Convert RestClient to Gitlab::HTTP for Prometheus Monitor

- Closes #60024

- Change PrometheusClient.new to accept a base url instead of an
  already created RestClient

- Use Gitlab::HTTP in PrometheusClient instead of creating RestClient
  in PrometheusService

- Move http_options from PrometheusService to
  PrometheusClient (follow_redirects: false)

- ensure that base urls don't have the trailing slash

- Created a `PrometheusClient#url` method that might not be strictly
  required

- Change rescued exceptions from RestClient::* to
  HTTParty::ResponseError where possible and StandardError for the
  rest

1 files changed, 5 insertions, 4 deletions

diff --git a/app/models/project_services/prometheus_service.rb b/app/models/project_services/prometheus_service.rb
index c68a9d923c8..6eff2ea2e3a 100644
--- a/app/models/project_services/prometheus_service.rb
+++ b/app/models/project_services/prometheus_service.rb
@@ -63,15 +63,16 @@ class PrometheusService < MonitoringService
 
   # Check we can connect to the Prometheus API
   def test(*args)
-    Gitlab::PrometheusClient.new(prometheus_client).ping
-
+    prometheus_client.ping
     { success: true, result: 'Checked API endpoint' }
   rescue Gitlab::PrometheusClient::Error => err
     { success: false, result: err }
   end
 
   def prometheus_client
-    RestClient::Resource.new(api_url, max_redirects: 0) if should_return_client?
+    return unless should_return_client?
+
+    Gitlab::PrometheusClient.new(api_url)
   end
 
   def prometheus_available?
@@ -84,7 +85,7 @@ class PrometheusService < MonitoringService
   private
 
   def should_return_client?
-    api_url && manual_configuration? && active? && valid?
+    api_url.present? && manual_configuration? && active? && valid?
   end
 
   def synchronize_service_state