feat: Add postgres_exporter role (#291)

* feat: Add postgres_exporter role

---------

Signed-off-by: anviar <[email protected]>

roles/postgres_exporter/README.md

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+<p><img src="https://www.circonus.com/wp-content/uploads/2015/03/sol-icon-itOps.png" alt="graph logo" title="graph" align="right" height="60" /></p>
+
+# Ansible Role: PostgreSQL exporter
+
+
+Deploy prometheus [postgresql exporter](https://github.com/prometheus-community/postgres_exporter) using ansible.
+
+## Requirements
+
+- Ansible >= 2.9 (It might work on previous versions, but we cannot guarantee it)
+- gnu-tar on Mac deployer host (`brew install gnu-tar`)
+- Passlib is required when using the basic authentication feature (`pip install passlib[bcrypt]`)
+
+## Role Variables
+All variables which can be overridden are stored in [defaults/main.yml](defaults/main.yml) file as well as in [meta/argument_specs.yml](meta/argument_specs.yml).
+Please refer to the [collection docs](https://prometheus-community.github.io/ansible/branch/main/postgres_exporter_role.html) for description and default values of the variables.
+
+## Example
+
+### Playbook
+
+Use it in a playbook as follows:
+```yaml
+- hosts: all
+  collections:
+    - prometheus.prometheus
+  roles:
+    - prometheus.prometheus.postgres_exporter
+```
+
+### TLS config
+
+Before running postgres_exporter role, the user needs to provision their own certificate and key.
+```yaml
+- hosts: all
+  pre_tasks:
+    - name: Create postgres_exporter cert dir
+      ansible.builtin.file:
+        path: "/etc/postgres_exporter"
+        state: directory
+        owner: root
+        group: root
+
+    - name: Create cert and key
+      community.crypto.x509_certificate:
+        path: /etc/postgres_exporter/tls.cert
+        csr_path: /etc/postgres_exporter/tls.csr
+        privatekey_path: /etc/postgres_exporter/tls.key
+        provider: selfsigned
+  collections:
+    - prometheus.prometheus
+  roles:
+    - prometheus.prometheus.postgres_exporter
+  vars:
+    postgres_exporter_tls_server_config:
+      cert_file: /etc/postgres_exporter/tls.cert
+      key_file: /etc/postgres_exporter/tls.key
+    postgres_exporter_basic_auth_users:
+      randomuser: examplepassword
+```
+
+
+### Demo site
+
+We provide an example site that demonstrates a full monitoring solution based on prometheus and grafana. The repository with code and links to running instances is [available on github](https://github.com/prometheus/demo-site) and the site is hosted on [DigitalOcean](https://digitalocean.com).
+
+## Local Testing
+
+The preferred way of locally testing the role is to use Docker and [molecule](https://github.com/ansible-community/molecule) (v3.x). You will have to install Docker on your system. See "Get started" for a Docker package suitable for your system. Running your tests is as simple as executing `molecule test`.
+
+## Continuous Integration
+
+Combining molecule and circle CI allows us to test how new PRs will behave when used with multiple ansible versions and multiple operating systems. This also allows use to create test scenarios for different role configurations. As a result we have quite a large test matrix which can take more time than local testing, so please be patient.
+
+## Contributing
+
+See [contributor guideline](CONTRIBUTING.md).
+
+## Troubleshooting
+
+See [troubleshooting](TROUBLESHOOTING.md).
+
+## License
+
+This project is licensed under MIT License. See [LICENSE](/LICENSE) for more details.

roles/postgres_exporter/TROUBLESHOOTING.md

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+# Troubleshooting
+
+## Bad requests (HTTP 400)
+
+This role downloads checksums from the Github project to verify the integrity of artifacts installed on your servers. When downloading the checksums, a "bad request" error might occur.
+
+This happens in environments which (knowningly or unknowling) use the [netrc mechanism](https://www.gnu.org/software/inetutils/manual/html_node/The-_002enetrc-file.html) to auto-login into servers.
+
+Unless netrc is needed by your playbook and ansible roles, please unset the var like so:
+
+```
+$ NETRC= ansible-playbook ...
+```
+
+Or:
+
+```
+$ export NETRC=
+$ ansible-playbook ...
+```

roles/postgres_exporter/defaults/main.yml

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+---
+postgres_exporter_version: 0.15.0
+postgres_exporter_binary_local_dir: ""
+postgres_exporter_binary_url: "https://github.com/{{ _postgres_exporter_repo }}/releases/download/v{{ postgres_exporter_version }}/\
+                           postgres_exporter-{{ postgres_exporter_version }}.linux-{{ go_arch }}.tar.gz"
+postgres_exporter_checksums_url: "https://github.com/{{ _postgres_exporter_repo }}/releases/download/v{{ postgres_exporter_version }}/sha256sums.txt"
+postgres_exporter_skip_install: false
+
+postgres_exporter_web_listen_address: "0.0.0.0:9187"
+postgres_exporter_web_telemetry_path: "/metrics"
+
+postgres_exporter_config_file: "postgres_exporter.yml"
+
+postgres_exporter_name: "postgresql:///postgres?host=/var/run/postgresql"
+postgres_exporter_uri: ""
+postgres_exporter_username: ""
+postgres_exporter_password: ""
+
+postgres_exporter_tls_server_config: {}
+
+postgres_exporter_http_server_config: {}
+
+postgres_exporter_basic_auth_users: {}
+
+postgres_exporter_enabled_collectors: []
+
+postgres_exporter_disabled_collectors: []
+
+# Internal variables.
+postgres_exporter_binary_install_dir: "/usr/local/bin"
+postgres_exporter_config_dir: "/etc/postgres_exporter"
+postgres_exporter_system_group: "postgres-exp"
+postgres_exporter_system_user: "{{ postgres_exporter_system_group }}"

