Description of problem:

When using ceph ansible to define a crush rule it is possible to define it as the default rule. The default rule ID is not enforced

Version-Release number of selected component (if applicable):
ceph-ansible-3.1.5-1.el7cp.noarch

How reproducible:

Always

Steps to Reproduce:
1.
    crush_rule_config: true
    crush_rules:
      - name: standard
        root: standard_root
        type: rack
        default: true
      - name: fast
        root: fast_root
        type: rack
        default: false
2. Create a pool
3. Check the pool crush_rule value

Actual results:

Rules are created but the default rule is not enforced

Expected results:

Rule configured as default should become the default rule.

Additional info:

# ceph osd pool create get_schwifty 64

# ceph osd pool get get_schwifty crush_rule
crush_rule: replicated_rule

Rules are created:
# ceph osd crush rule ls
replicated_rule
standard
fast

Looking at the running mon config, the default rule is set -1 which means “pick the rule with the lowest numerical ID and use that"

# ceph --admin-daemon  /var/run/ceph/ceph-mon.lab-controller01.asok config get osd_pool_default_crush_rule
{
    "osd_pool_default_crush_rule": "-1"
}

Looking at the ceph.conf file, it should contain the osd_pool_default_crush_rule = 1 parameter [1] but it does not
# grep osd_pool_default_crush_rule /etc/ceph/ceph.conf
-> empty

[1] https://github.com/ceph/ceph-ansible/blob/master/roles/ceph-mon/tasks/crush_rules.yml#L54

Looking at ceph-ansible logs we can see that the Mons "running" config seems to be correctly updated:

2018-10-10 08:56:44,348 p=32237 u=mistral |  TASK [ceph-mon : insert new default crush rule into daemon to prevent restart] ***
2018-10-10 08:56:44,348 p=32237 u=mistral |  Wednesday 10 October 2018  08:56:44 -0400 (0:00:00.083)       0:03:41.021 *****
2018-10-10 08:56:44,828 p=32237 u=mistral |  ok: [172.16.0.25 -> 172.16.0.22] => (item=172.16.0.22) => {"changed": false, "cmd": ["docker", "exec", "ceph-mon-lab-controller01", "ceph", "--cluster", "ceph", "daemon", "mon.lab-controller01", "config", "set", "osd_pool_defau
lt_crush_rule", "1"], "delta": "0:00:00.210402", "end": "2018-10-10 12:56:46.953167", "failed": false, "item": "172.16.0.22", "rc": 0, "start": "2018-10-10 12:56:46.742765", "stderr": "", "stderr_lines": [], "stdout": "{\n    \"success\": \"osd_pool_default_crush_rule = '
1' (not observed, change may require restart) \"\n}", "stdout_lines": ["{", "    \"success\": \"osd_pool_default_crush_rule = '1' (not observed, change may require restart) \"", "}"]}
2018-10-10 08:56:45,287 p=32237 u=mistral |  ok: [172.16.0.25 -> 172.16.0.24] => (item=172.16.0.24) => {"changed": false, "cmd": ["docker", "exec", "ceph-mon-lab-controller03", "ceph", "--cluster", "ceph", "daemon", "mon.lab-controller03", "config", "set", "osd_pool_defau
lt_crush_rule", "1"], "delta": "0:00:00.211802", "end": "2018-10-10 12:56:47.413902", "failed": false, "item": "172.16.0.24", "rc": 0, "start": "2018-10-10 12:56:47.202100", "stderr": "", "stderr_lines": [], "stdout": "{\n    \"success\": \"osd_pool_default_crush_rule = '
1' (not observed, change may require restart) \"\n}", "stdout_lines": ["{", "    \"success\": \"osd_pool_default_crush_rule = '1' (not observed, change may require restart) \"", "}"]}
2018-10-10 08:56:45,752 p=32237 u=mistral |  ok: [172.16.0.25 -> 172.16.0.25] => (item=172.16.0.25) => {"changed": false, "cmd": ["docker", "exec", "ceph-mon-lab-controller02", "ceph", "--cluster", "ceph", "daemon", "mon.lab-controller02", "config", "set", "osd_pool_defau
lt_crush_rule", "1"], "delta": "0:00:00.227841", "end": "2018-10-10 12:56:47.878438", "failed": false, "item": "172.16.0.25", "rc": 0, "start": "2018-10-10 12:56:47.650597", "stderr": "", "stderr_lines": [], "stdout": "{\n    \"success\": \"osd_pool_default_crush_rule = '
1' (not observed, change may require restart) \"\n}", "stdout_lines": ["{", "    \"success\": \"osd_pool_default_crush_rule = '1' (not observed, change may require restart) \"", "}"]}

The "add new default crush rule to ceph.conf" task appears to run fine but the option is not present in ceph.conf ...

2018-10-10 08:56:45,793 p=32237 u=mistral |  TASK [ceph-mon : add new default crush rule to ceph.conf] **********************
2018-10-10 08:56:45,793 p=32237 u=mistral |  Wednesday 10 October 2018  08:56:45 -0400 (0:00:01.444)       0:03:42.466 *****
2018-10-10 08:56:46,335 p=32237 u=mistral |  changed: [172.16.0.25 -> 172.16.0.22] => (item=172.16.0.22) => {"changed": true, "failed": false, "gid": 0, "group": "root", "item": "172.16.0.22", "mode": "0644", "msg": "option added", "owner": "root", "path": "/etc/ceph/ceph
.conf", "secontext": "system_u:object_r:etc_t:s0", "size": 1973, "state": "file", "uid": 0}
2018-10-10 08:56:46,564 p=32237 u=mistral |  changed: [172.16.0.25 -> 172.16.0.24] => (item=172.16.0.24) => {"changed": true, "failed": false, "gid": 0, "group": "root", "item": "172.16.0.24", "mode": "0644", "msg": "option added", "owner": "root", "path": "/etc/ceph/ceph
.conf", "secontext": "system_u:object_r:etc_t:s0", "size": 1973, "state": "file", "uid": 0}
2018-10-10 08:56:46,811 p=32237 u=mistral |  changed: [172.16.0.25 -> 172.16.0.25] => (item=172.16.0.25) => {"changed": true, "failed": false, "gid": 0, "group": "root", "item": "172.16.0.25", "mode": "0644", "msg": "option added", "owner": "root", "path": "/etc/ceph/ceph
.conf", "secontext": "system_u:object_r:etc_t:s0", "size": 1973, "state": "file", "uid": 0}

So my guess is that the default rule ID is indeed added to the Mons running config but adding it to ceph.conf somehow fails. The Mons are then restarted so they fall back to osd_pool_default_crush_rule = -1