[haproxy] Adds http/2 support to HAProxy

This change introduces haproxy_enable_http2 to let operators enable
http/2 on HAProxy frontends when kolla_enable_tls_external is enabled.

Change-Id: I2e00d3e9193a3052d43a228915ea249794490afe
Closes-Bug: #1850924

ansible/group_vars/all.yml

@@ -939,6 +939,8 @@ rabbitmq_datadir_volume: "rabbitmq"
 ####################
 haproxy_user: "openstack"
 haproxy_enable_external_vip: "{{ 'no' if kolla_same_external_internal_vip | bool else 'yes' }}"
+haproxy_enable_http2: "yes"
+haproxy_http2_protocol: "alpn h2,http/1.1"
 kolla_enable_tls_internal: "no"
 kolla_enable_tls_external: "{{ kolla_enable_tls_internal if kolla_same_external_internal_vip | bool else 'no' }}"
 kolla_certificates_dir: "{{ node_config }}/certificates"

ansible/roles/haproxy-config/templates/haproxy_single_service_split.cfg.j2

@@ -1,6 +1,8 @@
 #jinja2: lstrip_blocks: True
 {%- set external_tls_bind_info = 'ssl crt /etc/haproxy/haproxy.pem' if kolla_enable_tls_external|bool else '' %}
+{%- set external_tls_bind_info = "%s %s" % (external_tls_bind_info, haproxy_http2_protocol) if kolla_enable_tls_external|bool and haproxy_enable_http2|bool else external_tls_bind_info %}
 {%- set internal_tls_bind_info = 'ssl crt /etc/haproxy/haproxy-internal.pem' if kolla_enable_tls_internal|bool else '' %}
+{%- set internal_tls_bind_info = "%s %s" % (internal_tls_bind_info, haproxy_http2_protocol) if kolla_enable_tls_internal|bool and haproxy_enable_http2|bool else external_tls_bind_info %}
 
 {%- macro userlist_macro(service_name, auth_user, auth_pass) %}
 userlist {{ service_name }}-user

doc/source/reference/high-availability/haproxy-guide.rst

@@ -82,3 +82,13 @@ To set weight of backend per service, modify inventory file as below:
    server1 haproxy_nova_api_weight=10
    server2 haproxy_nova_api_weight=2 haproxy_keystone_internal_weight=10
    server3 haproxy_keystone_admin_weight=50
+
+HTTP/2 Support
+---------------
+
+HAProxy with HTTP/2 frontend support is enabled by default. It may be
+disabled by setting the following in ``/etc/kolla/globals.yml``:
+
+.. code-block:: yaml
+
+   haproxy_enable_http2: "no"

releasenotes/notes/add-haproxy-http2-support-3a8575889cabe064.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    Adds http/2 support to HAProxy frontends.