Determine matrix_architecture automatically

docs/alternative-architectures.md

@@ -1,26 +1,18 @@
 # Alternative architectures
 
-As stated in the [Prerequisites](prerequisites.md), currently only `x86_64` is fully supported. However, it is possible to set the target architecture, and some tools can be built on the host or other measures can be used.
+As stated in the [Prerequisites](prerequisites.md), currently only `amd64` (`x86_64`) is fully supported.
 
-To that end add the following variable to your `vars.yml` file (see [Configuring playbook](configuring-playbook.md)):
+The playbook automatically determines the target server's architecture (the `matrix_architecture` variable) to be one of the following:
 
-```yaml
-matrix_architecture: <your-matrix-server-architecture>
-```
-
-Currently supported architectures are the following:
-- `amd64` (the default)
-- `arm64`
+- `amd64` (`x86_64`)
 - `arm32`
+- `arm64`
 
-so for the Raspberry Pi, the following should be in your `vars.yml` file:
+Some tools and container images can be built on the host or other measures can be used to install on that architecture.
 
-```yaml
-matrix_architecture: "arm32"
-```
 
 ## Implementation details
 
 For `amd64`, prebuilt container images (see the [container images we use](container-images.md)) are used for all components (except [Hydrogen](configuring-playbook-client-hydrogen.md), which goes through self-building).
 
-For other architectures, components which have a prebuilt image make use of it. If the component is not available for the specific architecture, [self-building](self-building.md) will be used. Not all components support self-building though, so your mileage may vary.
+For other architecture (`arm64`, `arm32`), components which have a prebuilt image make use of it. If the component is not available for the specific architecture, [self-building](self-building.md) will be used. Not all components support self-building though, so your mileage may vary.

docs/self-building.md

@@ -6,11 +6,11 @@ The playbook supports self-building of various components, which don't have a co
 
 For other architectures (e.g. `arm32`, `arm64`), ready-made container images are used when available. If there's no ready-made image for a specific component and said component supports self-building, an image will be built on the host. Building images like this takes more time and resources (some build tools need to get installed by the playbook to assist building).
 
-To make use of self-building, you don't need to do anything besides change your architecture variable (e.g. `matrix_architecture: arm64`). If a component has an image for the specified architecture, the playbook will use it directly. If not, it will build the image on the server itself.
+To make use of self-building, you don't need to do anything. If a component has an image for the specified architecture, the playbook will use it directly. If not, it will build the image on the server itself.
 
 Note that **not all components support self-building yet**.
 
-List of roles where self-building the Docker image is currently possible:
+Possibly outdated list of roles where self-building the Docker image is currently possible:
 - `matrix-synapse`
 - `matrix-synapse-admin`
 - `matrix-client-element`

roles/custom/matrix-base/defaults/main.yml

@@ -86,7 +86,7 @@ matrix_federation_public_port: 8448
 # Recognized values by us are 'amd64', 'arm32' and 'arm64'.
 # Not all architectures support all services, so your experience (on non-amd64) may vary.
 # See docs/alternative-architectures.md
-matrix_architecture: amd64
+matrix_architecture: "{{ 'amd64' if ansible_architecture == 'x86_64' else ('arm64' if ansible_architecture == 'aarch64' else ('arm32' if ansible_architecture.startswith('armv') else '')) }}"
 
 # The architecture for Debian packages.
 # See: https://wiki.debian.org/SupportedArchitectures

roles/custom/matrix-base/tasks/sanity_check.yml

@@ -40,6 +40,7 @@
     - {'var': matrix_server_fqn_element, 'value': "{{ matrix_server_fqn_element | default('') }}"}
     - {'var': matrix_homeserver_container_url, 'value': "{{ matrix_homeserver_container_url | default('') }}"}
     - {'var': matrix_homeserver_container_federation_url, 'value': "{{ matrix_homeserver_container_federation_url | default('') }}"}
+    - {'var': matrix_architecture, 'value': "{{ matrix_architecture | default('') }}"}
   when: "item.value is none or item.value == ''"
 
 - name: Fail if uppercase domain used