Configuring haproxy v23

TPA will install and configure haproxy on instances whose role contains haproxy.

By default, haproxy listens on 127.0.0.1:5432 for requests forwarded by pgbouncer running on the same instance. You must specify a list of haproxy_backend_servers to forward requests to.

TPA will install the latest available version of haproxy by default. You can install a specific version instead by setting haproxy_package_version: 1.9.15* (for example).

Note: see limitations of using wildcards in package_version in tpaexec-configure.

Haproxy packages are selected according to the type of architecture. An EDB managed haproxy package may be used but requires a subscription. Packages from PGDG extras repo can be installed if required.

You can set the following variables on any haproxy instance.

Variable	Default value	Description
`haproxy_bind_address`	127.0.0.1	The address haproxy should bind to
`haproxy_port`	5432 (5444 for EPAS)	The TCP port haproxy should listen on
`haproxy_read_only_port`	5433 (5445 for EPAS)	TCP port for read-only load-balancer
`haproxy_backend_servers`	None	A list of Postgres instance names
`haproxy_maxconn`	`max_connections`×0.9	The maximum number of connections allowed per backend server; the default is derived from the backend's `max_connections` setting
`haproxy_peer_enabled`	True*	Add known haproxy hosts as `peer` list. *`False` if `failover_manager` is harp or patroni.

Read-Only load-balancer

Haproxy can be configured to listen on an additional port for read-only access to the database. At the moment this is only supported with the Patroni failover manager. The backend health check determines which postgres instances are currently acting as replicas and will send traffic using a roundrobin load balancing algorithm.

The read-only load balancer is disabled by default but can be turned on using the cluster_vars variable haproxy_read_only_load_balancer_enabled.

Server options

TPA will generate /etc/haproxy/haproxy.cfg with a backend that has a default-server line and one line per backend server. All but the first one will be marked as "backup" servers.

Set haproxy_default_server_extra_options to a list of options on the haproxy instance to add options to the default-server line; and set haproxy_server_options to a list of options on the backend server to add options (which will override the defaults) to the individual server lines for each backend.

Example

instances:
- Name: one
  vars:
    haproxy_server_options:
    - maxconn 33
- Name: two
…
- Name: proxy
  role:
  - haproxy
  vars:
    haproxy_backend_servers:
    - one
    - two
    haproxy_default_server_extra_options:
    - on-error mark-down
    - on-marked-down shutdown-sessions

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Reference

Configuring HARP