add ansible role for deployments to native machines (#37)

* add ansible role for installing as a systemd service, can be easily extended to service types for other distributions

* fixed README

ansible/roles/ansible-cassandra-exporter/README.md

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+Role Name
+=========
+
+Role to install `cassandra exporter java binary` as a `systemd` service
+
+Role Variables
+--------------
+
+| Name           | Default Value | Description                        |
+| -------------- | ------------- | -----------------------------------|
+| `cassandra_exporter_version` | 2.2.0 | Cassandra exporter package version |
+| `cassandra_exporter_binary_url` | https://github.com/criteo/cassandra_exporter/releases/download/{{cassandra_exporter_version}}/cassandra_exporter-{{cassandra_exporter_version}}-all.jar | Cassandra exporter jar download location |
+| `cassandra_exporter_config_url` | https://raw.githubusercontent.com/criteo/cassandra_exporter/master/config.yml | Cassandra exporter config download location |
+| `cassandra_exporter_user` | cassandra-exp | UNIX user to run the binary |
+| `cassandra_exporter_group` | cassandra-exp | UNIX group to run the binary |
+| `cassandra_exporter_root_dir` | /opt/cassandra_exporter | Base location where cassandra exporter stuff is downloaded |
+| `cassandra_exporter_dist_dir` | /opt/cassandra_exporter/dist | Location for binary and systemd service script |
+| `cassandra_exporter_config_dir` | /opt/cassandra_exporter/config | Location for config |
+
+
+Example Playbook
+----------------
+
+Including an example of how to use your role (for instance, with variables passed in as parameters) is always nice for users too:
+
+    - hosts: servers
+      become: true
+      become_method: sudo
+      roles:
+        - role: ansible-cassandra-exporter
+
+Usage
+-----
+
+You may install the role locally using `ansible-galaxy install -r requirements.yml -p roles/` where `requirements.yml` reads something like
+
+```
+- src: git+https://github.com/criteo/cassandra_exporter/ansible/roles
+  version: TBD
+```

ansible/roles/ansible-cassandra-exporter/defaults/main.yml

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+---
+
+cassandra_exporter_version: 2.2.0
+
+cassandra_exporter_binary_url: 'https://github.com/criteo/cassandra_exporter/releases/download/{{cassandra_exporter_version}}/cassandra_exporter-{{cassandra_exporter_version}}-all.jar'
+cassandra_exporter_config_url: 'https://raw.githubusercontent.com/criteo/cassandra_exporter/master/config.yml'
+
+cassandra_exporter_user: cassandra-exp
+cassandra_exporter_group: cassandra-exp
+
+cassandra_exporter_root_dir: /opt/cassandra_exporter
+cassandra_exporter_dist_dir: "{{ cassandra_exporter_root_dir }}/dist"
+cassandra_exporter_config_dir: "{{ cassandra_exporter_root_dir }}/config"

ansible/roles/ansible-cassandra-exporter/handlers/main.yml

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+---
+
+- name: reenable cassandra exporter service
+  command: systemctl reenable prometheus-cassandra-exporter.service
+
+- name: reinit cassandra exporter
+  command: initctl reload-configuration
+
+- name: restart cassandra exporter
+  service:
+    name: prometheus-cassandra-exporter
+    state: restarted

ansible/roles/ansible-cassandra-exporter/meta/main.yml

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+galaxy_info:
+  author: Pankaj M. Tolani
+  description: DevOps Engineer
+  company: Autonomous Thingz Pty Ltd
+
+  # If the issue tracker for your role is not on github, uncomment the
+  # next line and provide a value
+  # issue_tracker_url: http://example.com/issue/tracker
+
+  # Some suggested licenses:
+  # - BSD (default)
+  # - MIT
+  # - GPLv2
+  # - GPLv3
+  # - Apache
+  # - CC-BY
+  license: license (GPLv2, CC-BY, etc)
+
+  min_ansible_version: 2.4
+
+  # If this a Container Enabled role, provide the minimum Ansible Container version.
+  # min_ansible_container_version:
+
+  # Optionally specify the branch Galaxy will use when accessing the GitHub
+  # repo for this role. During role install, if no tags are available,
+  # Galaxy will use this branch. During import Galaxy will access files on
+  # this branch. If Travis integration is configured, only notifications for this
+  # branch will be accepted. Otherwise, in all cases, the repo's default branch
+  # (usually master) will be used.
+  #github_branch:
+
+  #
+  # Provide a list of supported platforms, and for each platform a list of versions.
+  # If you don't wish to enumerate all versions for a particular platform, use 'all'.
+  # To view available platforms and versions (or releases), visit:
+  # https://galaxy.ansible.com/api/v1/platforms/
+  #
+  # platforms:
+  # - name: Fedora
+  #   versions:
+  #   - all
+  #   - 25
+  # - name: SomePlatform
+  #   versions:
+  #   - all
+  #   - 1.0
+  #   - 7
+  #   - 99.99
+
+  galaxy_tags: Cassandra, JMX, Exporter, Systemd, Service
+    # List tags for your role here, one per line. A tag is a keyword that describes
+    # and categorizes the role. Users find roles by searching for tags. Be sure to
+    # remove the '[]' above, if you add tags to this list.
+    #
+    # NOTE: A tag is limited to a single word comprised of alphanumeric characters.
+    #       Maximum 20 tags per role.
+
+dependencies: []
+  # List your role dependencies here, one per line. Be sure to remove the '[]' above,
+  # if you add dependencies to this list.

