t/prometheus-metrics: test backend response metrics

Author: davidor

t/fixtures/configs/without_nginx_metrics.lua

@@ -0,0 +1,14 @@
+local PolicyChain = require('apicast.policy_chain')
+
+local policies = {
+  'apicast.policy.load_configuration',
+  'apicast.policy.find_service',
+  'apicast.policy.local_chain'
+}
+
+local policy_chain = PolicyChain.build(policies)
+
+return {
+  policy_chain = policy_chain,
+  port = { metrics = 9421 },
+}

t/prometheus-metrics.t

@@ -54,3 +54,68 @@ openresty_shdict_free_space{dict="prometheus_metrics"} 16662528
 --- error_code: 200
 --- no_error_log
 [error]
+
+=== TEST 2: metric endpoints shows backend responses when the APIcast policy is in the chain
+We do a couple of authorized requests to backend (2xx) and a couple of
+unauthorized ones (4xx) and check that those metrics are shown correctly when
+calling the prometheus metrics endpoint.
+To simplify the output of the metrics endpoint, we use an environment config
+that does not include the nginx metrics (tested in the previous test).
+--- environment_file: t/fixtures/configs/without_nginx_metrics.lua
+--- configuration
+{
+  "services": [
+    {
+      "id": 42,
+      "backend_version":  1,
+      "backend_authentication_type": "service_token",
+      "backend_authentication_value": "token-value",
+      "proxy": {
+        "api_backend": "http://test:$TEST_NGINX_SERVER_PORT/",
+        "proxy_rules": [
+          { "pattern": "/", "http_method": "GET", "metric_system_name": "hits", "delta": 1 }
+        ],
+        "policy_chain": [
+          { "name": "apicast.policy.apicast" }
+        ]
+      }
+    }
+  ]
+}
+--- upstream
+  location / {
+     content_by_lua_block {
+       ngx.say('yay, api backend');
+     }
+  }
+--- backend
+  location /transactions/authrep.xml {
+    content_by_lua_block {
+      -- Check only the user key and assume the rest of params are OK
+      if ngx.req.get_uri_args(0)['user_key'] == 'invalid' then
+        ngx.exit(403)
+      else
+        ngx.exit(200)
+      end
+    }
+  }
+--- request eval
+["GET /?user_key=valid", "GET /?user_key=valid", "GET /?user_key=invalid", "GET /?user_key=invalid", "GET /metrics"]
+--- more_headers eval
+["", "", "", "", "Host: metrics"]
+--- error_code eval
+[ 200, 200, 403, 403, 200 ]
+--- response_body eval
+[ "yay, api backend\x{0a}", "yay, api backend\x{0a}", "Authentication failed", "Authentication failed",
+<<'METRICS_OUTPUT'
+# HELP backend_response Response status codes from 3scale's backend
+# TYPE backend_response counter
+backend_response{status="2xx"} 2
+backend_response{status="4xx"} 2
+# HELP nginx_metric_errors_total Number of nginx-lua-prometheus errors
+# TYPE nginx_metric_errors_total counter
+nginx_metric_errors_total 0
+METRICS_OUTPUT
+]
+--- no_error_log
+[error]