patroni.dcs.etcd module

class patroni.dcs.etcd.AbstractEtcd(config: Dict[str, Any], mpp: patroni.postgresql.mpp.AbstractMPP, client_cls: Type[patroni.dcs.etcd.AbstractEtcdClientWithFailover], retry_errors_cls: Union[Type[Exception], Tuple[Type[Exception], ...]])

Bases: patroni.dcs.AbstractDCS

__init__(config: Dict[str, Any], mpp: patroni.postgresql.mpp.AbstractMPP, client_cls: Type[patroni.dcs.etcd.AbstractEtcdClientWithFailover], retry_errors_cls: Union[Type[Exception], Tuple[Type[Exception], ...]]) → None

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

Variables:configdict, reference to config section of selected DCS. i.e.: zookeeper for zookeeper, etcd for etcd, etc…
_abc_impl = <_abc_data object>
_client

return correct type of etcd client

_handle_exception(e: Exception, name: str = '', do_sleep: bool = False, raise_ex: Optional[Exception] = None) → None
_run_and_handle_exceptions(method: Callable[[...], Any], *args, **kwargs) → Any
get_etcd_client(config: Dict[str, Any], client_cls: Type[patroni.dcs.etcd.AbstractEtcdClientWithFailover]) → patroni.dcs.etcd.AbstractEtcdClientWithFailover
handle_etcd_exceptions(func: Callable[[...], Any], *args, **kwargs) → Any
reload_config(config: Union[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.
retry(method: Callable[[...], Any], *args, **kwargs) → Any
set_retry_timeout(retry_timeout: int) → None

Set the new value for retry_timeout.

set_socket_options(sock: socket.socket, socket_options: Optional[Collection[Tuple[int, int, int]]]) → None
set_ttl(ttl: int) → Optional[bool]

Set the new ttl value for DCS keys.

ttl

Get current ttl value.

class patroni.dcs.etcd.AbstractEtcdClientWithFailover(config: Dict[str, Any], dns_resolver: patroni.dcs.etcd.DnsCachingResolver, cache_ttl: int = 300)

Bases: abc.ABC, etcd.client.Client

__init__(config: Dict[str, Any], dns_resolver: patroni.dcs.etcd.DnsCachingResolver, cache_ttl: int = 300) → None

Initialize self. See help(type(self)) for accurate signature.

_abc_impl = <_abc_data object>
_calculate_timeouts(etcd_nodes: int, timeout: Optional[float] = None) → Tuple[int, float, int]

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: Optional[patroni.utils.Retry], machines_cache: List[str], request_executor: Callable[[...], urllib3.response.HTTPResponse], method: str, path: str, fields: Optional[Dict[str, Any]] = None, **kwargs) → urllib3.response.HTTPResponse
_get_headers() → Dict[str, str]
_get_machines_cache_from_config() → List[str]
_get_machines_cache_from_dns(host: str, port: int) → List[str]

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: Optional[str] = None) → List[str]

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]

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
_get_members(base_uri: str, **kwargs) → List[str]

returns: list of clientURLs

_load_machines_cache() → bool

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: Optional[float] = None) → Dict[str, Any]
_prepare_get_members(etcd_nodes: int) → Dict[str, Any]

returns: request parameters

_prepare_request(kwargs: Dict[str, Any], params: Optional[Dict[str, Any]] = None, method: Optional[str] = None) → Callable[[...], urllib3.response.HTTPResponse]

returns: request_executor

_refresh_machines_cache(machines_cache: Optional[List[str]] = None) → bool

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
api_execute(path: str, method: str, params: Optional[Dict[str, Any]] = None, timeout: Optional[float] = None) → Any

Executes the query.

static get_srv_record(host: str) → List[Tuple[str, int]]
machines

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.

