[Filebeat][httpjson] Add split_events_by config setting

CHANGELOG.next.asciidoc

@@ -52,6 +52,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Adds check on `<no value>` config option value for the azure input `resource_manager_endpoint`. {pull}18890[18890]
 - Okta module now requires objects instead of JSON strings for the `http_headers`, `http_request_body`, `pagination`, `rate_limit`, and `ssl` variables. {pull}18953[18953]
 - Adds oauth support for httpjson input. {issue}18415[18415] {pull}18892[18892]
+- Adds `split_events_by` option to httpjson input. {pull}19246[19246]
 
 *Heartbeat*
 

x-pack/filebeat/docs/inputs/input-httpjson.asciidoc

@@ -178,6 +178,73 @@ The config needs to specify `events` as the `json_objects_array` value.
   json_objects_array: events
 ----
 
+[float]
+==== `split_events_by`
+
+If the response body contains a JSON object containing an array then this option
+specifies the key containing that array. Each object in that array will generate
+an event, but will maintain the common fields of the document as well.
+
+["source","json",subs="attributes"]
+----
+{
+  "time": "2020-06-02 23:22:32 UTC",
+  "user": "Bob",
+  "events": [
+    {
+      "timestamp": "2020-05-02 11:10:03 UTC",
+      "event": {
+        "category": "authorization"
+      }
+    },
+    {
+      "timestamp": "2020-05-05 13:03:11 UTC",
+      "event": {
+        "category": "authorization"
+      }
+    }
+  ]
+}
+----
+
+The config needs to specify `events` as the `split_events_by` value.
+
+["source","yaml",subs="attributes"]
+----
+- type: httpjson
+  split_events_by: events
+----
+
+And will output the following events:
+
+["source","json",subs="attributes"]
+----
+[
+  {
+    "time": "2020-06-02 23:22:32 UTC",
+    "user": "Bob",
+    "events": {
+      "timestamp": "2020-05-02 11:10:03 UTC",
+      "event": {
+        "category": "authorization"
+      }
+    }
+  },
+  {
+    "time": "2020-06-02 23:22:32 UTC",
+    "user": "Bob",
+    "events": {
+      "timestamp": "2020-05-05 13:03:11 UTC",
+      "event": {
+        "category": "authorization"
+      }
+    }
+  }
+]
+----
+
+It can be used in combination with `json_objects_array`, which will look for the field inside each element.
+
 [float]
 ==== `no_http_body`
 

x-pack/filebeat/input/httpjson/config.go

@@ -26,6 +26,7 @@ type config struct {
 	HTTPRequestBody      common.MapStr     `config:"http_request_body"`
 	Interval             time.Duration     `config:"interval"`
 	JSONObjects          string            `config:"json_objects_array"`
+	SplitEventsBy        string            `config:"split_events_by"`
 	NoHTTPBody           bool              `config:"no_http_body"`
 	Pagination           *Pagination       `config:"pagination"`
 	RateLimit            *RateLimit        `config:"rate_limit"`

x-pack/filebeat/input/httpjson/httpjson_test.go

@@ -21,6 +21,8 @@ import (
 
 	"golang.org/x/sync/errgroup"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/elastic/beats/v7/filebeat/channel"
 	"github.com/elastic/beats/v7/filebeat/input"
 	"github.com/elastic/beats/v7/libbeat/beat"
@@ -38,7 +40,6 @@ const (
 
 var (
 	once sync.Once
-	url  string
 )
 
