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Problem: BigchainDB has un-necessary code to initialize a replica set…
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… and check if MongoDB was started with replicaSet (#2491)

Solution: Remove un-necessary code. Deployment of MongoDB with or without replicaSet should be the responsibility of MongoDB admin which can and cannot be a BigchainDB node operator. As far as BigchainDB is concerned replicaset, if provided in bigchaindb configs, should be used to establish connection with MongoDB.
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@shahbazn
shahbazn committed Aug 31, 2018
1 parent cb41826 commit 2d1f670
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Showing 3 changed files with 1 addition and 223 deletions.
137 changes: 0 additions & 137 deletions bigchaindb/backend/localmongodb/connection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@
# SPDX-License-Identifier: (Apache-2.0 AND CC-BY-4.0)
# Code is Apache-2.0 and docs are CC-BY-4.0

import time
import logging
from ssl import CERT_REQUIRED

Expand Down Expand Up @@ -88,23 +87,6 @@ def _connect(self):
"""

try:
if self.replicaset:
# we should only return a connection if the replica set is
# initialized. initialize_replica_set will check if the
# replica set is initialized else it will initialize it.
initialize_replica_set(self.host,
self.port,
self.connection_timeout,
self.dbname,
self.ssl,
self.login,
self.password,
self.ca_cert,
self.certfile,
self.keyfile,
self.keyfile_passphrase,
self.crlfile)

# FYI: the connection process might raise a
# `ServerSelectionTimeoutError`, that is a subclass of
# `ConnectionFailure`.
Expand Down Expand Up @@ -140,8 +122,6 @@ def _connect(self):

return client

# `initialize_replica_set` might raise `ConnectionFailure`,
# `OperationFailure` or `ConfigurationError`.
except (pymongo.errors.ConnectionFailure,
pymongo.errors.OperationFailure) as exc:
logger.info('Exception in _connect(): {}'.format(exc))
Expand All @@ -153,120 +133,3 @@ def _connect(self):
MONGO_OPTS = {
'socketTimeoutMS': 20000,
}


def initialize_replica_set(host, port, connection_timeout, dbname, ssl, login,
password, ca_cert, certfile, keyfile,
keyfile_passphrase, crlfile):
"""Initialize a replica set. If already initialized skip."""

# Setup a MongoDB connection
# The reason we do this instead of `backend.connect` is that
# `backend.connect` will connect you to a replica set but this fails if
# you try to connect to a replica set that is not yet initialized
try:
# The presence of ca_cert, certfile, keyfile, crlfile implies the
# use of certificates for TLS connectivity.
if ca_cert is None or certfile is None or keyfile is None or \
crlfile is None:
conn = pymongo.MongoClient(host,
port,
serverselectiontimeoutms=connection_timeout,
ssl=ssl,
**MONGO_OPTS)
if login is not None and password is not None:
conn[dbname].authenticate(login, password)
else:
logger.info('Connecting to MongoDB over TLS/SSL...')
conn = pymongo.MongoClient(host,
port,
serverselectiontimeoutms=connection_timeout,
ssl=ssl,
ssl_ca_certs=ca_cert,
ssl_certfile=certfile,
ssl_keyfile=keyfile,
ssl_pem_passphrase=keyfile_passphrase,
ssl_crlfile=crlfile,
ssl_cert_reqs=CERT_REQUIRED,
**MONGO_OPTS)
if login is not None:
logger.info('Authenticating to the database...')
conn[dbname].authenticate(login, mechanism='MONGODB-X509')

except (pymongo.errors.ConnectionFailure,
pymongo.errors.OperationFailure) as exc:
logger.info('Exception in _connect(): {}'.format(exc))
raise ConnectionError(str(exc)) from exc
except pymongo.errors.ConfigurationError as exc:
raise ConfigurationError from exc

_check_replica_set(conn)
host = '{}:{}'.format(bigchaindb.config['database']['host'],
bigchaindb.config['database']['port'])
config = {'_id': bigchaindb.config['database']['replicaset'],
'members': [{'_id': 0, 'host': host}]}

try:
conn.admin.command('replSetInitiate', config)
except pymongo.errors.OperationFailure as exc_info:
if exc_info.details['codeName'] == 'AlreadyInitialized':
return
raise
else:
_wait_for_replica_set_initialization(conn)
logger.info('Initialized replica set')
finally:
if conn is not None:
logger.info('Closing initial connection to MongoDB')
conn.close()


def _check_replica_set(conn):
"""Checks if the replSet option was enabled either through the command
line option or config file and if it matches the one provided by
bigchaindb configuration.
Note:
The setting we are looking for will have a different name depending
if it was set by the config file (`replSetName`) or by command
line arguments (`replSet`).
Raise:
:exc:`~ConfigurationError`: If mongod was not started with the
replSet option.
"""
options = conn.admin.command('getCmdLineOpts')
try:
repl_opts = options['parsed']['replication']
repl_set_name = repl_opts.get('replSetName', repl_opts.get('replSet'))
except KeyError:
raise ConfigurationError('mongod was not started with'
' the replSet option.')

