openstack/swift
Code Issues Proposed changes
62ab4f6f78
swift/swift/common/db_replicator.py
Clay Gerrard c1dc2fa624 Add two vector timestamps 
The normalized form of the X-Timestamp header looks like a float with a fixed
width to ensure stable string sorting - normalized timestamps look like
"1402464677.04188"

To support overwrites of existing data without modifying the original
timestamp but still maintain consistency a second internal offset
vector is append to the normalized timestamp form which compares and
sorts greater than the fixed width float format but less than a newer
timestamp.  The internalized format of timestamps looks like
"1402464677.04188_0000000000000000" - the portion after the underscore
is the offset and is a formatted hexadecimal integer.

The internalized form is not exposed to clients in responses from Swift.
Normal client operations will not create a timestamp with an offset.

The Timestamp class in common.utils supports internalized and normalized
formatting of timestamps and also comparison of timestamp values.  When the
offset value of a Timestamp is 0 - it's considered insignificant and need not
be represented in the string format; to support backwards compatibility during
a Swift upgrade the internalized and normalized form of a Timestamp with an
insignificant offset are identical.  When a timestamp includes an offset it
will always be represented in the internalized form, but is still excluded
from the normalized form.  Timestamps with an equivalent timestamp portion
(the float part) will compare and order by their offset.  Timestamps with a
greater timestamp portion will always compare and order greater than a
Timestamp with a lesser timestamp regardless of it's offset.  String
comparison and ordering is guaranteed for the internalized string format, and
is backwards compatible for normalized timestamps which do not include an
offset.

The reconciler currently uses a offset bump to ensure that objects can move to
the wrong storage policy and be moved back.  This use-case is valid because
the content represented by the user-facing timestamp is not modified in way.
Future consumers of the offset vector of timestamps should be mindful of HTTP
semantics of If-Modified and take care to avoid deviation in the response from
the object server without an accompanying change to the user facing timestamp.

DocImpact
Implements: blueprint storage-policies
Change-Id: Id85c960b126ec919a481dc62469bf172b7fb8549
2014-06-19 10:18:06 -07:00

750 lines
31 KiB
Python
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# Copyright (c) 2010-2012 OpenStack Foundation
#
# 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 os
import random
import math
import time
import shutil
import uuid
import errno
import re
from contextlib import contextmanager
from swift import gettext_ as _
from eventlet import GreenPool, sleep, Timeout
from eventlet.green import subprocess
import swift.common.db
from swift.common.direct_client import quote
from swift.common.utils import get_logger, whataremyips, storage_directory, \
renamer, mkdirs, lock_parent_directory, config_true_value, \
unlink_older_than, dump_recon_cache, rsync_ip, ismount, json, Timestamp
from swift.common import ring
from swift.common.http import HTTP_NOT_FOUND, HTTP_INSUFFICIENT_STORAGE
from swift.common.bufferedhttp import BufferedHTTPConnection
from swift.common.exceptions import DriveNotMounted, ConnectionTimeout
from swift.common.daemon import Daemon
from swift.common.swob import Response, HTTPNotFound, HTTPNoContent, \
HTTPAccepted, HTTPBadRequest
DEBUG_TIMINGS_THRESHOLD = 10
def quarantine_db(object_file, server_type):
"""
In the case that a corrupt file is found, move it to a quarantined area to
allow replication to fix it.
:param object_file: path to corrupt file
:param server_type: type of file that is corrupt
('container' or 'account')
"""
object_dir = os.path.dirname(object_file)
quarantine_dir = os.path.abspath(
os.path.join(object_dir, '..', '..', '..', '..', 'quarantined',
server_type + 's', os.path.basename(object_dir)))
try:
renamer(object_dir, quarantine_dir)
except OSError as e:
if e.errno not in (errno.EEXIST, errno.ENOTEMPTY):
raise
quarantine_dir = "%s-%s" % (quarantine_dir, uuid.uuid4().hex)
renamer(object_dir, quarantine_dir)
def roundrobin_datadirs(datadirs):
"""
Generator to walk the data dirs in a round robin manner, evenly
hitting each device on the system, and yielding any .db files
found (in their proper places). The partitions within each data
dir are walked randomly, however.
