Grok processor extracts only the first value if there are multiple matches

[gmarouli]

Elasticsearch Version

7.17.6, 8.x

Installed Plugins

No response

Java Version

bundled

OS Version

Doesn't depend on the OS Version

Problem Description

The Grok processor in the elasticsearch ingest pipelines does not extract multiple value that match a group but only the first one.

For example the following Grok expression:

^%{IPORHOST:source.address} (%{IPORHOST:source.address} )?

when given the following input:

"127.0.0.1 127.0.0.2"

It should match both values and not only the first one.

Steps to Reproduce

POST /_ingest/pipeline/_simulate
{
  "pipeline": {
    "description": "_description",
    "processors": [
      {
        "grok": {
          "field": "message",
          "patterns": [
            "^%{IPORHOST:source.address} (%{IPORHOST:source.address} )?"
          ]
        }
      }
    ]
  },
  "docs": [
    {
      "_index": "index",
      "_id": "id",
      "_source": {
        "message": "82.10.222.126 192.168.10.1"
      }
    }
  ]
}

The source.addresses in the response is:

{
  "docs": [
    {
      "doc": {
        "_index": "index",
        "_id": "id",
        "_version": "-3",
        "_source": {
          "message": "82.10.222.126 192.168.10.1",
          "apache": {
            "access": {
              "user": {
                "identity": "jean"
              }
            }
          },
          "source": {
            "address": "82.10.222.126"
          }
        },
        "_ingest": {
          "timestamp": "2022-12-01T09:10:24.439912308Z"
        }
      }
    }
  ]
}

While the expected value of source.address is:

{
  "docs": [
    {
      "doc": {
        "_index": "index",
        "_id": "id",
        "_version": "-3",
        "_source": {
          "message": "82.10.222.126 192.168.10.1",
          "apache": {
            "access": {
              "user": {
                "identity": "jean"
              }
            }
          },
          "source": {
            "address": [
              "82.10.222.126",
              "192.168.10.1"
            ]
          }
        },
        "_ingest": {
          "timestamp": "2022-12-01T09:10:24.439912308Z"
        }
      }
    }
  ]
}

### Logs (if relevant)

_No response_

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)