Allow conditional imports, see examples/playbook3.yml comments for a full explanation. Extensive

refactoring of playbooks now warranted, which we'll do before we move on.   This variable assignment
system makes nearly all possible magic possible, for we can use these variables however we like,
even as module names!

examples/playbooks/playbook3.yml

@@ -1,26 +1,51 @@
 ---
-# this is not so much an example playbook file as a playbook we sometimes use
-# for testing.  I have chosen to not comment this one so folks can get
-# an idea of what a concise playbook can look like...
+# this is a demo of conditional imports.  This is a powerful concept
+# and can be used to use the same recipe for different types of hosts,
+# based on variables that bubble up from the hosts from tools such
+# as ohai or facter.
+#
+# Here's an example use case:
+#
+# what to do if the service for apache is named 'httpd' on CentOS
+# but is named 'apache' on Debian?
+
+
+# there is only one play in this playbook, it runs on all hosts
+# as root
 
 - hosts: all
   user: root
-  vars:
-    http_port: 80
-    max_clients: 200
+
+# we have a common list of variables stored in /vars/external_vars.yml
+# that we will always import
+
+# next, we want to import files that are different per operating system
+# and if no per operating system file is found, load a defaults file.
+# for instance, if the OS was "CentOS", we'd try to load vars/CentOS.yml.
+# if that was found, we would immediately stop.  However if that wasn't
+# present, we'd try to load vars/defaults.yml.  If that in turn was not
+# found, we would fail immediately, because we had gotten to the end of
+# the list without importing anything.
+
+  vars_files:
+
+
+     - "vars/external_vars.yml"
+
+
+     - [ "vars/$facter_operatingsystem.yml", "vars/defaults.yml" ]
+
+# and this is just a regular task line from a playbook, as we're used to.
+# but with variables in it that come from above.  Note that the variables
+# from above are *also* available in templates
+     
   tasks:
-  - name: simulate long running op, wait for 45s, poll every 5
-    action: command /bin/sleep 15
-    async: 45
-    poll: 5
-  - include: tasks/base.yml favcolor=blue
-  - name: write the foo config file using vars set above
-    action: template src=foo.j2 dest=/etc/some_random_foo.conf
-    notify:
-    - restart apache
+
+  - name: ensure apache is latest
+    action: $packager pkg=$apache state=latest
   - name: ensure apache is running
-    action: service name=httpd state=running
-  - name: pointless test action
-    action: command /bin/echo {{ http_port }}
-  handlers:
-    - include: handlers/handlers.yml
+    action: service name=$apache state=running
+  - name: template step
+    action: template src=/tmp/test.j2 dest=/tmp/test.out
+ 
+

examples/playbooks/vars/CentOS.yml

@@ -0,0 +1,3 @@
+---
+apache: httpd
+packager: yum

examples/playbooks/vars/defaults.yml

@@ -0,0 +1,3 @@
+---
+packager: aptitude
+apache: apache