build.log

163: ==> default: ^M
164: ==> default: TASK: [(feature) Monitor Cluster Health and send email on poor health] ******** ^M
165: ==> default: fatal: [localhost] => error while evaluating conditional: payload.status == 200^M
166: ==> default: ^M
167: ==> default: FATAL: all hosts have already failed -- aborting^M
168: ==> default: ^M
169: ==> default: PLAY RECAP ******************************************************************** ^M
170: ==> default:            to retry, use: --limit @/root/provisioning.retry^M
171: ==> default: ^M

cluster_health_watch.json.j2

{
        "trigger": {
                "schedule": { "interval": "10s" }
        },
        "input": {
                "http": {
                        "request": {
                                "host": "localhost",
                                "port": "{{ es_http_port }}",
                                "path": "/_cluster/health"
                        }
                }
        },
        "condition": {
                "compare": {
                        "ctx.payload.status": {
                                "eq": "red"
                        }
                }
        },
        "actions": {
                "send_email": {
                        "email": {
                               "to": "{{ alert_email }}",
                               "subject": "{{ alert_subject }}",
                               "body": "Cluster is in poor health."
                        }
                }
        }
}

main.yml

---
cluster_health_watch_body: "{{ lookup('template', 'templates/cluster_health_watch.json.j2') }}"
es_http_port: 9200

playbook.yml

- hosts: all

  tasks:
    - name: (feature) Monitor Cluster Health and send email on poor health
    uri:
      url: http://localhost:{{ es_http_port }}/_watcher/watch/cluster_health_watch
      method: PUT
      user: "{{ es_admin }}"
      password: "{{ es_adminpw }}"
      HEADER_Content-Type: "application/json"
      return_content: yes
      body_format: json
      body: "{{ cluster_health_watch_body | to_json }}"
      status_code: 200,201
      register: payload
    failed_when: 
      - payload.status != 201
      - payload.status != 200
    changed_when: payload.content.find("created") == "true"

results.json

/* edited for content ..., */
{
  "created": "true"
}