Patroni configuration
There are 3 types of Patroni configuration:
- Global dynamic configuration.
These options are stored in the DCS (Distributed Configuration Store) and applied on all cluster nodes. Dynamic configuration can be set at any time using patronictl edit-config tool or Patroni REST API. If the options changed are not part of the startup configuration, they are applied asynchronously (upon the next wake up cycle) to every node, which gets subsequently reloaded. If the node requires a restart to apply the configuration (for PostgreSQL parameters with context postmaster, if their values have changed), a special flag
pending_restart
indicating this is set in the members.data JSON. Additionally, the node status indicates this by showing"restart_pending": true
.
- Local configuration file (patroni.yml).
These options are defined in the configuration file and take precedence over dynamic configuration.
patroni.yml
can be changed and reloaded at runtime (without restart of Patroni) by sending SIGHUP to the Patroni process, performingPOST /reload
REST-API request or executing patronictl reload. Local configuration can be either a single YAML file or a directory. When it is a directory, all YAML files in that directory are loaded one by one in sorted order. In case a key is defined in multiple files, the occurrence in the last file takes precedence.
- Environment configuration.
It is possible to set/override some of the “Local” configuration parameters with environment variables. Environment configuration is very useful when you are running in a dynamic environment and you don’t know some of the parameters in advance (for example it’s not possible to know your external IP address when you are running inside
docker
).
Important rules
PostgreSQL parameters controlled by Patroni
Some of the PostgreSQL parameters must hold the same values on the primary and the replicas. For those, values set either in the local patroni configuration files or via the environment variables take no effect. To alter or set their values one must change the shared configuration in the DCS. Below is the actual list of such parameters together with the default values:
max_connections: 100
max_locks_per_transaction: 64
max_worker_processes: 8
max_prepared_transactions: 0
wal_level: hot_standby
track_commit_timestamp: off
For the parameters below, PostgreSQL does not require equal values among the primary and all the replicas. However, considering the possibility of a replica to become the primary at any time, it doesn’t really make sense to set them differently; therefore, Patroni restricts setting their values to the dynamic configuration.
max_wal_senders: 5
max_replication_slots: 5
wal_keep_segments: 8
wal_keep_size: 128MB
These parameters are validated to ensure they are sane, or meet a minimum value.
There are some other Postgres parameters controlled by Patroni:
listen_addresses - is set either from
postgresql.listen
or fromPATRONI_POSTGRESQL_LISTEN
environment variableport - is set either from
postgresql.listen
or fromPATRONI_POSTGRESQL_LISTEN
environment variablecluster_name - is set either from
scope
or fromPATRONI_SCOPE
environment variablehot_standby: on
wal_log_hints: on - for Postgres 9.4 and newer.
To be on the safe side parameters from the above lists are not written into postgresql.conf
, but passed as a list of arguments to the pg_ctl start
which gives them the highest precedence, even above ALTER SYSTEM
There also are some parameters like postgresql.listen, postgresql.data_dir that can be set only locally, i.e. in the Patroni config file or via configuration variable. In most cases the local configuration will override the dynamic configuration.
When applying the local or dynamic configuration options, the following actions are taken:
The node first checks if there is a postgresql.base.conf file or if the
custom_conf
parameter is set.If the
custom_conf
parameter is set, the file it specifies is used as the base configuration, ignoring postgresql.base.conf and postgresql.conf.If the
custom_conf
parameter is not set and postgresql.base.conf exists, it contains the renamed “original” configuration and is used as the base configuration.If there is no
custom_conf
nor postgresql.base.conf, the original postgresql.conf is renamed to postgresql.base.conf and used as the base configuration.The dynamic options (with the exceptions above) are dumped into the postgresql.conf and an include is set in postgresql.conf to the base configuration (either postgresql.base.conf or the file at
custom_conf
). Therefore, we would be able to apply new options without re-reading the configuration file to check if the include is present or not.Some parameters that are essential for Patroni to manage the cluster are overridden using the command line.
If an option that requires restart is changed (we should look at the context in pg_settings and at the actual values of those options), a pending_restart flag is set on that node. This flag is reset on any restart.
The parameters would be applied in the following order (run-time are given the highest priority):
load parameters from file postgresql.base.conf (or from a
custom_conf
file, if set)load parameters from file postgresql.conf
load parameters from file postgresql.auto.conf
run-time parameter using -o –name=value
This allows configuration for all the nodes (2), configuration for a specific node using ALTER SYSTEM
(3) and ensures that parameters essential to the running of Patroni are enforced (4), as well as leaves room for configuration tools that manage postgresql.conf directly without involving Patroni (1).