 func testSetup(t *testing.T) {
@@ -91,6 +92,10 @@ func createServer(newServer func(handler http.Handler) *httptest.Server) *httpte
 				"embedded": map[string]string{
 					"hello": "world",
 				},
+				"list": []map[string]interface{}{
+					{"foo": "bar"},
+					{"hello": "world"},
+				},
 			}
 			b, _ := json.Marshal(message)
 			w.Header().Set("Content-Type", "application/json")
@@ -157,8 +162,24 @@ func createCustomServerWithArrayResponse(newServer func(handler http.Handler) *h
 	return newServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		message := map[string]interface{}{
-			"hello": []map[string]string{
-				{"foo": "bar"},
+			"hello": []map[string]interface{}{
+				{
+					"foo": "bar",
+					"list": []map[string]interface{}{
+						{"foo": "bar"},
+						{"hello": "world"},
+					},
+				},
+				{
+					"foo": "bar",
+					"list": []map[string]interface{}{
+						{"foo": "bar"},
+					},
+				},
+				{
+					"bar":  "foo",
+					"list": []map[string]interface{}{},
+				},
 				{"bar": "foo"},
 			},
 		}
@@ -604,3 +625,105 @@ func TestOAuth2(t *testing.T) {
 		}
 	})
 }
+
+func TestSplitResponseWithKey(t *testing.T) {
+	m := map[string]interface{}{
+		"http_method":     "GET",
+		"split_events_by": "list",
+		"interval":        0,
+	}
+	ts := createTestServer(HTTPTestServer)
+	runTest(t, ts, m, func(input *HttpjsonInput, out *stubOutleter, t *testing.T) {
+		group, _ := errgroup.WithContext(context.Background())
+		group.Go(input.run)
+
+		events, ok := out.waitForEvents(2)
+		if !ok {
+			t.Fatalf("Expected 2 events, but got %d.", len(events))
+		}
+		input.Stop()
+
+		if err := group.Wait(); err != nil {
+			t.Fatal(err)
+		}
+	})
+}
+
+func TestSplitResponseWithoutKey(t *testing.T) {
+	m := map[string]interface{}{
+		"http_method":     "GET",
+		"split_events_by": "not_found",
+		"interval":        0,
+	}
+	ts := createTestServer(HTTPTestServer)
+	runTest(t, ts, m, func(input *HttpjsonInput, out *stubOutleter, t *testing.T) {
+		group, _ := errgroup.WithContext(context.Background())
+		group.Go(input.run)
+
+		events, ok := out.waitForEvents(1)
+		if !ok {
+			t.Fatalf("Expected 1 events, but got %d.", len(events))
+		}
+		input.Stop()
+
+		if err := group.Wait(); err != nil {
+			t.Fatal(err)
+		}
+	})
+}
+
+func TestArrayWithSplitResponse(t *testing.T) {
+	m := map[string]interface{}{
+		"http_method":        "GET",
+		"json_objects_array": "hello",
+		"split_events_by":    "list",
+		"interval":           0,
+	}
+
+	expectedFields := []string{
+		`{
+			"foo": "bar",
+			"list": {
+				"foo": "bar"
+			}
+		}`,
+		`{
+			"foo": "bar",
+			"list": {
+				"hello": "world"
+			}
+		}`,
+		`{
+			"foo": "bar",
+			"list": {
+				"foo": "bar"
+			}
+		}`,
+		`{
+			"bar":  "foo",
+			"list": []
+		}`,
+		`{"bar": "foo"}`,
+	}
+
+	ts := createTestServer(ArrayResponseServer)
+	runTest(t, ts, m, func(input *HttpjsonInput, out *stubOutleter, t *testing.T) {
+		group, _ := errgroup.WithContext(context.Background())
+		group.Go(input.run)
+
+		events, ok := out.waitForEvents(5)
+		if !ok {
+			t.Fatalf("Expected 5 events, but got %d.", len(events))
+		}
+		input.Stop()
+
+		if err := group.Wait(); err != nil {
+			t.Fatal(err)
+		}
+
+		for i, e := range events {
+			message, _ := e.GetValue("message")
+			assert.JSONEq(t, expectedFields[i], message.(string))
+		}
+	})
+}

x-pack/filebeat/input/httpjson/input.go

@@ -181,24 +181,61 @@ func (in *HttpjsonInput) createHTTPRequest(ctx context.Context, ri *RequestInfo)
 
 // processEventArray publishes an event for each object contained in the array. It returns the last object in the array and an error if any.
 func (in *HttpjsonInput) processEventArray(events []interface{}) (map[string]interface{}, error) {
-	var m map[string]interface{}
+	var last map[string]interface{}
 	for _, t := range events {
 		switch v := t.(type) {
 		case map[string]interface{}:
-			m = v
-			d, err := json.Marshal(v)
-			if err != nil {
-				return nil, errors.Wrapf(err, "failed to marshal %+v", v)
-			}
-			ok := in.outlet.OnEvent(makeEvent(string(d)))
-			if !ok {
-				return nil, errors.New("function OnEvent returned false")
+			for _, e := range in.splitEvent(v) {
+				last = e
+				d, err := json.Marshal(e)
+				if err != nil {
+					return nil, errors.Wrapf(err, "failed to marshal %+v", e)
+				}
+				ok := in.outlet.OnEvent(makeEvent(string(d)))
+				if !ok {
+					return nil, errors.New("function OnEvent returned false")
+				}
 			}
 		default:
 			return nil, errors.Errorf("expected only JSON objects in the array but got a %T", v)
 		}
 	}
-	return m, nil
+	return last, nil
+}
+
+func (in *HttpjsonInput) splitEvent(event map[string]interface{}) []map[string]interface{} {
+	m := common.MapStr(event)
+
+	hasSplitKey, _ := m.HasKey(in.config.SplitEventsBy)
+	if in.config.SplitEventsBy == "" || !hasSplitKey {
+		return []map[string]interface{}{event}
+	}
+
+	splitOnIfc, _ := m.GetValue(in.config.SplitEventsBy)
+	splitOn, ok := splitOnIfc.([]interface{})
+	// if not an array or is empty, we do nothing
+	if !ok || len(splitOn) == 0 {
+		return []map[string]interface{}{event}
+	}
+
+	var events []map[string]interface{}
+	for _, split := range splitOn {
+		s, ok := split.(map[string]interface{})
+		// if not an object, we do nothing
+		if !ok {
+			return []map[string]interface{}{event}
+		}
+
+		mm := m.Clone()
+		_, err := mm.Put(in.config.SplitEventsBy, s)
+		if err != nil {
+			return []map[string]interface{}{event}
+		}
+
+		events = append(events, mm)
+	}
+
+	return events
 }
 
 // getNextLinkFromHeader retrieves the next URL for pagination from the HTTP Header of the response