pg_autoctl create postgres¶
pg_autoctl create postgres - Initialize a pg_auto_failover postgres node
Synopsis¶
The command pg_autoctl create postgres
initializes a standalone Postgres
node to a pg_auto_failover monitor. The monitor is then handling
auto-failover for this Postgres node (as soon as a secondary has been
registered too, and is known to be healthy).
usage: pg_autoctl create postgres
--pgctl path to pg_ctl
--pgdata path to data directory
--pghost PostgreSQL's hostname
--pgport PostgreSQL's port number
--listen PostgreSQL's listen_addresses
--username PostgreSQL's username
--dbname PostgreSQL's database name
--name pg_auto_failover node name
--hostname hostname used to connect from the other nodes
--formation pg_auto_failover formation
--monitor pg_auto_failover Monitor Postgres URL
--auth authentication method for connections from monitor
--skip-pg-hba skip editing pg_hba.conf rules
--pg-hba-lan edit pg_hba.conf rules for --dbname in detected LAN
--ssl-self-signed setup network encryption using self signed certificates (does NOT protect against MITM)
--ssl-mode use that sslmode in connection strings
--ssl-ca-file set the Postgres ssl_ca_file to that file path
--ssl-crl-file set the Postgres ssl_crl_file to that file path
--no-ssl don't enable network encryption (NOT recommended, prefer --ssl-self-signed)
--server-key set the Postgres ssl_key_file to that file path
--server-cert set the Postgres ssl_cert_file to that file path
--candidate-priority priority of the node to be promoted to become primary
--replication-quorum true if node participates in write quorum
--maximum-backup-rate maximum transfer rate of data transferred from the server during initial sync
Description¶
Three different modes of initialization are supported by this command, corresponding to as many implementation strategies.
Initialize a primary node from scratch
This happens when
--pgdata
(or the environment variablePGDATA
) points to an non-existing or empty directory. Then the given--hostname
is registered to the pg_auto_failover--monitor
as a member of the--formation
.The monitor answers to the registration call with a state to assign to the new member of the group, either SINGLE or WAIT_STANDBY. When the assigned state is SINGLE, then
pg_autoctl create postgres
proceeds to initialize a new PostgreSQL instance.Initialize an already existing primary server
This happens when
--pgdata
(or the environment variablePGDATA
) points to an already existing directory that belongs to a PostgreSQL instance. The standard PostgreSQL toolpg_controldata
is used to recognize whether the directory belongs to a PostgreSQL instance.In that case, the given
--hostname
is registered to the monitor in the tentative SINGLE state. When the given--formation
and--group
is currently empty, then the monitor accepts the registration and thepg_autoctl create
prepares the already existing primary server for pg_auto_failover.Initialize a secondary node from scratch
This happens when
--pgdata
(or the environment variablePGDATA
) points to a non-existing or empty directory, and when the monitor registration call assigns the state WAIT_STANDBY in step 1.In that case, the
pg_autoctl create
command steps through the initial states of registering a secondary server, which includes preparing the primary server PostgreSQL HBA rules and creating a replication slot.When the command ends successfully, a PostgreSQL secondary server has been created with
pg_basebackup
and is now started, catching-up to the primary server.Initialize a secondary node from an existing data directory
When the data directory pointed to by the option
--pgdata
or the environment variablePGDATA
already exists, then pg_auto_failover verifies that the system identifier matches the one of the other nodes already existing in the same group.The system identifier can be obtained with the command
pg_controldata
. All nodes in a physical replication setting must have the same system identifier, and so in pg_auto_failover all the nodes in a same group have that constraint too.When the system identifier matches the already registered system identifier of other nodes in the same group, then the node is set-up as a standby and Postgres is started with the primary conninfo pointed at the current primary.
The --auth
option allows setting up authentication method to be used
when monitor node makes a connection to data node with
pgautofailover_monitor
user. As with the
pg_autoctl create monitor command, you could use --auth trust
when playing with pg_auto_failover at first and consider something
production grade later. Also, consider using --skip-pg-hba
if you
already have your own provisioning tools with a security compliance process.
See Security settings for pg_auto_failover for notes on .pgpass
Options¶
The following options are available to pg_autoctl create postgres
:
- --pgctl
Path to the
pg_ctl
tool to use for the version of PostgreSQL you want to use.Defaults to the
pg_ctl
found in the PATH when there is a single entry forpg_ctl
in the PATH. Check your setup usingwhich -a pg_ctl
.When using an RPM based distribution such as RHEL or CentOS, the path would usually be
/usr/pgsql-13/bin/pg_ctl
for Postgres 13.When using a debian based distribution such as debian or ubuntu, the path would usually be
/usr/lib/postgresql/13/bin/pg_ctl
for Postgres 13. Those distributions also use the packagepostgresql-common
which provides/usr/bin/pg_config
. This tool can be automatically used bypg_autoctl
to discover the default version of Postgres to use on your setup.- --pgdata
Location where to initialize a Postgres database cluster, using either
pg_ctl initdb
orpg_basebackup
. Defaults to the environment variablePGDATA
.- --pghost
Hostname to use when connecting to the local Postgres instance from the
pg_autoctl
process. By default, this field is left blank in the connection string, allowing to use Unix Domain Sockets with the default path compiled in yourlibpq
version, usually provided by the Operating System. That would be/var/run/postgresql
when using debian or ubuntu.- --pgport
Postgres port to use, defaults to 5432.
- --listen
PostgreSQL’s
listen_addresses
to setup. At the moment only one address is supported in this command line option.- --username
PostgreSQL’s username to use when connecting to the local Postgres instance to manage it.
