feat(compute): Add filename label to remote ext requests metric (#11091)

## Problem

We realized that we may use this metric for more 'live' info about
extension installations vs. what we have with installed extensions
metric, which is only updated at start, atm.

## Summary of changes

Add `filename` label to `compute_ctl_remote_ext_requests_total`. Note
that it contains the raw archive name with `.tar.zst` at the end, so the
consumer may need to strip this suffix.

Closes https://github.com/neondatabase/cloud/issues/24694

compute_tools/src/extension_server.rs

@@ -253,27 +253,31 @@ pub fn create_control_files(remote_extensions: &RemoteExtSpec, pgbin: &str) {
     }
 }
 
-// Do request to extension storage proxy, i.e.
+// Do request to extension storage proxy, e.g.,
 // curl http://pg-ext-s3-gateway/latest/v15/extensions/anon.tar.zst
-// using HHTP GET
-// and return the response body as bytes
-//
+// using HTTP GET and return the response body as bytes.
 async fn download_extension_tar(ext_remote_storage: &str, ext_path: &str) -> Result<Bytes> {
     let uri = format!("{}/{}", ext_remote_storage, ext_path);
+    let filename = Path::new(ext_path)
+        .file_name()
+        .unwrap_or_else(|| std::ffi::OsStr::new("unknown"))
+        .to_str()
+        .unwrap_or("unknown")
+        .to_string();
 
-    info!("Download extension {} from uri {}", ext_path, uri);
+    info!("Downloading extension file '{}' from uri {}", filename, uri);
 
     match do_extension_server_request(&uri).await {
         Ok(resp) => {
             info!("Successfully downloaded remote extension data {}", ext_path);
             REMOTE_EXT_REQUESTS_TOTAL
-                .with_label_values(&[&StatusCode::OK.to_string()])
+                .with_label_values(&[&StatusCode::OK.to_string(), &filename])
                 .inc();
             Ok(resp)
         }
         Err((msg, status)) => {
             REMOTE_EXT_REQUESTS_TOTAL
-                .with_label_values(&[&status])
+                .with_label_values(&[&status, &filename])
                 .inc();
             bail!(msg);
         }

compute_tools/src/metrics.rs

@@ -54,9 +54,7 @@ pub(crate) static REMOTE_EXT_REQUESTS_TOTAL: Lazy<IntCounterVec> = Lazy::new(||
     register_int_counter_vec!(
         "compute_ctl_remote_ext_requests_total",
         "Total number of requests made by compute_ctl to download extensions from S3 proxy by status",
-        // Do not use any labels like extension name yet.
-        // We can add them later if needed.
-        &["http_status"]
+        &["http_status", "filename"]
     )
     .expect("failed to define a metric")
 });

test_runner/regress/test_download_extensions.py

@@ -137,6 +137,8 @@ def test_remote_extensions(
     metrics = parse_metrics(raw_metrics)
     remote_ext_requests = metrics.query_all(
         "compute_ctl_remote_ext_requests_total",
+        # Check that we properly report the filename in the metrics
+        {"filename": "anon.tar.zst"},
     )
     assert len(remote_ext_requests) == 1
     for sample in remote_ext_requests: