version		# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information		# See top-level LICENSE file for more information

import random		import random

from .copier import ArchiverCopier		from .copier import ArchiverCopier
from .. import get_storage		from .. import get_storage

from datetime import datetime		from datetime import datetime


class ArchiverWorker(): # This class should probably extend a Celery Task.		class ArchiverWorker():
""" Do the required backups on a given batch of contents.		""" Do the required backups on a given batch of contents.

Process the content of a content batch in order to do the needed backups on		Process the content of a content batch in order to do the needed backups on
the slaves servers.		the slaves servers.

Attributes:		Attributes:
batch: The content this worker has to archive, which is a dictionary		batch: The content this worker has to archive, which is a dictionary
that associates a content's sha1 id to the list of servers where		that associates a content's sha1 id to the list of servers where
the content is present or missing		the content is present or missing
(see ArchiverDirector::get_unarchived_content).		(see ArchiverDirector::get_unarchived_content).
master_storage_args: The connection argument to initialize the		master_storage_args: The connection argument to initialize the
master storage where is the content location.		master storage where is the content location.
		ardumontUnsubmitted Done Inline Actions s/where is the content location/(db connection url, content location)/ ardumont: s/where is the content location/(db connection url, content location)/
slave_storages: A map that associates server_id to the remote server.		slave_storages: A map that associates server_id to the remote server.
retention_policy: The required number of copies for a content to be		retention_policy: The required number of copies for a content to be
		ardumontUnsubmitted Done Inline Actions For the sake of coherence with the rest of your diff, you forgot to adapt the docstring on config argument. ardumont: For the sake of coherence with the rest of your diff, you forgot to adapt the docstring on…
considered safe.		considered safe.
"""		"""
def __init__(self, batch, master_storage_args,		def __init__(self, batch, master_storage_args, slave_storages, config):
slave_storages, retention_policy):
""" Constructor of the ArchiverWorker class.		""" Constructor of the ArchiverWorker class.

Args:		Args:
batch: A batch of content, which is a dictionnary that associates		batch: A batch of content, which is a dictionnary that associates
a content's sha1 id to the list of servers where the content		a content's sha1 id to the list of servers where the content
is present.		is present.
master_storage: The master storage where is the whole content.		master_storage_args: The master storage arugments.
		ardumontUnsubmitted Done Inline Actions arguments. ardumont: arguments.
slave_storages: A map that associates server_id to the remote		slave_storages: A map that associates server_id to the remote
server.		server.
retention_policy: The required number of copies for a content to		config: Archiver_configuration. A dictionnary that must contains
be considered safe.		the following keys.
		objstorage_path (string): the path of the objstorage of the
		master.
		batch_max_size (int): The number of content items that can be
		given to the same archiver worker.
		archival_max_age (int): Delay given to the worker to cpy all
		the files in a given batch.
		retention_policy (int): Required number of copies for the
		content to be considered safe.
		asynchronous (boolean): Indicate whenever the archival should
		run in asynchronous mode or not.
"""		"""
self.batch = batch		self.batch = batch
self.master_storage = get_storage('local_storage', master_storage_args)		self.master_storage = get_storage('local_storage', master_storage_args)
self.slave_storages = slave_storages		self.slave_storages = slave_storages
self.retention_policy = retention_policy		self.config = config

def __choose_backup_servers(self, allowed_storage, backup_number):		def __choose_backup_servers(self, allowed_storage, backup_number):
""" Choose the slave servers for archival.		""" Choose the slave servers for archival.

Choose the given amount of servers among those which don't already		Choose the given amount of servers among those which don't already
contain a copy of the content.		contain a copy of the content.

Args:		Args:
Show All 9 Lines	def __choose_backup_servers(self, allowed_storage, backup_number):

# TODO Find a better (or a good) policy to choose the backup servers.		# TODO Find a better (or a good) policy to choose the backup servers.
# The random choice should be equivalently distributed between		# The random choice should be equivalently distributed between
# servers for a great amount of data, but don't take care of servers		# servers for a great amount of data, but don't take care of servers
# capacities.		# capacities.
return random.sample(allowed_storage, backup_number)		return random.sample(allowed_storage, backup_number)

def __get_archival_status(self, content_id, server):		def __get_archival_status(self, content_id, server):
		""" Get the archival status of the required content.

		Attributes:
		content_id (string): Sha1 of the content.
		server: Tuple (archive_id, archive_url) of the archive server.
		Returns:
		A dict that contains all the required data : 'content_id',
		'archive_id', 'status', and 'mtime'
		"""
t, = list(		t, = list(
self.master_storage.db.content_archive_get(content_id, server[0])		self.master_storage.db.content_archive_get(content_id, server[0])
)		)
return {		return {
'content_id': t[0],		'content_id': t[0],
'archive_id': t[1],		'archive_id': t[1],
'status': t[2],		'status': t[2],
'mtime': t[3]		'mtime': t[3]
}		}

def __content_archive_update(self, content_id, archive_id,		def __content_archive_update(self, content_id, archive_id,
new_status=None):		new_status=None):
""" Update the status of a archive content and set it's mtime to now()		""" Update the status of a archive content and set it's mtime to now()

Change the last modification time of an archived content and change		Change the last modification time of an archived content and change
its status to the given one.		its status to the given one.

