How to send aggregation key one by one to webhook action

[sai7276p (Sai)]

Hi

I am trying to send an aggregated hosts keys to webhook actions in parameters fields..
When I use single action and this template
//{{#ctx.payload.hosts}}{{key}} {{/ctx.payload.hosts}}
It perfectly sends an array in the parameter, like below in Hostname,

Watcher Result

"actions": [
      {
        "id": "my_webhook",
        "type": "webhook",
        "status": "simulated",
        "webhook": {
          "request": {
            "host": "###############",
            "port": ######,
            "scheme": "https",
            "method": "post",
            "path": "/jenkins/job/Testv2/buildWithParameters",
            "params": {
              "Hostname": "CZ98NWOMAN CZ98PORIAN CZ98DSORAN CZ98DORAN "
            },

But when I use iteration in webhook action, it return null in the parameter for all iterations,
If you see below, watcher returning null in the Hostname parameter ""

"actions": [
      {
        "id": "my_webhook",
        "type": "webhook",
        "status": "simulated",
        "number_of_actions_executed": 6,
        "foreach": [
          {
            "webhook": {
              "request": {
                "host": "###############",
                "port": ###,
                "scheme": "https",
                "method": "post",
                "path": "/jenkins/job/Testv2/buildWithParameters",
                "params": {
                  "Hostname": ""
                },

Please help.. How can I parse an array to send a key at a time to each webhook iteration...

Watcher :

{
  "trigger": {
    "schedule": {
      "interval": "5m"
    }
  },
  "input": {
    "search": {
      "request": {
        "search_type": "query_then_fetch",
        "indices": [
          "metricbeat-*"
        ],
        "rest_total_hits_as_int": true,
        "body": {
          "aggs": {
            "host": {
              "terms": {
                "field": "host.hostname",
                "order": {
                  "disk_usage": "desc"
                }
              },
              "aggs": {
                "disk_usage": {
                  "max": {
                    "field": "system.memory.used.pct"
                  }
                }
              }
            }
          },
          "query": {
            "bool": {
              "filter": [
                {
                  "range": {
                    "@timestamp": {
                      "gte": "now-{{ctx.metadata.window_period}}"
                    }
                  }
                },
                {
                  "range": {
                    "system.memory.used.pct": {
                      "gte": "{{ctx.metadata.threshold}}"
                    }
                  }
                }
              ]
            }
          }
        }
      }
    }
  },
  "condition": {
    "compare": {
      "ctx.payload.hits.total": {
        "gt": 0
      }
    }
  },
  "actions": {
    "my_webhook": {
    "foreach" : "ctx.payload.hosts", 
      "max_iterations" : 15,
      "webhook": {
        "scheme": "https",
        "host": "##############",
        "port": #####,
        "method": "post",
        "path": "/jenkins/job/Testv2/buildWithParameters",
        "params": {
          "Hostname": "{{#ctx.payload.hosts}}{{key}} {{/ctx.payload.hosts}}"
        },
      "auth": {
          "basic": {
            "username": "########",
            "password": "############"
          }
        }
      }
    }
  },
  "metadata": {
    "window_period": "5m",
    "threshold": 0.001
  },
  "transform": {
    "script": {
      "source": "def threshold_p = ctx.metadata.threshold*100; return [ 'threshold': (int)threshold_p, 'hosts': ctx.payload.aggregations.host.buckets.stream().map(p -> [ 'key': p.key, 'disk_usage': (int) (p.disk_usage.value*100)]).collect(Collectors.toList()) ];",
      "lang": "painless"
    }
  }
}