We start by defining an index template:

PUT _template/readings_template                 1
{
  "index_patterns": ["readings*"],              2
  "settings": {                                 3
    "number_of_shards": 1
  },
  "mappings": {                                 4
    "properties": {
      "sensorId": {
        "type": "keyword"
      },
      "timestamp": {
        "type": "date"
      },
      "reading": {
        "type": "double"
      }
    }
  }
}

In this _template call, we define the following things:

• A template with the name readings_template.
• The index name patterns that will match this template. We configured readings* as the one and only index pattern. Any attempt to index into an index that does not exist but matches this pattern would use this template.
• The settings to be applied to the newly created index from this template.
• The mappings to be applied to the newly created index from this template.

Let's try to index data into this new index.