Ensure systemd services are running when doing --tags=start

Fixes #129 (Github Issue).

Unfortunately, we rely on `service_facts`, which is only available
in Ansible >= 2.5.

There's little reason to stick to an old version such as Ansible 2.4:
- some time has passed since we've raised version requirements - it's
time to move into the future (a little bit)
- we've recently (in 82b4640072) improved the way one can run
Ansible in a Docker container

From now on, Ansible >= 2.5 is required.

docs/ansible.md

@@ -8,9 +8,9 @@ If your local computer cannot run Ansible, you can also run Ansible on some serv
 
 ## Supported Ansible versions
 
-Generally, Ansible 2.4 or later is required.
+Ansible 2.5 or newer is required.
 
-If you're on Ansible 2.5.x, then at least Ansible 2.5.2 is required.
+If you're on Ansible 2.5.x, due to bugs in Ansible 2.5.0 and 2.5.1, at least Ansible 2.5.2 is required.
 
 
 ## Checking your Ansible version
@@ -20,7 +20,7 @@ The playbook will try to detect it and tell you if you're on an unsupported vers
 
 To manually check which verison of Ansible you're on, run: `ansible --version`.
 
-If you're on an old version of Ansible, you should upgrade to a newer version.
+If you're on an old version of Ansible, you should [upgrade Ansible to a newer version](#upgrading-ansible) or [use Ansible via Docker](#using-ansible-via-docker).
 
 
 ## Upgrading Ansible

roles/matrix-base/tasks/sanity_check.yml

@@ -3,10 +3,10 @@
 - set_fact:
     matrix_ansible_outdated_fail_msg: "You are running on Ansible {{ ansible_version.string }}, which is not supported. See our guide about Ansible: https://github.com/spantaleev/matrix-docker-ansible-deploy/blob/master/docs/ansible.md"
 
-- name: Fail if running on Ansible < 2.4
+- name: Fail if running on Ansible < 2.5
   fail:
     msg: "{{ matrix_ansible_outdated_fail_msg }}"
-  when: "ansible_version.major <= 2 and ansible_version.minor < 4"
+  when: "ansible_version.major <= 2 and ansible_version.minor < 5"
 
 # Ansible 2.5.0 and 2.5.1 are known to have a bug with `include_tasks` + `with_items`.
 # The bug has been fixed in Ansible 2.5.2.

roles/matrix-common-after/tasks/start.yml

@@ -15,4 +15,27 @@
     name: "{{ item }}"
     enabled: yes
     state: started
-  with_items: "{{ matrix_systemd_services_list }}"
+  with_items: "{{ matrix_systemd_services_list }}"
+
+# If we check service state immediately, we may succeed,
+# because it takes some time for the service to attempt to start and actually fail.
+#
+# Waiting too long (30s) may not work for a similar reason,
+# as we may run into systemd's automatic restart logic retrying the service.
+- name: Wait a bit, so that services can start (or fail)
+  wait_for:
+    timeout: 5
+  delegate_to: 127.0.0.1
+  become: false
+
+- name: Populate service facts
+  service_facts:
+
+- name: Fail if service isn't detected to be running
+  fail:
+    msg: >-
+      {{ item }} was not detected to be running.
+      It's possible that there's a configuration problem or another service on your server interferes with it (uses the same ports, etc.).
+      Try running `systemctl status {{ item }}` and `systemctl -fu {{ item }}` on the server to investigate.
+  with_items: "{{ matrix_systemd_services_list }}"
+  when: "ansible_facts.services[item + '.service']|default(none) is none or ansible_facts.services[item + '.service'].state != 'running'"