M1 v23

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A Postgres cluster with one or more active locations, each with the same number of Postgres nodes and an extra Barman node. Optionally, there can also be a location containing only a witness node, or a location containing only a single node, even if the active locations have more than one.

This architecture is suitable for production and is also suited to testing, demonstrating and learning due to its simplicity and ability to be configured with no proprietary components.

If you select subscription-only EDB software with this architecture it will be sourced from EDB Repos 2.0 and you will need to provide a token. See How TPA uses 2ndQuadrant and EDB repositories for more detail on this topic.

Application and backup failover

The M1 architecture implements failover management in that it ensures that a replica will be promoted to take the place of the primary should the primary become unavailable. However it does not provide any automatic facility to reroute application traffic to the primary. If you require, automatic failover of application traffic you will need to configure this at the application itself (for example using multi-host connections) or by using an appropriate proxy or load balancer and the facilities offered by your selected failover manager.

The above is also true of the connection between the backup node and the primary created by TPA. The backup will not be automatically adjusted to target the new primary in the event of failover, instead it will remain connected to the original primary. If you are performing a manual failover and wish to connect the backup to the new primary, you may simply re-run tpaexec deploy. If you wish to automatically change the backup source, you should implement this using your selected failover manager as noted above.

Cluster configuration

Overview of configuration options

An example invocation of tpaexec configure for this architecture is shown below.

tpaexec configure ~/clusters/m1 \
         --architecture M1 \
         --platform aws --region eu-west-1 --instance-type t3.micro \
         --distribution Debian \
         --postgresql 14 \
         --failover-manager repmgr \
         --data-nodes-per-location 3

You can list all available options using the help command.

tpaexec configure --architecture M1 --help

The tables below describe the mandatory options for M1 and additional important options. More detail on the options is provided in the following section.

Mandatory Options

Parameter	Description
`--architecture` (`-a`)	Must be set to `M1`.
Postgres flavour and version (e.g. `--postgresql 15`)	A valid flavour and version specifier.
One of: `--failover-manager {efm, repmgr, patroni}` `--enable-efm` `--enable-repmgr` `--enable-patroni`	Select the failover manager from `efm`, `repmgr` and `patroni`.

Additional Options

Parameter	Description	Behaviour if omitted
`--platform`	One of `aws`, `docker`, `bare`.	Defaults to `aws`.
`--location-names`	A space-separated list of location names. The number of active locations is equal to the number of names supplied, minus one for each of the witness-only location and the single-node location if they are requested.	A single location called "main" is used.
`--primary-location`	The location where the primary server will be. Must be a member of `location-names`.	The first listed location is used.
`--data-nodes-per-location`	A number from 1 upwards. In each location, one node will be configured to stream directly from the cluster's primary node, and the other nodes, if present, will stream from that one.	Defaults to 2.
`--witness-only-location`	A location name, must be a member of `location-names`.	No witness-only location is added.
`--single-node-location`	A location name, must be a member of `location-names`.	No single-node location is added.
`--enable-haproxy`	2 additional nodes will be added as a load balancer layer. Only supported with Patroni as the failover manager.	HAproxy nodes will not be added to the cluster.
`--patroni-dcs`	Select the Distributed Configuration Store backend for patroni. Only option is `etcd` at this time. Only supported with Patroni as the failover manager.	Defaults to `etcd`.

More detail about M1 configuration

You may also specify any of the options described by tpaexec help configure-options.