Cluster configuration v23

The tpaexec configure command generates a YAML cluster configuration file that is required by subsequent stages in the provision/deploy/test cycle.

Quickstart

[tpa]$ tpaexec configure ~/clusters/speedy --architecture M1 \
        --postgresql 14 \
        --failover-manager repmgr

This command will create a directory named ~/clusters/speedy and generate a configuration file named config.yml that follows the layout of the architecture named M1 (single primary, N replicas). It will create a git repository in the new directory and make an initial commit containing the generated config.yml.

The command also accepts various options (some specific to the selected architecture or platform) to modify the configuration, but the defaults are sensible and intended to be usable straightaway. You are encouraged to read the generated config.yml and fine-tune the configuration to suit your needs. (Here's an overview of configuration settings that affect the deployment.)

It's possible to write config.yml entirely by hand, but it's much easier to edit the generated file.

Configuration options

The first argument must be the cluster directory, e.g., speedy or ~/clusters/speedy (the cluster will be named speedy in both cases). We recommend that you keep all your clusters in a common directory, e.g., ~/clusters in the example above.

The next argument must be --architecture <name> to select an architecture, e.g., M1 or BDR-Always-ON. For a complete list of architectures, run tpaexec info architectures.

Next, you must specify a flavour and version of Postgres to install.

The arguments above are always mandatory. The rest of the options described here may be safely omitted, as in the example above; the defaults will lead to a usable result.

Run tpaexec help configure-options for a list of common options.

Architecture-specific options

The architecture you select determines what other options are accepted. Typically, each architecture accepts some unique options as well as the generic options described below.

For example, with M1 you can use --num-cascaded-replicas 3 to create a cluster with three cascaded replicas. Please consult the documentation for an architecture for a list of options that it accepts (or, in some cases, requires).

Platform options

Next, you may use --platform <name> to select a platform, e.g., aws or bare.

An architecture may or may not support a particular platform. If not, it will fail to configure the cluster.

The choice of platform affects the interpretation of certain options. For example, if you choose aws, the arguments to --region <region> and --instance-type <type> must be a valid AWS region name and EC2 instance type respectively. Please refer to the platform documentation for more details.

If you do not explicitly select a platform, the default is currently aws.

Note: TPA fully supports creating clusters with instances on different platforms, but tpaexec configure cannot currently generate such a configuration. You must edit config.yml to specify multiple platforms.

Owner

Specify --owner <name> to associate the cluster (by some platform-specific means, e.g., AWS tags) with the name of a person responsible for it. This is especially important for cloud platforms. By default, the owner is set to the login name of the user running tpaexec provision.

(You may use your initials, or "Firstname Lastname", or anything else that identifies you uniquely.)

Region

Specify --region <region> to select a region.

This option is meaningful only for cloud platforms. The default for AWS is eu-west-1.

Note: TPA fully supports creating clusters that span multiple regions, but tpaexec configure cannot currently generate such a configuration. You must edit config.yml to specify multiple regions.

Network configuration

By default, each cluster will be configured with a number of randomly selected /28 subnets from the CIDR range 10.33.0.0/16, depending on the selected architecture.

Specify --network 192.168.0.0/16 to assign subnets from a different network.

Note: On AWS clusters, this corresponds to the VPC CIDR. See aws documentation for details.

Specify --subnet-prefix 26 to assign subnets of a different size, /26 instead of /28 in this case.

Specify --no-shuffle-subnets to allocate subnets from the start of the network CIDR range, without randomisation, e.g. 10.33.0.0/28, then 10.33.0.16/28 and so on.

Specify --exclude-subnets-from <directory> to exclude subnets that are already used in existing cluster config.yml files. You can specify this argument multiple times for each directory.

Note: These options are not meaningful for the "bare" platform, where TPA will not alter the network configuration of existing servers.

Instance type

Specify --instance-type <type> to select an instance type.

This option is meaningful only for cloud platforms. The default for AWS is t3.micro.

