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patroni.dcs.etcd module

class _patroni.dcs.etcd.AbstractEtcd(_config: Dict[ str, Any], mpp: AbstractMPP, client_cls: Type[AbstractEtcdClientWithFailover], retry_errors_cls: Type[ Exception] | Tuple[ Type[ Exception], …]) View on GitHub 

Bases: AbstractDCS +

__init\\__(config: Dict[ str, Any], mpp: AbstractMPP, client_cls: Type[AbstractEtcdClientWithFailover], retry_errors_cls: Type[ Exception] | Tuple[ Type[ Exception], …]) → 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>_

abstract property \\__client: AbstractEtcdClientWithFailover_

return correct type of etcd client +

handle_exception(_e: Exception, name: str = '', do_sleep: bool = False, raise_ex: Exception | None = None) → None View on GitHub 

run_and_handle_exceptions(_method: Callable[[…], Any], *args: Any, **kwargs: Any) → Any View on GitHub 

get_etcd_client(config: Dict[ str, Any], client_cls: Type[AbstractEtcdClientWithFailover]) → AbstractEtcdClientWithFailover View on GitHub 

handle_etcd_exceptions(func: Callable[[…], Any], *args: Any, **kwargs: Any) → Any 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 and retry_timeout properties. +

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

retry(method: Callable[[…], Any], *args: Any, **kwargs: Any) → Any View on GitHub 

set_retry_timeout(retry_timeout: int) → None View on GitHub 

Set the new value for retry_timeout. +

set_socket_options(sock: socket, socket_options: Collection[ Tuple[ int, int, int]] | None) → None View on GitHub 

set_ttl(ttl: int) → bool | None View on GitHub 

Set the new ttl value for DCS keys. +

property _ttl: int_

Get current ttl value.

class _patroni.dcs.etcd.AbstractEtcdClientWithFailover(_config: Dict[ str, Any], dns_resolver: DnsCachingResolver, cache_ttl: int = 300) View on GitHub 

Bases: ABC, Client +

ERROR_CLS_: Type[ Exception]_

__init\\__(config: Dict[ str, Any], dns_resolver: DnsCachingResolver, cache_ttl: int = 300) → None View on GitHub 

abc_impl = <_abc._abc_data object>_

calculate_timeouts(_etcd_nodes: int, timeout: float | None = None) → Tuple[ int, float, int] View on GitHub 

Calculate a request timeout and number of retries per single etcd node. In case if the timeout per node is too small (less than one second) we will reduce the number of nodes. For the cluster with only one node we will try to do 2 retries. For clusters with 2 nodes we will try to do 1 retry for every node. No retries for clusters with 3 or more nodes. We better rely on switching to a different node. +

do http_request(retry: Retry | None, machines_cache: List[ str], request_executor: Callable[[…], HTTPResponse], method: str, path: str, fields: Dict[ str, Any] | None = None, **kwargs: Any) → HTTPResponse View on GitHublink:#patroni.dcs.etcd.AbstractEtcdClientWithFailover.do http_request[]

_get_headers() → Dict[ str, str] View on GitHub 

_get_machines_cache_from_config() → List[ str] View on GitHub 

get_machines_cache_from_dns(_host: str, port: int) → List[ str] View on GitHub 

One host might be resolved into multiple ip addresses. We will make list out of it +

get_machines_cache_from_srv(_srv: str, srv_suffix: str | None = None) → List[ str] View on GitHub 

