Cant access fields from log using query template for Elasticsearch filter in Logstash

[james.garside]

Cant access fields from log using query template

I have an instance of logstash which I want to use to enrich a field on incomming logs by querying elasticsearch then add the result to the recieved log.
I have configured it using the resources available however the field is not being updated.

My configurations are below.

pipeline.yml

mutate { add_field => { "destination.geo.name" => "none" }}
elasticsearch {
	hosts => ["https://eshost1"]
	#ssl => true (Not used due to a mention there is a bug with using ssl and instead use https)
	ca_file => "/path/to/cert.crt"
	user => "logstash"
	password => "password"
	index => "index-ap*"
	query_template => "/path/to/ap_query.json"
	fields => { "Map Location" => "destination.geo.name" }
	}

ap_query.json

{
    "size": 1,
    "sort" : [ { "@timestamp" : "desc" } ],
    "query": {
	    "match_phrase": {
		    "Base Radio MAC Address": "%{[destination][address]}"
		    }
	    },
    "_source": ["Map Location"]
}

Logstash is opertaing completly as expected apart from this section.
Any help would be greatly appreciated.