Merge #1894

1894: Fix the 99th percentile in the analytics r=gmourier a=irevoire



Co-authored-by: Irevoire <tamo@meilisearch.com>

meilisearch-http/src/analytics/segment_analytics.rs

@@ -1,4 +1,4 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::{BinaryHeap, HashMap, HashSet};
 use std::fs;
 use std::path::Path;
 use std::sync::Arc;
@@ -286,7 +286,7 @@ pub struct SearchAggregator {
     // requests
     total_received: usize,
     total_succeeded: usize,
-    time_spent: Vec<usize>,
+    time_spent: BinaryHeap<usize>,
 
     // sort
     sort_with_geo_point: bool,
@@ -398,17 +398,21 @@ impl SearchAggregator {
         self.max_offset = self.max_offset.max(other.max_offset);
     }
 
-    pub fn into_event(mut self, user: &User, event_name: &str) -> Option<Track> {
+    pub fn into_event(self, user: &User, event_name: &str) -> Option<Track> {
         if self.total_received == 0 {
             None
         } else {
+            // the index of the 99th percentage of value
             let percentile_99th = 0.99 * (self.total_succeeded as f64 - 1.) + 1.;
-            self.time_spent.drain(percentile_99th as usize..);
+            // we get all the values in a sorted manner
+            let time_spent = self.time_spent.into_sorted_vec();
+            // We are only intersted by the slowest value of the 99th fastest results
+            let time_spent = time_spent[percentile_99th as usize];
 
             let properties = json!({
                 "user-agent": self.user_agents,
                 "requests": {
-                    "99th_response_time":  format!("{:.2}", self.time_spent.iter().sum::<usize>() as f64 / self.time_spent.len() as f64),
+                    "99th_response_time":  format!("{:.2}", time_spent),
                     "total_succeeded": self.total_succeeded,
                     "total_failed": self.total_received.saturating_sub(self.total_succeeded), // just to be sure we never panics
                     "total_received": self.total_received,