Patroni configuration parameters
Also the following Patroni configuration options can be changed only dynamically:
ttl: 30
loop_wait: 10
retry_timeouts: 10
maximum_lag_on_failover: 1048576
max_timelines_history: 0
check_timeline: false
postgresql.use_slots: true
Upon changing these options, Patroni will read the relevant section of the configuration stored in DCS and change its run-time values.
Patroni nodes are dumping the state of the DCS options to disk upon for every change of the configuration into the file patroni.dynamic.json
located in the Postgres data directory. Only the leader is allowed to restore these options from the on-disk dump if these are completely absent from the DCS or if they are invalid.
Configuration generation and validation
Patroni provides command-line interfaces for a Patroni local configuration generation and validation. Using the patroni
executable you can:
Create a sample local Patroni configuration;
Create a Patroni configuration file for the locally running PostgreSQL instance (e.g. as a preparation step for the Patroni integration);
Validate a given Patroni configuration file.
Sample Patroni configuration
patroni --generate-sample-config [configfile]
Description
Generate a sample Patroni configuration file in yaml
format.
Parameter values are defined using the Environment configuration, otherwise, if not set, the defaults used in Patroni or the #FIXME
string for the values that should be later defined by the user.
Some default values are defined based on the local setup:
postgresql.listen: the IP address returned by
gethostname
call for the current machine’s hostname and the standard5432
port.postgresql.connect_address: the IP address returned by
gethostname
call for the current machine’s hostname and the standard5432
port.postgresql.authentication.rewind: is only defined if the PostgreSQL version can be defined from the binary and the version is 11 or later.
restapi.listen: IP address returned by
gethostname
call for the current machine’s hostname and the standard8008
port.restapi.connect_address: IP address returned by
gethostname
call for the current machine’s hostname and the standard8008
port.
Parameters
configfile
- full path to the configuration file used to store the result. If not provided, the result is sent to stdout
.
Patroni configuration for a running instance
patroni --generate-config [--dsn DSN] [configfile]
Description
Generate a Patroni configuration in yaml
format for the locally running PostgreSQL instance.
Either the provided DSN (takes precedence) or PostgreSQL environment variables will be used for the PostgreSQL connection. If the password is not provided, it should be entered via prompt.
All the non-internal GUCs defined in the source Postgres instance, independently if they were set through a configuration file, through the postmaster command-line, or through environment variables, will be used as the source for the following Patroni configuration parameters:
scope:
cluster_name
GUC value;postgresql.listen:
listen_addresses
andport
GUC values;postgresql.datadir:
data_directory
GUC value;postgresql.parameters:
archive_command
,restore_command
,archive_cleanup_command
,recovery_end_command
,ssl_passphrase_command
,hba_file
,ident_file
,config_file
GUC values;bootstrap.dcs: all other gathered PostgreSQL GUCs.
If scope
, postgresql.listen
or postgresql.datadir
is not set from the Postgres GUCs, the respective Environment configuration value is used.
Other rules applied for the values definition:
name:
PATRONI_NAME
environment variable value if set, otherwise the current machine’s hostname.postgresql.bin_dir: path to the Postgres binaries gathered from the running instance.
postgresql.connect_address: the IP address returned by
gethostname
call for the current machine’s hostname and the port used for the instance connection or theport
GUC value.postgresql.authentication.superuser: the configuration used for the instance connection;
postgresql.pg_hba: the lines gathered from the source instance’s
hba_file
.postgresql.pg_ident: the lines gathered from the source instance’s
ident_file
.restapi.listen: IP address returned by
gethostname
call for the current machine’s hostname and the standard8008
port.restapi.connect_address: IP address returned by
gethostname
call for the current machine’s hostname and the standard8008
port.
Other parameters defined using Environment configuration are also included into the configuration.
Parameters
configfile
Full path to the configuration file used to store the result. If not provided, result is sent to
stdout
.dsn
Optional DSN string for the local PostgreSQL instance to get GUC values from.
Validate Patroni configuration
patroni --validate-config [configfile]
Description
Validate the given Patroni configuration and print the information about the failed checks.
Parameters
configfile
Full path to the configuration file to check. If not given or file does not exist, will try to read from the
PATRONI_CONFIG_VARIABLE
environment variable or, if not set, from the Patroni environment variables.