[Monitoring] Remove node_resolver Setting (#21181)

This is a breaking change that removes the
`xpack.monitoring.node_resolver` setting. This setting was deprecated in
5.6, and in 6.1 the setting was limited to `uuid` explicitly. Beginning in
7.0, after this is merged, the setting will no longer exist.

docs/migration/migrate_7_0.asciidoc

@@ -4,7 +4,7 @@
 This section discusses the changes that you need to be aware of when migrating
 your application to Kibana 7.0.
 
-See also <<release-highlights>> and <<release-notes>>. 
+See also <<release-highlights>> and <<release-notes>>.
 
 [float]
 === Removed support for tribe nodes
@@ -23,11 +23,11 @@ Kibana 7.0 will only use the Node.js distribution included in the package.
 [float]
 === Advanced setting query:queryString:options no longer applies to filters
 *Details:* In previous versions of Kibana the Advanced Setting `query:queryString:options` was applied to both queries
-and custom filters using the `query_string` query. This could cause errors if a custom filter used options that 
+and custom filters using the `query_string` query. This could cause errors if a custom filter used options that
 conflicted with the Advanced Setting. In 7.0 `query:queryString:options` will no longer be applied to filters so that
 users can have full control over their custom filters.
 
-*Impact:* You must ensure that any saved searches with a `query_string` filter aren't relying implicitly on 
+*Impact:* You must ensure that any saved searches with a `query_string` filter aren't relying implicitly on
 `query:queryString:options`.
 
 [float]
@@ -41,4 +41,12 @@ so we no longer need this workaround.
 *Impact:* Since we'll no longer send the `default_field` parameter in Kibana's query_string query, Elasticsearch
 will use the index setting instead. The default for the index setting is also `*`, so most users should not be impacted.
 If some of your indices have a non-default `default_field` setting, you may want to update it or re-add the parameter
-to Kibana's advanced setting.
+to Kibana's advanced setting.
+
+[float]
+=== Deprecated kibana.yml setting `xpack.monitoring.node_resolver` has been removed
+*Details:* This setting has been deprecated since 5.6, when it was explicitly recommended to use `uuid` as its value.
+
+*Impact:* This setting is no longer necessary. If you enable {monitoring} across the Elastic Stack, a monitoring agent runs
+on each Elasticsearch node, Logstash node, Kibana instance, and Beat to collect and index metrics. Each node and instance is
+considered unique based on its persistent UUID, which is written to the path.data directory when the node or instance starts.

x-pack/plugins/monitoring/__tests__/deprecations.js

@@ -112,21 +112,4 @@ describe('monitoring plugin deprecations', function () {
     expect(log.called).to.be(false);
   });
 
-  it('should log when deprecating node_resolver', function () {
-    const settings = {
-      node_resolver: 'uuid'
-    };
-
-    const log = sinon.spy();
-    transformDeprecations(settings, log);
-    expect(log.calledOnce).to.be(true);
-  });
-
-  it(`shouldn't log when node_resolver isn't present`, function () {
-    const settings = { };
-
-    const log = sinon.spy();
-    transformDeprecations(settings, log);
-    expect(log.called).to.be(false);
-  });
 });

x-pack/plugins/monitoring/config.js

@@ -57,7 +57,6 @@ export const config = (Joi) => {
     min_interval_seconds: number().default(10),
     show_license_expiration: boolean().default(true),
     report_stats: boolean().default(true),
-    node_resolver: string().valid('uuid').default('uuid'), // deprecated in 5.6; we can make them set it properly before we remove it
     agent: object({
       interval: string().regex(/[\d\.]+[yMwdhms]/).default('10s')
     }).default(),

x-pack/plugins/monitoring/deprecations.js

@@ -31,12 +31,6 @@ export const deprecations = ({ rename }) => {
       log('Config key "xpack.monitoring.elasticsearch.ssl.verify" is deprecated. ' +
           'It has been replaced with "xpack.monitoring.elasticsearch.ssl.verificationMode"');
     },
-    (settings, log) => {
-      if (has(settings, 'node_resolver')) {
-        log('Config key "xpack.monitoring.node_resolver" is deprecated. ' +
-            'The only possible value is "uuid". This config key will be removed in 7.0.');
-      }
-    },
     (settings, log) => {
       if (has(settings, 'report_stats')) {
         log('Config key "xpack.monitoring.report_stats" is deprecated and will be removed in 7.0. ' +