Add a Prometheus API per environment

The api will proxy requests to the environment's prometheus server.
The Prometheus::ProxyService class can be reused when we add support for
group prometheus servers.

1 files changed, 47 insertions, 0 deletions

diff --git a/app/controllers/projects/environments/prometheus_api_controller.rb b/app/controllers/projects/environments/prometheus_api_controller.rb
new file mode 100644
index 00000000000..337b7fdf65d
--- /dev/null
+++ b/app/controllers/projects/environments/prometheus_api_controller.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+class Projects::Environments::PrometheusApiController < Projects::ApplicationController
+  before_action :authorize_read_prometheus!
+  before_action :environment
+
+  def proxy
+    permitted = permit_params
+
+    result = Prometheus::ProxyService.new(
+      environment,
+      request.method,
+      permitted[:proxy_path],
+      permitted.except(:proxy_path) # rubocop: disable CodeReuse/ActiveRecord
+    ).execute
+
+    if result.nil?
+      render status: :accepted, json: {
+        status: 'processing',
+        message: 'Not ready yet. Try again later.'
+      }
+      return
+    end
+
+    if result[:status] == :success
+      render status: result[:http_status], json: result[:body]
+    else
+      render status: result[:http_status] || :bad_request, json: {
+          status: result[:status],
+          message: result[:message]
+        }
+    end
+  end
+
+  private
+
+  def permit_params
+    params.permit([
+      :proxy_path, :query, :time, :timeout, :start, :end, :step, { match: [] },
+      :match_target, :metric, :limit
+    ])
+  end
+
+  def environment
+    @environment ||= project.environments.find(params[:id])
+  end
+end