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Gsub processor

The gsub processor performs a regular expression search-and-replace operation on string fields in incoming documents. If the field contains an array of strings, the operation is applied to all elements in the array. However, if the field contains non-string values, the processor throws an exception. Use cases for the gsub processor include removing sensitive information from log messages or user-generated content, normalizing data formats or conventions (for example, converting date formats, removing special characters), and extracting or transforming substrings from field values for further processing or analysis.

The following is the syntax for the gsub processor:

"gsub": {
  "field": "field_name",
  "pattern": "regex_pattern",
  "replacement": "replacement_string"
}

Configuration parameters

The following table lists the required and optional parameters for the gsub processor.

Parameter Required/Optional Description
field Required The field to apply the replacement to.
pattern Required The pattern to be replaced.
replacement Required The string that will replace the matching patterns.
target_field Optional The name of the field in which to store the parsed data. If target_field is not specified, the parsed data replaces the original data in the field field. Default is field.
if Optional A condition for running the processor.
ignore_missing Optional Specifies whether the processor should ignore documents that do not contain the specified field. Default is false.
ignore_failure Optional Specifies whether the processor continues execution even if it encounters an error. If set to true, then failures are ignored. Default is false.
on_failure Optional A list of processors to run if the processor fails.
tag Optional An identifier tag for the processor. Useful for debugging in order to distinguish between processors of the same type.

Using the processor

Follow these steps to use the processor in a pipeline.

Step 1: Create a pipeline

The following query creates a pipeline named gsub_pipeline that uses the gsub processor to replace all occurrences of the word error with the word warning in the message field:

PUT _ingest/pipeline/gsub_pipeline
{
  "description": "Replaces 'error' with 'warning' in the 'message' field",
  "processors": [
    {
      "gsub": {
        "field": "message",
        "pattern": "error",
        "replacement": "warning"
      }
    }
  ]
}

Step 2 (Optional): Test the pipeline

It is recommended that you test your pipeline before you ingest documents.

To test the pipeline, run the following query:

POST _ingest/pipeline/gsub_pipeline/_simulate
{
  "docs": [
    {
      "_source": {
        "message": "This is an error message"
      }
    }
  ]
}

Response

The following response confirms that the pipeline is working as expected:

{
  "docs": [
    {
      "doc": {
        "_index": "_index",
        "_id": "_id",
        "_source": {
          "message": "This is an warning message"
        },
        "_ingest": {
          "timestamp": "2024-05-22T19:47:00.645687211Z"
        }
      }
    }
  ]
}

Step 3: Ingest a document

The following query ingests a document into an index named logs:

PUT logs/_doc/1?pipeline=gsub_pipeline
{
  "message": "This is an error message"
}

Response

The following response shows that the request indexed the document into the index named logs and that the gsub processor replaced all occurrences of the word error with the word warning in the message field:

{
  "_index": "logs",
  "_id": "1",
  "_version": 1,
  "result": "created",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "_seq_no": 0,
  "_primary_term": 1
}

Step 4 (Optional): Retrieve the document

To retrieve the document, run the following query:

GET logs/_doc/1

Response

The following response shows the document with the modified message field value:

{
  "_index": "logs",
  "_id": "1",
  "_version": 1,
  "_seq_no": 0,
  "_primary_term": 1,
  "found": true,
  "_source": {
    "message": "This is an warning message"
  }
}

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