Args:		Args:
content_id (string): The content id.		content_id (string): The content id.
archive_id (string): The id of the concerned archive.		archive_id (string): The id of the concerned archive.
new_status (string): One of missing, ongoing or present, this		new_status (string): One of missing, ongoing or present, this
status will replace the previous one. If not given, the		status will replace the previous one. If not given, the
function only changes the mtime of the content.		function only changes the mtime of the content.
"""		"""
query = """UPDATE content_archive		self.master_storage.db.content_archive_update(
SET %(fields)s		content_id,
WHERE content_id='%(content_id)s'		archive_id,
and archive_id='%(archive_id)s'		new_status
"""		)
fields = []
if new_status:
fields.append("status='%s'" % new_status)
fields.append("mtime=now()")

d = {'fields': ', '.join(fields),
'content_id': content_id,
'archive_id': archive_id}

with self.master_storage.db.transaction() as cur:
cur.execute(query % d)

def run(self):
""" Do the task expected from the archiver worker.

Process the content in the batch, ensure that the elements still need
an archival, and spawn copiers to copy files in each destinations.
"""

def content_filter(content, destination):		def need_archival(self, content, destination):
""" Indicates whenever a content need archivage.		""" Indicates whenever a content need archivage.

Filter function that returns True if a given content		Filter function that returns True if a given content
still require to be archived.		still require to be archived.

Args:		Args:
content (str):		content (str): Sha1 of a content.
		destination: Tuple (archive id, archive url).
"""		"""
archival_status = self.__get_archival_status(		archival_status = self.__get_archival_status(
content,		content,
destination		destination
)		)
if archival_status:
status = archival_status['status']		status = archival_status['status']
		mtime = archival_status['mtime']
# If the archive is already present, no need to backup.		# If the archive is already present, no need to backup.
if status == 'present':		if status == 'present':
return False		return False
# If the content is ongoing but still have time, there is		# If the content is ongoing but still have time, there is
# another worker working on this content.		# another worker working on this content.
elif status == 'ongoing':		elif status == 'ongoing':
elapsed = datetime.now() - archival_status['mtime']\		mtime = mtime.replace(tzinfo=None)
.total_seconds()		elapsed = (datetime.now() - mtime).total_seconds()
if elapsed < self.master_storage.archival_max_age:		if elapsed <= self.config['archival_max_age']:
return False		return False
return True		return True
else:
# TODO this is an error case, the content should always exists.
return None

		def sort_content_by_archive(self):
		""" Create a map {archive_server -> list of content)

		Create a mapping that associate to a archive server all the
		contents that needs to be archived in it by the current worker.

		The map is in the form of :
		{
		(archive_1, archive_1_url): [content1, content2, content_3]
		(archive_2, archive_2_url): [content1, content3]
		}

		Returns:
		The created mapping.
		"""
slaves_copy = {}		slaves_copy = {}
for content_id in self.batch:		for content_id in self.batch:
# Choose some servers to upload the content		# Choose some servers to upload the content among the missing ones.
server_data = self.batch[content_id]		server_data = self.batch[content_id]
		nb_present = len(server_data['present'])
		nb_backup = self.config['retention_policy'] - nb_present
backup_servers = self.__choose_backup_servers(		backup_servers = self.__choose_backup_servers(
server_data['missing'],		server_data['missing'],
self.retention_policy - len(server_data['present'])		nb_backup
)		)
# Fill the map destination -> content to upload		# Fill the map destination -> content to upload
for server in backup_servers:		for server in backup_servers:
slaves_copy.setdefault(server, []).append(content_id)		slaves_copy.setdefault(server, []).append(content_id)
		return slaves_copy

		def run(self):
		""" Do the task expected from the archiver worker.

		Process the content in the batch, ensure that the elements still need
		an archival, and spawn copiers to copy files in each destinations.
		"""
		# Get a map (archive -> [contents])
		slaves_copy = self.sort_content_by_archive()

# At this point, check the archival status of the content in order to		# At this point, re-check the archival status in order to know if the
# know if it is still needed.		# job have been done by another worker.
for destination in slaves_copy:		for destination in slaves_copy:
contents = []		# list() is needed because filter's result will be consumed twice.
for content in slaves_copy[destination]:		slaves_copy[destination] = list(filter(
if content_filter(content, destination):		lambda content_id: self.need_archival(content_id, destination),
contents.append(content)		slaves_copy[destination]
slaves_copy[destination] = contents		))
		for content_id in slaves_copy[destination]:
		self.__content_archive_update(content_id, destination[0],
		new_status='ongoing')

# Spawn a copier for each destination that will copy all the		# Spawn a copier for each destination
# needed content.
for destination in slaves_copy:		for destination in slaves_copy:
ac = ArchiverCopier(		self.run_copier(destination, slaves_copy[destination])
destination, slaves_copy[destination],
self.master_storage)		def run_copier(self, destination, contents):
		""" Run a copier in order to archive the given contents

		ardumontUnsubmitted Done Inline Actions You might want to add in the docstring the fact that if the copier fails to run (returns False), we consider the content not being copied (because no update takes place). ardumont: You might want to add in the docstring the fact that if the copier fails to run (returns False)…
		Upload the given contents to the given archive.

		Attributes:
		ardumontUnsubmitted Done Inline Actions ...archive_url) of the destination. ardumont: ...archive_url) of the destination.
		destination: Tuple (archive_id, archvie_url) of the destiantion.
		ardumontUnsubmitted Done Inline Actions List of contents ardumont: List of contents
		contents: List of content to archive.
		"""
		ac = ArchiverCopier(destination, contents, self.master_storage)
if ac.run():		if ac.run():
# Once the archival complete, update the database.		# Once the archival complete, update the database.
for content_id in slaves_copy[destination]:		for content_id in contents:
self.__content_archive_update(content_id, destination[0],		self.__content_archive_update(content_id, destination[0],
new_status='present')		new_status='present')
		ardumontUnsubmitted Done Inline Actions If one copier fails significantly badly (e.g. by throwing something), the remaining copier won't even be triggered. We may want to trigger the other ones even though one or more fail. This could dealt with in the run_copier method. ardumont: If one copier fails significantly badly (e.g. by throwing something), the remaining copier…