Adding README file for "join" example

Change-Id: Ib46f41be63b9fbd0f82d37ed0a1f522a28bbdf07

examples/v2/capabilities/join/README.md

@@ -0,0 +1,40 @@
+"join" control example (based on v2 API/DSL)
+=============================================
+
+Workflow "create_vm_with_volume" demonstrates usage of "join" workflow control
+to synchronize multiple workflow routes. Specifically, it creates a virtual
+machine and Cinder volume in parallel, waits till their completion using "join"
+and attaches the volume to the newly created virtual machine.
+
+Note: Unlike some other examples this example doesn't use workbook concept.
+File "create_vm_with_volume" contains a workflow definition in the first place
+so in order to load the workflow "mistral workflow-create" CLI command must be
+used (not "mistral workbook-create").
+
+To run the example:
+
+1. Load workflow create_vm_with_volume.yaml:
+
+        mistral workflow-create create_vm_with_volume.yaml
+
+1. Create input.json file containing workflow input parameters as follows:
+
+        {
+            "server_name": "mistral_test_vm",
+            "image_id": "aaacd887-5afa-4cb7-a33d-1ef0b72d21c4",
+            "flavor_id": "2",
+            "ssh_username": "ubuntu",
+            "ssh_password": "my_pass",
+            "volume_name": "mistral_test_volume"
+        }
+
+1. Start workflow:
+
+        mistral execution-create create_vm_with_volume input.json
+
+1. Using execution id from the previous step wait for completion (workflow SUCCESS state):
+
+        mistral execution-get <execution_id>
+
+1. Make sure that a virtual machine and a volume have been created.
+It can be done by opening Horizon UI or using Nova client (python-novaclient).