feat: add PostgreSQL infrastructure for App2

- Add PostgreSQL role for installing and configuring PostgreSQL 17
- Add postgres_exporter role for PostgreSQL metrics collection
- Add deploy-postgres-app2.yml playbook for deployment
- Configure test database 'testdb' with user 'testuser'
- Set up postgres_exporter user for monitoring
- Include firewall configuration for PostgreSQL (5432) and postgres_exporter (9187)
- Follow existing role structure pattern from node_exporter

roles/postgres_exporter/defaults/main.yml

@@ -0,0 +1,12 @@
+---
+# Postgres Exporter
+postgres_exporter_version: "0.15.0"
+postgres_exporter_port: 9187
+postgres_exporter_user: "postgres_exporter"
+postgres_exporter_password: "exporterpassword123"
+
+# Connection settings
+postgres_exporter_data_source_name: "user={{ postgres_exporter_user }} password={{ postgres_exporter_password }} host=localhost port=5432 dbname=postgres sslmode=disable"
+
+# Systemd service
+postgres_exporter_service_name: "postgres_exporter"

roles/postgres_exporter/tasks/main.yml

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+---
+- name: Install required packages
+  apt:
+    name:
+      - wget
+      - tar
+    state: present
+    update_cache: yes
+  tags: postgres_exporter
+
+- name: Create postgres_exporter user
+  user:
+    name: postgres_exporter
+    system: yes
+    shell: /bin/false
+    home: /nonexistent
+    comment: "Postgres Exporter Service User"
+  tags: postgres_exporter
+
+- name: Download Postgres Exporter
+  get_url:
+    url: "https://github.com/prometheus-community/postgres_exporter/releases/download/v{{ postgres_exporter_version }}/postgres_exporter-{{ postgres_exporter_version }}.linux-amd64.tar.gz"
+    dest: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.tar.gz"
+    timeout: 30
+    validate_certs: no
+  tags: postgres_exporter
+
+- name: Extract Postgres Exporter
+  unarchive:
+    src: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.tar.gz"
+    dest: "/tmp/"
+    remote_src: yes
+    creates: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.linux-amd64"
+  tags: postgres_exporter
+
+- name: Install Postgres Exporter binary
+  copy:
+    src: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.linux-amd64/postgres_exporter"
+    dest: "/usr/local/bin/postgres_exporter"
+    owner: postgres_exporter
+    group: postgres_exporter
+    mode: '0755'
+    remote_src: yes
+  tags: postgres_exporter
+
+- name: Create systemd service
+  template:
+    src: postgres_exporter.service.j2
+    dest: /etc/systemd/system/{{ postgres_exporter_service_name }}.service
+    owner: root
+    group: root
+    mode: '0644'
+  tags: postgres_exporter
+
+- name: Clean up temp files
+  file:
+    path: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.tar.gz"
+    state: absent
+  tags: postgres_exporter
+
+- name: Clean up extracted directory
+  file:
+    path: "/tmp/postgres_exporter-{{ postgres_exporter_version }}.linux-amd64"
+    state: absent
+  tags: postgres_exporter
+
+- name: Reload systemd
+  systemd:
+    daemon_reload: yes
+  tags: postgres_exporter
+
+- name: Enable and start Postgres Exporter
+  systemd:
+    name: "{{ postgres_exporter_service_name }}"
+    enabled: yes
+    state: started
+    daemon_reload: yes
+  tags: postgres_exporter
+
+- name: Configure UFW for Postgres Exporter
+  ufw:
+    rule: allow
+    port: "{{ postgres_exporter_port }}"
+    proto: tcp
+    comment: "Postgres Exporter metrics"
+  tags: postgres_exporter
+
+- name: Verify Postgres Exporter is running
+  wait_for:
+    port: "{{ postgres_exporter_port }}"
+    host: "{{ ansible_host }}"
+    delay: 3
+    timeout: 60
+  tags: postgres_exporter

roles/postgres_exporter/templates/postgres_exporter.service.j2

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+[Unit]
+Description=Postgres Exporter
+After=network.target postgresql.service
+Wants=postgresql.service
+
+[Service]
+Type=simple
+User=postgres_exporter
+Group=postgres_exporter
+Environment=DATA_SOURCE_NAME="{{ postgres_exporter_data_source_name }}"
+ExecStart=/usr/local/bin/postgres_exporter --web.listen-address=:{{ postgres_exporter_port }}
+Restart=always
+RestartSec=5
+
+[Install]
+WantedBy=multi-user.target