make trace-agent payloads generate in a reasonable amount of time

Signed-off-by: Brian L. Troutwine <brian.troutwine@datadoghq.com>

CHANGELOG.md

@@ -6,6 +6,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.14.0-rc5]
+## Changed
+- Adjusted trace-agent msgpack payload generation to be much faster at the cost
+  of some memory during the generation process.
+
 ## [0.14.0-rc4]
 ## Changed
 - Adjusted internal TCP generator metrics to be registered where possible.

src/payload/trace_agent.rs

@@ -176,7 +176,7 @@ impl crate::payload::Serialize for TraceAgent {
         // obeyed, as an example. We could then have a 'shrink' or 'expand'
         // method on that tree to avoid this loop.
         let mut members: Vec<Vec<Span>> = vec![];
-        let mut remaining = 1_000;
+        let mut remaining = 10_000;
         while remaining > 0 {
             let total = rng.gen_range(0..=remaining);
             let spans: Vec<Span> = Standard.sample_iter(&mut rng).take(total).collect();
@@ -198,8 +198,7 @@ impl crate::payload::Serialize for TraceAgent {
                 break;
             }
 
-            let total = rng.gen_range(0..=100);
-            members.push(Standard.sample_iter(&mut rng).take(total).collect());
+            members.push(Standard.sample_iter(&mut rng).take(5_000).collect());
         }
 
         // Search for an encoding that's just right.