Fix: Logs: Pipelines: add nil check for grok parser parseFrom field in generated collector config (#4286)

* chore: add test validating grok parser doesn't spam logs if parse from is missing

* chore: add nil check for grok parser parseFrom

pkg/query-service/app/logparsingpipeline/pipelineBuilder.go

@@ -101,6 +101,15 @@ func getOperators(ops []PipelineOperator) ([]PipelineOperator, error) {
 					),
 				)
 
+			} else if operator.Type == "grok_parser" {
+				parseFromNotNilCheck, err := fieldNotNilCheck(operator.ParseFrom)
+				if err != nil {
+					return nil, fmt.Errorf(
+						"couldn't generate nil check for parseFrom of grok op %s: %w", operator.Name, err,
+					)
+				}
+				operator.If = parseFromNotNilCheck
+
 			} else if operator.Type == "json_parser" {
 				parseFromNotNilCheck, err := fieldNotNilCheck(operator.ParseFrom)
 				if err != nil {

pkg/query-service/app/logparsingpipeline/pipelineBuilder_test.go

@@ -386,8 +386,19 @@ func TestNoCollectorErrorsFromProcessorsForMismatchedLogs(t *testing.T) {
 			makeTestLog("mismatching log", map[string]string{
 				"test_timestamp": "not-an-epoch",
 			}),
+		}, {
+			"grok parser should ignore logs with missing parse from field",
+			PipelineOperator{
+				ID:        "grok",
+				Type:      "grok_parser",
+				Enabled:   true,
+				Name:      "grok parser",
+				ParseFrom: "attributes.test",
+				Pattern:   "%{GREEDYDATA}",
+				ParseTo:   "attributes.test_parsed",
+			},
+			makeTestLog("test log with missing parse from field", map[string]string{}),
 		},
-		// TODO(Raj): see if there is an error scenario for grok parser.
 		// TODO(Raj): see if there is an error scenario for trace parser.
 		// TODO(Raj): see if there is an error scenario for Add operator.
 	}