From 6afe3f8e6c1c1cbfe875749a975af58a6e0597b8 Mon Sep 17 00:00:00 2001
From: Mariusz Klochowicz <mariusz@klochowicz.com>
Date: Wed, 17 Nov 2021 15:27:26 +1030
Subject: [PATCH] Disallow calls to tokio::spawn outside dedicated extension
 trait

Prevent accidentally spawning a task that could outlive the actor system
and become a zombie.

Any long-lived task should be tied to its owner by keeping RemoteHandle around.
---
 daemon/clippy.toml      | 3 +++
 daemon/src/lib.rs       | 1 -
 daemon/src/tokio_ext.rs | 4 ++++
 3 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 daemon/clippy.toml

diff --git a/daemon/clippy.toml b/daemon/clippy.toml
new file mode 100644
index 0000000..1e152c1
--- /dev/null
+++ b/daemon/clippy.toml
@@ -0,0 +1,3 @@
+disallowed-methods = [
+  "tokio::spawn", # tasks can outlive the actor system, prefer spawn_with_handle()
+]
diff --git a/daemon/src/lib.rs b/daemon/src/lib.rs
index 7530aec..3f31aa0 100644
--- a/daemon/src/lib.rs
+++ b/daemon/src/lib.rs
@@ -1,6 +1,5 @@
 #![cfg_attr(not(test), warn(clippy::unwrap_used))]
 #![warn(clippy::disallowed_method)]
-
 use crate::db::load_all_cfds;
 use crate::maker_cfd::{FromTaker, NewTakerOnline};
 use crate::model::cfd::{Cfd, Order, UpdateCfdProposals};
diff --git a/daemon/src/tokio_ext.rs b/daemon/src/tokio_ext.rs
index f5783b2..c004af6 100644
--- a/daemon/src/tokio_ext.rs
+++ b/daemon/src/tokio_ext.rs
@@ -10,6 +10,8 @@ where
     F: Future<Output = Result<(), E>> + Send + 'static,
     E: fmt::Display,
 {
+    // we want to disallow calls to tokio::spawn outside FutureExt
+    #[allow(clippy::disallowed_method)]
     tokio::spawn(async move {
         if let Err(e) = future.await {
             tracing::warn!("Task failed: {:#}", e);
@@ -40,6 +42,8 @@ where
         Self: Future<Output = ()> + Send + 'static,
     {
         let (future, handle) = self.remote_handle();
+        // we want to disallow calls to tokio::spawn outside FutureExt
+        #[allow(clippy::disallowed_method)]
         tokio::spawn(future);
         handle
     }