{"record":{"id":"d96e1994663ef5fd","repo":"SigNoz/signoz","slug":"couldn-t-generate-nil-check-for-parsefrom-of-grok","errorCode":null,"errorMessage":"couldn't generate nil check for parseFrom of grok op %s: %w","messagePattern":"couldn't generate nil check for parseFrom of grok op (.+?): %w","errorType":"validation","errorClass":null,"httpStatus":400,"severity":"error","filePath":"pkg/query-service/app/logparsingpipeline/pipelineBuilder.go","lineNumber":118,"sourceCode":"\t\t\t\tif err != nil {\n\t\t\t\t\treturn nil, fmt.Errorf(\n\t\t\t\t\t\t\"couldn't generate nil check for parseFrom of regex op %s: %w\", operator.Name, err,\n\t\t\t\t\t)\n\t\t\t\t}\n\t\t\t\toperator.If = fmt.Sprintf(\n\t\t\t\t\t`%s && %s matches \"%s\"`,\n\t\t\t\t\tparseFromNotNilCheck,\n\t\t\t\t\toperator.ParseFrom,\n\t\t\t\t\tstrings.ReplaceAll(\n\t\t\t\t\t\tstrings.ReplaceAll(operator.Regex, `\\`, `\\\\`),\n\t\t\t\t\t\t`\"`, `\\\"`,\n\t\t\t\t\t),\n\t\t\t\t)\n\n\t\t\t} else if operator.Type == \"grok_parser\" {\n\t\t\t\tparseFromNotNilCheck, err := fieldNotNilCheck(operator.ParseFrom)\n\t\t\t\tif err != nil {\n\t\t\t\t\treturn nil, fmt.Errorf(\n\t\t\t\t\t\t\"couldn't generate nil check for parseFrom of grok op %s: %w\", operator.Name, err,\n\t\t\t\t\t)\n\t\t\t\t}\n\t\t\t\toperator.If = parseFromNotNilCheck\n\n\t\t\t} else if operator.Type == \"json_parser\" {\n\t\t\t\toperators, err := processJSONParser(&operator)\n\t\t\t\tif err != nil {\n\t\t\t\t\treturn nil, fmt.Errorf(\"couldn't process json_parser op %s: %s\", operator.Name, err)\n\t\t\t\t}\n\n\t\t\t\tfilteredOp = append(filteredOp, operators...)\n\t\t\t\tcontinue // Continue here to skip deduplication of json_parser operator\n\t\t\t} else if operator.Type == \"add\" {\n\t\t\t\tif strings.HasPrefix(operator.Value, \"EXPR(\") && strings.HasSuffix(operator.Value, \")\") {\n\t\t\t\t\texpression := strings.TrimSuffix(strings.TrimPrefix(operator.Value, \"EXPR(\"), \")\")\n\t\t\t\t\tfieldsNotNilCheck, err := fieldsReferencedInExprNotNilCheck(expression)\n\t\t\t\t\tif err != nil {","sourceCodeStart":100,"sourceCodeEnd":136,"githubUrl":"https://github.com/SigNoz/signoz/blob/5069bf80b08f1f00d7e014eccc09902f9871004f/pkg/query-service/app/logparsingpipeline/pipelineBuilder.go#L100-L136","documentation":"Identical mechanism to the regex case, but for enabled grok_parser operators: getOperators calls fieldNotNilCheck(operator.ParseFrom) and wraps any failure with the operator name. A grok parser must state which field it parses; an empty or invalid ParseFrom aborts PreparePipelineProcessor.","triggerScenarios":"Enabling a grok_parser with empty/malformed parse_from, then applying pipelines via PreparePipelineProcessor / ApplyPipelines.","commonSituations":"Pipeline YAML with grok_parser missing parse_from; UI form with optional-looking parse_from left blank; migrated configs from a format that defaulted parse_from to body implicitly.","solutions":["Unwrap the error to find the underlying cause from fieldNotNilCheck.","Add parse_from (e.g. attributes.body) to the grok_parser operator.","Add schema validation for operator configs before calling the API: grok_parser requires parse_from and pattern.","Disable the operator (enabled: false) if it is a leftover placeholder you do not need."],"exampleFix":"// before\n- type: grok_parser\n  enabled: true\n  name: parse-nginx\n  # parse_from missing\n\n// after\n- type: grok_parser\n  enabled: true\n  name: parse-nginx\n  parse_from: attributes.body\n  pattern: \"%{HTTP_COMBINEDLOG}\"","handlingStrategy":"validation","validationCode":"if op.Type == \"grok_parser\" && op.Enabled && strings.TrimSpace(op.ParseFrom) == \"\" {\n\treturn fmt.Errorf(\"grok_parser %s requires parse_from\", op.Name)\n}","typeGuard":"func isGrokOpValid(op pipelinetypes.PipelineOperator) bool {\n\treturn op.Type != \"grok_parser\" || !op.Enabled || strings.TrimSpace(op.ParseFrom) != \"\"\n}","tryCatchPattern":null,"preventionTips":["Require parse_from for grok_parser in client-side schema validation.","Test pipeline configs with a dry-run/validate API before applying to production logs."],"tags":["log-pipelines","grok-parser","ottl","validation","pipeline-builder"],"backgroundTag":"pipeline-operator-validation-failed","analyzedSha":"5069bf80b08f1f00d7e014eccc09902f9871004f","analyzedAt":"2026-08-28T06:22:12.824Z","schemaVersion":2},"datasetVersion":"2026-08-28T11:17:15.048Z"}