How to change Ambari alert threshold values for disks

[#1]

First you need to get the ID of the alert definition in your system:

curl -H "X-Requested-By: ambari" -u admin:<password> -X GET http://<ambari_host>:<ambari_port>/api/v1/clusters/<cluster_name>/alert_definitions?AlertDefinition/...

Get the alert definition with the id from prevoius step:

curl -H "X-Requested-By: ambari" -u admin:<password> -X GET http://<ambari_host>:<ambari_port>/api/v1/clusters/<cluster_name>/alert_definitions/61

Set the new thresholds by changing the JSON alert definition:

curl -H "X-Requested-By: ambari" -u admin:<password> -i -X PUT -d '
{
   "AlertDefinition":{
      "cluster_name":"xyz",
      "component_name":"AMBARI_AGENT",
      "description":"This host-level alert is triggered if the amount of disk space used on a host goes above specific thresholds. The default values are 85% for WARNING and 90% for CRITICAL.",
      "enabled":true,
      "id":61,
      "ignore_host":false,
      "interval":1,
      "label":"Ambari Agent Disk Usage",
      "name":"ambari_agent_disk_usage",
      "scope":"HOST",
      "service_name":"AMBARI",
      "source":{
         "parameters":[
            {
               "name":"minimum.free.space",
               "display_name":"Minimum Free Space",
               "units":"bytes",
               "value":1.0E9,
               "description":"The overall amount of free disk space left before an alert is triggered.",
               "type":"NUMERIC",
               "threshold":"WARNING"
            },
            {
               "name":"percent.used.space.warning.threshold",
               "display_name":"Warning",
               "units":"%",
               "value":0.85,
               "description":"The percent of disk space consumed before a warning is triggered.",
               "type":"PERCENT",
               "threshold":"WARNING"
            },
            {
               "name":"percent.free.space.critical.threshold",
               "display_name":"Critical",
               "units":"%",
               "value":0.9,
               "description":"The percent of disk space consumed before a critical alert is triggered.",
               "type":"PERCENT",
               "threshold":"CRITICAL"
            }
         ],
         "path":"alert_disk_space.py",
         "type":"SCRIPT"
      }
   }
}' http://<ambari_host>:<ambari_port>/api/v1/clusters/<cluster_name>/alert_definitions/61

Ambari API Reference: https://github.com/apache/ambari/blob/trunk/ambari-server/docs/api/v1/index.md

[#2]

I found it easier to download the json to a file, edit it on disk, then use the `-d @filename.json` in the final step to avoid lengthy command lines. The only caveat: the "href" line needs to be deleted from the json obtained in step two.