Disk space

Specify --root-volume-size 64 to set the size of the root volume in GB. (Depending on the platform, there may be a minimum size required for the root volume.)

The --postgres-volume-size <size> and --barman-volume-size <size> options are available to set the sizes of the Postgres and Barman volumes on those architectures and platforms that support separate volumes for Postgres and Barman.

None of these options is meaningful for the "bare" platform, where TPA has no control over volume sizes.

Hostnames

By default, tpaexec configure will randomly select as many hostnames as it needs from a pre-approved list of several dozen names. This should be enough for most clusters.

Specify --hostnames-from <filename> to select hostnames from a file with one name per line. The file must contain at least as many valid hostnames as there are instances in your cluster. Each line may contain an optional IP address after the name; if present, this address will be set as the ip_address for the corresponding instance in config.yml.

Use --hostnames-pattern '…pattern…' to limit the selection to lines matching an egrep pattern.

Use --hostnames-sorted-by="--dictionary-order" to select a sort(1) option other than --random-sort (which is the default).

Use --hostnames-unsorted to not sort hostnames at all. In this case, they will be assigned in the order they are found in the hostnames file. This is the default when a hostnames file is explicitly specified.

Hostnames may contain only letters (a-z), digits (0-9), and '-'. They may be FQDNs, depending on the selected platform. Hostnames should be in lowercase; any uppercase characters will be converted to lowercase internally, and any references to these hostnames in config.yml (e.g., upstream: hostname) must use the lowercase version.

Software selection

Distribution

Specify --distribution <name> to select a distribution.

The selected platform determines which distributions are available, and which one is used by default.

In general, you should be able to use "Debian", "RedHat", "Ubuntu", and "SLES" to select the right images.

This option is not meaningful for the "bare" platform, where TPA has no control over which distribution is installed.

2ndQuadrant and EDB repositories

TPA can enable any 2ndQuadrant or EDB software repository that you have access to through a subscription.

By default, it will install the 2ndQuadrant public repository (which does not need a subscription) and add on any product repositories that the architecture may require (e.g., the PGD repository).

More detailed explanation of how TPA uses 2ndQuadrant and EDB repositories is available here

Specify --2Q-repositories source/name/maturity … or --edb-repositories repository … to specify the complete list of 2ndQuadrant or EDB repositories to install on each instance in addition to the 2ndQuadrant public repository.

If any EDB repositories are specified, any 2ndQuadrant ones will be ignored.

Use this option with care. TPA will configure the named repositories with no attempt to make sure the combination is appropriate.

To use these options, you must export TPA_2Q_SUBSCRIPTION_TOKEN=xxx or export EDB_SUBSCRIPTION_TOKEN=xxx before you run tpaexec. You can get a 2ndQuadrant token from the 2ndQuadrant Portal under "Company info" in the left menu, then "Company". You can get an EDB token from enterprisedb.com/repos.

Local repository support

Use --enable-local-repo to create a local package repository from which to ship packages to target instances.

In environments with restricted network access, you can instead use --use-local-repo-only to create a local repository and disable all other package repositories on target instances, so that packages are installed only from the local repository.

The page about Local repository support has more details.

Software versions

Postgres flavour and version

TPA supports PostgreSQL, EDB Postgres Extended, and EDB Postgres Advanced Server (EPAS) versions 11 through 15.

You must specify both the flavour (or distribution) and major version of Postgres to install, for example:

• --postgresql 14 will install PostgreSQL 14

• --edb-postgres-extended 15 will install EDB Postgres Extended 15

• --edb-postgres-advanced 15 --redwood will install EPAS 15 in "Redwood" mode

• --edb-postgres-advanced 15 --no-redwood will install EPAS 15 in non-Redwood mode

If you are installing EPAS, you must specify whether it should operate in --redwood or --no-redwood mode, i.e., whether to enable or disable its Oracle compatibility features.

Installing EDB Postgres Extended or Postgres Advanced Server requires a valid EDB repository subscription.

