Move check to module and add specs

This also changes to use `Kernel.warn` (which goes to stderr)
instead of printing to stdout. Also ignore Rails runner env.

config/initializers/1_postgresql_only.rb

@@ -3,26 +3,4 @@
 raise "PostgreSQL is the only supported database from GitLab 12.1" unless
   Gitlab::Database.postgresql?
 
-begin
-  puts ERB.new(Rainbow.new.wrap(<<~EOS).red).result unless Gitlab::Database.postgresql_minimum_supported_version? # rubocop:disable Rails/Output
-
-              ██     ██  █████  ██████  ███    ██ ██ ███    ██  ██████ 
-              ██     ██ ██   ██ ██   ██ ████   ██ ██ ████   ██ ██      
-              ██  █  ██ ███████ ██████  ██ ██  ██ ██ ██ ██  ██ ██   ███ 
-              ██ ███ ██ ██   ██ ██   ██ ██  ██ ██ ██ ██  ██ ██ ██    ██ 
-               ███ ███  ██   ██ ██   ██ ██   ████ ██ ██   ████  ██████  
-
-    ******************************************************************************
-      You are using PostgreSQL <%= Gitlab::Database.version %>, but PostgreSQL >= <%= Gitlab::Database::MINIMUM_POSTGRES_VERSION %>
-      is required for this version of GitLab.
-      <% if Rails.env.development? || Rails.env.test? %>
-      If using gitlab-development-kit, please find the relevant steps here:
-        https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/master/doc/howto/postgresql.md#upgrade-postgresql
-      <% end %>
-      Please upgrade your environment to a supported PostgreSQL version, see
-      https://docs.gitlab.com/ee/install/requirements.html#database for details.
-    ******************************************************************************
-  EOS
-rescue ActiveRecord::ActiveRecordError, PG::Error
-  # ignore - happens when Rake tasks yet have to create a database, e.g. for testing
-end
+Gitlab::Database.check_postgres_version_and_print_warning

lib/gitlab/database.rb

@@ -111,6 +111,33 @@ module Gitlab
       version.to_f >= 9.5
     end
 
+    def self.check_postgres_version_and_print_warning
+      return if Gitlab::Database.postgresql_minimum_supported_version?
+      return if Gitlab::Runtime.rails_runner?
+
+      Kernel.warn ERB.new(Rainbow.new.wrap(<<~EOS).red).result
+
+                  ██     ██  █████  ██████  ███    ██ ██ ███    ██  ██████ 
+                  ██     ██ ██   ██ ██   ██ ████   ██ ██ ████   ██ ██      
+                  ██  █  ██ ███████ ██████  ██ ██  ██ ██ ██ ██  ██ ██   ███ 
+                  ██ ███ ██ ██   ██ ██   ██ ██  ██ ██ ██ ██  ██ ██ ██    ██ 
+                   ███ ███  ██   ██ ██   ██ ██   ████ ██ ██   ████  ██████  
+
+        ******************************************************************************
+          You are using PostgreSQL <%= Gitlab::Database.version %>, but PostgreSQL >= <%= Gitlab::Database::MINIMUM_POSTGRES_VERSION %>
+          is required for this version of GitLab.
+          <% if Rails.env.development? || Rails.env.test? %>
+          If using gitlab-development-kit, please find the relevant steps here:
+            https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/master/doc/howto/postgresql.md#upgrade-postgresql
+          <% end %>
+          Please upgrade your environment to a supported PostgreSQL version, see
+          https://docs.gitlab.com/ee/install/requirements.html#database for details.
+        ******************************************************************************
+      EOS
+    rescue ActiveRecord::ActiveRecordError, PG::Error
+      # ignore - happens when Rake tasks yet have to create a database, e.g. for testing
+    end
+
     # map some of the function names that changed between PostgreSQL 9 and 10
     # https://wiki.postgresql.org/wiki/New_in_postgres_10
     def self.pg_wal_lsn_diff

spec/lib/gitlab/database_spec.rb

@@ -115,6 +115,47 @@ RSpec.describe Gitlab::Database do
     end
   end
 
+  describe '.check_postgres_version_and_print_warning' do
+    subject { described_class.check_postgres_version_and_print_warning }
+
+    it 'prints a warning if not compliant with minimum postgres version' do
+      allow(described_class).to receive(:postgresql_minimum_supported_version?).and_return(false)
+
+      expect(Kernel).to receive(:warn).with(/You are using PostgreSQL/)
+
+      subject
+    end
+
+    it 'doesnt print a warning if compliant with minimum postgres version' do
+      allow(described_class).to receive(:postgresql_minimum_supported_version?).and_return(true)
+
+      expect(Kernel).not_to receive(:warn).with(/You are using PostgreSQL/)
+
+      subject
+    end
+
+    it 'doesnt print a warning in Rails runner environment' do
+      allow(described_class).to receive(:postgresql_minimum_supported_version?).and_return(false)
+      allow(Gitlab::Runtime).to receive(:rails_runner?).and_return(true)
+
+      expect(Kernel).not_to receive(:warn).with(/You are using PostgreSQL/)
+
+      subject
+    end
+
+    it 'ignores ActiveRecord errors' do
+      allow(described_class).to receive(:postgresql_minimum_supported_version?).and_raise(ActiveRecord::ActiveRecordError)
+
+      expect { subject }.not_to raise_error
+    end
+
+    it 'ignores Postgres errors' do
+      allow(described_class).to receive(:postgresql_minimum_supported_version?).and_raise(PG::Error)
+
+      expect { subject }.not_to raise_error
+    end
+  end
+
   describe '.replication_slots_supported?' do
     it 'returns false when using PostgreSQL 9.3' do
       allow(described_class).to receive(:version).and_return('9.3.1')