Fetch list of etcd-cluster member by resolving _etcd-server._tcp. SRV record. This record should contain list of host and peer ports which could be used to run ‘GET http://{host}:{port}/members’ request (peer protocol) +

get_machines_list(_machines_cache: List[ str]) → List[ str] View on GitHub 

Gets list of members from Etcd cluster using API +

Parameters: machines_cache – initial list of Etcd members
Returns: list of clientURLs retrieved from Etcd cluster
Raises: EtcdConnectionFailed – if failed +

abstract \\__get_members(_base_uri: str, **kwargs: Any) → List[ str] View on GitHub 

returns: list of clientURLs +

_load_machines_cache() → bool View on GitHub 

This method should fill up _machines_cache from scratch. It could happen only in two cases: 1. During class initialization 2. When all etcd members failed +

prepare_common_parameters(_etcd_nodes: int, timeout: float | None = None) → Dict[ str, Any] View on GitHub 

abstract \\__prepare_get_members(_etcd_nodes: int) → Dict[ str, Any] View on GitHub 

returns: request parameters +

abstract \\__prepare_request(_kwargs: Dict[ str, Any], params: Dict[ str, Any] | None = None, method: str | None = None) → Callable[[…], HTTPResponse] View on GitHub 

returns: request_executor +

refresh_machines_cache(_machines_cache: List[ str] | None = None) → bool View on GitHub 

Get etcd cluster topology using Etcd API and put it to self._machines_cache +

Parameters: machines_cache – the list of nodes we want to run through executing API request in addition to values stored in the self._machines_cache
Returns: True if self._machines_cache was updated with new values
Raises: EtcdException – if failed to get topology and machines_cache was specified.
The self._machines_cache will not be updated if nodes from the list are not accessible or if they are not returning correct results. +

static \\__update_dns_cache(_func: Callable[[ str, int], None], machines: List[ str]) → None View on GitHub 

api_execute(path: str, method: str, params: Dict[ str, Any] | None = None, timeout: float | None = None) → Any View on GitHub 

Executes the query. +

static _get_srv_record(_host: str) → List[ Tuple[ str, int]] View on GitHub 

property _machines: List[ str]_

Original machines method(property) of etcd.Client class raise exception when it failed to get list of etcd cluster members. This method is being called only when request failed on one of the etcd members during api_execute call. For us it’s more important to execute original request rather then get new topology of etcd cluster. So we will catch this exception and return empty list of machines. Later, during next api_execute call we will forcefully update machines_cache.
Also this method implements the same timeout-retry logic as api_execute, because the original method was retrying 2 times with the read_timeout on each node.
After the next refactoring the whole logic was moved to the _get_machines_list() method. +

property _machines_cache: List[ str]_

reload_config(config: Dict[ str, Any]) → None View on GitHub 

set_base_uri(value: str) → None View on GitHub 

set_machines_cache_ttl(cache_ttl: int) → None View on GitHub 

set_read_timeout(timeout: float) → None View on GitHub 

class _patroni.dcs.etcd.DnsCachingResolver(_cache_time: float = 600.0, cache_fail_time: float = 30.0) View on GitHub 

Bases: Thread +

__init\\__(cache_time: float = 600.0, cache_fail_time: float = 30.0) → None View on GitHub : This constructor should always be called with keyword arguments. Arguments are:
group should be None; reserved for future extension when a ThreadGroup class is implemented.
target is the callable object to be invoked by the run() method. Defaults to None, meaning nothing is called.
name is the thread name. By default, a unique name is constructed of the form “Thread-N” where N is a small decimal number.
args is a list or tuple of arguments for the target invocation. Defaults to ().
kwargs is a dictionary of keyword arguments for the target invocation. Defaults to \{}.
If a subclass overrides the constructor, it must make sure to invoke the base class constructor (Thread.__init\\__()) before doing anything else to the thread. +
static \\__do_resolve(_host: str, port: int) → List[ Tuple[AddressFamily, SocketKind, int, str, Tuple[ str, int] | Tuple[ str, int, int, int]]] View on GitHub : +
remove(host: str, port: int) → None View on GitHub : +
resolve(host: str, port: int) → List[ Tuple[AddressFamily, SocketKind, int, str, Tuple[ str, int] | Tuple[ str, int, int, int]]] View on GitHub : +
resolve_async(host: str, port: int, attempt: int = 0) → None View on GitHub : +
run() → None View on GitHub : Method representing the thread’s activity. + You may override this method in a subclass. The standard run() method invokes the callable object passed to the object’s constructor as the target argument, if any, with sequential and keyword arguments taken from the args and kwargs arguments, respectively.