Package versions

By default, we always install the latest version of every package. This is usually the desired behaviour, but in some testing scenarios, it may be necessary to select specific package versions using any of the following options:

1. --postgres-package-version 10.4-2.pgdg90+1
2. --repmgr-package-version 4.0.5-1.pgdg90+1
3. --barman-package-version 2.4-1.pgdg90+1
4. --pglogical-package-version '2.2.0*'
5. --bdr-package-version '3.0.2*'
6. --pgbouncer-package-version '1.8*'

You may use any version specifier that apt or yum would accept.

If your version does not match, try appending a * wildcard. This is often necessary when the package version has an epoch qualifier like 2:....

You may also specify --extra-packages p1 p2 … or --extra-postgres-packages p1 p2 … to install additional packages. The former lists packages to install along with system packages, while the latter lists packages to install later along with postgres packages. (If you mention packages that depend on Postgres in the former list, the installation will fail because Postgres will not yet be installed.) The arguments are passed on to the package manager for installation without any modifications.

The --extra-optional-packages p1 p2 … option behaves like --extra-packages, but it is not an error if the named packages cannot be installed.

Known issue with wildcard use

Please note that the use of wildcards in *_package_version when added permanently to config.yml, can result in unexpected updates to installed software during tpaexec deploy on nodes with RHEL 8 and above (or derivative OSs which use dnf such as Rocky Linux). When deploy runs on an existing cluster that already has packages installed ansible may be unable to match the full package version. For example, if the value for bdr_package_version was set to 3.6* then ansible would not be able to match this to an installed version of PGD, it would assume no package is installed, and it would attempt to install the latest version available of the package with the same name in the configured repository, e.g. 3.7.

We are aware of this limitation as an ansible dnf module bug and hope to address this in a future release of TPA.

Building and installing from source

If you specify --install-from-source postgres, Postgres will be built and installed from a git repository instead of installed from packages. Use 2ndqpostgres instead of postgres to build and install 2ndQPostgres. By default, this will build the appropriate REL_nnn_STABLE branch.

You may use --install-from-source 2ndqpostgres pglogical3 bdr3 to build and install all three components from source, or just use --install-from-source pglogical3 bdr3 to use packages for 2ndQPostgres, but build and install pglogical v3 and PGD v3 from source. By default, this will build the master branch of pglogical and PGD.

To build a different branch, append :branchname to the corresponding argument. For example --install-from-source 2ndqpostgres:dev/xxx, or pglogical:bug/nnnn.

You may not be able to install packages that depend on a package that you chose to replace with a source installation instead. For example, PGD v3 packages depend on pglogical v3 packages, so you can't install pglogical from its source repository and PGD from packages. Likewise, you can't install Postgres from source and pglogical from packages.

Overrides

You may optionally specify --overrides-from a.yml … to load one or more YAML files with settings to merge into the generated config.yml.

Any file specified here is first expanded as a Jinja2 template, and the result is loaded as a YAML data structure, and merged recursively into the arguments used to generate config.yml (comprising architecture and platform defaults and arguments from the command-line). This process is repeated for each additional override file specified; this means that settings defined by one file will be visible to any subsequent files.

For example, your override file might contain:

cluster_tags:
  some_tag: "{{ lookup('env', 'SOME_ENV_VAR') }}"

cluster_vars:
  synchronous_commit: remote_write
  postgres_conf_settings:
    effective_cache_size: 4GB

These settings will augment cluster_tags and cluster_vars that would otherwise be in config.yml. Settings are merged recursively, so cluster_tags will end up containing both the default Owner tag as well as some_tag. Similarly, the effective_cache_size setting will override that variable, leaving other postgres_conf_settings (if any) unaffected. In other words, you can set or override specific subkeys in config.yml, but you can't empty or replace cluster_tags or any other hash altogether.

The merging only applies to hash structures, so you cannot use this mechanism to change the list of instances within config.yml. It is most useful to augment cluster_vars and instance_defaults with common settings for your environment.

That said, the mechanism does not enforce any restrictions, so please exercise due caution. It is a good idea to generate two configurations with and without the overrides and diff the two config.yml files to make sure you understand the effect of all the overrides.

