Add a proxy method to PrometheusClient

- Also refactor the get and json_api_get methods so that the get method
can be reused by the new proxy method.
- The new proxy method makes no changes to the request to the prometheus
server and response from the prometheus server. This allows it to be
used as a proxy to the Prometheus server, hence the name.

1 files changed, 72 insertions, 7 deletions

diff --git a/spec/lib/gitlab/prometheus_client_spec.rb b/spec/lib/gitlab/prometheus_client_spec.rb
index 2517ee71f24..f15ae83a02c 100644
--- a/spec/lib/gitlab/prometheus_client_spec.rb
+++ b/spec/lib/gitlab/prometheus_client_spec.rb
@@ -60,15 +60,13 @@ describe Gitlab::PrometheusClient do
   end
 
   describe 'failure to reach a provided prometheus url' do
-    let(:prometheus_url) {"https://prometheus.invalid.example.com"}
+    let(:prometheus_url) {"https://prometheus.invalid.example.com/api/v1/query?query=1"}
 
-    subject { described_class.new(RestClient::Resource.new(prometheus_url)) }
-
-    context 'exceptions are raised' do
+    shared_examples 'exceptions are raised' do
       it 'raises a Gitlab::PrometheusClient::Error error when a SocketError is rescued' do
         req_stub = stub_prometheus_request_with_exception(prometheus_url, SocketError)
 
-        expect { subject.send(:get, '/', {}) }
+        expect { subject }
           .to raise_error(Gitlab::PrometheusClient::Error, "Can't connect to #{prometheus_url}")
         expect(req_stub).to have_been_requested
       end
@@ -76,7 +74,7 @@ describe Gitlab::PrometheusClient do
       it 'raises a Gitlab::PrometheusClient::Error error when a SSLError is rescued' do
         req_stub = stub_prometheus_request_with_exception(prometheus_url, OpenSSL::SSL::SSLError)
 
-        expect { subject.send(:get, '/', {}) }
+        expect { subject }
           .to raise_error(Gitlab::PrometheusClient::Error, "#{prometheus_url} contains invalid SSL data")
         expect(req_stub).to have_been_requested
       end
@@ -84,11 +82,23 @@ describe Gitlab::PrometheusClient do
       it 'raises a Gitlab::PrometheusClient::Error error when a RestClient::Exception is rescued' do
         req_stub = stub_prometheus_request_with_exception(prometheus_url, RestClient::Exception)
 
-        expect { subject.send(:get, '/', {}) }
+        expect { subject }
           .to raise_error(Gitlab::PrometheusClient::Error, "Network connection error")
         expect(req_stub).to have_been_requested
       end
     end
+
+    context 'ping' do
+      subject { described_class.new(RestClient::Resource.new(prometheus_url)).ping }
+
+      it_behaves_like 'exceptions are raised'
+    end
+
+    context 'proxy' do
+      subject { described_class.new(RestClient::Resource.new(prometheus_url)).proxy('query', { query: '1' }) }
+
+      it_behaves_like 'exceptions are raised'
+    end
   end
 
   describe '#query' do
@@ -258,4 +268,59 @@ describe Gitlab::PrometheusClient do
       it { is_expected.to eq(step) }
     end
   end
+
+  describe 'proxy' do
+    context 'get API' do
+      let(:prometheus_query) { prometheus_cpu_query('env-slug') }
+      let(:query_url) { prometheus_query_url(prometheus_query) }
+
+      around do |example|
+        Timecop.freeze { example.run }
+      end
+
+      context 'when response status code is 200' do
+        it 'returns response object' do
+          req_stub = stub_prometheus_request(query_url, body: prometheus_value_body('vector'))
+
+          response = subject.proxy('query', { query: prometheus_query })
+          json_response = JSON.parse(response.body)
+
+          expect(response.code).to eq(200)
+          expect(json_response).to eq({
+            'status' => 'success',
+            'data' => {
+              'resultType' => 'vector',
+              'result' => [{ "metric" => {}, "value" => [1488772511.004, "0.000041021495238095323"] }]
+            }
+          })
+          expect(req_stub).to have_been_requested
+        end
+      end
+
+      context 'when response status code is not 200' do
+        it 'returns response object' do
+          req_stub = stub_prometheus_request(query_url, status: 400, body: { error: 'error' })
+
+          response = subject.proxy('query', { query: prometheus_query })
+          json_response = JSON.parse(response.body)
+
+          expect(req_stub).to have_been_requested
+          expect(response.code).to eq(400)
+          expect(json_response).to eq('error' => 'error')
+        end
+      end
+
+      context 'when RestClient::Exception is raised' do
+        before do
+          stub_prometheus_request_with_exception(query_url, RestClient::Exception)
+        end
+
+        it 'raises PrometheusClient::Error' do
+          expect { subject.proxy('query', { query: prometheus_query }) }.to(
+            raise_error(Gitlab::PrometheusClient::Error, 'Network connection error')
+          )
+        end
+      end
+    end
+  end
 end