Finding XML Objects with Neighboring Keys in Ansible

The most efficient way to find all XML entries where <current>yes</current> exists and extract corresponding <version> values in Ansible is to use the xml module with XPath expressions. This approach allows you to directly query the XML structure and extract the required data in a single, readable operation.

Contents:

• Understanding XML Processing in Ansible
• Using Ansible’s xml Module with XPath
• Alternative Approach with find and Jinja2
• Python-Based XML Processing in Ansible
• Best Practices for XML Processing in Ansible
• Complete Playbook Example

Understanding XML Processing in Ansible

Ansible provides several methods for processing XML data, each with its own strengths:

• xml module: Purpose-built for parsing and manipulating XML documents
• xpath filter: Useful for extracting specific data from XML strings
• find module: Can locate elements based on content
• Python integration: For complex processing using Python’s xml libraries

When dealing with XML where you need to find elements based on neighboring elements (like finding <version> when <current>yes</current> exists), XPath expressions are typically the most efficient solution. XPath allows you to navigate the XML document structure and select nodes based on various criteria, including content of sibling elements.

The key advantage of using XPath in this scenario is that it can directly express the relationship between elements in a way that’s both concise and powerful. For example, you can write an XPath expression that says “find all <entry> elements that have a <current> child with value ‘yes’, and then return the <version> child of those elements.”

Using Ansible’s xml Module with XPath

The Ansible xml module is specifically designed for working with XML documents. To find all entries with <current>yes</current> and extract their corresponding versions, you can use the following approach:

- name: Parse XML to find current versions
  ansible.builtin.xml:
    path: /path/to/your/file.xml
    xpath: '//entry[current="yes"]/version'
  register: current_versions

This XPath expression //entry[current="yes"]/version does exactly what you need:

• //entry finds all <entry> elements in the document
• [current="yes"] filters these to only include entries where the <current> element has the value “yes”
• /version selects the <version> child of each matching entry

The result will contain the text content of all matching <version> elements in the matches attribute of the returned variable.

For processing XML content directly rather than from a file, use the content parameter instead of path:

- name: Process XML content from variable
  ansible.builtin.xml:
    content: "{{ xml_output }}"
    xpath: '//entry[current="yes"]/version'
  register: current_versions

After this task, current_versions.matches will contain a list of version strings for all entries where <current>yes</current> exists.

For more complex processing, you can extract entire entry elements and then process them:

- name: Find all current entries
  ansible.builtin.xml:
    content: "{{ xml_output }}"
    xpath: '//entry[current="yes"]'
  register: current_entries

- name: Extract versions from current entries
  set_fact:
    current_versions: "{{ current_entries.matches | map(attribute='version') | list }}"

This approach gives you more flexibility to work with the entire entry structure if needed.

Alternative Approach with find and Jinja2

If you prefer not to use the xml module, you can use a combination of the find module with Jinja2 templating. This approach is less efficient for large XML documents but can be useful for simpler scenarios:

- name: Find entries with current=yes using find
  ansible.builtin.find:
    paths: /path/to/your/xml
    patterns: "*.xml"
  register: xml_files

- name: Process each XML file
  ansible.builtin.include_tasks: process_xml.yml
  loop: "{{ xml_files.files }}"
  loop_control:
    loop_var: xml_file

- name: Extract versions using Jinja2
  set_fact:
    current_versions: "{{ xml_output | from_xml | dict2items | 
                         selectattr('value.current', 'equalto', 'yes') | 
                         map(attribute='value.version') | list }}"

In this approach:

1. We first find all XML files
2. We process each file (you’d need a separate task file process_xml.yml)
3. We use Jinja2 filters to parse the XML and extract the required information

While this approach works, it’s generally less efficient and more verbose than using XPath directly.

Python-Based XML Processing in Ansible

For more complex XML processing or when XPath expressions become too cumbersome, you can use Python’s built-in XML libraries directly within Ansible:

- name: Process XML using Python
  ansible.builtin.debug:
    msg: "{{ current_versions }}"
  vars:
    current_versions: >-
      {{
        (xml_output | from_xml).result.sw_updates.versions.entry |
        selectattr('current', 'equalto', 'yes') |
        map(attribute='version') |
        list
      }}

This approach uses Ansible’s built-in filters to:

1. Parse the XML into a Python dictionary structure using from_xml
2. Navigate the dictionary structure to reach the entries
3. Use selectattr to filter entries where current equals ‘yes’
4. Extract the version attribute from each matching entry
5. Convert the result to a list

This method is particularly useful when:

• Your XML structure is complex and XPath becomes difficult to manage
• You need to perform additional processing on the extracted data
• You’re working with XML that doesn’t have a consistent structure

