fix(gifs): bound shard cache memory

fluxer_svc/src/metrics.rs

@@ -2,9 +2,11 @@
 
 use libc::{CLOCK_MONOTONIC, clock_gettime, timespec};
 use std::fmt::Write;
+use std::sync::Arc;
 use std::sync::atomic::{AtomicI64, AtomicU64, Ordering};
 
 const ORDERING: Ordering = Ordering::Relaxed;
+pub(crate) type AdditionalMetricsRenderer = Arc<dyn Fn(&mut String) + Send + Sync>;
 
 const HISTOGRAM_BUCKETS_MS: &[u64] = &[
     1, 5, 10, 25, 50, 100, 250, 500, 1000, 2500, 5000, 10000, 30000,
@@ -71,6 +73,7 @@ pub struct ServiceMetrics {
     pub shard_forwards_total: AtomicU64,
     pub request_duration: Histogram,
     start_ms: AtomicI64,
+    additional_renderer: Option<AdditionalMetricsRenderer>,
 }
 
 impl Default for ServiceMetrics {
@@ -83,11 +86,19 @@ impl Default for ServiceMetrics {
             shard_forwards_total: AtomicU64::new(0),
             request_duration: Histogram::new(),
             start_ms: AtomicI64::new(0),
+            additional_renderer: None,
         }
     }
 }
 
 impl ServiceMetrics {
+    pub(crate) fn with_additional_renderer(renderer: AdditionalMetricsRenderer) -> Self {
+        Self {
+            additional_renderer: Some(renderer),
+            ..Self::default()
+        }
+    }
+
     pub fn init(&self) {
         self.start_ms.store(now_ms(), ORDERING);
     }
@@ -167,6 +178,10 @@ impl ServiceMetrics {
             uptime_ms as f64 / 1000.0,
         );
 
+        if let Some(renderer) = self.additional_renderer.as_ref() {
+            renderer(&mut out);
+        }
+
         out
     }
 }

fluxer_svc/src/shard.rs

@@ -16,6 +16,7 @@ pub trait ShardService: Send + Sync + 'static {
     type Response: serde::Serialize + serde::de::DeserializeOwned + Send + 'static;
 
     fn service_name(&self) -> &str;
+    fn render_prometheus_metrics(&self, _output: &mut String) {}
     fn handle(
         &self,
         request: Self::Request,
@@ -36,7 +37,12 @@ where
     let shard_subject = format!("svc.{name}.shard.{shard_id}");
     let health_addr = config.listen_addr;
 
-    let metrics = Arc::new(ServiceMetrics::default());
+    let metrics_service = service.clone();
+    let additional_renderer: Arc<dyn Fn(&mut String) + Send + Sync> =
+        Arc::new(move |output| metrics_service.render_prometheus_metrics(output));
+    let metrics = Arc::new(ServiceMetrics::with_additional_renderer(
+        additional_renderer,
+    ));
     metrics.init();
 
     let is_serving = Arc::new(AtomicBool::new(false));