roles/postgres_exporter/handlers/main.yml

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+---
+- name: Restart postgres_exporter
+  listen: "restart postgres_exporter"
+  become: true
+  ansible.builtin.systemd:
+    daemon_reload: true
+    name: postgres_exporter
+    state: restarted
+  when:
+    - not ansible_check_mode

roles/postgres_exporter/meta/argument_specs.yml

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+---
+# yamllint disable rule:line-length
+argument_specs:
+  main:
+    short_description: "Prometheus PostgreSQL Exporter"
+    description:
+      - "Deploy prometheus L(postgres_exporter,https://github.com/prometheus-community/postgres_exporter) using ansible"
+    author:
+      - "Prometheus Community"
+    options:
+      postgres_exporter_version:
+        description: "PostgreSQL exporter package version. Also accepts latest as parameter."
+        default: "0.15.0"
+      postgres_exporter_skip_install:
+        description: "PostgreSQL installation tasks gets skipped when set to true."
+        type: bool
+        default: false
+      postgres_exporter_binary_local_dir:
+        description:
+          - "Enables the use of local packages instead of those distributed on github."
+          - "The parameter may be set to a directory where the C(postgres_exporter) binary is stored on the host where ansible is run."
+          - "This overrides the I(postgres_exporter_version) parameter"
+      postgres_exporter_binary_url:
+        description: "URL of the postgres_exporter binaries .tar.gz file"
+        default: "https://github.com/{{ _postgres_exporter_repo }}/download/v{{ postgres_exporter_version }}/postgres_exporter-{{ postgres_exporter_version }}.linux-{{ go_arch }}.tar.gz"
+      postgres_exporter_checksums_url:
+        description: "URL of the postgres_exporter checksums file"
+        default: "https://github.com/{{ _postgres_exporter_repo }}/releases/download/v{{ postgres_exporter_version }}/sha256sums.txt"
+      postgres_exporter_web_listen_address:
+        description: "Address on which postgres_exporter will listen"
+        default: "0.0.0.0:9187"
+      postgres_exporter_web_telemetry_path:
+        description: "Path under which to expose metrics"
+        default: "/metrics"
+      postgres_exporter_config_dir:
+        description: "The path where exporter configuration is stored"
+        default: "/etc/postgres_exporter"
+      postgres_exporter_config_file:
+        description: "The filename of the postgres exporter config file"
+        default: "/etc/postgres_exporter/postgres_exporter.yml"
+      postgres_exporter_name:
+        description: "The target PostgreSQL L(URI, https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING-URIS)"
+        default: "postgresql:///postgres?host=/var/run/postgresql"
+      postgres_exporter_uri:
+        description: "The target PostgreSQL, alternative format, single target only is supported. You should set postgres_exporter_name to empty string to use it. Read more L(here,https://github.com/prometheus-community/postgres_exporter?tab=readme-ov-file#environment-variables)"
+      postgres_exporter_username:
+        description: "The username for PostgreSQL login, required for postgres_exporter_uri"
+        default: "exporter"
+      postgres_exporter_password:
+        description: "The password for PostgreSQL password, required for postgres_exporter_uri"
+        default: "secret"
+      postgres_exporter_enabled_collectors:
+        description:
+          - "List of dicts defining additionally enabled collectors and their configuration."
+          - "It adds collectors to L(those enabled by default,https://github.com/prometheus-community/postgres_exporter?tab=readme-ov-file#flags)."
+        type: "list"
+        default: []
+      postgres_exporter_disabled_collectors:
+        description:
+          - "List of disabled collectors."
+          - "By default postgres_exporter disables collectors listed L(here,https://github.com/prometheus-community/postgres_exporter?tab=readme-ov-file#flags)."
+        type: "list"
+        elements: "str"
+      postgres_exporter_tls_server_config:
+        description:
+          - "Configuration for TLS authentication."
+          - "Keys and values are the same as in L(prometheus docs,https://github.com/prometheus/exporter-toolkit/blob/master/docs/web-configuration.md)."
+        type: "dict"
+      postgres_exporter_http_server_config:
+        description:
+          - "Config for HTTP/2 support."
+          - "Keys and values are the same as in L(prometheus docs,https://github.com/prometheus/exporter-toolkit/blob/master/docs/web-configuration.md)."
+        type: "dict"
+      postgres_exporter_basic_auth_users:
+        description: "Dictionary of users and password for basic authentication. Passwords are automatically hashed with bcrypt."
+        type: "dict"
+      postgres_exporter_binary_install_dir:
+        description:
+          - "I(Advanced)"
+          - "Directory to install postgres_exporter binary"
+        default: "/usr/local/bin"
+      postgres_exporter_system_group:
+        description:
+          - "I(Advanced)"
+          - "System group for PostgreSQL Exporter"
+        default: "postgres-exp"
+      postgres_exporter_system_user:
+        description:
+          - "I(Advanced)"
+          - "PostgreSQL Exporter user"
+        default: "postgres-exp"

