[Fix #190] Add httpjson tags support

plugins/httpjson/README.md

@@ -0,0 +1,69 @@
+# HTTP JSON Plugin
+
+The httpjson plugin can collect data from remote URLs which respond with JSON. Then it flattens JSON and finds all numeric values, treating them as floats.
+
+For example, if you have a service called _mycollector_, which has HTTP endpoint for gathering stats http://my.service.com/_stats:
+
+```
+[[httpjson.services]]
+  name = "mycollector"
+
+  servers = [
+    "http://my.service.com/_stats"
+  ]
+
+  # HTTP method to use (case-sensitive)
+  method = "GET"
+```
+
+The name is used as a prefix for the measurements.
+
+The `method` specifies HTTP method to use for requests.
+
+You can specify which keys from server response should be considered as tags:
+
+```
+[[httpjson.services]]
+  ...
+
+  tagKeys = [
+    "role",
+    "version"
+  ]
+```
+
+**NOTE**: tag values should be strings.
+
+You can also specify additional request parameters for the service:
+
+```
+[[httpjson.services]]
+  ...
+
+ [httpjson.services.parameters]
+    event_type = "cpu_spike"
+    threshold = "0.75"
+
+```
+
+
+# Sample
+
+Let's say that we have a service named "mycollector", which responds with:
+```json
+{
+    "a": 0.5,
+    "b": {
+        "c": "some text",
+        "d": 0.1,
+        "e": 5
+    }
+}
+```
+
+The collected metrics will be:
+```
+httpjson_mycollector_a value=0.5
+httpjson_mycollector_b_d value=0.1
+httpjson_mycollector_b_e value=5
+```

plugins/httpjson/httpjson.go

@@ -22,6 +22,7 @@ type Service struct {
 	Name       string
 	Servers    []string
 	Method     string
+	TagKeys    []string
 	Parameters map[string]string
 }
 
@@ -61,6 +62,12 @@ var sampleConfig = `
     # HTTP method to use (case-sensitive)
     method = "GET"
 
+    # List of tag names to extract from server response
+    # tagKeys = [
+    # 	"my_tag_1",
+    # 	"my_tag_2"
+    # ]
+
     # HTTP parameters (all values must be strings)
     [httpjson.services.parameters]
       event_type = "cpu_spike"
@@ -126,7 +133,7 @@ func (h *HttpJson) gatherServer(acc plugins.Accumulator, service Service, server
 		return err
 	}
 
-	var jsonOut interface{}
+	var jsonOut map[string]interface{}
 	if err = json.Unmarshal([]byte(resp), &jsonOut); err != nil {
 		return errors.New("Error decoding JSON response")
 	}
@@ -135,6 +142,14 @@ func (h *HttpJson) gatherServer(acc plugins.Accumulator, service Service, server
 		"server": serverURL,
 	}
 
+	for _, tag := range service.TagKeys {
+		switch v := jsonOut[tag].(type) {
+		case string:
+			tags[tag] = v
+		}
+		delete(jsonOut, tag)
+	}
+
 	processResponse(acc, service.Name, tags, jsonOut)
 	return nil
 }

plugins/httpjson/httpjson_test.go

@@ -28,6 +28,13 @@ const validJSON = `
 		}
 	}`
 
+const validJSONTags = `
+	{
+		"value": 15,
+		"role": "master",
+		"build": "123"
+	}`
+
 const invalidJSON = "I don't think this is JSON"
 
 const empty = ""
@@ -87,15 +94,19 @@ func genMockHttpJson(response string, statusCode int) *HttpJson {
 			},
 			Service{
 				Servers: []string{
-					"http://server1.example.com/metrics/",
-					"http://server2.example.com/metrics/",
+					"http://server3.example.com/metrics/",
+					"http://server4.example.com/metrics/",
 				},
 				Name:   "other_webapp",
 				Method: "POST",
 				Parameters: map[string]string{
 					"httpParam1": "12",
 					"httpParam2": "the second parameter",
 				},
+				TagKeys: []string{
+					"role",
+					"build",
+				},
 			},
 		},
 	}
@@ -185,3 +196,28 @@ func TestHttpJsonEmptyResponse(t *testing.T) {
 	assert.Equal(t, len(strings.Split(err.Error(), "\n")), 4)
 	assert.Equal(t, 0, len(acc.Points))
 }
+
+// Test that the proper values are ignored or collected
+func TestHttpJson200Tags(t *testing.T) {
+	httpjson := genMockHttpJson(validJSONTags, 200)
+
+	var acc testutil.Accumulator
+	err := httpjson.Gather(&acc)
+	require.NoError(t, err)
+
+	assert.Equal(t, 4, len(acc.Points))
+
+	for _, service := range httpjson.Services {
+		if service.Name == "other_webapp" {
+			for _, srv := range service.Servers {
+				require.NoError(t,
+					acc.ValidateTaggedValue(
+						fmt.Sprintf("%s_value", service.Name),
+						15.0,
+						map[string]string{"server": srv, "role": "master", "build": "123"},
+					),
+				)
+			}
+		}
+	}
+}