From 148e202fa3bf8ec2919635ace9e8733d4cbcf780 Mon Sep 17 00:00:00 2001
From: Brian Hardock <brian.hardock@fermyon.com>
Date: Wed, 5 Nov 2025 14:11:19 -0700
Subject: [PATCH] Allow configurable max buffer size for HTTP connections

Signed-off-by: Brian Hardock <brian.hardock@fermyon.com>
---
 crates/trigger-http/src/lib.rs                       | 11 +++++++++++
 crates/trigger-http/src/server.rs                    | 12 +++++++++++-
 .../src/runtimes/in_process_spin.rs                  |  2 +-
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/crates/trigger-http/src/lib.rs b/crates/trigger-http/src/lib.rs
index cc14d35f0c..2aaeb9582d 100644
--- a/crates/trigger-http/src/lib.rs
+++ b/crates/trigger-http/src/lib.rs
@@ -52,6 +52,10 @@ pub struct CliArgs {
     #[clap(long, env = "SPIN_TLS_KEY", requires = "tls-cert")]
     pub tls_key: Option<PathBuf>,
 
+    /// Sets the maximum buffer size (in bytes) for the HTTP connection. The minimum value allowed is 8192.
+    #[clap(long, env = "SPIN_HTTP1_MAX_BUF_SIZE")]
+    pub http1_max_buf_size: Option<usize>,
+
     #[clap(long = "find-free-port")]
     pub find_free_port: bool,
 }
@@ -78,6 +82,7 @@ pub struct HttpTrigger {
     listen_addr: SocketAddr,
     tls_config: Option<TlsConfig>,
     find_free_port: bool,
+    http1_max_buf_size: Option<usize>,
 }
 
 impl<F: RuntimeFactors> Trigger<F> for HttpTrigger {
@@ -88,12 +93,14 @@ impl<F: RuntimeFactors> Trigger<F> for HttpTrigger {
 
     fn new(cli_args: Self::CliArgs, app: &spin_app::App) -> anyhow::Result<Self> {
         let find_free_port = cli_args.find_free_port;
+        let http1_max_buf_size = cli_args.http1_max_buf_size;
 
         Self::new(
             app,
             cli_args.address,
             cli_args.into_tls_config(),
             find_free_port,
+            http1_max_buf_size,
         )
     }
 
@@ -117,6 +124,7 @@ impl HttpTrigger {
         listen_addr: SocketAddr,
         tls_config: Option<TlsConfig>,
         find_free_port: bool,
+        http1_max_buf_size: Option<usize>,
     ) -> anyhow::Result<Self> {
         Self::validate_app(app)?;
 
@@ -124,6 +132,7 @@ impl HttpTrigger {
             listen_addr,
             tls_config,
             find_free_port,
+            http1_max_buf_size,
         })
     }
 
@@ -136,12 +145,14 @@ impl HttpTrigger {
             listen_addr,
             tls_config,
             find_free_port,
+            http1_max_buf_size,
         } = self;
         let server = Arc::new(HttpServer::new(
             listen_addr,
             tls_config,
             find_free_port,
             trigger_app,
+            http1_max_buf_size,
         )?);
         Ok(server)
     }
diff --git a/crates/trigger-http/src/server.rs b/crates/trigger-http/src/server.rs
index 917f4c4fb6..6aa53f6fa2 100644
--- a/crates/trigger-http/src/server.rs
+++ b/crates/trigger-http/src/server.rs
@@ -58,6 +58,8 @@ pub struct HttpServer<F: RuntimeFactors> {
     listen_addr: SocketAddr,
     /// The TLS configuration for the server.
     tls_config: Option<TlsConfig>,
+    /// The maximum buffer size for an HTTP1 connection.
+    http1_max_buf_size: Option<usize>,
     /// Whether to find a free port if the specified port is already in use.
     find_free_port: bool,
     /// Request router.
@@ -77,6 +79,7 @@ impl<F: RuntimeFactors> HttpServer<F> {
         tls_config: Option<TlsConfig>,
         find_free_port: bool,
         trigger_app: TriggerApp<F>,
+        http1_max_buf_size: Option<usize>,
     ) -> anyhow::Result<Self> {
         // This needs to be a vec before building the router to handle duplicate routes
         let component_trigger_configs = trigger_app
@@ -139,6 +142,7 @@ impl<F: RuntimeFactors> HttpServer<F> {
             find_free_port,
             router,
             trigger_app,
+            http1_max_buf_size,
             component_trigger_configs,
             component_handler_types,
         })
@@ -491,7 +495,13 @@ impl<F: RuntimeFactors> HttpServer<F> {
         client_addr: SocketAddr,
     ) {
         task::spawn(async move {
-            if let Err(err) = Builder::new(TokioExecutor::new())
+            let mut server_builder = Builder::new(TokioExecutor::new());
+
+            if let Some(http1_max_buf_size) = self.http1_max_buf_size {
+                server_builder.http1().max_buf_size(http1_max_buf_size);
+            }
+
+            if let Err(err) = server_builder
                 .serve_connection(
                     TokioIo::new(stream),
                     service_fn(move |request| {
diff --git a/tests/testing-framework/src/runtimes/in_process_spin.rs b/tests/testing-framework/src/runtimes/in_process_spin.rs
index 5387ecbdf7..4656d272fa 100644
--- a/tests/testing-framework/src/runtimes/in_process_spin.rs
+++ b/tests/testing-framework/src/runtimes/in_process_spin.rs
@@ -104,7 +104,7 @@ async fn initialize_trigger(
     .await?;
 
     let app = spin_app::App::new("my-app", locked_app);
-    let trigger = HttpTrigger::new(&app, "127.0.0.1:80".parse().unwrap(), None, false)?;
+    let trigger = HttpTrigger::new(&app, "127.0.0.1:80".parse().unwrap(), None, false, None)?;
     let mut builder = TriggerAppBuilder::<_, FactorsBuilder>::new(trigger);
     let trigger_app = builder
         .build(