Fix license ID field name

[ycombinator]

This PR fixes the license ID field name from id to uid. This makes Metricbeat-indexed stack monitoring documents have parity with internally-indexed ones.

Testing this PR

1. Spin up an Elasticsearch node.
2. Build Metricbeat with this PR.

   cd $GOPATH/src/github.com/elastic/beats
   mage build
   

3. Enable the elasticsearch-xpack Metricbeat module.

   ./metricbeat modules enable elasticsearch-xpack
   

4. Run Metricbeat.

   ./metricbeat -e
   

5. Verify that the latest document in .monitoring-es-*-mb-* of type: cluster_stats has the license.uid field.

   http://localhost:9200/.monitoring-*-mb-*/_search?q=type:cluster_stats&sort=timestamp:desc&size=1&filter_path=hits.hits._source.license
   

[elasticmachine]

Pinging @elastic/stack-monitoring (Stack monitoring)

[kaiyan-sheng]

changelog maybe?

[ycombinator]

Thanks @kaiyan-sheng. I added a CHANGELOG entry in fe2585cb27d1c92bda0004e1b9df1f87b8b1c80b.

[ycombinator]

jenkins, test this

[cachedout]

I tested this and verified that uid does appear in the output:

{
    "hits": {
        "hits": [
            {
                "_source": {
                    "license": {
                        "cluster_needs_tls": false,
                        "issue_date": "2019-11-19T13:22:30.234Z",
                        "issue_date_in_millis": 1574169750234,
                        "issued_to": "elasticsearch",
                        "issuer": "elasticsearch",
                        "max_nodes": 1000,
                        "start_date_in_millis": -1,
                        "status": "active",
                        "type": "basic",
                        "uid": "5d88b23d-96ad-4bc4-8f0d-9983354e42c8"
                    }
                }
            }
        ]
    }
}

[chrisronline]

LGTM!

POST .monitoring-es-7-mb-2019.11.19/_search?filter_path=hits.hits._source.license
{
  "size": 1,
  "sort": [
    {
      "timestamp": {
        "order": "desc"
      }
    }
  ],
  "query": {
    "term": {
      "type": {
        "value": "cluster_stats"
      }
    }
  }
}

yields:

{
  "hits" : {
    "hits" : [
      {
        "_source" : {
          "license" : {
            "status" : "active",
            "expiry_date" : "2019-12-19T01:55:30.299Z",
            "type" : "trial",
            "issue_date_in_millis" : 1574128530299,
            "max_nodes" : 1000,
            "issuer" : "elasticsearch",
            "start_date_in_millis" : -1,
            "cluster_needs_tls" : true,
            "uid" : "2a18bf38-a9bb-4e39-81b5-fb5fae31b426",
            "issued_to" : "elasticsearch",
            "expiry_date_in_millis" : 1576720530299,
            "issue_date" : "2019-11-19T01:55:30.299Z"
          }
        }
      }
    ]
  }
}

[ycombinator]

jenkins, test this

[ycombinator]

Travis CI is green and Jenkins CI failures are unrelated. Merging.