start sketching out internal metrics

targets/otlp/src/data/metrics.rs

@@ -23,6 +23,7 @@ pub(crate) struct EventEncoder {
 
 pub(crate) struct SumEncoder {
     pub single_point_per_sample: bool,
+    // TODO: delta to cumulative
 }
 
 impl SumEncoder {

targets/otlp/src/internal_metrics.rs

@@ -0,0 +1,42 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+use emit::Clock;
+
+macro_rules! increment {
+    ($metric:path) => {
+        increment!($metric, 1);
+    };
+    ($metic:path, $by:expr) => {
+        $metic.fetch_add($by, std::sync::atomic::Ordering::Relaxed);
+    };
+}
+
+pub(crate) static INTERNAL_METRICS: InternalMetrics = InternalMetrics {
+    log_batches_sent: AtomicUsize::new(0),
+};
+
+pub(crate) struct InternalMetrics {
+    pub(crate) log_batches_sent: AtomicUsize,
+}
+
+impl InternalMetrics {
+    pub(crate) fn emit(&self) {
+        let InternalMetrics {
+            ref log_batches_sent,
+        } = self;
+
+        let rt = emit::runtime::internal();
+
+        let extent = rt.now();
+
+        emit::info!(
+            rt,
+            extent,
+            "{metric_value} {signal} batches sent",
+            metric_name: "batches_sent",
+            metric_agg: "count",
+            metric_value: log_batches_sent.load(Ordering::Relaxed),
+            signal: "logs"
+        );
+    }
+}

targets/otlp/src/lib.rs

@@ -1,5 +1,7 @@
 #![feature(stmt_expr_attributes, proc_macro_hygiene)]
 
+#[macro_use]
+mod internal_metrics;
 mod client;
 pub mod data;
 mod error;