:param datadirs: a list of (path, node_id) to walk
:returns: A generator of (partition, path_to_db_file, node_id)
"""
def walk_datadir(datadir, node_id):
partitions = os.listdir(datadir)
random.shuffle(partitions)
for partition in partitions:
part_dir = os.path.join(datadir, partition)
if not os.path.isdir(part_dir):
continue
suffixes = os.listdir(part_dir)
for suffix in suffixes:
suff_dir = os.path.join(part_dir, suffix)
if not os.path.isdir(suff_dir):
continue
hashes = os.listdir(suff_dir)
for hsh in hashes:
hash_dir = os.path.join(suff_dir, hsh)
if not os.path.isdir(hash_dir):
continue
object_file = os.path.join(hash_dir, hsh + '.db')
if os.path.exists(object_file):
yield (partition, object_file, node_id)
its = [walk_datadir(datadir, node_id) for datadir, node_id in datadirs]
while its:
for it in its:
try:
yield it.next()
except StopIteration:
its.remove(it)
class ReplConnection(BufferedHTTPConnection):
"""
Helper to simplify REPLICATEing to a remote server.
"""
def __init__(self, node, partition, hash_, logger):
""
self.logger = logger
self.node = node
host = "%s:%s" % (node['replication_ip'], node['replication_port'])
BufferedHTTPConnection.__init__(self, host)
self.path = '/%s/%s/%s' % (node['device'], partition, hash_)
def replicate(self, *args):
"""
Make an HTTP REPLICATE request
:param args: list of json-encodable objects
:returns: bufferedhttp response object
"""
try:
body = json.dumps(args)
self.request('REPLICATE', self.path, body,
{'Content-Type': 'application/json'})
response = self.getresponse()
response.data = response.read()
return response
except (Exception, Timeout):
self.logger.exception(
_('ERROR reading HTTP response from %s'), self.node)
return None
class Replicator(Daemon):
"""
Implements the logic for directing db replication.
"""
def __init__(self, conf, logger=None):
self.conf = conf
self.logger = logger or get_logger(conf, log_route='replicator')
self.root = conf.get('devices', '/srv/node')
self.mount_check = config_true_value(conf.get('mount_check', 'true'))
self.port = int(conf.get('bind_port', self.default_port))
concurrency = int(conf.get('concurrency', 8))
self.cpool = GreenPool(size=concurrency)
swift_dir = conf.get('swift_dir', '/etc/swift')
self.ring = ring.Ring(swift_dir, ring_name=self.server_type)
self._local_device_ids = set()
self.per_diff = int(conf.get('per_diff', 1000))
self.max_diffs = int(conf.get('max_diffs') or 100)
self.interval = int(conf.get('interval') or
conf.get('run_pause') or 30)
self.vm_test_mode = config_true_value(conf.get('vm_test_mode', 'no'))
self.node_timeout = int(conf.get('node_timeout', 10))
self.conn_timeout = float(conf.get('conn_timeout', 0.5))
self.reclaim_age = float(conf.get('reclaim_age', 86400 * 7))
swift.common.db.DB_PREALLOCATION = \
config_true_value(conf.get('db_preallocation', 'f'))
self._zero_stats()
self.recon_cache_path = conf.get('recon_cache_path',
'/var/cache/swift')
self.recon_replicator = '%s.recon' % self.server_type
self.rcache = os.path.join(self.recon_cache_path,
self.recon_replicator)
self.extract_device_re = re.compile('%s%s([^%s]+)' % (
self.root, os.path.sep, os.path.sep))
def _zero_stats(self):
"""Zero out the stats."""
