[opentelemetry][callback] add option to support enabling plugin in the CI (#3498)

* [opentelemetry][callback] add option to support enabling plugin in the CI only

* [opentelemetry][callback] add changelog fragment

* Apply suggestions from code review

Co-authored-by: Ajpantuso <ajpantuso@gmail.com>

* [opentelemetry][callback] use enable_from_environment

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

* [opentelemetry] ensure the value is true otherwise the plugin is not enabled

* [opentelemetry][changelog] update entry with the new option

Co-authored-by: Ajpantuso <ajpantuso@gmail.com>
Co-authored-by: Felix Fontein <felix@fontein.de>

changelogs/fragments/3498-callback_opentelemetry-only_in_ci.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - opentelemetry callback plugin - added option ``enable_from_environment`` to support enabling the plugin only if the given environment variable exists and it is set to true (https://github.com/ansible-collections/community.general/pull/3498).

plugins/callback/opentelemetry.py

@@ -23,6 +23,17 @@ DOCUMENTATION = '''
           - Hide the arguments for a task.
         env:
           - name: ANSIBLE_OPENTELEMETRY_HIDE_TASK_ARGUMENTS
+      enable_from_environment:
+        type: str
+        description:
+          - Whether to enable this callback only if the given environment variable exists and it is set to C(true).
+          - This is handy when you use Configuration as Code and want to send distributed traces
+            if running in the CI rather when running Ansible locally.
+          - For such, it evaluates the given I(enable_from_environment) value as environment variable
+            and if set to true this plugin will be enabled.
+        env:
+          - name: ANSIBLE_OPENTELEMETRY_ENABLE_FROM_ENVIRONMENT
+        version_added: 3.8.0
       otel_service_name:
         default: ansible
         type: str
@@ -57,6 +68,7 @@ examples: |
 '''
 
 import getpass
+import os
 import socket
 import sys
 import time
@@ -325,6 +337,12 @@ class CallbackModule(CallbackBase):
                                                 var_options=var_options,
                                                 direct=direct)
 
+        environment_variable = self.get_option('enable_from_environment')
+        if environment_variable is not None and os.environ.get(environment_variable, 'false').lower() != 'true':
+            self.disabled = True
+            self._display.warning("The `enable_from_environment` option has been set and {0} is not enabled. "
+                                  "Disabling the `opentelemetry` callback plugin.".format(environment_variable))
+
         self.hide_task_arguments = self.get_option('hide_task_arguments')
 
         self.otel_service_name = self.get_option('otel_service_name')