improvement(rpc-server): rpc server dynamic port allocation

mm2src/mm2_bin_lib/src/lib.rs

@@ -41,7 +41,14 @@ fn mm2_status() -> MainStatus {
         Err(_) => return MainStatus::NoRpc,
     };
 
-    if *ctx.rpc_started.get().unwrap_or(&false) {
+    #[cfg(not(target_arch = "wasm32"))]
+    match ctx.rpc_port.get() {
+        Some(_) => MainStatus::RpcIsUp,
+        None => MainStatus::NoRpc,
+    }
+
+    #[cfg(target_arch = "wasm32")]
+    if ctx.wasm_rpc.get().is_some() {
         MainStatus::RpcIsUp
     } else {
         MainStatus::NoRpc

mm2src/mm2_core/src/mm_ctx.rs

@@ -76,8 +76,9 @@ pub struct MmCtx {
     /// If there are things that are loaded in background then they should be separately optional,
     /// without invalidating the entire state.
     pub initialized: OnceLock<bool>,
-    /// True if the RPC HTTP server was started.
-    pub rpc_started: OnceLock<bool>,
+    /// RPC port of the HTTP server if it was started.
+    #[cfg(not(target_arch = "wasm32"))]
+    pub rpc_port: OnceLock<u16>,
     /// Data transfer bridge between server and client where server (which is the mm2 runtime) initiates the request.
     pub(crate) data_asker: DataAsker,
     /// A manager for the event streaming system. To be used to start/stop/communicate with event streamers.
@@ -153,7 +154,8 @@ impl MmCtx {
             log: log::LogArc::new(log),
             metrics: MetricsArc::new(),
             initialized: OnceLock::default(),
-            rpc_started: OnceLock::default(),
+            #[cfg(not(target_arch = "wasm32"))]
+            rpc_port: OnceLock::default(),
             data_asker: DataAsker::default(),
             event_stream_manager: Default::default(),
             stop: OnceLock::default(),
@@ -229,8 +231,9 @@ impl MmCtx {
             },
             None => 7783, // Default port if `rpcport` does not exist in the config
         };
-        if port < 1000 {
-            return ERR!("rpcport < 1000");
+        // A 0 value indicates that the rpc interface should bind on any available port.
+        if port != 0 && port < 1024 {
+            return ERR!("rpcport < 1024");
         }
         if port > u16::MAX as u64 {
             return ERR!("rpcport > u16");

mm2src/mm2_main/src/rpc.rs

@@ -412,7 +412,7 @@ pub extern "C" fn spawn_rpc(ctx_h: u32) {
                         $port,
                         now_sec()
                     );
-                    let _ = $ctx.rpc_started.set(true);
+                    let _ = $ctx.rpc_port.set($port);
                     server
                 });
             }
@@ -450,6 +450,7 @@ pub extern "C" fn spawn_rpc(ctx_h: u32) {
         // Create a TcpListener
         let incoming =
             AddrIncoming::bind(&rpc_ip_port).unwrap_or_else(|err| panic!("Can't bind on {}: {}", rpc_ip_port, err));
+        let bound_to_addr = incoming.local_addr();
         let acceptor = TlsAcceptor::builder()
             .with_single_cert(cert_chain, privkey)
             .unwrap_or_else(|err| panic!("Can't set certificate for TlsAcceptor: {}", err))
@@ -461,15 +462,16 @@ pub extern "C" fn spawn_rpc(ctx_h: u32) {
             .serve(make_svc!(TlsStream))
             .with_graceful_shutdown(get_shutdown_future!(ctx));
 
-        spawn_server!(server, ctx, rpc_ip_port.ip(), rpc_ip_port.port());
+        spawn_server!(server, ctx, bound_to_addr.ip(), bound_to_addr.port());
     } else {
         let server = Server::try_bind(&rpc_ip_port)
-            .unwrap_or_else(|err| panic!("Can't bind on {}: {}", rpc_ip_port, err))
+            .unwrap_or_else(|err| panic!("Failed to bind rpc server on {}: {}", rpc_ip_port, err))
             .http1_half_close(false)
-            .serve(make_svc!(AddrStream))
-            .with_graceful_shutdown(get_shutdown_future!(ctx));
+            .serve(make_svc!(AddrStream));
+        let bound_to_addr = server.local_addr();
+        let graceful_shutdown_server = server.with_graceful_shutdown(get_shutdown_future!(ctx));
 
-        spawn_server!(server, ctx, rpc_ip_port.ip(), rpc_ip_port.port());
+        spawn_server!(graceful_shutdown_server, ctx, bound_to_addr.ip(), bound_to_addr.port());
     }
 }
 
@@ -518,10 +520,6 @@ pub fn spawn_rpc(ctx_h: u32) {
         error!("'MmCtx::wasm_rpc' is initialized already");
         return;
     };
-    if ctx.rpc_started.set(true).is_err() {
-        error!("'MmCtx::rpc_started' is set already");
-        return;
-    }
 
     log_tag!(
         ctx,