roles/postgres_exporter/meta/main.yml

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+---
+galaxy_info:
+  author: "Prometheus Community"
+  description: "Prometheus PostgreSQL Exporter"
+  license: "Apache"
+  min_ansible_version: "2.9"
+  platforms:
+    - name: "Ubuntu"
+      versions:
+        - "focal"
+        - "jammy"
+    - name: "Debian"
+      versions:
+        - "bullseye"
+        - "buster"
+    - name: "EL"
+      versions:
+        - "7"
+        - "8"
+        - "9"
+    - name: "Fedora"
+      versions:
+        - "37"
+        - '38'
+  galaxy_tags:
+    - "monitoring"
+    - "prometheus"
+    - "exporter"
+    - "metrics"
+    - "system"
+    - "postgresql"

roles/postgres_exporter/molecule/alternative/molecule.yml

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+---
+provisioner:
+  inventory:
+    group_vars:
+      all:
+        postgres_exporter_binary_local_dir: "/tmp/postgres_exporter-linux-amd64"
+        postgres_exporter_web_listen_address:
+          - '127.0.0.1:8080'
+          - '127.0.1.1:8080'
+        postgres_exporter_enabled_collectors:
+          - postmaster
+        postgres_exporter_disabled_collectors:
+          - replication
+
+        postgres_exporter_tls_server_config:
+          cert_file: /etc/postgres_exporter/tls.cert
+          key_file: /etc/postgres_exporter/tls.key
+        postgres_exporter_http_server_config:
+          http2: true
+        postgres_exporter_basic_auth_users:
+          randomuser: examplepassword
+        go_arch: amd64
+        postgres_exporter_version: 0.15.0

roles/postgres_exporter/molecule/alternative/prepare.yml

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+---
+- name: Run local preparation
+  hosts: localhost
+  gather_facts: false
+  tasks:
+    - name: Download postgres_exporter binary to local folder
+      become: false
+      ansible.builtin.get_url:
+        url: "https://github.com/prometheus-community/postgres_exporter/releases/download/v{{\
+          \ postgres_exporter_version }}/postgres_exporter-{{ postgres_exporter_version\
+          \ }}.linux-{{ go_arch }}.tar.gz"
+        dest: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.linux-{{ go_arch\
+          \ }}.tar.gz"
+        mode: 0644
+      register: _download_binary
+      until: _download_binary is succeeded
+      retries: 5
+      delay: 2
+      check_mode: false
+
+    - name: Unpack postgres_exporter binary
+      become: false
+      ansible.builtin.unarchive:
+        src: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.linux-{{ go_arch\
+          \ }}.tar.gz"
+        dest: "/tmp"
+        creates: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.linux-{{ go_arch\
+          \ }}/postgres_exporter"
+      check_mode: false
+
+    - name: Link to postgres_exporter binaries directory
+      become: false
+      ansible.builtin.file:
+        src: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.linux-amd64"
+        dest: "/tmp/postgres_exporter-linux-amd64"
+        state: link
+      check_mode: false
+
+    - name: Install pyOpenSSL for certificate generation
+      ansible.builtin.pip:
+        name: "pyOpenSSL"
+
+    - name: Create private key
+      community.crypto.openssl_privatekey:
+        path: "/tmp/tls.key"
+
+    - name: Create CSR
+      community.crypto.openssl_csr:
+        path: "/tmp/tls.csr"
+        privatekey_path: "/tmp/tls.key"
+
+    - name: Create certificate
+      community.crypto.x509_certificate:
+        path: "/tmp/tls.cert"
+        csr_path: "/tmp/tls.csr"
+        privatekey_path: "/tmp/tls.key"
+        provider: selfsigned
+
+- name: Run target preparation
+  hosts: all
+  any_errors_fatal: true
+  tasks:
+    - name: Create postgres_exporter cert dir
+      ansible.builtin.file:
+        path: "{{ postgres_exporter_tls_server_config.cert_file | dirname }}"
+        state: directory
+        owner: root
+        group: root
+        mode: u+rwX,g+rwX,o=rX
+
+    - name: Copy cert and key
+      ansible.builtin.copy:
+        src: "{{ item.src }}"
+        dest: "{{ item.dest }}"
+        mode: "{{ item.mode | default('0644') }}"
+      loop:
+        - src: "/tmp/tls.cert"
+          dest: "{{ postgres_exporter_tls_server_config.cert_file }}"
+        - src: "/tmp/tls.key"
+          dest: "{{ postgres_exporter_tls_server_config.key_file }}"