Rename queue-selector to experimental-queue-selector

We want the ability to react quickly to changes, so while this is
documented, we need to make sure that people are aware that using this
while it's still experimental is a significant risk of having to deal
with breaking changes.

doc/administration/operations/extra_sidekiq_processes.md

@@ -86,9 +86,18 @@ you list:
 
 > [Introduced](https://gitlab.com/gitlab-com/gl-infra/scalability/issues/45) in [GitLab Starter](https://about.gitlab.com/pricing/) 12.8.
 
-In addition to selecting queues by name, as above, the `queue_selector`
-option allows queue groups to be selected in a more general way using
-the following components:
+CAUTION: **Caution:**
+As this is marked as **experimental**, it is subject to change at any
+time, including **breaking backwards compatibility**. This is so that we
+can react to changes we need for our GitLab.com deployment. We have a
+tracking issue open to [remove the experimental
+designation](https://gitlab.com/gitlab-com/gl-infra/scalability/issues/147)
+from this feature; please comment there if you are interested in using
+this in your own deployment.
+
+In addition to selecting queues by name, as above, the
+`experimental_queue_selector` option allows queue groups to be selected
+in a more general way using the following components:
 
 - Attributes that can be selected.
 - Operators used to construct a query.
@@ -97,7 +106,8 @@ the following components:
 
 From the [list of all available
 attributes](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/workers/all_queues.yml),
-`queue_selector` allows selecting of queues by the following attributes:
+`experimental_queue_selector` allows selecting of queues by the
+following attributes:
 
 - `feature_category` - the [GitLab feature
   category](https://about.gitlab.com/direction/maturity/#category-maturity) the
@@ -122,8 +132,8 @@ considered false.
 
 ### Available operators
 
-`queue_selector` supports the following operators, listed from highest
-to lowest precedence:
+`experimental_queue_selector` supports the following operators, listed
+from highest to lowest precedence:
 
 - `|` - the logical OR operator. For example, `query_a|query_b` (where `query_a`
   and `query_b` are queries made up of the other operators here) will include
@@ -150,7 +160,7 @@ In `/etc/gitlab/gitlab.rb`:
 
 ```ruby
 sidekiq_cluster['enable'] = true
-sidekiq_cluster['queue_selector'] = true
+sidekiq_cluster['experimental_queue_selector'] = true
 sidekiq_cluster['queue_groups'] = [
   # Run all non-CPU-bound queues that are latency sensitive
   'resource_boundary!=cpu&latency_sensitive=true',

ee/lib/gitlab/sidekiq_cluster/cli.rb

@@ -45,7 +45,7 @@ module Gitlab
         queue_names = SidekiqConfig::CliMethods.worker_queues(@rails_path)
 
         queue_groups =
-          if @queue_selector
+          if @experimental_queue_selector
             # When using the experimental queue query syntax, we treat
             # each queue group as a worker attribute query, and resolve
             # the queues for the queue group using this query.
@@ -160,8 +160,8 @@ module Gitlab
             @rails_path = path
           end
 
-          opt.on('--queue-selector', 'EXPERIMENTAL: Run workers based on the provided selector') do |queue_selector|
-            @queue_selector = queue_selector
+          opt.on('--experimental-queue-selector', 'EXPERIMENTAL: Run workers based on the provided selector') do |experimental_queue_selector|
+            @experimental_queue_selector = experimental_queue_selector
           end
 
           opt.on('-n', '--negate', 'Run workers for all queues in sidekiq_queues.yml except the given ones') do

ee/spec/bin/sidekiq_cluster_spec.rb

@@ -7,7 +7,7 @@ describe 'ee/bin/sidekiq-cluster' do
 
   where(:args, :included, :excluded) do
     %w[--negate cronjob] | '-qdefault,1' | '-qcronjob,1'
-    %w[--queue-selector resource_boundary=cpu] | '-qupdate_merge_requests,1' | '-qdefault,1'
+    %w[--experimental-queue-selector resource_boundary=cpu] | '-qupdate_merge_requests,1' | '-qdefault,1'
   end
 
   with_them do

ee/spec/lib/gitlab/sidekiq_cluster/cli_spec.rb

@@ -79,7 +79,7 @@ describe Gitlab::SidekiqCluster::CLI do
         end
       end
 
-      context 'with --queue-selector' do
+      context 'with --experimental-queue-selector' do
         where do
           {
             'memory-bound queues' => {
@@ -125,7 +125,7 @@ describe Gitlab::SidekiqCluster::CLI do
               []
             end
 
-            cli.run(%W(--queue-selector #{query}))
+            cli.run(%W(--experimental-queue-selector #{query}))
           end
 
           it 'works when negated' do
@@ -137,7 +137,7 @@ describe Gitlab::SidekiqCluster::CLI do
               []
             end
 
-            cli.run(%W(--negate --queue-selector #{query}))
+            cli.run(%W(--negate --experimental-queue-selector #{query}))
           end
         end
 
@@ -147,13 +147,13 @@ describe Gitlab::SidekiqCluster::CLI do
                   .with([['chat_notification'], ['project_export']], default_options)
                   .and_return([])
 
-          cli.run(%w(--queue-selector feature_category=chatops&latency_sensitive=true resource_boundary=memory&feature_category=source_code_management))
+          cli.run(%w(--experimental-queue-selector feature_category=chatops&latency_sensitive=true resource_boundary=memory&feature_category=importers))
         end
 
         it 'errors on an invalid query multiple queue groups correctly' do
           expect(Gitlab::SidekiqCluster).not_to receive(:start)
 
-          expect { cli.run(%w(--queue-selector unknown_field=chatops)) }
+          expect { cli.run(%w(--experimental-queue-selector unknown_field=chatops)) }
             .to raise_error(Gitlab::SidekiqConfig::CliMethods::QueryError)
         end
       end