x-pack/filebeat/input/httpjson/internal/v2: allow split chains to continue past empty targets

CHANGELOG.next.asciidoc

@@ -749,6 +749,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Add base64 Encode functionality to httpjson input. {pull}27681[27681]
 - Add `join` and `sprintf` functions to `httpjson` input. {pull}27735[27735]
 - Improve memory usage of line reader of `log` and `filestream` input. {pull}27782[27782]
+- Add `ignore_empty_value` flag to `httpjson` `split` processor. {pull}27880[27880]
 
 
 *Heartbeat*

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

@@ -566,6 +566,11 @@ Required if using split type of `string`.  This is the sub string used to split
 
 Valid when used with `type: map`. When not empty, defines a new field where the original key value will be stored.
 
+[float]
+==== `response.split[].ignore_empty_value`
+
+If set to true, empty or missing value will be ignored and processing will pass on to the next nested split operation instead of failing with an error. Default: `false`.
+
 [float]
 ==== `response.split[].split`
 

x-pack/filebeat/input/httpjson/internal/v2/config_response.go

@@ -24,13 +24,14 @@ type responseConfig struct {
 }
 
 type splitConfig struct {
-	Target          string           `config:"target" validation:"required"`
-	Type            string           `config:"type"`
-	Transforms      transformsConfig `config:"transforms"`
-	Split           *splitConfig     `config:"split"`
-	KeepParent      bool             `config:"keep_parent"`
-	KeyField        string           `config:"key_field"`
-	DelimiterString string           `config:"delimiter"`
+	Target           string           `config:"target" validation:"required"`
+	Type             string           `config:"type"`
+	Transforms       transformsConfig `config:"transforms"`
+	Split            *splitConfig     `config:"split"`
+	KeepParent       bool             `config:"keep_parent"`
+	KeyField         string           `config:"key_field"`
+	DelimiterString  string           `config:"delimiter"`
+	IgnoreEmptyValue bool             `config:"ignore_empty_value"`
 }
 
 func (c *responseConfig) Validate() error {

x-pack/filebeat/input/httpjson/internal/v2/split.go

@@ -21,18 +21,24 @@ var (
 	errExpectedSplitString = errors.New("split was expecting field to be a string")
 )
 
+// split is a split processor chain element. Split processing is executed
+// by applying elements of the chain's linked list to an input until completed
+// or an error state is encountered.
 type split struct {
-	log        *logp.Logger
-	targetInfo targetInfo
-	kind       string
-	transforms []basicTransform
-	child      *split
-	keepParent bool
-	keyField   string
-	isRoot     bool
-	delimiter  string
+	log              *logp.Logger
+	targetInfo       targetInfo
+	kind             string
+	transforms       []basicTransform
+	child            *split
+	keepParent       bool
+	ignoreEmptyValue bool
+	keyField         string
+	isRoot           bool
+	delimiter        string
 }
 
+// newSplitResponse returns a new split based on the provided config and
+// logging to the provided logger, tagging the split as the root of the chain.
 func newSplitResponse(cfg *splitConfig, log *logp.Logger) (*split, error) {
 	if cfg == nil {
 		return nil, nil
@@ -42,11 +48,13 @@ func newSplitResponse(cfg *splitConfig, log *logp.Logger) (*split, error) {
 	if err != nil {
 		return nil, err
 	}
-	// we want to be able to identify which split is the root of the chain
+	// We want to be able to identify which split is the root of the chain.
 	split.isRoot = true
 	return split, nil
 }
 
+// newSplit returns a new split based on the provided config and
+// logging to the provided logger.
 func newSplit(c *splitConfig, log *logp.Logger) (*split, error) {
 	ti, err := getTargetInfo(c.Target)
 	if err != nil {
@@ -71,29 +79,40 @@ func newSplit(c *splitConfig, log *logp.Logger) (*split, error) {
 	}
 
 	return &split{
-		log:        log,
-		targetInfo: ti,
-		kind:       c.Type,
-		keepParent: c.KeepParent,
-		keyField:   c.KeyField,
-		delimiter:  c.DelimiterString,
-		transforms: ts,
-		child:      s,
+		log:              log,
+		targetInfo:       ti,
+		kind:             c.Type,
+		keepParent:       c.KeepParent,
+		ignoreEmptyValue: c.IgnoreEmptyValue,
+		keyField:         c.KeyField,
+		delimiter:        c.DelimiterString,
+		transforms:       ts,
+		child:            s,
 	}, nil
 }
 
+// run runs the split operation on the contents of resp, sending successive
+// split results on ch. ctx is passed to transforms that are called during
+// the split.
 func (s *split) run(ctx *transformContext, resp transformable, ch chan<- maybeMsg) error {
 	root := resp.body()
 	return s.split(ctx, root, ch)
 }
 
+// split recursively executes the split processor chain.
 func (s *split) split(ctx *transformContext, root common.MapStr, ch chan<- maybeMsg) error {
 	v, err := root.GetValue(s.targetInfo.Name)
 	if err != nil && err != common.ErrKeyNotFound {
 		return err
 	}
 
 	if v == nil {
+		if s.ignoreEmptyValue {
+			if s.child != nil {
+				return s.child.split(ctx, root, ch)
+			}
+			return nil
+		}
 		if s.isRoot {
 			return errEmptyRootField
 		}
@@ -109,6 +128,12 @@ func (s *split) split(ctx *transformContext, root common.MapStr, ch chan<- maybe
 		}
 
 		if len(varr) == 0 {
+			if s.ignoreEmptyValue {
+				if s.child != nil {
+					return s.child.split(ctx, root, ch)
+				}
+				return nil
+			}
 			if s.isRoot {
 				return errEmptyRootField
 			}
@@ -130,6 +155,12 @@ func (s *split) split(ctx *transformContext, root common.MapStr, ch chan<- maybe
 		}
 
 		if len(vmap) == 0 {
+			if s.ignoreEmptyValue {
+				if s.child != nil {
+					return s.child.split(ctx, root, ch)
+				}
+				return nil
+			}
 			if s.isRoot {
 				return errEmptyRootField
 			}
@@ -151,6 +182,12 @@ func (s *split) split(ctx *transformContext, root common.MapStr, ch chan<- maybe
 		}
 
 		if len(vstr) == 0 {
+			if s.ignoreEmptyValue {
+				if s.child != nil {
+					return s.child.split(ctx, root, ch)
+				}
+				return nil
+			}
 			if s.isRoot {
 				return errEmptyRootField
 			}
@@ -169,6 +206,8 @@ func (s *split) split(ctx *transformContext, root common.MapStr, ch chan<- maybe
 	return errors.New("unknown split type")
 }
 
+// sendMessage sends an array or map split result value, v, on ch after performing
+// any necessary transformations. If key is "", the value is an element of an array.
 func (s *split) sendMessage(ctx *transformContext, root common.MapStr, key string, v interface{}, ch chan<- maybeMsg) error {
 	obj, ok := toMapStr(v)
 	if !ok {
@@ -220,6 +259,8 @@ func toMapStr(v interface{}) (common.MapStr, bool) {
 	return common.MapStr{}, false
 }
 
+// sendMessage sends a string split result value, v, on ch after performing any
+// necessary transformations. If key is "", the value is an element of an array.
 func (s *split) sendMessageSplitString(ctx *transformContext, root common.MapStr, v string, ch chan<- maybeMsg) error {
 	clone := root.Clone()
 	_, _ = clone.Put(s.targetInfo.Name, v)