Patroni 核心代码解读

class Cluster(NamedTuple('Cluster',
                         [('initialize', Optional[str]),
                          ('config', Optional[ClusterConfig]),
                          ('leader', Optional[Leader]),
                          ('status', Status),
                          ('members', List[Member]),
                          ('failover', Optional[Failover]),
                          ('sync', SyncState),
                          ('history', Optional[TimelineHistory]),
                          ('failsafe', Optional[Dict[str, str]]),
                          ('workers', Dict[int, 'Cluster'])])):

# 处理存储在 DCS 的数据并构造 Cluster 对象
AbstractDCS._cluster_loader
AbstractDCS._citus_cluster_loader
AbstractDCS._load_cluster

# 创建和更新 leader
AbstractDCS.attempt_to_acquire_leader
AbstractDCS._update_leader

# 创建 initialze
AbstractDCS.initialize

AbstractDCS.take_leader: method to create a new leader key in the DCS.
AbstractDCS.set_ttl: method for setting TTL value in DCS.
AbstractDCS.ttl: property which returns the current TTL.
AbstractDCS.set_retry_timeout: method for setting ``retry_timeout`` in DCS backend.
AbstractDCS._write_leader_optime: compatibility method to write WAL LSN to DCS.
AbstractDCS._write_status: method to write WAL LSN for slots to the DCS.
AbstractDCS._write_failsafe: method to write cluster topology to the DCS, used by failsafe mechanism.
AbstractDCS.touch_member: method to update individual member key in the DCS.
AbstractDCS.set_history_value: method to set the ``history`` key in the DCS.

AbstractDCS.set_failover_value: method to create and/or update the ``failover`` key in the DCS.
AbstractDCS.set_config_value: method to create and/or update the ``failover`` key in the DCS.
AbstractDCS.set_sync_state_value: method to set the synchronous state ``sync`` key in the DCS.

AbstractDCS.delete_sync_state
AbstractDCS.delete_cluster
AbstractDCS._delete_leader
AbstractDCS.cancel_initialization

@catch_etcd_errors
def initialize(self, create_new: bool = True, sysid: str = "") -> bool:
    return bool(self.retry(self._client.write, self.initialize_path, sysid, prevExist=(not create_new)))

etcdctl get /service/batman/members/postgresql1
{"conn_url":"postgres://127.0.0.1:5433/postgres","api_url":"http://127.0.0.1:8009/patroni","state":"running","role":"replica","version":"3.1.2","xlog_location":117441640,"replication_state":"streaming","timeline":7}

def notify_citus_coordinator(self, event: str) -> None:
    if self.state_handler.citus_handler.is_worker():
        coordinator = self.dcs.get_citus_coordinator()
        if coordinator and coordinator.leader and coordinator.leader.conn_url:
            try:
                data = {'type': event,
                        'group': self.state_handler.citus_handler.group(),
                        'leader': self.state_handler.name,
                        'timeout': self.dcs.ttl,
                        'cooldown': self.patroni.config['retry_timeout']}
                timeout = self.dcs.ttl if event == 'before_demote' else 2
                self.patroni.request(coordinator.leader.member, 'post', 'citus', data, timeout=timeout, retries=0)
            except Exception as e:
                logger.warning('Request to Citus coordinator leader %s %s failed: %r',
                                coordinator.leader.name, coordinator.leader.member.api_url, e)

scope: batman
name: postgresql0

restapi:
  listen: 127.0.0.1:8008
  connect_address: 127.0.0.1:8008

etcd:
  host: 127.0.0.1:2379

bootstrap:
  # This section will be written into Etcd:/<namespace>/<scope>/config after initializing new cluster
  # and all other cluster members will use it as a `global configuration`.
  # WARNING! If you want to change any of the parameters that were set up
  # via `bootstrap.dcs` section, please use `patronictl edit-config`!
  dcs:
    ttl: 30
    loop_wait: 10
    retry_timeout: 10
    maximum_lag_on_failover: 1048576

