Make use of new field for metrics

Summary: This diff is to make use of the new struct & field as added in D69181178 to allow removal of the prevous field

Reviewed By: andreacampi

Differential Revision: D69182275

fbshipit-source-id: 46c8bbbb3c46d191fc1111f2a0e9003b1f85152b

configerator/structs/scm/mononoke/ratelimiting/ratelimits.thrift

@@ -1,10 +1,11 @@
-// @generated SignedSource<<41ef2b9c15ea5e3de6bd2710a291fad9>>
+// @generated SignedSource<<2d2949fa8c5121c12983e72a5e6e1321>>
 // DO NOT EDIT THIS FILE MANUALLY!
 // This file is a mechanical copy of the version in the configerator repo. To
 // modify it, edit the copy in the configerator repo instead and copy it over by
 // running the following in your fbcode directory:
 //
 // configerator-thrift-updater scm/mononoke/ratelimiting/ratelimits.thrift
+# @oncall scm_server_infra
 include "thrift/annotation/cpp.thrift"
 include "thrift/annotation/rust.thrift"
 
@@ -99,8 +100,8 @@ struct RateLimitBody {
   1: RateLimitStatus status;
   // The limit above which requests will be rate limited
   2: double limit;
-  // Within ratelimits use window within FciMetric struct instead
-  3: optional i64 window;
+// Deprecated
+// 3: optional i64 window;
 }
 
 @rust.Exhaustive
@@ -127,6 +128,23 @@ struct LoadShedLimit {
   3: optional Target target;
   // The limit above which requests will be rate limited
   4: i64 limit;
+  // The metric used to load shed
+  5: LoadSheddingMetric load_shedding_metric;
+}
+
+// The metric used for load shedding.
+union LoadSheddingMetric {
+  // A counter exposed by the binary itself, i.e. starting with "mononoke.".
+  1: string local_fb303_counter;
+  // A counter not exposed by the binary.
+  2: ExternalOdsCounter external_ods_counter;
+}
+@rust.Exhaustive
+struct ExternalOdsCounter {
+  // The entity of the ODS counter.
+  1: string entity;
+  // The key of the ODS counter.
+  2: string key;
 }
 
 @rust.Exhaustive

eden/mononoke/rate_limiting/src/lib.rs

@@ -30,6 +30,7 @@ mod oss;
 pub use facebook::create_rate_limiter;
 #[cfg(not(fbcode_build))]
 pub use oss::create_rate_limiter;
+pub use rate_limiting_config::LoadSheddingMetric;
 pub use rate_limiting_config::RateLimitStatus;
 
 pub mod config;
@@ -186,9 +187,18 @@ impl LoadShedLimit {
             return LoadShedResult::Pass;
         }
 
+        // Fetch the counter
+        let value = match self.raw_config.load_shedding_metric.clone() {
+            LoadSheddingMetric::local_fb303_counter(metric) => {
+                let metric = metric.to_string();
+                STATS::load_shed_counter.get_value(fb, (metric.clone(),))
+            }
+            _ => None,
+        };
+
         let metric = self.raw_config.metric.to_string();
 
-        match STATS::load_shed_counter.get_value(fb, (metric.clone(),)) {
+        match value {
             Some(value) if value > self.raw_config.limit => {
                 log_or_enforce_status(self.raw_config.clone(), metric, value, scuba)
             }