patroni.dcs.zookeeper module
- class patroni.dcs.zookeeper.PatroniKazooClient(hosts='127.0.0.1:2181', timeout=10.0, client_id=None, handler=None, default_acl=None, auth_data=None, sasl_options=None, read_only=None, randomize_hosts=True, connection_retry=None, command_retry=None, logger=None, keyfile=None, keyfile_password=None, certfile=None, ca=None, use_ssl=False, verify_certs=True, **kwargs)View on GitHub
Bases:
KazooClient
- class patroni.dcs.zookeeper.PatroniSequentialThreadingHandler(connect_timeout: int | float)View on GitHub
Bases:
SequentialThreadingHandler
- __init__(connect_timeout: int | float) None View on GitHub
Create a
SequentialThreadingHandler
instance
- create_connection(*args: Any, **kwargs: Any) socket View on GitHub
- This method is trying to establish connection with one of the zookeeper nodes.
Somehow strategy “fail earlier and retry more often” works way better comparing to the original strategy “try to connect with specified timeout”. Since we want to try connect to zookeeper more often (with the smaller connect_timeout), he have to override create_connection method in the SequentialThreadingHandler class (which is used by kazoo.Client).
- Parameters:
args – always contains tuple(host, port) as the first element and could contain connect_timeout (negotiated session timeout) as the second element.
- select(*args: Any, **kwargs: Any) Any View on GitHub
Python 3.XY may raise following exceptions if select/poll are called with an invalid socket: - ValueError: because fd == -1 - TypeError: Invalid file descriptor: -1 (starting from kazoo 2.9) Python 2.7 may raise the IOError instead of socket.error (starting from kazoo 2.9)
When it is appropriate we map these exceptions to socket.error.
- set_connect_timeout(connect_timeout: int | float) None View on GitHub
- class patroni.dcs.zookeeper.ZooKeeper(config: Dict[str, Any], mpp: AbstractMPP)View on GitHub
Bases:
AbstractDCS
- __init__(config: Dict[str, Any], mpp: AbstractMPP) None View on GitHub
Prepare DCS paths, MPP object, initial values for state information and processing dependencies.
- Variables:
config –
dict
, reference to config section of selected DCS. i.e.:zookeeper
for zookeeper,etcd
for etcd, etc…
- _abc_impl = <_abc._abc_data object>
- _cancel_initialization() None View on GitHub
- _delete_leader(leader: Leader) bool View on GitHub
Remove leader key from DCS.
This method should remove leader key if current instance is the leader.
- Parameters:
leader –
Leader
object with information about the leader.- Returns:
True
if successfully committed to DCS.
- _kazoo_connect(*args: Any) Tuple[int | float, int | float] View on GitHub
Kazoo is using Ping’s to determine health of connection to zookeeper. If there is no response on Ping after Ping interval (1/2 from read_timeout) it will consider current connection dead and try to connect to another node. Without this “magic” it was taking up to 2/3 from session timeout (ttl) to figure out that connection was dead and we had only small time for reconnect and retry.
This method is needed to return different value of read_timeout, which is not calculated from negotiated session timeout but from value of loop_wait. And it is 2 sec smaller than loop_wait, because we can spend up to 2 seconds when calling touch_member() and write_leader_optime() methods, which also may hang…
- _load_cluster(path: str, loader: Callable[[str], Cluster | Dict[int, Cluster]]) Cluster | Dict[int, Cluster] View on GitHub
Main abstract method that implements the loading of
Cluster
instance.Note
Internally this method should call the loader method that will build
Cluster
object which represents current state and topology of the cluster in DCS. This method supposed to be called only by theget_cluster()
method.- Parameters:
path – the path in DCS where to load Cluster(s) from.
loader – one of
_postgresql_cluster_loader()
or_mpp_cluster_loader()
.
- Raise:
DCSError
in case of communication problems with DCS. If the current node was running as a primary and exception raised, instance would be demoted.
- _mpp_cluster_loader(path: str) Dict[int, Cluster] View on GitHub
Load and build all PostgreSQL clusters from a single MPP cluster.
- Parameters:
path – the path in DCS where to load Cluster(s) from.
- Returns:
all MPP groups as
dict
, with group IDs as keys andCluster
objects as values.
- _postgresql_cluster_loader(path: str) Cluster View on GitHub
Load and build the
Cluster
object from DCS, which represents a single PostgreSQL cluster.- Parameters:
path – the path in DCS where to load
Cluster
from.- Returns:
Cluster
instance.
- _set_or_create(key: str, value: str, version: int | None = None, retry: bool = False, do_not_create_empty: bool = False) int | bool View on GitHub
- _update_leader(leader: Leader) bool View on GitHub
Update
leader
key (or session) ttl.Note
You have to use CAS (Compare And Swap) operation in order to update leader key, for example for etcd
prevValue
parameter must be used.If update fails due to DCS not being accessible or because it is not able to process requests (hopefully temporary), the
DCSError
exception should be raised.- Parameters:
leader – a reference to a current
leader
object.- Returns:
True
ifleader
key (or session) has been updated successfully.
