Allow a solana-validator to join a cluster established by solana-test-validator (backport #18394) (#18399)

* Report 404 instead of 502 when a snapshot file is not found

This provides the client with more useful information about why their
request failed

(cherry picked from commit 40d696fcbc)

* As a last resort try to download an uncompressed snapshot

`solana-test-validator` creates uncompressed snapshots and it can be
useful to attach another validator to a `solana-test-validator` cluster
from time to time

(cherry picked from commit e36247d187)

Co-authored-by: Michael Vines <mvines@gmail.com>

download-utils/src/lib.rs

@@ -258,6 +258,7 @@ pub fn download_snapshot<'a, 'b>(
         ArchiveFormat::TarZstd,
         ArchiveFormat::TarGzip,
         ArchiveFormat::TarBzip2,
+        ArchiveFormat::Tar, // `solana-test-validator` creates uncompressed snapshots
     ] {
         let desired_snapshot_package = snapshot_utils::get_snapshot_archive_path(
             snapshot_output_dir.to_path_buf(),
@@ -269,7 +270,7 @@ pub fn download_snapshot<'a, 'b>(
             return Ok(());
         }
 
-        if download_file(
+        match download_file(
             &format!(
                 "http://{}/{}",
                 rpc_addr,
@@ -282,11 +283,13 @@ pub fn download_snapshot<'a, 'b>(
             &desired_snapshot_package,
             use_progress_bar,
             progress_notify_callback,
-        )
+        ) {
-        .is_ok()
+            Ok(()) => return Ok(()),
-        {
+            Err(err) => info!("{}", err),
-            return Ok(());
         }
     }
-    Err("Snapshot couldn't be downloaded".to_string())
+    Err(format!(
+        "Failed to download a snapshot for slot {} from {}",
+        desired_snapshot_hash.0, rpc_addr
+    ))
 }

rpc/src/rpc_service.rs

@@ -165,7 +165,11 @@ impl RpcRequestMiddleware {
             should_validate_hosts: true,
             response: Box::pin(async {
                 match Self::open_no_follow(filename).await {
-                    Err(_) => Ok(Self::internal_server_error()),
+                    Err(err) => Ok(if err.kind() == std::io::ErrorKind::NotFound {
+                        Self::not_found()
+                    } else {
+                        Self::internal_server_error()
+                    }),
                     Ok(file) => {
                         let stream =
                             FramedRead::new(file, BytesCodec::new()).map_ok(|b| b.freeze());