self.stats = {'attempted': 0, 'success': 0, 'failure': 0, 'ts_repl': 0,
'no_change': 0, 'hashmatch': 0, 'rsync': 0, 'diff': 0,
'remove': 0, 'empty': 0, 'remote_merge': 0,
'start': time.time(), 'diff_capped': 0}
def _report_stats(self):
"""Report the current stats to the logs."""
now = time.time()
self.logger.info(
_('Attempted to replicate %(count)d dbs in %(time).5f seconds '
'(%(rate).5f/s)'),
{'count': self.stats['attempted'],
'time': now - self.stats['start'],
'rate': self.stats['attempted'] /
(now - self.stats['start'] + 0.0000001)})
self.logger.info(_('Removed %(remove)d dbs') % self.stats)
self.logger.info(_('%(success)s successes, %(failure)s failures')
% self.stats)
dump_recon_cache(
{'replication_stats': self.stats,
'replication_time': now - self.stats['start'],
'replication_last': now},
self.rcache, self.logger)
self.logger.info(' '.join(['%s:%s' % item for item in
self.stats.items() if item[0] in
('no_change', 'hashmatch', 'rsync', 'diff', 'ts_repl',
'empty', 'diff_capped')]))
def _rsync_file(self, db_file, remote_file, whole_file=True):
"""
Sync a single file using rsync. Used by _rsync_db to handle syncing.
:param db_file: file to be synced
:param remote_file: remote location to sync the DB file to
:param whole-file: if True, uses rsync's --whole-file flag
:returns: True if the sync was successful, False otherwise
"""
popen_args = ['rsync', '--quiet', '--no-motd',
'--timeout=%s' % int(math.ceil(self.node_timeout)),
'--contimeout=%s' % int(math.ceil(self.conn_timeout))]
if whole_file:
popen_args.append('--whole-file')
popen_args.extend([db_file, remote_file])
proc = subprocess.Popen(popen_args)
proc.communicate()
if proc.returncode != 0:
self.logger.error(_('ERROR rsync failed with %(code)s: %(args)s'),
{'code': proc.returncode, 'args': popen_args})
return proc.returncode == 0
def _rsync_db(self, broker, device, http, local_id,
replicate_method='complete_rsync', replicate_timeout=None):
"""
Sync a whole db using rsync.
:param broker: DB broker object of DB to be synced
:param device: device to sync to
:param http: ReplConnection object
:param local_id: unique ID of the local database replica
:param replicate_method: remote operation to perform after rsync
:param replicate_timeout: timeout to wait in seconds
"""
device_ip = rsync_ip(device['replication_ip'])
if self.vm_test_mode:
remote_file = '%s::%s%s/%s/tmp/%s' % (
device_ip, self.server_type, device['replication_port'],
device['device'], local_id)
else:
remote_file = '%s::%s/%s/tmp/%s' % (
device_ip, self.server_type, device['device'], local_id)
mtime = os.path.getmtime(broker.db_file)
if not self._rsync_file(broker.db_file, remote_file):
return False
# perform block-level sync if the db was modified during the first sync
if os.path.exists(broker.db_file + '-journal') or \
os.path.getmtime(broker.db_file) > mtime:
# grab a lock so nobody else can modify it
with broker.lock():
if not self._rsync_file(broker.db_file, remote_file, False):
return False
with Timeout(replicate_timeout or self.node_timeout):
response = http.replicate(replicate_method, local_id)
return response and response.status >= 200 and response.status < 300
def _usync_db(self, point, broker, http, remote_id, local_id):
"""
Sync a db by sending all records since the last sync.
:param point: synchronization high water mark between the replicas
:param broker: database broker object
:param http: ReplConnection object for the remote server
:param remote_id: database id for the remote replica
:param local_id: database id for the local replica
:returns: boolean indicating completion and success
"""
self.stats['diff'] += 1
self.logger.increment('diffs')
self.logger.debug('Syncing chunks with %s', http.host)
sync_table = broker.get_syncs()
objects = broker.get_items_since(point, self.per_diff)
diffs = 0
while len(objects) and diffs < self.max_diffs:
diffs += 1
with Timeout(self.node_timeout):
response = http.replicate('merge_items', objects, local_id)
if not response or response.status >= 300 or response.status < 200:
if response:
self.logger.error(_('ERROR Bad response %(status)s from '
'%(host)s'),
{'status': response.status,
'host': http.host})
return False
point = objects[-1]['ROWID']
objects = broker.get_items_since(point, self.per_diff)
if objects:
self.logger.debug(
'Synchronization for %s has fallen more than '
'%s rows behind; moving on and will try again next pass.',
broker, self.max_diffs * self.per_diff)
self.stats['diff_capped'] += 1
self.logger.increment('diff_caps')
else:
with Timeout(self.node_timeout):
response = http.replicate('merge_syncs', sync_table)
if response and response.status >= 200 and response.status < 300:
broker.merge_syncs([{'remote_id': remote_id,
'sync_point': point}],
incoming=False)
return True
return False
def _in_sync(self, rinfo, info, broker, local_sync):
"""
Determine whether or not two replicas of a databases are considered
to be in sync.
:param rinfo: remote database info
:param info: local database info
:param broker: database broker object
:param local_sync: cached last sync point between replicas
:returns: boolean indicating whether or not the replicas are in sync
"""
if max(rinfo['point'], local_sync) >= info['max_row']:
self.stats['no_change'] += 1
self.logger.increment('no_changes')
return True
if rinfo['hash'] == info['hash']:
self.stats['hashmatch'] += 1
self.logger.increment('hashmatches')
broker.merge_syncs([{'remote_id': rinfo['id'],
'sync_point': rinfo['point']}],
incoming=False)
return True
def _http_connect(self, node, partition, db_file):
"""
Make an http_connection using ReplConnection
:param node: node dictionary from the ring
:param partition: partition partition to send in the url
:param db_file: DB file
:returns: ReplConnection object
"""
return ReplConnection(node, partition,
os.path.basename(db_file).split('.', 1)[0],
self.logger)
def _gather_sync_args(self, info):
"""
Convert local replication_info to sync args tuple.
"""
sync_args_order = ('max_row', 'hash', 'id', 'created_at',
'put_timestamp', 'delete_timestamp', 'metadata')
return tuple(info[key] for key in sync_args_order)
def _repl_to_node(self, node, broker, partition, info):
"""
Replicate a database to a node.
:param node: node dictionary from the ring to be replicated to
:param broker: DB broker for the DB to be replication
:param partition: partition on the node to replicate to
:param info: DB info as a dictionary of {'max_row', 'hash', 'id',
'created_at', 'put_timestamp', 'delete_timestamp',
'metadata'}
:returns: True if successful, False otherwise
"""
with ConnectionTimeout(self.conn_timeout):
http = self._http_connect(node, partition, broker.db_file)
if not http:
self.logger.error(
_('ERROR Unable to connect to remote server: %s'), node)
return False
sync_args = self._gather_sync_args(info)
with Timeout(self.node_timeout):
response = http.replicate('sync', *sync_args)
if not response:
return False
return self._handle_sync_response(node, response, info, broker, http)
def _handle_sync_response(self, node, response, info, broker, http):
if response.status == HTTP_NOT_FOUND: # completely missing, rsync
self.stats['rsync'] += 1
self.logger.increment('rsyncs')
return self._rsync_db(broker, node, http, info['id'])
elif response.status == HTTP_INSUFFICIENT_STORAGE:
raise DriveNotMounted()
elif response.status >= 200 and response.status < 300:
rinfo = json.loads(response.data)
local_sync = broker.get_sync(rinfo['id'], incoming=False)
if self._in_sync(rinfo, info, broker, local_sync):
return True
# if the difference in rowids between the two differs by
# more than 50%, rsync then do a remote merge.
if rinfo['max_row'] / float(info['max_row']) < 0.5:
self.stats['remote_merge'] += 1
self.logger.increment('remote_merges')
return self._rsync_db(broker, node, http, info['id'],
replicate_method='rsync_then_merge',
replicate_timeout=(info['count'] / 2000))
# else send diffs over to the remote server
return self._usync_db(max(rinfo['point'], local_sync),
broker, http, rinfo['id'], info['id'])
def _post_replicate_hook(self, broker, info, responses):
"""
:param broker: the container that just replicated
:param info: pre-replication full info dict
:param responses: a list of bools indicating success from nodes
"""
pass
def _replicate_object(self, partition, object_file, node_id):
"""
Replicate the db, choosing method based on whether or not it
already exists on peers.
:param partition: partition to be replicated to
:param object_file: DB file name to be replicated
:param node_id: node id of the node to be replicated to
"""
start_time = now = time.time()
self.logger.debug('Replicating db %s', object_file)
self.stats['attempted'] += 1
self.logger.increment('attempts')
shouldbehere = True
try:
broker = self.brokerclass(object_file, pending_timeout=30)
broker.reclaim(now - self.reclaim_age,
now - (self.reclaim_age * 2))
info = broker.get_replication_info()
bpart = self.ring.get_part(
info['account'], info.get('container'))
if bpart != int(partition):
partition = bpart
# Important to set this false here since the later check only
# checks if it's on the proper device, not partition.
shouldbehere = False
name = '/' + quote(info['account'])
if 'container' in info:
name += '/' + quote(info['container'])
self.logger.error(
'Found %s for %s when it should be on partition %s; will '
'replicate out and remove.' % (object_file, name, bpart))
except (Exception, Timeout) as e:
if 'no such table' in str(e):
self.logger.error(_('Quarantining DB %s'), object_file)
quarantine_db(broker.db_file, broker.db_type)
else:
self.logger.exception(_('ERROR reading db %s'), object_file)
self.stats['failure'] += 1
self.logger.increment('failures')
return
# The db is considered deleted if the delete_timestamp value is greater
# than the put_timestamp, and there are no objects.
delete_timestamp = Timestamp(info.get('delete_timestamp') or 0)
put_timestamp = Timestamp(info.get('put_timestamp') or 0)
if delete_timestamp < (now - self.reclaim_age) and \
delete_timestamp > put_timestamp and \
info['count'] in (None, '', 0, '0'):
if self.report_up_to_date(info):
self.delete_db(object_file)
self.logger.timing_since('timing', start_time)
return
responses = []
nodes = self.ring.get_part_nodes(int(partition))
if shouldbehere:
shouldbehere = bool([n for n in nodes if n['id'] == node_id])
# See Footnote [1] for an explanation of the repl_nodes assignment.
i = 0
while i < len(nodes) and nodes[i]['id'] != node_id:
i += 1
repl_nodes = nodes[i + 1:] + nodes[:i]
more_nodes = self.ring.get_more_nodes(int(partition))
for node in repl_nodes:
success = False
try:
success = self._repl_to_node(node, broker, partition, info)
except DriveNotMounted:
repl_nodes.append(more_nodes.next())
self.logger.error(_('ERROR Remote drive not mounted %s'), node)
except (Exception, Timeout):
self.logger.exception(_('ERROR syncing %(file)s with node'
' %(node)s'),
{'file': object_file, 'node': node})
self.stats['success' if success else 'failure'] += 1
self.logger.increment('successes' if success else 'failures')
responses.append(success)
try:
self._post_replicate_hook(broker, info, responses)
except (Exception, Timeout):
self.logger.exception('UNHANDLED EXCEPTION: in post replicate '
'hook for %s', broker.db_file)
if not shouldbehere and all(responses):
# If the db shouldn't be on this node and has been successfully
# synced to all of its peers, it can be removed.
self.delete_db(broker)
self.logger.timing_since('timing', start_time)
def delete_db(self, broker):
object_file = broker.db_file
hash_dir = os.path.dirname(object_file)
suf_dir = os.path.dirname(hash_dir)
with lock_parent_directory(object_file):
shutil.rmtree(hash_dir, True)
try:
os.rmdir(suf_dir)
except OSError as err:
if err.errno not in (errno.ENOENT, errno.ENOTEMPTY):
self.logger.exception(
_('ERROR while trying to clean up %s') % suf_dir)
self.stats['remove'] += 1
device_name = self.extract_device(object_file)
self.logger.increment('removes.' + device_name)
def extract_device(self, object_file):
"""
Extract the device name from an object path. Returns "UNKNOWN" if the
path could not be extracted successfully for some reason.
:param object_file: the path to a database file.
"""
match = self.extract_device_re.match(object_file)
if match:
return match.groups()[0]
return "UNKNOWN"
def report_up_to_date(self, full_info):
return True
def run_once(self, *args, **kwargs):
"""Run a replication pass once."""
self._zero_stats()
dirs = []
ips = whataremyips()
if not ips:
self.logger.error(_('ERROR Failed to get my own IPs?'))
return
self._local_device_ids = set()
for node in self.ring.devs:
if (node and node['replication_ip'] in ips and
node['replication_port'] == self.port):
if self.mount_check and not ismount(
os.path.join(self.root, node['device'])):
self.logger.warn(
_('Skipping %(device)s as it is not mounted') % node)
continue
unlink_older_than(
os.path.join(self.root, node['device'], 'tmp'),
time.time() - self.reclaim_age)
datadir = os.path.join(self.root, node['device'], self.datadir)
if os.path.isdir(datadir):
self._local_device_ids.add(node['id'])
dirs.append((datadir, node['id']))
self.logger.info(_('Beginning replication run'))
for part, object_file, node_id in roundrobin_datadirs(dirs):
self.cpool.spawn_n(
self._replicate_object, part, object_file, node_id)
self.cpool.waitall()
self.logger.info(_('Replication run OVER'))
self._report_stats()
def run_forever(self, *args, **kwargs):
"""
Replicate dbs under the given root in an infinite loop.
"""
sleep(random.random() * self.interval)
while True:
begin = time.time()
try:
self.run_once()
except (Exception, Timeout):
self.logger.exception(_('ERROR trying to replicate'))
elapsed = time.time() - begin
if elapsed < self.interval:
sleep(self.interval - elapsed)
class ReplicatorRpc(object):
"""Handle Replication RPC calls. TODO(redbo): document please :)"""
def __init__(self, root, datadir, broker_class, mount_check=True,
logger=None):
self.root = root
self.datadir = datadir
self.broker_class = broker_class
self.mount_check = mount_check
self.logger = logger or get_logger({}, log_route='replicator-rpc')
def dispatch(self, replicate_args, args):
if not hasattr(args, 'pop'):
return HTTPBadRequest(body='Invalid object type')
op = args.pop(0)
drive, partition, hsh = replicate_args
if self.mount_check and not ismount(os.path.join(self.root, drive)):
return Response(status='507 %s is not mounted' % drive)
db_file = os.path.join(self.root, drive,
storage_directory(self.datadir, partition, hsh),
hsh + '.db')
if op == 'rsync_then_merge':
return self.rsync_then_merge(drive, db_file, args)
if op == 'complete_rsync':
return self.complete_rsync(drive, db_file, args)
else:
# someone might be about to rsync a db to us,
# make sure there's a tmp dir to receive it.
mkdirs(os.path.join(self.root, drive, 'tmp'))
if not os.path.exists(db_file):
return HTTPNotFound()
return getattr(self, op)(self.broker_class(db_file), args)
@contextmanager
def debug_timing(self, name):
timemark = time.time()
yield
timespan = time.time() - timemark
if timespan > DEBUG_TIMINGS_THRESHOLD:
self.logger.debug(
'replicator-rpc-sync time for %s: %.02fs' % (
name, timespan))
def _parse_sync_args(self, args):
"""
Convert remote sync args to remote_info dictionary.
"""
(remote_sync, hash_, id_, created_at, put_timestamp,
delete_timestamp, metadata) = args[:7]
remote_metadata = {}
if metadata:
try:
remote_metadata = json.loads(metadata)
except ValueError:
self.logger.error("Unable to decode remote metadata %r",
metadata)
remote_info = {
'point': remote_sync,
'hash': hash_,
'id': id_,
'created_at': created_at,
'put_timestamp': put_timestamp,
'delete_timestamp': delete_timestamp,
'metadata': remote_metadata,
}
return remote_info
def sync(self, broker, args):
remote_info = self._parse_sync_args(args)
return self._handle_sync_request(broker, remote_info)
def _get_synced_replication_info(self, broker, remote_info):
"""
Apply any changes to the broker based on remote_info and return the
current replication info.
:param broker: the database broker
:param remote_info: the remote replication info
:returns: local broker replication info
"""
return broker.get_replication_info()
def _handle_sync_request(self, broker, remote_info):
"""
Update metadata, timestamps, sync points.
"""
with self.debug_timing('info'):
try:
info = self._get_synced_replication_info(broker, remote_info)
except (Exception, Timeout) as e:
if 'no such table' in str(e):
self.logger.error(_("Quarantining DB %s"), broker)
quarantine_db(broker.db_file, broker.db_type)
return HTTPNotFound()
raise
if remote_info['metadata']:
with self.debug_timing('update_metadata'):
broker.update_metadata(remote_info['metadata'])
sync_timestamps = ('created_at', 'put_timestamp', 'delete_timestamp')
if any(info[ts] != remote_info[ts] for ts in sync_timestamps):
with self.debug_timing('merge_timestamps'):
broker.merge_timestamps(*(remote_info[ts] for ts in
sync_timestamps))
with self.debug_timing('get_sync'):
info['point'] = broker.get_sync(remote_info['id'])
if remote_info['hash'] == info['hash'] and \
info['point'] < remote_info['point']:
with self.debug_timing('merge_syncs'):
translate = {
'remote_id': 'id',
'sync_point': 'point',
}
data = dict((k, remote_info[v]) for k, v in translate.items())
broker.merge_syncs([data])
info['point'] = remote_info['point']
return Response(json.dumps(info))
def merge_syncs(self, broker, args):
broker.merge_syncs(args[0])
return HTTPAccepted()
def merge_items(self, broker, args):
broker.merge_items(args[0], args[1])
return HTTPAccepted()
def complete_rsync(self, drive, db_file, args):
old_filename = os.path.join(self.root, drive, 'tmp', args[0])
if os.path.exists(db_file):
return HTTPNotFound()
if not os.path.exists(old_filename):
return HTTPNotFound()
broker = self.broker_class(old_filename)
broker.newid(args[0])
renamer(old_filename, db_file)
return HTTPNoContent()
def rsync_then_merge(self, drive, db_file, args):
old_filename = os.path.join(self.root, drive, 'tmp', args[0])
if not os.path.exists(db_file) or not os.path.exists(old_filename):
return HTTPNotFound()
new_broker = self.broker_class(old_filename)
existing_broker = self.broker_class(db_file)
point = -1
objects = existing_broker.get_items_since(point, 1000)
while len(objects):
new_broker.merge_items(objects)
point = objects[-1]['ROWID']
objects = existing_broker.get_items_since(point, 1000)
sleep()
new_broker.newid(args[0])
renamer(old_filename, db_file)
return HTTPNoContent()
# Footnote [1]:
# This orders the nodes so that, given nodes a b c, a will contact b then c,
# b will contact c then a, and c will contact a then b -- in other words, each
# node will always contact the next node in the list first.
# This helps in the case where databases are all way out of sync, so each
# node is likely to be sending to a different node than it's receiving from,
# rather than two nodes talking to each other, starving out the third.
# If the third didn't even have a copy and the first two nodes were way out
# of sync, such starvation would mean the third node wouldn't get any copy
# until the first two nodes finally got in sync, which could take a while.
# This new ordering ensures such starvation doesn't occur, making the data
# more durable.
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