fix: drop geth's stderr handle (#2104)

* fix: drop geth's stderr handle

* fix: consume geth stderr in separate thread

* nit

* fix test

* nit

---------

Co-authored-by: Yash Atreya <44857776+yash-atreya@users.noreply.github.com>

Author: mattsse

crates/node-bindings/Cargo.toml

@@ -37,6 +37,7 @@ thiserror.workspace = true
 tracing.workspace = true
 url.workspace = true
 
+
 [dev-dependencies]
 ci_info.workspace = true
 tokio = { workspace = true, features = ["macros", "rt-multi-thread"] }

crates/node-bindings/src/nodes/geth.rs

@@ -202,6 +202,7 @@ pub struct Geth {
     data_dir: Option<PathBuf>,
     chain_id: Option<u64>,
     insecure_unlock: bool,
+    keep_err: bool,
     genesis: Option<Genesis>,
     mode: NodeMode,
     clique_private_key: Option<SigningKey>,
@@ -369,6 +370,14 @@ impl Geth {
         self
     }
 
+    /// Keep the handle to geth's stderr in order to read from it.
+    ///
+    /// Caution: if the stderr handle isn't used, this can end up blocking.
+    pub const fn keep_stderr(mut self) -> Self {
+        self.keep_err = true;
+        self
+    }
+
     /// Adds an argument to pass to `geth`.
     ///
     /// Pass any arg that is not supported by the builder.
@@ -635,7 +644,20 @@ impl Geth {
             }
         }
 
-        child.stderr = Some(reader.into_inner());
+        if self.keep_err {
+            // re-attach the stderr handle if requested
+            child.stderr = Some(reader.into_inner());
+        } else {
+            // We need to consume the stderr otherwise geth is non-responsive and RPC server results
+            // in connection refused.
+            // See: <https://github.com/alloy-rs/alloy/issues/2091#issuecomment-2676134147>
+            std::thread::spawn(move || {
+                let mut buf = String::new();
+                loop {
+                    let _ = reader.read_line(&mut buf);
+                }
+            });
+        }
 
         Ok(GethInstance {
             pid: child,

crates/provider/src/ext/admin.rs

@@ -107,9 +107,14 @@ mod test {
         async_ci_only(|| async move {
             run_with_tempdir("geth-test-1", |temp_dir_1| async move {
                 run_with_tempdir("geth-test-2", |temp_dir_2| async move {
-                    let geth1 = Geth::new().disable_discovery().data_dir(&temp_dir_1).spawn();
-                    let mut geth2 =
-                        Geth::new().disable_discovery().port(0u16).data_dir(&temp_dir_2).spawn();
+                    let geth1 =
+                        Geth::new().disable_discovery().keep_stderr().data_dir(&temp_dir_1).spawn();
+                    let mut geth2 = Geth::new()
+                        .disable_discovery()
+                        .keep_stderr()
+                        .port(0u16)
+                        .data_dir(&temp_dir_2)
+                        .spawn();
 
                     let provider1 = ProviderBuilder::new().on_http(geth1.endpoint_url());
                     let provider2 = ProviderBuilder::new().on_http(geth2.endpoint_url());