Object storage proxy (#11357)

Service targeted for storing and retrieving LFC prewarm data.
Can be used for proxying S3 access for Postgres extensions like
pg_mooncake as well.

Requests must include a Bearer JWT token.
Token is validated using a pemfile (should be passed in infra/).

Note: app is not tolerant to extra trailing slashes, see app.rs
`delete_prefix` test for comments.

Resolves: https://github.com/neondatabase/cloud/issues/26342
Unrelated changes: gate a `rename_noreplace` feature and disable it in
`remote_storage` so as `object_storage` can be built with musl

libs/utils/src/fs_ext.rs

@@ -3,7 +3,9 @@ use std::{fs, io, path::Path};
 
 use anyhow::Context;
 
+#[cfg(feature = "rename_noreplace")]
 mod rename_noreplace;
+#[cfg(feature = "rename_noreplace")]
 pub use rename_noreplace::rename_noreplace;
 
 pub trait PathExt {

libs/utils/src/fs_ext/rename_noreplace.rs

@@ -8,7 +8,7 @@ pub fn rename_noreplace<P1: ?Sized + NixPath, P2: ?Sized + NixPath>(
     dst: &P2,
 ) -> nix::Result<()> {
     {
-        #[cfg(target_os = "linux")]
+        #[cfg(all(target_os = "linux", target_env = "gnu"))]
         {
             nix::fcntl::renameat2(
                 None,
@@ -29,7 +29,7 @@ pub fn rename_noreplace<P1: ?Sized + NixPath, P2: ?Sized + NixPath>(
             })??;
             nix::errno::Errno::result(res).map(drop)
         }
-        #[cfg(not(any(target_os = "linux", target_os = "macos")))]
+        #[cfg(not(any(all(target_os = "linux", target_env = "gnu"), target_os = "macos")))]
         {
             std::compile_error!("OS does not support no-replace renames");
         }

libs/utils/src/signals.rs

@@ -1,6 +1,8 @@
 pub use signal_hook::consts::TERM_SIGNALS;
 pub use signal_hook::consts::signal::*;
 use signal_hook::iterator::Signals;
+use tokio::signal::unix::{SignalKind, signal};
+use tracing::info;
 
 pub enum Signal {
     Quit,
@@ -36,3 +38,30 @@ impl ShutdownSignals {
         Ok(())
     }
 }
+
+/// Runs in a loop since we want to be responsive to multiple signals
+/// even after triggering shutdown (e.g. a SIGQUIT after a slow SIGTERM shutdown)
+/// <https://github.com/neondatabase/neon/issues/9740>
+pub async fn signal_handler(token: tokio_util::sync::CancellationToken) {
+    let mut sigint = signal(SignalKind::interrupt()).unwrap();
+    let mut sigterm = signal(SignalKind::terminate()).unwrap();
+    let mut sigquit = signal(SignalKind::quit()).unwrap();
+
+    loop {
+        let signal = tokio::select! {
+            _ = sigquit.recv() => {
+                info!("Got signal SIGQUIT. Terminating in immediate shutdown mode.");
+                std::process::exit(111);
+            }
+            _ = sigint.recv() => "SIGINT",
+            _ = sigterm.recv() => "SIGTERM",
+        };
+
+        if !token.is_cancelled() {
+            info!("Got signal {signal}. Terminating gracefully in fast shutdown mode.");
+            token.cancel();
+        } else {
+            info!("Got signal {signal}. Already shutting down.");
+        }
+    }
+}