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
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__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.
- 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>¶
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abstract property
_client
¶ return correct type of etcd client
-
_cluster
: Optional[patroni.dcs.Cluster]¶
-
_handle_exception
(e: Exception, name: str = '', do_sleep: bool = False, raise_ex: Optional[Exception] = None) → None¶
-
_run_and_handle_exceptions
(method: Callable[[…], Any], *args: Any, **kwargs: Any) → Any¶
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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: Any, **kwargs: Any) → Any¶
-
reload_config
(config: Union[Config, Dict[str, Any]]) → None¶ 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.
-
retry
(method: Callable[[…], Any], *args: Any, **kwargs: Any) → Any¶
-
set_socket_options
(sock: socket.socket, socket_options: Optional[Collection[Tuple[int, int, int]]]) → None¶
-
property
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._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: Any) → urllib3.response.HTTPResponse¶
-
_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)
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_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
-
_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
-
abstract
_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.
-
api_execute
(path: str, method: str, params: Optional[Dict[str, Any]] = None, timeout: Optional[float] = None) → Any¶ Executes the query.
-
property
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.
-
property
machines_cache
¶
-
-
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.
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static
_do_resolve
(host: str, port: int) → List[Tuple[socket.AddressFamily, socket.SocketKind, int, str, Union[Tuple[str, int], Tuple[str, int, int, int]]]]¶
-
resolve
(host: str, port: int) → List[Tuple[socket.AddressFamily, socket.SocketKind, int, str, Union[Tuple[str, int], Tuple[str, int, int, int]]]]¶
-
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.
- 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>¶
-
property
_client
¶ return correct type of etcd client
-
_cluster
: Optional[patroni.dcs.Cluster]¶
-
_cluster_from_nodes
(etcd_index: int, nodes: Dict[str, etcd.EtcdResult]) → patroni.dcs.Cluster¶
-
_delete_leader
(*args: Any, **kwargs: Any) → Any¶ 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], 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 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, 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 andCluster
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: Any)¶ 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.
-
_write_failsafe
(*args: Any, **kwargs: Any) → Any¶ 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¶ 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¶ 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)¶ 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.
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cancel_initialization
(*args: Any, **kwargs: Any) → Any¶ Removes the
initialize
key for a cluster.- Returns
True
if successfully committed to DCS.
-
delete_cluster
(*args: Any, **kwargs: Any) → Any¶ Delete cluster from DCS.
- Returns
True
if successfully committed to DCS.
-
delete_sync_state
(*args: Any, **kwargs: Any) → Any¶ 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¶ 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.
-
static
member
(node: etcd.EtcdResult) → patroni.dcs.Member¶
-
set_config_value
(*args: Any, **kwargs: Any) → Any¶ 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
(*args: Any, **kwargs: Any) → Any¶ 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.
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set_history_value
(*args: Any, **kwargs: Any) → Any¶ 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¶ 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.
-
take_leader
(*args: Any, **kwargs: Any) → Any¶ 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
(*args: Any, **kwargs: Any) → Any¶ 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: 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
patroni.dcs.etcd.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._abc_data object>¶
-
-
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¶