bdb_repl_set_name = bigchaindb.config['database']['replicaset']
if repl_set_name != bdb_repl_set_name:
raise ConfigurationError('The replicaset configuration of '
'bigchaindb (`{}`) needs to match '
'the replica set name from MongoDB'
' (`{}`)'.format(bdb_repl_set_name,
repl_set_name))


def _wait_for_replica_set_initialization(conn):
"""Wait for a replica set to finish initialization.
If a replica set is being initialized for the first time it takes some
time. Nodes need to discover each other and an election needs to take
place. During this time the database is not writable so we need to wait
before continuing with the rest of the initialization
"""

# I did not find a better way to do this for now.
# To check if the database is ready we will poll the mongodb logs until
# we find the line that says the database is ready
logger.info('Waiting for mongodb replica set initialization')
while True:
logs = conn.admin.command('getLog', 'rs')['log']
if any('database writes are now permitted' in line for line in logs):
return
time.sleep(0.1)
2 changes: 1 addition & 1 deletion docs/server/source/server-reference/configuration.md
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ The settings with names of the form `database.*` are for the backend database
* `database.name` is a user-chosen name for the database inside MongoDB, e.g. `bigchain`.
* `database.connection_timeout` is the maximum number of milliseconds that BigchainDB will wait before giving up on one attempt to connect to the backend database.
* `database.max_tries` is the maximum number of times that BigchainDB will try to establish a connection with the backend database. If 0, then it will try forever.
* `database.replicaset` is the name of the MongoDB replica set. The default value is `null` because in BighainDB 2.0+, each BigchainDB node has its own independent MongoDB database and no replica set is necessary.
* `database.replicaset` is the name of the MongoDB replica set. The default value is `null` because in BighainDB 2.0+, each BigchainDB node has its own independent MongoDB database and no replica set is necessary. Replica set must already exist if this option is configured, BigchainDB will not create it.

There are three ways for BigchainDB Server to authenticate itself with MongoDB (or a specific MongoDB database): no authentication, username/password, and x.509 certificate authentication.

Expand Down
85 changes: 0 additions & 85 deletions tests/backend/localmongodb/test_connection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,6 @@
import pytest
import pymongo
from pymongo import MongoClient
from pymongo.database import Database


pytestmark = [pytest.mark.bdb, pytest.mark.tendermint]
Expand Down Expand Up @@ -109,87 +108,3 @@ def test_connection_with_credentials(mock_authenticate):
password='secret')
conn.connect()
assert mock_authenticate.call_count == 1


def test_check_replica_set_not_enabled(mongodb_connection):
from bigchaindb.backend.localmongodb.connection import _check_replica_set
from bigchaindb.common.exceptions import ConfigurationError

# no replSet option set
cmd_line_opts = {'argv': ['mongod', '--dbpath=/data'],
'ok': 1.0,
'parsed': {'storage': {'dbPath': '/data'}}}
with mock.patch.object(Database, 'command', return_value=cmd_line_opts):
with pytest.raises(ConfigurationError):
_check_replica_set(mongodb_connection)


def test_check_replica_set_command_line(mongodb_connection,
mock_cmd_line_opts):
from bigchaindb.backend.localmongodb.connection import _check_replica_set

# replSet option set through the command line
with mock.patch.object(Database, 'command',
return_value=mock_cmd_line_opts):
assert _check_replica_set(mongodb_connection) is None


def test_check_replica_set_config_file(mongodb_connection, mock_config_opts):
from bigchaindb.backend.localmongodb.connection import _check_replica_set

# replSet option set through the config file
with mock.patch.object(Database, 'command', return_value=mock_config_opts):
assert _check_replica_set(mongodb_connection) is None


def test_check_replica_set_name_mismatch(mongodb_connection,
mock_cmd_line_opts):
from bigchaindb.backend.localmongodb.connection import _check_replica_set
from bigchaindb.common.exceptions import ConfigurationError

# change the replica set name so it does not match the bigchaindb config
mock_cmd_line_opts['parsed']['replication']['replSet'] = 'rs0'

with mock.patch.object(Database, 'command',
return_value=mock_cmd_line_opts):
with pytest.raises(ConfigurationError):
_check_replica_set(mongodb_connection)


def test_wait_for_replica_set_initialization(mongodb_connection):
from bigchaindb.backend.localmongodb.connection import _wait_for_replica_set_initialization # noqa

with mock.patch.object(Database, 'command') as mock_command:
mock_command.side_effect = [
{'log': ['a line']},
{'log': ['database writes are now permitted']},
]

# check that it returns
assert _wait_for_replica_set_initialization(mongodb_connection) is None


def test_initialize_replica_set(mock_cmd_line_opts):
from bigchaindb.backend.localmongodb.connection import initialize_replica_set

with mock.patch.object(Database, 'command') as mock_command:
mock_command.side_effect = [
mock_cmd_line_opts,
None,
{'log': ['database writes are now permitted']},
]

# check that it returns
assert initialize_replica_set('host', 1337, 1000, 'dbname', False, None, None,
None, None, None, None, None) is None

# test it raises OperationError if anything wrong
with mock.patch.object(Database, 'command') as mock_command:
mock_command.side_effect = [
mock_cmd_line_opts,
pymongo.errors.OperationFailure(None, details={'codeName': ''})
]

with pytest.raises(pymongo.errors.OperationFailure):
initialize_replica_set('host', 1337, 1000, 'dbname', False, None,
None, None, None, None, None, None) is None

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