- _watcher(event: WatchedEvent) None View on GitHub
- _write_failsafe(value: str) bool View on GitHub
Write current cluster topology to DCS that will be used by failsafe mechanism (if enabled).
- Parameters:
value – failsafe topology serialized in JSON format.
- Returns:
True
if successfully committed to DCS.
- _write_leader_optime(last_lsn: str) bool View on GitHub
Write current WAL LSN into
/optime/leader
key in DCS.- Parameters:
last_lsn – absolute WAL LSN in bytes.
- Returns:
True
if successfully committed to DCS.
- _write_status(value: str) bool View on GitHub
Write current WAL LSN and
confirmed_flush_lsn
of permanent slots into the/status
key in DCS.- Parameters:
value – status serialized in JSON format.
- Returns:
True
if successfully committed to DCS.
- attempt_to_acquire_leader() bool View on GitHub
Attempt to acquire leader lock.
Note
This method should create
/leader
key with the value_name
.The key must be created atomically. In case the key already exists it should not be overwritten and
False
must be returned.If key creation fails due to DCS not being accessible or because it is not able to process requests (hopefully temporary), the
DCSError
exception should be raised.- Returns:
True
if key has been created successfully.
- cancel_initialization() bool View on GitHub
Removes the
initialize
key for a cluster.- Returns:
True
if successfully committed to DCS.
- delete_cluster() bool View on GitHub
Delete cluster from DCS.
- Returns:
True
if successfully committed to DCS.
- delete_sync_state(version: int | None = None) bool View on GitHub
Delete the synchronous state from DCS.
- Parameters:
version – for conditional deletion of the key/object.
- Returns:
True
if delete successful.
- get_children(key: str) List[str] View on GitHub
- get_node(key: str, watch: Callable[[WatchedEvent], None] | None = None) Tuple[str, ZnodeStat] | None View on GitHub
- initialize(create_new: bool = True, sysid: str = '') bool View on GitHub
Race for cluster initialization.
This method should atomically create
initialize
key and returnTrue
, otherwise it should returnFalse
.- Parameters:
create_new –
False
if the key should already exist (in the case we are setting the system_id).sysid – PostgreSQL cluster system identifier, if specified, is written to the key.
- Returns:
True
if key has been created successfully.
- load_members(path: str) List[Member] View on GitHub
- static member(name: str, value: str, znode: ZnodeStat) Member View on GitHub
- reload_config(config: Config | Dict[str, Any]) None View on GitHub
Load and set relevant values from configuration.
Sets
loop_wait
,ttl
andretry_timeout
properties.- Parameters:
config – Loaded configuration information object or dictionary of key value pairs.
- set_config_value(value: str, version: int | None = None) bool View on GitHub
Create or update
/config
key in DCS.- Parameters:
value – new value to set in the
config
key.version – for conditional update of the key/object.
- Returns:
True
if successfully committed to DCS.
- set_failover_value(value: str, version: int | None = None) bool View on GitHub
Create or update
/failover
key.- Parameters:
value – value to set.
version – for conditional update of the key/object.
- Returns:
True
if successfully committed to DCS.
- set_history_value(value: str) bool View on GitHub
Set value for
history
in DCS.- Parameters:
value – new value of
history
key/object.- Returns:
True
if successfully committed to DCS.
- set_retry_timeout(retry_timeout: int) None View on GitHub
Set the new value for retry_timeout.
- set_sync_state_value(value: str, version: int | None = None) int | bool View on GitHub
Set synchronous state in DCS.
- Parameters:
value – the new value of
/sync
key.version – for conditional update of the key/object.
- Returns:
version of the new object or
False
in case of error.
- set_ttl(ttl: int) bool | None View on GitHub
It is not possible to change ttl (session_timeout) in zookeeper without destroying old session and creating the new one. This method returns !True if session_timeout has been changed (restart() has been called).
- take_leader() bool View on GitHub
Establish a new leader in DCS.
Note
This method should create leader key with value of
_name
andttl
ofttl
.Since it could be called only on initial cluster bootstrap it could create this key regardless, overwriting the key if necessary.
- Returns:
True
if successfully committed to DCS.
- touch_member(data: Dict[str, Any]) bool View on GitHub
Update member key in DCS.
Note
This method should create or update key with the name with
/members/
+_name
and the value of data in a given DCS.- Parameters:
data – information about an instance (including connection strings).
- Returns:
True
if successfully committed to DCS.
- watch(leader_version: int | None, timeout: float) bool View on GitHub
Sleep if the current node is a leader, otherwise, watch for changes of leader key with a given timeout.
- Parameters:
leader_version – version of a leader key.
timeout – timeout in seconds.
- Returns:
if
True
this will reschedule the next run of the HA cycle.
- exception patroni.dcs.zookeeper.ZooKeeperError(value: Any)View on GitHub
Bases:
DCSError