patroni.dcs.raft module

class patroni.dcs.raft.DynMemberSyncObj(selfAddress: str | None, partnerAddrs: Collection[str], conf: SyncObjConf, retry_timeout: int = 10)

Bases: SyncObj

__init__(selfAddress: str | None, partnerAddrs: Collection[str], conf: SyncObjConf, retry_timeout: int = 10) → None

Main SyncObj class, you should inherit your own class from it.

Parameters:

  • selfNode (Node or str) – object representing the self-node or address of the current node server ‘host:port’

  • otherNodes (iterable of Node or iterable of str) – objects representing the other nodes or addresses of partner nodes [‘host1:port1’, ‘host2:port2’, …]

  • conf (SyncObjConf) – configuration object

  • consumers (list of SyncObjConsumer inherited objects) – objects to be replicated

  • nodeClass (class) – class used for representation of nodes

  • transport (Transport or None) – transport object; if None, transportClass is used to initialise such an object

  • transportClass (class) – the Transport subclass to be used for transferring messages to and from other nodes

_onTick(timeToWait: float = 0.0)
getMembers(args: Any, callback: Callable[[Any, Any], Any]) → None
class patroni.dcs.raft.KVStoreTTL(on_ready: Callable[[...], Any] | None, on_set: Callable[[str, Dict[str, Any]], None] | None, on_delete: Callable[[str], None] | None, **config: Any)

Bases: DynMemberSyncObj

__check_requirements(**kwargs: Any) → bool
__expire_keys() → None
__init__(on_ready: Callable[[...], Any] | None, on_set: Callable[[str, Dict[str, Any]], None] | None, on_delete: Callable[[str], None] | None, **config: Any) → None

Main SyncObj class, you should inherit your own class from it.

Parameters:

  • selfNode (Node or str) – object representing the self-node or address of the current node server ‘host:port’

  • otherNodes (iterable of Node or iterable of str) – objects representing the other nodes or addresses of partner nodes [‘host1:port1’, ‘host2:port2’, …]

  • conf (SyncObjConf) – configuration object

  • consumers (list of SyncObjConsumer inherited objects) – objects to be replicated

  • nodeClass (class) – class used for representation of nodes

  • transport (Transport or None) – transport object; if None, transportClass is used to initialise such an object

  • transportClass (class) – the Transport subclass to be used for transferring messages to and from other nodes

__pop(key: str) → None
__values_match(new: Dict[str, Any]) → bool
_autoTickThread() → None
_delete(key: str, recursive: bool = False, **kwargs: Any) → bool
_delete_v0(key: str, recursive: bool = False, **kwargs: Any) → bool
_expire(key: str, value: Dict[str, Any], callback: Callable[[...], Any] | None = None) → None
_expire_v0(key: str, value: Dict[str, Any], callback: Callable[[...], Any] | None = None) → None
_onTick(timeToWait: float = 0.0) → None
_set(key: str, value: Dict[str, Any], **kwargs: Any) → bool | Dict[str, Any]
_set_v0(key: str, value: Dict[str, Any], **kwargs: Any) → bool | Dict[str, Any]
delete(key: str, recursive: bool = False, **kwargs: Any) → bool
destroy() → None

Correctly destroy SyncObj. Stop autoTickThread, close connections, etc.

get(key: str, recursive: bool = False) → Dict[str, Any] | None
retry(func: Callable[[...], Any], *args: Any, **kwargs: Any) → Any
set(key: str, value: str, ttl: int | None = None, handle_raft_error: bool = True, **kwargs: Any) → bool | Dict[str, Any]
set_retry_timeout(retry_timeout: int) → None
startAutoTick() → None
class patroni.dcs.raft.Raft(config: Dict[str, Any], mpp: AbstractMPP)

Bases: AbstractDCS

__init__(config: Dict[str, Any], mpp: AbstractMPP) → None

Prepare DCS paths, MPP object, initial values for state information and processing dependencies.

Parameters:

  • config – dict, reference to config section of selected DCS. i.e.: zookeeper for zookeeper, etcd for etcd, etc…

  • mpp – an object implementing AbstractMPP interface.

_abc_impl = <_abc._abc_data object>
_cluster_from_nodes(nodes: Dict[str, Any]) → Cluster
_delete_leader(leader: Leader) → bool

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.

_load_cluster(path: str, loader: Callable[[str], Cluster | Dict[int, Cluster]]) → Cluster | Dict[int, Cluster]

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 the get_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]

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 and Cluster objects as values.

_on_delete(key: str) → None
_on_set(key: str, value: Dict[str, Any]) → None
_postgresql_cluster_loader(path: str) → Cluster

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.

_update_leader(leader: Leader) → bool

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 if leader key (or session) has been updated successfully.

_write_failsafe(value: str) → bool

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

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

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

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

Removes the initialize key for a cluster.

Returns:

True if successfully committed to DCS.

delete_cluster() → bool

Delete cluster from DCS.

Returns:

True if successfully committed to DCS.

delete_sync_state(version: int | None = None) → bool

Delete the synchronous state from DCS.

Parameters:

version – for conditional deletion of the key/object.

Returns:

True if delete successful.

initialize(create_new: bool = True, sysid: str = '') → bool

Race for cluster initialization.

This method should atomically create initialize key and return True, otherwise it should return False.

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.

static member(key: str, value: Dict[str, Any]) → Member
reload_config(config: Config | Dict[str, Any]) → None

Load and set relevant values from configuration.

Sets loop_wait, ttl and retry_timeout properties.

Parameters:

config – Loaded configuration information object or dictionary of key value pairs.

set_config_value(value: str, version: int | None = None) → bool

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

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

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

Set the new value for retry_timeout.

set_sync_state_value(value: str, version: int | None = None) → int | bool

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

Set the new ttl value for DCS keys.

take_leader() → bool

Establish a new leader in DCS.

Note

This method should create leader key with value of _name and ttl of ttl.

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

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.

property ttl: int

Get current ttl value.

watch(leader_version: int | None, timeout: float) → bool

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.raft.RaftError(value: Any)

Bases: DCSError

class patroni.dcs.raft.SyncObjUtility(otherNodes: Collection[str | TCPNode], conf: SyncObjConf, retry_timeout: int = 10)

Bases: object

__init__(otherNodes: Collection[str | TCPNode], conf: SyncObjConf, retry_timeout: int = 10) → None
executeCommand(command: List[Any]) → Any
getMembers() → List[str] | None
class patroni.dcs.raft._TCPTransport(syncObj: DynMemberSyncObj, selfNode: TCPNode | None, otherNodes: Collection[TCPNode])

Bases: TCPTransport

__init__(syncObj: DynMemberSyncObj, selfNode: TCPNode | None, otherNodes: Collection[TCPNode]) → None

Initialise the TCP transport. On normal (non-read-only) nodes, this will start a TCP server. On all nodes, it will initiate relevant connections to other nodes.

Parameters:

  • syncObj (SyncObj) – SyncObj

  • selfNode (TCPNode or None) – current node (None if this is a read-only node)

  • otherNodes (iterable of TCPNode) – partner nodes

_connectIfNecessarySingle(node: TCPNode) → bool

Connect to a node if necessary.

Parameters:

node (Node) – node to connect to

patroni.dcs.raft.resolve_host(self: TCPNode) → str | None