@SuppressWarnings("deprecation")
    private static Slime doMetricsRequest(URI hostURI) {
        HttpGet get = new HttpGet(hostURI);
        try (CloseableHttpResponse response = httpClient.execute(get)) {
            byte[] body = EntityUtils.toByteArray(response.getEntity());
            return SlimeUtils.jsonToSlime(body);
        } catch (IOException e) {
            log.info("Was unable to fetch metrics from " + hostURI + " : " + Exceptions.toMessageString(e));
            return new Slime();
        }
    }
Call the metrics API on each host and aggregate the metrics
into a single value, grouped by cluster.
configserver/src/main/java/com/yahoo/vespa/config/server/metrics/ClusterDeploymentMetricsRetriever.java