Best Practices for XML Processing in Ansible

When working with XML in Ansible, consider these best practices:

1. Validate XML structure: Always validate that your XML is well-formed before processing it:

   yaml

   - name: Validate XML structure
     ansible.builtin.assert:
       that:
         - xml_output is defined
         - xml_output | from_xml is success
     fail_msg: "Invalid XML structure detected"
   

2. Handle namespaces: If your XML uses namespaces, include them in your XPath expressions:

   yaml

   - name: Process XML with namespaces
     ansible.builtin.xml:
       content: "{{ xml_output }}"
       xpath: "//ns:entry[ns:current='yes']/ns:version"
       namespaces: {"ns": "http://example.com/namespace"}
   

3. Error handling: Always include error handling for XML processing:

   yaml

   - name: Process XML with error handling
     block:
       - ansible.builtin.xml:
           content: "{{ xml_output }}"
           xpath: '//entry[current="yes"]/version'
         register: current_versions
       - ansible.builtin.set_fact:
           current_versions: "{{ current_versions.matches | default([]) }}"
     rescue:
       - ansible.builtin.set_fact:
           current_versions: []
   

4. Performance considerations: For large XML files:

   • Use the xml module with XPath rather than converting to Python dictionaries
   • Consider processing the XML in chunks if possible
   • Use more specific XPath expressions to limit the search space

5. Idempotency: Ensure your XML operations are idempotent:

   yaml

   - name: Idempotent XML processing
     ansible.builtin.xml:
       path: /path/to/config.xml
       xpath: '//entry[current="yes"]/version'
       pretty_print: yes
       state: present
   

Complete Playbook Example

Here’s a complete playbook that demonstrates how to find all objects with a neighboring key in XML:

---
- name: Process firewall software versions
  hosts: your_firewall_group
  gather_facts: no
  
  vars:
    xml_output: |
      <response status="success">
          <result>
              <sw-updates last-updated-at="2025/10/10 11:11:11">
                  <msg/>
                  <versions>
                      <entry>
                          <version>6.3.1</version>
                          <downloaded>no</downloaded>
                          <current>no</current>
                          <latest>no</latest>
                          <uploaded>no</uploaded>
                          <sha256>7e3505720ecbe981f3ce744b7530844eb2d892f340bcf967b66486112ff11808</sha256>
                      </entry>
                      <entry>
                          <version>6.3.1-c383</version>
                          <downloaded>no</downloaded>
                          <current>yes</current>
                          <latest>no</latest>
                          <uploaded>no</uploaded>
                          <sha256>8a76ee798630ae3669ffe09f5a1805dd531d3cbc7c29b2e37dc6802223775f87</sha256>
                      </entry>
                      <entry>
                          <version>6.3.0</version>
                          <downloaded>no</downloaded>
                          <current>no</current>
                          <latest>no</latest>
                          <uploaded>no</uploaded>
                          <sha256>67a83ff5206d5b4a2aaf13bce3212de270cabe6204a4df1561c35aa4c1bc0f44</sha256>
                      </entry>
                  </versions>
              </sw-updates>
          </result>
      </response>

  tasks:
    - name: Extract current versions using XPath
      ansible.builtin.xml:
        content: "{{ xml_output }}"
        xpath: '//entry[current="yes"]/version'
      register: current_versions

    - name: Display current versions
      ansible.builtin.debug:
        msg: "Current version: {{ item }}"
      loop: "{{ current_versions.matches }}"

    - name: Get complete information for current versions
      ansible.builtin.xml:
        content: "{{ xml_output }}"
        xpath: '//entry[current="yes"]'
      register: current_entries

    - name: Display complete entry information for current versions
      ansible.builtin.debug:
        msg: "Version: {{ item.version }}, Downloaded: {{ item.downloaded }}, Latest: {{ item.latest }}"
      loop: "{{ current_entries.matches }}"

This playbook demonstrates both extracting just the version numbers and retrieving complete information for entries where the software is current. You can adapt it to your specific needs, such as updating the firewall software based on the extracted version information.

Conclusion

To summarize the key points for finding XML objects with neighboring keys in Ansible:

1. Use XPath expressions with the xml module for efficient XML processing - this is generally the most readable and performant approach.

2. The XPath expression //entry[current="yes"]/version directly finds entries where <current>yes</current> exists and extracts their corresponding version values.

3. For complex XML structures, consider using Python’s XML libraries through Ansible’s filters or by using the script module to run custom Python code.

4. Always include error handling when processing XML to ensure your playbooks remain robust.

5. Consider performance implications when working with large XML files - XPath expressions typically perform better than converting the entire XML to Python dictionaries.

By following these approaches, you can efficiently process XML data in Ansible to find elements based on neighboring elements and extract the information you need for your automation tasks.