From 00d246bc01cd8e18be35a22d2e328dcbf4580b72 Mon Sep 17 00:00:00 2001
From: Paul Loyd <pavelko95@gmail.com>
Date: Tue, 9 Apr 2024 16:59:36 +0200
Subject: [PATCH] fix(core/telemetry) do not produce allocator metrics if not
 enabled

---
 CHANGELOG.md                             |  1 +
 elfo-core/src/supervisor/measure_poll.rs | 20 +++++++++++++++-----
 examples/Cargo.toml                      |  4 ++++
 examples/examples/usage/main.rs          |  6 ++++++
 4 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1b0fff55..fba31be1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - telemetry: now `elfo_message_handling_time_seconds` doesn't include the time of task switching if an actor is preempted due to elfo's budget system.
+- telemetry: don't produce allocator metrics if not enabled.
 - telemeter: validate quantiles (0.0..=1.0) in the config.
 
 ## [0.2.0-alpha.14] - 2024-02-27
diff --git a/elfo-core/src/supervisor/measure_poll.rs b/elfo-core/src/supervisor/measure_poll.rs
index 1a4e7c56..9f9b3ad2 100644
--- a/elfo-core/src/supervisor/measure_poll.rs
+++ b/elfo-core/src/supervisor/measure_poll.rs
@@ -54,11 +54,7 @@ impl<F: Future> Future for MeasurePoll<F> {
             let res = this.inner.poll(cx);
             let elapsed = Instant::now().secs_f64_since(start_time);
             recorder.record_histogram(&BUSY_TIME_SECONDS, elapsed);
-            crate::scope::with(|scope| {
-                recorder.increment_counter(&ALLOCATED_BYTES, scope.take_allocated_bytes() as u64);
-                recorder
-                    .increment_counter(&DEALLOCATED_BYTES, scope.take_deallocated_bytes() as u64);
-            });
+            publish_alloc_metrics(recorder);
             res
         } else {
             crate::coop::reset(None);
@@ -72,3 +68,17 @@ impl<F: Future> Future for MeasurePoll<F> {
         result
     }
 }
+
+fn publish_alloc_metrics(recorder: &dyn metrics::Recorder) {
+    crate::scope::with(|scope| {
+        let allocated = scope.take_allocated_bytes();
+        let deallocated = scope.take_deallocated_bytes();
+
+        if allocated > 0 {
+            recorder.increment_counter(&ALLOCATED_BYTES, allocated as u64);
+        }
+        if deallocated > 0 {
+            recorder.increment_counter(&DEALLOCATED_BYTES, deallocated as u64);
+        }
+    });
+}
diff --git a/examples/Cargo.toml b/examples/Cargo.toml
index ea0a6d76..bc1e05f8 100644
--- a/examples/Cargo.toml
+++ b/examples/Cargo.toml
@@ -9,8 +9,12 @@ license.workspace = true
 edition.workspace = true
 readme.workspace = true
 
+[features]
+unstable = ["elfo/unstable", "elfo-telemeter/unstable"]
+
 [dev-dependencies]
 elfo = { path = "../elfo", features = ["full", "network", "test-util"] }
+elfo-telemeter = { path = "../elfo-telemeter" } # for `AllocatorStats`
 
 anyhow = "1.0.40"
 futures = "0.3.12"
diff --git a/examples/examples/usage/main.rs b/examples/examples/usage/main.rs
index 4d4869bc..e7c1cfd8 100644
--- a/examples/examples/usage/main.rs
+++ b/examples/examples/usage/main.rs
@@ -311,6 +311,12 @@ fn topology() -> elfo::Topology {
 //                setup
 //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+// Optionally, the allocation statistics can be also enabled.
+#[cfg(feature = "unstable")] // TODO: stabilize it
+#[global_allocator]
+static ALLOCATOR: elfo_telemeter::AllocatorStats<std::alloc::System> =
+    elfo_telemeter::AllocatorStats::new(std::alloc::System);
+
 #[tokio::main]
 async fn main() {
     elfo::init::start(topology()).await;