ansible/roles/ansible-cassandra-exporter/tasks/main.yml

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+---
+
+- name: 'create cassandra exporter group'
+  group:
+    name: '{{ cassandra_exporter_group }}'
+    system: yes
+    state: present
+
+- name: 'create cassandra exporter user'
+  user:
+    name: '{{ cassandra_exporter_user }}'
+    system: yes
+    shell: '/sbin/nologin'
+    group: '{{ cassandra_exporter_group }}'
+    createhome: no
+
+- name: 'create cassandra exporter directories'
+  file:
+    path: '{{ item }}'
+    state: directory
+    owner: '{{ cassandra_exporter_user }}'
+    group: '{{ cassandra_exporter_group }}'
+    mode: 0755
+  with_items:
+    - '{{ cassandra_exporter_root_dir }}'
+    - '{{ cassandra_exporter_dist_dir }}'
+
+- name: 'download cassandra exporter binary'
+  get_url:
+    url: '{{ cassandra_exporter_binary_url }}'
+    dest: '{{ cassandra_exporter_dist_dir }}/cassandra.jar'
+
+- name: 'download cassandra exporter config'
+  get_url:
+    url: '{{ cassandra_exporter_config_url }}'
+    dest: '{{ cassandra_exporter_config_dir }}/config.yml'
+
+- name: 'generate the shell script'
+  template:
+    src: cassandra_exporter.sh.j2
+    dest: '{{ cassandra_exporter_dist_dir }}/cassandra_exporter.sh'
+    owner: root
+    group: root
+    mode: 0755
+  register: prometheus_cassandra_exporter_updated
+  notify:
+    - restart cassandra exporter
+
+- name: 'update group and owner for files'
+  file:
+    path: '{{ item }}'
+    state: file
+    owner: '{{ cassandra_exporter_user }}'
+    group: '{{ cassandra_exporter_group }}'
+  with_items:
+    - '{{ cassandra_exporter_dist_dir }}/cassandra.jar'
+    - '{{ cassandra_exporter_config_dir }}/config.yml'
+  when: prometheus_cassandra_exporter_updated is changed
+
+- name: 'create systemd service unit'
+  template:
+    src: etc/systemd/system/prometheus-cassandra-exporter.service.j2
+    dest: /etc/systemd/system/prometheus-cassandra-exporter.service
+    owner: root
+    group: root
+    mode: 0644
+  when: service_mgr | default(ansible_service_mgr) == 'systemd'
+  notify:
+    - reenable cassandra exporter service
+    - restart cassandra exporter
+
+- meta: flush_handlers
+
+- name: 'ensure prometheus cassandra exporter service is enabled and started'
+  service:
+    name: prometheus-cassandra-exporter
+    state: started
+    enabled: yes

ansible/roles/ansible-cassandra-exporter/templates/cassandra_exporter.sh.j2

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+#!/bin/bash
+java -jar {{ cassandra_exporter_dist_dir }}/cassandra.jar {{ cassandra_exporter_config_dir }}/config.yml

ansible/roles/ansible-cassandra-exporter/templates/etc/systemd/system/prometheus-cassandra-exporter.service.j2

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+[Unit]
+Description=Prometheus Cassandra Exporter
+After=network.target
+
+[Service]
+Type=simple
+User={{ cassandra_exporter_user }}
+Group={{ cassandra_exporter_group }}
+ExecStart={{ cassandra_exporter_dist_dir }}/cassandra_exporter.sh
+
+SyslogIdentifier=prometheus_cassandra_exporter
+Restart=always
+
+[Install]
+WantedBy=multi-user.target

ansible/roles/ansible-cassandra-exporter/tests/inventory

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+localhost
+

ansible/roles/ansible-cassandra-exporter/tests/test.yml

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+---
+- hosts: localhost
+  become: true
+  become_method: sudo
+  roles:
+    - ansible-cassandra-exporter

ansible/roles/ansible-cassandra-exporter/vars/main.yml

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+---