machines_cache
reload_config(config: Dict[str, Any]) → None
set_base_uri(value: str) → None
set_machines_cache_ttl(cache_ttl: int) → None
set_read_timeout(timeout: float) → None
class patroni.dcs.etcd.DnsCachingResolver(cache_time: float = 600.0, cache_fail_time: float = 30.0)

Bases: threading.Thread

__init__(cache_time: float = 600.0, cache_fail_time: float = 30.0) → None

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 the argument tuple 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[socket.AddressFamily, socket.SocketKind, int, str, Union[Tuple[str, int], Tuple[str, int, int, int]]]]
remove(host: str, port: int) → None
resolve(host: str, port: int) → List[Tuple[socket.AddressFamily, socket.SocketKind, int, str, Union[Tuple[str, int], Tuple[str, int, int, int]]]]
resolve_async(host: str, port: int, attempt: int = 0) → None
run() → None

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: patroni.postgresql.mpp.AbstractMPP)

Bases: patroni.dcs.etcd.AbstractEtcd

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

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

Variables:configdict, reference to config section of selected DCS. i.e.: zookeeper for zookeeper, etcd for etcd, etc…
_abc_impl = <_abc_data object>
_client

return correct type of etcd client

_cluster_from_nodes(etcd_index: int, nodes: Dict[str, etcd.EtcdResult]) → patroni.dcs.Cluster
_delete_leader(*args, **kwargs) → Any
_do_attempt_to_acquire_leader() → bool
_do_update_leader() → bool
_load_cluster(path: str, loader: Callable[[str], Union[patroni.dcs.Cluster, Dict[int, patroni.dcs.Cluster]]]) → Union[patroni.dcs.Cluster, Dict[int, patroni.dcs.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, patroni.dcs.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.
_postgresql_cluster_loader(path: str) → patroni.dcs.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(**kwargs)
_write_failsafe(*args, **kwargs) → Any
_write_leader_optime(*args, **kwargs) → Any
_write_status(*args, **kwargs) → Any
attempt_to_acquire_leader(**kwargs)
cancel_initialization(*args, **kwargs) → Any
delete_cluster(*args, **kwargs) → Any
delete_sync_state(*args, **kwargs) → Any
initialize(*args, **kwargs) → Any
static member(node: etcd.EtcdResult) → patroni.dcs.Member
set_config_value(*args, **kwargs) → Any
set_failover_value(*args, **kwargs) → Any
set_history_value(*args, **kwargs) → Any
set_sync_state_value(*args, **kwargs) → Any
set_ttl(ttl: int) → Optional[bool]

Set the new ttl value for DCS keys.

take_leader(*args, **kwargs) → Any
touch_member(*args, **kwargs) → Any
watch(leader_version: Optional[int], 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.

class patroni.dcs.etcd.EtcdClient(config: Dict[str, Any], dns_resolver: patroni.dcs.etcd.DnsCachingResolver, cache_ttl: int = 300)

Bases: patroni.dcs.etcd.AbstractEtcdClientWithFailover

ERROR_CLS

alias of EtcdError

__init__(config: Dict[str, Any], dns_resolver: patroni.dcs.etcd.DnsCachingResolver, cache_ttl: int = 300) → None

Initialize self. See help(type(self)) for accurate signature.

_abc_impl = <_abc_data object>
_get_members(base_uri: str, **kwargs) → List[str]

returns: list of clientURLs

_prepare_get_members(etcd_nodes: int) → Dict[str, Any]

returns: request parameters

_prepare_request(kwargs: Dict[str, Any], params: Optional[Dict[str, Any]] = None, method: Optional[str] = None) → Callable[[...], urllib3.response.HTTPResponse]

returns: request_executor

exception patroni.dcs.etcd.EtcdError(value: Any)

Bases: patroni.exceptions.DCSError

exception patroni.dcs.etcd.EtcdRaftInternal(message=None, payload=None)

Bases: etcd.EtcdException

Raft Internal Error

patroni.dcs.etcd.catch_etcd_errors(func: Callable[[...], Any]) → Any