- --dbname
PostgreSQL’s database name to use in your application. Defaults to being the same as the
--username
, or topostgres
when none of those options are used.- --name
Node name used on the monitor to refer to this node. The hostname is a technical information, and given Postgres requirements on the HBA setup and DNS resolution (both forward and reverse lookups), IP addresses are often used for the hostname.
The
--name
option allows using a user-friendly name for your Postgres nodes.- --hostname
Hostname or IP address (both v4 and v6 are supported) to use from any other node to connect to this node.
When not provided, a default value is computed by running the following algorithm.
We get this machine’s “public IP” by opening a connection to the given monitor hostname or IP address. Then we get TCP/IP client address that has been used to make that connection.
We then do a reverse DNS lookup on the IP address found in the previous step to fetch a hostname for our local machine.
If the reverse DNS lookup is successful , then
pg_autoctl
does a forward DNS lookup of that hostname.
When the forward DNS lookup response in step 3. is an IP address found in one of our local network interfaces, then
pg_autoctl
uses the hostname found in step 2. as the default--hostname
. Otherwise it uses the IP address found in step 1.You may use the
--hostname
command line option to bypass the whole DNS lookup based process and force the local node name to a fixed value.- --formation
Formation to register the node into on the monitor. Defaults to the
default
formation, that is automatically created in the monitor in the pg_autoctl create monitor command.- --monitor
Postgres URI used to connect to the monitor. Must use the
autoctl_node
username and target thepg_auto_failover
database name. It is possible to show the Postgres URI from the monitor node using the command pg_autoctl show uri.- --auth
Authentication method used by
pg_autoctl
when editing the Postgres HBA file to open connections to other nodes. No default value, must be provided by the user. The value--trust
is only a good choice for testing and evaluation of pg_auto_failover, see Security settings for pg_auto_failover for more information.- --skip-pg-hba
When this option is used then
pg_autoctl
refrains from any editing of the Postgres HBA file. Please note that editing the HBA file is still needed so that other nodes can connect using either read privileges or replication streaming privileges.When
--skip-pg-hba
is used,pg_autoctl
still outputs the HBA entries it needs in the logs, it only skips editing the HBA file.- --pg-hba-lan
When this option is used
pg_autoctl
determines the local IP address used to connect to the monitor, and retrieves its netmask, and uses that to compute your local area network CIDR. This CIDR is then opened for connections in the Postgres HBA rules.For instance, when the monitor resolves to
192.168.0.1
and your local Postgres node uses an inferface with IP address192.168.0.2/255.255.255.0
to connect to the monitor, then the LAN CIDR is computed to be192.168.0.0/24
.- --candidate-priority
Sets this node replication setting for candidate priority to the given value (between 0 and 100) at node registration on the monitor. Defaults to 50.
- --replication-quorum
Sets this node replication setting for replication quorum to the given value (either
true
orfalse
) at node registration on the monitor. Defaults totrue
, which enables synchronous replication.- --maximum-backup-rate
Sets the maximum transfer rate of data transferred from the server during initial sync. This is used by
pg_basebackup
. Defaults to100M
.- --run
Immediately run the
pg_autoctl
service after having created this node.- --ssl-self-signed
Generate SSL self-signed certificates to provide network encryption. This does not protect against man-in-the-middle kinds of attacks. See Security settings for pg_auto_failover for more about our SSL settings.
- --ssl-mode
SSL Mode used by
pg_autoctl
when connecting to other nodes, including when connecting for streaming replication.- --ssl-ca-file
Set the Postgres
ssl_ca_file
to that file path.- --ssl-crl-file
Set the Postgres
ssl_crl_file
to that file path.- --no-ssl
Don’t enable network encryption. This is not recommended, prefer
--ssl-self-signed
.- --server-key
Set the Postgres
ssl_key_file
to that file path.- --server-cert
Set the Postgres
ssl_cert_file
to that file path.
Environment¶
PGDATA
Postgres directory location. Can be used instead of the
--pgdata
option.
PG_AUTOCTL_MONITOR
Postgres URI to connect to the monitor node, can be used instead of the
--monitor
option.
PG_AUTOCTL_NODE_NAME
Node name to register to the monitor, can be used instead of the
--name
option.
PG_AUTOCTL_REPLICATION_QUORUM
Can be used instead of the
--replication-quorum
option.
PG_AUTOCTL_CANDIDATE_PRIORITY
Can be used instead of the
--candidate-priority
option.
PG_CONFIG
Can be set to the absolute path to the pg_config Postgres tool. This is mostly used in the context of building extensions, though it can be a useful way to select a Postgres version when several are installed on the same system.
PATH
Used the usual way mostly. Some entries that are searched in the PATH by the
pg_autoctl
command are expected to be found only once, to avoid mistakes with Postgres major versions.
PGHOST, PGPORT, PGDATABASE, PGUSER, PGCONNECT_TIMEOUT, …
See the Postgres docs about Environment Variables for details.
TMPDIR
The pgcopydb command creates all its work files and directories in
${TMPDIR}/pgcopydb
, and defaults to/tmp/pgcopydb
.
XDG_CONFIG_HOME
The pg_autoctl command stores its configuration files in the standard place XDG_CONFIG_HOME. See the XDG Base Directory Specification.
XDG_DATA_HOME
The pg_autoctl command stores its internal states files in the standard place XDG_DATA_HOME, which defaults to
~/.local/share
. See the XDG Base Directory Specification.