Clear aggregator queue when API key resolution fails to avoid retries… (#785)

Clear aggregator queue when API key resolution fails to avoid retries
and prevent wasted billing time.

Test:
| Scenario | Log | Observation |
|--------|--------|--------|
| Baseline+good DD_API_KEY | REPORT RequestId:
cac9fb53-c84f-4c4b-b5fb-f2965589e559 **Duration: 126.62 ms Billed
Duration: 127 ms** Memory Size: 1024 MB Max Memory Used: 94 MB | Normal
|
|Baseline+bad DD_API_KEY|REPORT RequestId:
bfff6cc0-3ab2-4a35-86a5-0ba29d1ba1d6 **Duration: 120000.00 ms Billed
Duration: 120000 ms** Memory Size: 1024 MB Max Memory Used: 90 MB
Status: timeout|Time out with excessive billed time|
|Change+good DD_API_KEY|REPORT RequestId:
58ef36bf-7b05-47da-8173-a204d0c74ff6 **Duration: 46.62 ms Billed
Duration: 47 ms** Memory Size: 1024 MB Max Memory Used: 94 MB|Normal|
|Change+bad DD_API_KEY|REPORT RequestId:
333cd454-6765-4817-98d9-95a9b754f567 **Duration: 67.33 ms Billed
Duration: 68 ms** Memory Size: 1024 MB Max Memory Used: 94 MB|Fail fast
w/o excessive billed time|

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Author: litianningdatadog

bottlecap/src/traces/proxy_aggregator.rs

@@ -30,4 +30,9 @@ impl Aggregator {
     pub fn get_batch(&mut self) -> Vec<ProxyRequest> {
         std::mem::take(&mut self.queue)
     }
+
+    /// Flush the queue.
+    pub fn clear(&mut self) {
+        self.queue.clear();
+    }
 }

bottlecap/src/traces/proxy_flusher.rs

@@ -82,7 +82,13 @@ impl Flusher {
         retry_requests: Option<Vec<reqwest::RequestBuilder>>,
     ) -> Option<Vec<reqwest::RequestBuilder>> {
         let Some(api_key) = self.api_key_factory.get_api_key().await else {
-            error!("Skipping flush in proxy flusher: Failed to resolve API key");
+            error!(
+                "Purging the aggregated data and skipping flush in proxy flusher: Failed to resolve API key."
+            );
+            {
+                let mut aggregator = self.aggregator.lock().await;
+                aggregator.clear();
+            }
             return None;
         };