Add Geo current node check

- It always outputs the current node name.
- On success, it also outputs the current node type (primary
  or secondary).
- On failure, it also outputs the names of all nodes in the DB.

changelogs/unreleased/mk-add-geo-node-name-to-check-task.yml

+---
+title: 'Geo: Check current node in gitlab:geo:check Rake task'
+merge_request: 22436
+author:
+type: added

doc/administration/geo/replication/troubleshooting.md

@@ -51,6 +51,7 @@ Checking Geo ...
 
 GitLab Geo is available ... yes
 GitLab Geo is enabled ... yes
+This machine's Geo node name matches a database record ... yes, found a secondary node named "Shanghai"
 GitLab Geo secondary database is correctly configured ... yes
 Database replication enabled? ... yes
 Database replication working? ... yes
@@ -115,34 +116,36 @@ Any **secondary** nodes should point only to read-only instances.
 
 #### Can Geo detect the current node correctly?
 
-Geo finds the current machine's name in `/etc/gitlab/gitlab.rb` by:
+Geo finds the current machine's Geo node name in `/etc/gitlab/gitlab.rb` by:
 
 - Using the `gitlab_rails['geo_node_name']` setting.
 - If that is not defined, using the `external_url` setting.
 
-To get a machine's name, run:
-
-```sh
-sudo gitlab-rails runner "puts GeoNode.current_node_name"
-```
-
 This name is used to look up the node with the same **Name** in
 **Admin Area > Geo**.
 
-To check if current machine is correctly finding its node:
+To check if the current machine has a node name that matches a node in the
+database, run the check task:
 
 ```sh
-sudo gitlab-rails runner "puts Gitlab::Geo.current_node.inspect"
+sudo gitlab-rake gitlab:geo:check
 ```
 
-and expect something like:
+It displays the current machine's node name and whether the matching database
+record is a **primary** or **secondary** node.
 
-```ruby
-#<GeoNode id: 2, schema: "https", host: "gitlab.example.com", port: 443, relative_url_root: "", primary: false, ...>
+```
+This machine's Geo node name matches a database record ... yes, found a secondary node named "Shanghai"
 ```
 
-By running the command above, `primary` should be `true` when executed in
-the **primary** node, and `false` on any **secondary** node.
+```
+This machine's Geo node name matches a database record ... no
+  Try fixing it:
+  You could add or update a Geo node database record, setting the name to "https://example.com/".
+  Or you could set this machine's Geo node name to match the name of an existing database record: "London", "Shanghai"
+  For more information see:
+  doc/administration/geo/replication/troubleshooting.md#can-geo-detect-the-current-node-correctly
+```
 
 ## Fixing errors found when running the Geo check rake task
 

ee/lib/system_check/geo/current_node_check.rb

+# frozen_string_literal: true
+
+module SystemCheck
+  module Geo
+    class CurrentNodeCheck < SystemCheck::BaseCheck
+      set_name "This machine's Geo node name matches a database record"
+
+      # Overriding so we can output current node name and what record it matches, in case either is unexpected
+      def self.check_pass
+        node_type = Gitlab::Geo.primary? ? 'primary' : 'secondary'
+
+        "yes, found a #{node_type} node named \"#{GeoNode.current_node_name}\""
+      end
+
+      def check?
+        GeoNode.current_node.present?
+      end
+
+      def show_error
+        configured_name = GeoNode.current_node_name
+        db_names = GeoNode.all.map(&:name)
+
+        try_fixing_it(
+          "You could add or update a Geo node database record, setting the name to match this machine's Geo node name \"#{configured_name}\".",
+          "Or you could set this machine's Geo node name to match the name of an existing database record: \"#{db_names.join('", "')}\""
+        )
+
+        for_more_information('doc/administration/geo/replication/troubleshooting.md#can-geo-detect-the-current-node-correctly')
+      end
+    end
+  end
+end

ee/lib/system_check/rake_task/geo_task.rb

@@ -20,6 +20,7 @@ module SystemCheck
         [
           SystemCheck::Geo::LicenseCheck,
           SystemCheck::Geo::EnabledCheck,
+          SystemCheck::Geo::CurrentNodeCheck,
           SystemCheck::Geo::HTTPCloneEnabledCheck,
           SystemCheck::Geo::ClocksSynchronizationCheck,
           SystemCheck::App::GitUserDefaultSSHConfigCheck,

ee/spec/lib/system_check/geo/current_node_check_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rake_helper'
+
+describe SystemCheck::Geo::CurrentNodeCheck, :geo do
+  describe '#check?' do
+    context 'when the current machine has a matching GeoNode' do
+      it 'returns true' do
+        create(:geo_node, :primary, name: GeoNode.current_node_name)
+
+        expect(subject.check?).to be_truthy
+      end
+    end
+
+    context 'when the current machine does not have a matching GeoNode' do
+      it 'returns false' do
+        expect(GeoNode).to receive(:current_node_name).and_return('Foo')
+
+        expect(subject.check?).to be_falsey
+      end
+    end
+  end
+
+  describe '.check_pass' do
+    it 'outputs additional helpful info' do
+      allow(GeoNode).to receive(:current_node_name).and_return('Foo')
+      create(:geo_node, :primary, name: GeoNode.current_node_name)
+
+      expect(described_class.check_pass).to eq('yes, found a primary node named "Foo"')
+    end
+  end
+end

ee/spec/lib/system_check/rake_task/geo_task_spec.rb

@@ -9,6 +9,7 @@ describe SystemCheck::RakeTask::GeoTask do
     [
       SystemCheck::Geo::LicenseCheck,
       SystemCheck::Geo::EnabledCheck,
+      SystemCheck::Geo::CurrentNodeCheck,
       SystemCheck::Geo::HTTPCloneEnabledCheck,
       SystemCheck::Geo::ClocksSynchronizationCheck,
       SystemCheck::App::GitUserDefaultSSHConfigCheck,