add memcached_exporter (#1)

* add memcached_exporter
* remove user/group and add consul service
* fix consul tags
* unpack bin from tarball

Signed-off-by: Jakub Sokołowski <jakub@status.im>

README.md

@@ -1,6 +1,12 @@
 # Description
 
-This role installs and configures [memcached](https://memcached.org/) service.
+This role installs and configures [memcached](https://memcached.org/) and [memcached\_exporter](https://github.com/prometheus/memcached_exporter/) services.
+
+The exporter is available on port `9150` and the prometheus metrics can be fetched via the `/metrics` http endpoint:
+
+```
+curl 0.0.0.0:9150/metrics
+```
 
 # Configuration
 
@@ -11,3 +17,9 @@ memcached_port: 11211
 memcached_size_mb: 64
 memcached_maxconn: 1024
 ```
+
+The installation of `memcached_exporter` is optional. It is installed by default but can be disabled by setting:
+
+```yaml
+memcached_exporter_enabled: false
+```

defaults/main.yml

@@ -15,3 +15,13 @@ memcached_cfg_file: '/etc/memcached.conf'
 memcached_consul_tags_default: ['memcached', 'cache']
 memcached_consul_tags_extra: []
 memcached_consul_tags: '{{ memcached_consul_tags_default + memcached_consul_tags_extra }}'
+
+memcached_exporter_enabled: true
+memcached_exporter_port: 9150
+memcached_exporter_version: '0.8.0'
+memcached_exporter_release_name: 'memcached_exporter-{{ memcached_exporter_version }}.linux-amd64'
+memcached_exporter_url: 'https://github.com/prometheus/memcached_exporter/releases/download/v{{ memcached_exporter_version }}/{{ memcached_exporter_release_name }}.tar.gz'
+memcached_exporter_checksum: '0a666f41d733ebdc20cf2dc66fbb0c2899afc237002db67b7a31ff7f9f7dde3f'
+
+memcached_exporter_consul_service: 'memcached_exporter'
+memcached_exporter_consul_tags: '{{ memcached_consul_tags + ["exporter", "metrics"] }}'

handlers/main.yml

@@ -0,0 +1,6 @@
+---
+- name: restart memcached_exporter
+  systemd:
+    daemon_reload: true
+    name: memcached_exporter
+    state: restarted

tasks/main.yml

@@ -18,6 +18,9 @@
     state: restarted
   when: memcached_config.changed
 
+- include_tasks: memcached_exporter.yml
+  when: memcached_exporter_enabled
+
 - name: Create Consul service definition
   include_role: name=consul-service
   vars:

tasks/memcached_exporter.yml

@@ -0,0 +1,42 @@
+- name: Download memcached_exporter tarball
+  get_url:
+    url: '{{ memcached_exporter_url }}'
+    dest: '/tmp/{{ memcached_exporter_release_name }}.tar.gz'
+    checksum: 'sha256:{{ memcached_exporter_checksum }}'
+    mode: 0644
+
+- name: Unpack binary from tarball
+  unarchive:
+    src: '/tmp/{{ memcached_exporter_release_name }}.tar.gz'
+    dest: '/usr/local/bin'
+    creates: '/usr/local/bin/memcached_exporter'
+    remote_src: true
+    extra_ops:
+      - '--wildcards'
+      - '--strip=1'
+      - '*/memcached_exporter'
+  notify: restart memcached_exporter
+
+- name: Copy the memcached_exporter systemd service file
+  template:
+    src: 'memcached_exporter.service.j2'
+    dest: '/lib/systemd/system/memcached_exporter.service'
+    owner: root
+    group: root
+    mode: 0644
+  notify: restart memcached_exporter
+
+- name: Create Consul service definition
+  include_role: name=consul-service
+  vars:
+    consul_config_name: '{{ memcached_exporter_consul_service }}'
+    consul_services:
+      - name: '{{ memcached_exporter_consul_service }}'
+        tags: '{{ memcached_exporter_consul_tags }}'
+        port: '{{ memcached_exporter_port }}'
+        address: '{{ memcached_addr }}'
+        checks:
+          - id: '{{ memcached_exporter_consul_service }}-health'
+            name: '{{ memcached_exporter_consul_service }}'
+            type: 'tcp'
+            tcp: '{{ memcached_addr }}:{{ memcached_exporter_port }}'

templates/memcached_exporter.service.j2

@@ -0,0 +1,12 @@
+[Unit]
+Description="Memcached Exporter for Prometheus"
+Documentation=https://github.com/prometheus/memcached_exporter
+Requires=network-online.target
+After=network-online.target
+
+[Service]
+ExecStart=/usr/local/bin/memcached_exporter --memcached.address={{ memcached_addr }}:{{ memcached_port }}
+Restart=on-failure
+
+[Install]
+WantedBy=multi-user.target