Send json query to Apache Solr

The following code shows how to send an aggregation query to Solr

Assuming docs having the following minimal structure:

{
  "response_payload": Long,
  "ip": String,
  "country_name": String
}

Then using curl to send a http request:

json='{
  "bytes_transferred_per_country": {
    "facet": {
      "bytes_transferred": "sum(response_payload)", 
      "sources": "unique(ip)"
    }, 
    "limit": 25,
    "field": "country_name",
    "type": "terms"
  }}'

curl -X GET http(s)://{host}/solr/{node}/select?q=*:*&json.facet={$json}&wt=json