The following guide will help you understand and troubleshoot some of the common log related issues you might encounter.
Field mapping types
To make your search engine queries and analytics are more effective, OpenSearch Dashboards maps each field by a data type, so it knows how to display it according to its capabilities. There are two types of mapping fields:
- Dynamic - This is the default mapping type, determined by the value of the log fields mapped at the beginning of each day.
- Explicit - This is a forced mapping type, and when chosen, OpenSearch will always map this field as the same data type.
For example, if the value of the log field is "yourField":123, OpenSearch will map it as a number (Long).
“yourField”:”abc” will be mapped as a Keyword (String).
“yourField”:{“someField”:”someValue”} will be mapped as an Object.
yourField.someField will be mapped as a Keyword (String).
If a field is mapped as a string, OpenSearch won’t allow you to run any mathematical queries on the field.
If it’s an analyzed field, such as message, tags, or geoip_location, OpenSearch won’t let you use it in an alert, a visualization, or a group by rule.
Field data type determines how each field is indexed and shown in OpenSearch Dashboards. Account admins can change the data types according to a predefined set of options:
Changing a field’s data type may affect any dashboards, visualizations, searches, alerts, optimizers, and integrations using that field.
Mapping errors
Your logs are mapped daily, and each field is assigned a Dynamic or Explicit data type.
Dynamic mappings are automatically determined as logs are received, meaning the fields’ data type is known. When a field is marked as Explicit, its data type is unclear.
Mapping errors occur when different data types are sent to the same field. For example, if field weather receives the numeric value 35, then gets the value hot, it’ll result in a mapping error since the same field can’t contain two different types of inputs.
The type field is changed to logzio-index-failure, and the tags field is added to the log to identify the issue.
Here are some of the common mapping errors you might encounter and why they happen:
| MPE | Description |
| object mapping for [FIELD_NAME] tried to parse field [FIELD_NAME] as object, but found a concrete value | Field is mapped as a JSON object but is being sent as a string (or is being stringified by other means) |
| Can’t get text on a START_OBJECT | Field is mapped as a string, but is sent as a JSON object |
| failed to parse field [FIELD_NAME] of type [DATA_TYPE] | Field is being mapped as one data type but being sent as another |
| Index -1 out of bounds for length 0 | A field exists in the log with a dot “.” in its name. For these cases, the system treats the field as an object when mapping it. For example: log.level, app.kubernetes, etc. |
| Numeric value (NUMBER) out of range of long (-9223372036854775808 - 9223372036854775807) | Field mapped as a number, but its value is outside the range of the “Long” data type |
Invalid logs
What causes an invalid log?
When a log that includes specific issues is received, the log is flattened and ingested, the type field is changed to logzio-invalid-log, and the tags field is added to the log to identify the issue.
Invalid log tags
The tags in the table below explain the character or field issues that may cause a log to be labeled with the logzio-invalid-log field.
| Tag | Description |
|---|---|
| MAX_LOG_LINE_LENGTH | Exceeded the maximum of 500K characters per log |
| MAX_FIELD_KEY_SIZE -or- INVALID_FIELD_VALUE_LENGTH |
Exceeded the maximum of 32700 characters per field |
| MAX_JSON_DEPTH | Exceeded the maximum of 10 field nesting levels per log message |
| MAX_FIELDS_NUMBER -or- INVALID_FIELDS_NUMBER |
Exceeded the maximum of 1000 fields per log message |
| FIELDS_MISSING | This error is related to required fields that are missing from your logs: For example, @timestamp.Check if the parsing rules remove or rename the relevant fields. |
| ARRAY_INDEX_OUT_OF_BOUNDS_EXCEPTION | One of the field names in the log has a dot (.) as a name: To resolve the issue, flatten the field that the . is nested under. If the field is inside an array, you’ll need to flatten the array field. For example, you’d need to flatten the field xxx.yyy |