Add a way to specify mon/mgr count (#39)

Author: mnasiadka

roles/cephadm/README.md

@@ -40,6 +40,9 @@ All Ceph hosts must be in the `ceph` group.
     * `cephadm_ssh_public_key`: Location where ssh public key used by cephadm will be saved (default: /etc/ceph/cephadm.pub)
     * `cephadm_ssh_private_key`: Location where ssh private key used by cephadm will be saved (default: /etc/ceph/cephadm.id)
     * `cephadm_ssh_user`: Pre-existing user name that should be used for bootstrapping the cluster. User must have passwordless sudo enabled. Since 1.4.0 (default: `ansible_user`)
+  * MONs and MGRs
+    * `cephadm_mon_count`: Number of MONs to deploy (default: equals to number of hosts in `mons` Ansible group)
+    * `cephadm_mgr_count`: Number of MGRs to deploy (default: equals to number of hosts in `mgrs` Ansible group)
   * OSDs
     * `cephadm_osd_devices`: List of /dev/device paths to use (e.g. for multipath devices that can't be used using an OSD spec)
       Example:

roles/cephadm/defaults/main.yml

@@ -20,6 +20,9 @@ cephadm_install_ceph_cli: False
 cephadm_ssh_public_key: "/etc/ceph/cephadm.pub"
 cephadm_ssh_private_key: "/etc/ceph/cephadm.id"
 cephadm_ssh_user: "{{ ansible_user }}"
+# MONs and MGRs
+cephadm_mon_count: "{{ groups.get('mons', []) | length }}"
+cephadm_mgr_count: "{{ groups.get('mgrs', []) | length }}"
 # Networking
 cephadm_admin_interface: "{{ cephadm_public_interface }}"
 cephadm_public_interface: ""

roles/cephadm/templates/cluster.yml.j2

@@ -21,10 +21,12 @@ labels:
 ---
 service_type: mon
 placement:
+  count: {{ cephadm_mon_count }}
   label: "mon"
 ---
 service_type: mgr
 placement:
+  count: {{ cephadm_mgr_count }}
   label: "mgr"
 ---
 service_type: crash