[chore] Use elapsed() if possible when calculating durations (#750)

Author: danielsn

src/stats_processor.rs

@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use std::sync::Arc;
-use std::time::{SystemTime, UNIX_EPOCH};
+use std::time::UNIX_EPOCH;
 
 use async_trait::async_trait;
 use hyper::{http, Body, Request, Response, StatusCode};
@@ -63,11 +63,7 @@ impl StatsProcessor for ServerlessStatsProcessor {
             };
 
         if !stats.stats.is_empty() {
-            let start = SystemTime::now();
-            let timestamp = start
-                .duration_since(UNIX_EPOCH)
-                .unwrap_or_default()
-                .as_nanos();
+            let timestamp = UNIX_EPOCH.elapsed().unwrap_or_default().as_nanos();
             stats.stats[0].start = timestamp as u64;
         }
 

src/trace_processor.rs

@@ -122,11 +122,7 @@ impl TraceProcessor for ServerlessTraceProcessor {
 mod tests {
     use datadog_trace_obfuscation::obfuscation_config::ObfuscationConfig;
     use hyper::Request;
-    use std::{
-        collections::HashMap,
-        sync::Arc,
-        time::{SystemTime, UNIX_EPOCH},
-    };
+    use std::{collections::HashMap, sync::Arc, time::UNIX_EPOCH};
     use tokio::sync::mpsc::{self, Receiver, Sender};
 
     use crate::{
@@ -142,10 +138,7 @@ mod tests {
     use ddcommon::Endpoint;
 
     fn get_current_timestamp_nanos() -> i64 {
-        SystemTime::now()
-            .duration_since(UNIX_EPOCH)
-            .unwrap()
-            .as_nanos() as i64
+        UNIX_EPOCH.elapsed().unwrap().as_nanos() as i64
     }
 
     fn create_test_config() -> Config {