traffic attribution: log fetch cause to the blobstore as well

Summary: log fetch cause to the blobstore as well

Reviewed By: lmvasquezg

Differential Revision: D72170849

fbshipit-source-id: 39491bfa48949fda5e5c719f34f52b30e8411f8f

Author: Liubov Dmitrieva

eden/mononoke/blobstore/multiplexedblob/src/scuba.rs

@@ -48,6 +48,9 @@ fn record_scuba_common(
     if let Some(client_info) = ctx.client_request_info() {
         scuba.add_client_request_info(client_info);
     }
+    if let Some(fetch_cause) = ctx.metadata().fetch_cause() {
+        scuba.add_fetch_cause(fetch_cause);
+    }
 }
 
 pub fn record_put<T>(

eden/mononoke/common/scuba_ext/src/lib.rs

@@ -194,6 +194,11 @@ impl MononokeScubaSampleBuilder {
         self
     }
 
+    pub fn add_fetch_cause(&mut self, fetch_cause: &str) -> &mut Self {
+        self.inner.add("fetch_cause", fetch_cause);
+        self
+    }
+
     pub fn sample_for_identities(&mut self, identities: &impl MononokeIdentitySetExt) {
         // Details of quicksand traffic aren't particularly interesting because all Quicksand tasks are
         // doing effectively the same thing at the same time. If we need real-time debugging, we can