Dynamic Configuration Settings

Dynamic configuration is stored in the DCS (Distributed Configuration Store) and applied on all cluster nodes.

In order to change the dynamic configuration you can use either patronictl edit-config tool or Patroni REST API .

• loop_wait : the number of seconds the loop will sleep. Default value: 10, minimum possible value: 1

• ttl : the TTL to acquire the leader lock (in seconds). Think of it as the length of time before initiation of the automatic failover process. Default value: 30, minimum possible value: 20

• retry_timeout : timeout for DCS and PostgreSQL operation retries (in seconds). DCS or network issues shorter than this will not cause Patroni to demote the leader. Default value: 10, minimum possible value: 3

loop_wait + 2 * retry_timeout <= ttl

• maximum_lag_on_failover : the maximum bytes a follower may lag to be able to participate in leader election.

• maximum_lag_on_syncnode : the maximum bytes a synchronous follower may lag before it is considered as an unhealthy candidate and swapped by healthy asynchronous follower. Patroni utilize the max replica lsn if there is more than one follower, otherwise it will use leader’s current wal lsn. Default is -1, Patroni will not take action to swap synchronous unhealthy follower when the value is set to 0 or below. Please set the value high enough so Patroni won’t swap synchrounous follower fequently during high transaction volume.

• max_timelines_history : maximum number of timeline history items kept in DCS. Default value: 0. When set to 0, it keeps the full history in DCS.

• primary_start_timeout : the amount of time a primary is allowed to recover from failures before failover is triggered (in seconds). Default is 300 seconds. When set to 0 failover is done immediately after a crash is detected if possible. When using asynchronous replication a failover can cause lost transactions. Worst case failover time for primary failure is: loop_wait + primary_start_timeout + loop_wait, unless primary_start_timeout is zero, in which case it’s just loop_wait. Set the value according to your durability/availability tradeoff.

• primary_stop_timeout : The number of seconds Patroni is allowed to wait when stopping Postgres and effective only when synchronous_mode is enabled. When set to > 0 and the synchronous_mode is enabled, Patroni sends SIGKILL to the postmaster if the stop operation is running for more than the value set by primary_stop_timeout. Set the value according to your durability/availability tradeoff. If the parameter is not set or set <= 0, primary_stop_timeout does not apply.

• synchronous_mode : turns on synchronous replication mode. In this mode a replica will be chosen as synchronous and only the latest leader and synchronous replica are able to participate in leader election. Synchronous mode makes sure that successfully committed transactions will not be lost at failover, at the cost of losing availability for writes when Patroni cannot ensure transaction durability. See replication modes documentation for details.

• synchronous_mode_strict : prevents disabling synchronous replication if no synchronous replicas are available, blocking all client writes to the primary. See replication modes documentation for details.

• failsafe_mode : Enables DCS Failsafe Mode . Defaults to false .

• postgresql :

  • use_pg_rewind : whether or not to use pg_rewind. Defaults to false .

  • use_slots : whether or not to use replication slots. Defaults to true on PostgreSQL 9.4+.

  • recovery_conf : additional configuration settings written to recovery.conf when configuring follower. There is no recovery.conf anymore in PostgreSQL 12, but you may continue using this section, because Patroni handles it transparently.

  • parameters : list of configuration settings for Postgres.

  • pg_hba : list of lines that Patroni will use to generate pg_hba.conf . Patroni ignores this parameter if hba_file PostgreSQL parameter is set to a non-default value.

    • - host all all 0.0.0.0/0 md5

    • - host replication replicator 127.0.0.1/32 md5 : A line like this is required for replication.

  • pg_ident : list of lines that Patroni will use to generate pg_ident.conf . Patroni ignores this parameter if ident_file PostgreSQL parameter is set to a non-default value.

    • - mapname1 systemname1 pguser1

    • - mapname1 systemname2 pguser2

• standby_cluster : if this section is defined, we want to bootstrap a standby cluster.

  • host : an address of remote node

  • port : a port of remote node

  • primary_slot_name : which slot on the remote node to use for replication. This parameter is optional, the default value is derived from the instance name (see function slot_name_from_member_name ).

  • create_replica_methods : an ordered list of methods that can be used to bootstrap standby leader from the remote primary, can be different from the list defined in PostgreSQL

  • restore_command : command to restore WAL records from the remote primary to nodes in a standby cluster, can be different from the list defined in PostgreSQL

  • archive_cleanup_command : cleanup command for standby leader

  • recovery_min_apply_delay : how long to wait before actually apply WAL records on a standby leader

• slots : define permanent replication slots. These slots will be preserved during switchover/failover. Permanent slots that don’t exist will be created by Patroni. With PostgreSQL 11 onwards permanent physical slots are created on all nodes and their position is advanced every loop_wait seconds. For PostgreSQL versions older than 11 permanent physical replication slots are maintained only on the current primary. The logical slots are copied from the primary to a standby with restart, and after that their position advanced every loop_wait seconds (if necessary). Copying logical slot files performed via libpq connection and using either rewind or superuser credentials (see postgresql.authentication section). There is always a chance that the logical slot position on the replica is a bit behind the former primary, therefore application should be prepared that some messages could be received the second time after the failover. The easiest way of doing so - tracking confirmed_flush_lsn . Enabling permanent replication slots requires postgresql.use_slots to be set to true . If there are permanent logical replication slots defined Patroni will automatically enable the hot_standby_feedback . Since the failover of logical replication slots is unsafe on PostgreSQL 9.6 and older and PostgreSQL version 10 is missing some important functions, the feature only works with PostgreSQL 11+.

  • my_slot_name : the name of the permanent replication slot. If the permanent slot name matches with the name of the current node it will not be created on this node. If you add a permanent physical replication slot which name matches the name of a Patroni member, Patroni will ensure that the slot that was created is not removed even if the corresponding member becomes unresponsive, situation which would normally result in the slot’s removal by Patroni. Although this can be useful in some situations, such as when you want replication slots used by members to persist during temporary failures or when importing existing members to a new Patroni cluster (see Convert a Standalone to a Patroni Cluster for details), caution should be exercised by the operator that these clashes in names are not persisted in the DCS, when the slot is no longer required, due to its effect on normal functioning of Patroni.

    • type : slot type. Could be physical or logical . If the slot is logical, you have to additionally define database and plugin .

    • database : the database name where logical slots should be created.

    • plugin : the plugin name for the logical slot.

• ignore_slots : list of sets of replication slot properties for which Patroni should ignore matching slots. This configuration/feature/etc. is useful when some replication slots are managed outside of Patroni. Any subset of matching properties will cause a slot to be ignored.

  • name : the name of the replication slot.

  • type : slot type. Can be physical or logical . If the slot is logical, you may additionally define database and/or plugin .

  • database : the database name (when matching a logical slot).

  • plugin : the logical decoding plugin (when matching a logical slot).

Note: slots is a hashmap while ignore_slots is an array. For example:

slots:
  permanent_logical_slot_name:
    type: logical
    database: my_db
    plugin: test_decoding
  permanent_physical_slot_name:
    type: physical
  ...
ignore_slots:
  - name: ignored_logical_slot_name
    type: logical
    database: my_db
    plugin: test_decoding
  - name: ignored_physical_slot_name
    type: physical
  ...

Note: if cluster topology is static (fixed number of nodes that never change their names) you can configure permanent physical replication slots with names corresponding to names of nodes to avoid recycling of WAL files while replica is temporary down:

slots:
  node_name1:
    type: physical
  node_name2:
    type: physical
  node_name3:
    type: physical
  ...