private void writeToLogger(Collection<EsMetricPayload> batch) {
        for (EsMetricPayload payload : batch) {
            try {
                METRICS_LOGGER.info(JsonUtil.getObjectMapper().writeValueAsString(payload));
            } catch (JsonProcessingException e) {
                throw new RuntimeException(e);
            }
        }
    }
Process the next item in the queue.
gateway/engine/es/src/main/java/io/apiman/gateway/engine/es/EsMetrics.java