local drain: iterate logarithmically to produce histograms

lib/src/metrics/local_drain.rs

@@ -132,7 +132,7 @@ pub fn filter_histogram(hist: &Histogram<u32>) -> FilteredMetrics {
     let mut count = 0;
     let mut buckets = Vec::new();
 
-    for value in hist.iter_linear(10) {
+    for value in hist.iter_log(1, 2.0) {
         count += value.count_since_last_iteration();
 
         buckets.push(Bucket {
@@ -174,6 +174,7 @@ impl MetricsMap {
         let mut filtered_metrics = BTreeMap::new();
         for (name, metric) in to_filter {
             filtered_metrics.insert(name.to_owned(), metric.to_filtered());
+
             // convert time metrics to a histogram format, on top of percentiles
             match metric {
                 AggregatedMetric::Time(ref hist) => {