class _patroni.dcs.etcd.Etcd(_config: Dict[ str, Any], mpp: AbstractMPP) View on GitHub 

Bases: AbstractEtcd +

__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>_

property \\__client: EtcdClient_

return correct type of etcd client +

cluster_from_nodes(_etcd_index: int, nodes: Dict[ str, EtcdResult]) → Cluster View on GitHub 

delete_leader(*args: Any, _**kwargs: Any) → Any 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. +

_do_attempt_to_acquire_leader() → bool View on GitHub 

_do_update_leader() → bool View on GitHub 

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 the `+get_cluster()+` method.
  +
  Parameters:::
  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 and Cluster 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. +

update_leader(**kwargs: Any) 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+` if `+leader+` key (or session) has been updated successfully. +

write_failsafe(*args: Any, _**kwargs: Any) → Any 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(*args: Any, _**kwargs: Any) → Any 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(*args: Any, _**kwargs: Any) → Any 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(**kwargs: Any) 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(*args: Any, **kwargs: Any) → Any View on GitHub 

Removes the initialize key for a cluster. +

Returns

True if successfully committed to DCS. +

delete_cluster(*args: Any, **kwargs: Any) → Any View on GitHub 

Delete cluster from DCS. +

Returns

True if successfully committed to DCS. +

delete_sync_state(*args: Any, **kwargs: Any) → Any View on GitHub 

Delete the synchronous state from DCS. +

Parameters

version – for conditional deletion of the key/object.

Returns

True if delete successful. +

initialize(*args: Any, **kwargs: Any) → Any View on GitHub 

Race for cluster initialization. + This method should atomically create initialize key and return True, otherwise it should return False. +

Parameters

Returns

True if key has been created successfully. +

static _member(_node: EtcdResult) → Member View on GitHub 

+

set_config_value(*args: Any, **kwargs: Any) → Any View on GitHub 

Create or update /config key in DCS. +

Parameters

Returns

True if successfully committed to DCS. +

set_failover_value(*args: Any, **kwargs: Any) → Any View on GitHub 

Create or update /failover key. +

Parameters

Returns

True if successfully committed to DCS. +

set_history_value(*args: Any, **kwargs: Any) → Any 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_sync_state_value(*args: Any, **kwargs: Any) → Any View on GitHub 

Set synchronous state in DCS. +

Parameters

Returns

version of the new object or False in case of error. +

set_ttl(ttl: int) → bool | None View on GitHub 

Set the new ttl value for DCS keys. +

take_leader(*args: Any, **kwargs: Any) → Any View on GitHub 

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(*args: Any, **kwargs: Any) → Any 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

Returns

if True this will reschedule the next run of the HA cycle.

class _patroni.dcs.etcd.EtcdClient(_config: Dict[ str, Any], dns_resolver: DnsCachingResolver, cache_ttl: int = 300) View on GitHub 

Bases: AbstractEtcdClientWithFailover +

ERROR_CLS View on GitHub 

alias of EtcdError +

__init\\__(config: Dict[ str, Any], dns_resolver: DnsCachingResolver, cache_ttl: int = 300) → None View on GitHub 

+

abc_impl = <_abc._abc_data object>_

+

get_members(_base_uri: str, **kwargs: Any) → List[ str] View on GitHub 

returns: list of clientURLs +

prepare_get_members(_etcd_nodes: int) → Dict[ str, Any] View on GitHub 

returns: request parameters +

prepare_request(_kwargs: Dict[ str, Any], params: Dict[ str, Any] | None = None, method: str | None = None) → Callable[[…], HTTPResponse] View on GitHub 

returns: request_executor

exception _patroni.dcs.etcd.EtcdError(_value: Any) View on GitHub 

Bases: DCSError

exception _patroni.dcs.etcd.EtcdRaftInternal(_message=None, payload=None) View on GitHub 

Bases: EtcdException + Raft Internal Error

patroni.dcs.etcd.catch_etcd_errors(func: Callable[[…], Any]) → Any View on GitHub 

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