    postgresql:
      use_pg_rewind: true
      pg_hba:
      - host replication replicator 127.0.0.1/32 md5
      - host all all 0.0.0.0/0 md5

  initdb:  # Note: It needs to be a list (some options need values, others are switches)
  - encoding: UTF8
  - data-checksums

  users:
    admin:
      password: admin%
      options:
        - createrole
        - createdb

postgresql:
  listen: 127.0.0.1:5432
  connect_address: 127.0.0.1:5432

  data_dir: data/postgresql0
  pgpass: /tmp/pgpass0
  authentication:
    replication:
      username: replicator
      password: rep-pass
    superuser:
      username: postgres
      password: zalando
    rewind:  # Has no effect on postgres 10 and lower
      username: rewind_user
      password: rewind_password

  parameters:
    unix_socket_directories: '..'  # parent directory of data_dir

tags:
    nofailover: false
    noloadbalance: false
    clonefrom: false
    nosync: false

scope: batman
name: postgresql1

restapi:
  listen: 127.0.0.1:8009
  connect_address: 127.0.0.1:8009

etcd:
  host: 127.0.0.1:2379

bootstrap:
  # This section will be written into Etcd:/<namespace>/<scope>/config after initializing new cluster
  # and all other cluster members will use it as a `global configuration`.
  # WARNING! If you want to change any of the parameters that were set up
  # via `bootstrap.dcs` section, please use `patronictl edit-config`!
  dcs:
    ttl: 30
    loop_wait: 10
    retry_timeout: 10
    maximum_lag_on_failover: 1048576
    postgresql:
      use_pg_rewind: true
      pg_hba:
      - host replication replicator 127.0.0.1/32 md5
      - host all all 0.0.0.0/0 md5

  initdb:  # Note: It needs to be a list (some options need values, others are switches)
  - encoding: UTF8
  - data-checksums

postgresql:
  listen: 127.0.0.1:5433
  connect_address: 127.0.0.1:5433
  data_dir: data/postgresql1
  pgpass: /tmp/pgpass1
  authentication:
    replication:
      username: replicator
      password: rep-pass
    superuser:
      username: postgres
      password: zalando
    rewind:  # Has no effect on postgres 10 and lower
      username: rewind_user
      password: rewind_password
  parameters:
    unix_socket_directories: '..'  # parent directory of data_dir
  basebackup:
      - verbose
      - max-rate: 100M

tags:
    nofailover: false
    noloadbalance: false
    clonefrom: false

scope: batman
name: postgresql2

restapi:
  listen: 127.0.0.1:8010
  connect_address: 127.0.0.1:8010

etcd:
  host: 127.0.0.1:2379

bootstrap:
  # This section will be written into Etcd:/<namespace>/<scope>/config after initializing new cluster
  # and all other cluster members will use it as a `global configuration`.
  # WARNING! If you want to change any of the parameters that were set up
  # via `bootstrap.dcs` section, please use `patronictl edit-config`!
  dcs:
    ttl: 30
    loop_wait: 10
    retry_timeout: 10
    maximum_lag_on_failover: 1048576
    postgresql:
      use_pg_rewind: true
      pg_hba:
      - host replication replicator 127.0.0.1/32 md5
      - host all all 0.0.0.0/0 md5

  initdb:  # Note: It needs to be a list (some options need values, others are switches)
  - encoding: UTF8
  - data-checksums

postgresql:
  listen: 127.0.0.1:5434
  connect_address: 127.0.0.1:5434
  data_dir: data/postgresql2
  pgpass: /tmp/pgpass2
  authentication:
    replication:
      username: replicator
      password: rep-pass
    superuser:
      username: postgres
      password: zalando
    rewind:  # Has no effect on postgres 10 and lower
      username: rewind_user
      password: rewind_password
  parameters:
    unix_socket_directories: '..'  # parent directory of data_dir
tags:
    nofailover: false
    noloadbalance: false
    clonefrom: false