Source code for baseplate.lib.live_data.zookeeper

"""Helpers for interacting with ZooKeeper."""
from typing import Optional

from kazoo.client import KazooClient

from baseplate.lib import config
from baseplate.lib.secrets import SecretsStore

[docs]def zookeeper_client_from_config( secrets: SecretsStore, app_config: config.RawConfig, read_only: Optional[bool] = None ) -> KazooClient: """Configure and return a ZooKeeper client. There are several configuration options: ``zookeeper.hosts`` A comma-delimited list of hosts with optional ``chroot`` at the end. For example ``zk01:2181,zk02:2181`` or ``zk01:2181,zk02:2181/some/root``. ``zookeeper.credentials`` (Optional) A comma-delimited list of paths to secrets in the secrets store that contain ZooKeeper authentication credentials. Secrets should be of the "simple" type and contain ``username:password``. ``zookeeper.timeout`` (Optional) A time span of how long to wait for each connection attempt. The client will attempt forever to reconnect on connection loss. :param secrets: A secrets store object :param raw_config: The application configuration which should have settings for the ZooKeeper client. :param read_only: Whether or not to allow connections to read-only ZooKeeper servers. """ full_cfg = config.parse_config( app_config, { "zookeeper": { "hosts": config.String, "credentials": config.Optional(config.TupleOf(config.String), default=[]), "timeout": config.Optional(config.Timespan, default=config.Timespan("5 seconds")), } }, ) # pylint: disable=maybe-no-member cfg = full_cfg.zookeeper auth_data = [] for path in cfg.credentials: credentials = secrets.get_simple(path) auth_data.append(("digest", credentials.decode("utf8"))) return KazooClient( cfg.hosts, timeout=cfg.timeout.total_seconds(), auth_data=auth_data, read_only=read_only, # this retry policy tells Kazoo how often it should attempt connections # to ZooKeeper from its worker thread/greenlet. when the connection is # lost during normal operation (i.e. after it was first established) # Kazoo will do retries quietly in the background while the application # continues forward. because of this, we want it to retry forever so # that it doesn't just give up at some point. the application can still # decide if it wants to exit after being disconnected for an amount of # time by polling the KazooClient.connected property. # # note: KazooClient.start() has a timeout parameter which defaults to # 15 seconds and controls the maximum amount of time start() will block # waiting for the background thread to confirm it has established a # connection. so even though we do infinite retries here, users of this # function can configure the amount of time they are willing to wait # for initial connection. connection_retry=dict( max_tries=-1, # keep reconnecting forever delay=0.1, # initial delay backoff=2, # exponential backoff max_jitter=1, # maximum amount to jitter sleeptimes max_delay=60, # never wait longer than this ), )