Mitogen: deprecate the use of mitogen and remove coverage from CI (#8147)

docs/ansible.md

@@ -251,7 +251,7 @@ For more information about Ansible and bastion hosts, read
 
 ## Mitogen
 
-You can use [mitogen](/docs/mitogen.md) to speed up kubespray.
+Mitogen support is deprecated, please see [mitogen related docs](/docs/mitogen.md) for useage and reasons for deprecation.
 
 ## Beyond ansible 2.9
 

docs/mitogen.md

@@ -1,5 +1,7 @@
 # Mitogen
 
+*Warning:* Mitogen support is now deprecated in kubespray due to upstream not releasing an updated version to support ansible 4.x (ansible-base 2.11.x) and above. The CI support has been stripped for mitogen and we are no longer validating any support or regressions for it. The supporting mitogen install playbook and integration documentation will be removed in a later version.
+
 [Mitogen for Ansible](https://mitogen.networkgenomics.com/ansible_detailed.html) allow a 1.25x - 7x speedup and a CPU usage reduction of at least 2x, depending on network conditions, modules executed, and time already spent by targets on useful work. Mitogen cannot improve a module once it is executing, it can only ensure the module executes as quickly as possible.
 
 ## Install
@@ -8,6 +10,21 @@
 ansible-playbook mitogen.yml
 ```
 
+Ensure to enable mitogen use by environment varialbles:
+
+```ShellSession
+export ANSIBLE_STRATEGY=mitogen_linear
+export ANSIBLE_STRATEGY_PLUGINS=plugins/mitogen/ansible_mitogen/plugins/strategy
+```
+
+... or `ansible.cfg` setup:
+
+```ini
+[defaults]
+strategy_plugins = plugins/mitogen/ansible_mitogen/plugins/strategy
+strategy=mitogen_linear
+```
+
 ## Limitation
 
 If you are experiencing problems, please see the [documentation](https://mitogen.networkgenomics.com/ansible_detailed.html#noteworthy-differences).