Ansible Tower

Use the --use-ansible-tower and --tower-git-repository options to create a cluster adapted for deployment with Ansible Tower. See Ansible Tower for details.

git repository

By default, a git repository is created with an initial branch named after the cluster, and a single commit is made, with the configure options you used in the commit message. If you don't have git in your $PATH, tpaexec will not raise an error but the repository will not be created. To suppress creation of the git repository, use the --no-git option. (Note that in an Ansible Tower cluster, a git repository is required and will be created later by tpaexec provision if it does not already exist.)

Examples

Let's see what happens when we run the following command:

[tpa]$ tpaexec configure ~/clusters/speedy --architecture M1 \
        --num-cascaded-replicas 2 --distribution Debian \
        --platform aws --region us-east-1 --network 10.33.0.0/16 \
        --instance-type t2.medium --root-volume-size 32 \
        --postgres-volume-size 64 --barman-volume-size 128 \
        --postgresql 14 \
        --failover-manager repmgr
[tpa]$

There is no output, so there were no errors. The cluster directory has been created and populated.

$ ls ~/clusters/speedy
total 8
drwxr-xr-x 2 ams ams 4096 Aug  4 16:23 commands
-rw-r--r-- 1 ams ams 1374 Aug  4 16:23 config.yml
lrwxrwxrwx 1 ams ams   51 Aug  4 16:23 deploy.yml ->
                         /home/ams/work/2ndq/TPA/architectures/M1/deploy.yml

The cluster configuration is in config.yml, and its neighbours are links to architecture-specific support files that you need not interact with directly. Here's what the configuration looks like:

---
architecture: M1
cluster_name: speedy
cluster_tags: {}

cluster_rules:
- cidr_ip: 0.0.0.0/0
  from_port: 22
  proto: tcp
  to_port: 22
- cidr_ip: 10.33.76.176/28
  from_port: 0
  proto: tcp
  to_port: 65535
- cidr_ip: 10.33.148.240/28
  from_port: 0
  proto: tcp
  to_port: 65535
ec2_ami:
  Name: debian-10-amd64-20210721-710
  Owner: '136693071363'
ec2_instance_reachability: public
ec2_vpc:
  us-east-1:
    Name: Test
    cidr: 10.33.0.0/16

cluster_vars:
  enable_pg_backup_api: false
  failover_manager: repmgr
  postgres_flavour: postgresql
  postgres_version: '14'
  preferred_python_version: python3
  use_volatile_subscriptions: false

locations:
- Name: main
  az: us-east-1a
  region: us-east-1
  subnet: 10.33.76.176/28
- Name: dr
  az: us-east-1b
  region: us-east-1
  subnet: 10.33.148.240/28

instance_defaults:
  default_volumes:
  - device_name: root
    encrypted: true
    volume_size: 32
    volume_type: gp2
  - device_name: /dev/sdf
    encrypted: true
    vars:
      volume_for: postgres_data
    volume_size: 64
    volume_type: gp2
  platform: aws
  type: t2.medium
  vars:
    ansible_user: admin

instances:
- Name: upsets
  backup: kayak
  location: main
  node: 1
  role:
  - primary
- Name: zebra
  location: main
  node: 2
  role:
  - replica
  upstream: upsets
- Name: kayak
  location: main
  node: 3
  role:
  - barman
  - log-server
  - monitoring-server
  - witness
  upstream: upsets
  volumes:
  - device_name: /dev/sdf
    encrypted: true
    vars:
      volume_for: barman_data
    volume_size: 128
    volume_type: gp2
- Name: queen
  location: dr
  node: 4
  role:
  - replica
  upstream: zebra
- Name: knock
  location: dr
  node: 5
  role:
  - replica
  upstream: zebra

The next step is to run tpaexec provision or learn more about how to customise the configuration of the cluster as a whole or how to configure an individual instance.

• On this page
• Quickstart
• Configuration options
• Software selection
• Overrides
• Ansible Tower
• git repository
• Examples