From 35ed95ec5e1609b13393138e08d807c173411912 Mon Sep 17 00:00:00 2001
From: Russ Smith <russ@bashme.org>
Date: Mon, 22 Jun 2026 16:34:01 -0700
Subject: [PATCH] Close fiber_channel on Server#shutdown to avoid fiber leak.
 Fixes #110

During Server#shutdown the fiber_channel was never closed, so the
process_subscribed_messages fiber was left blocked on receive against an
orphaned channel. Since Cable.restart builds a fresh Server (with a fresh
channel) on every restart, each restart leaked a fiber and channel.

Close the channel at the end of shutdown, and switch the receive loop to
receive? so the fiber exits cleanly instead of raising Channel::ClosedError
on a closed channel.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BMW1EsdCMExBhm3tg7TQhs
---
 spec/cable/server_spec.cr | 19 +++++++++++++++++++
 src/cable/server.cr       |  5 ++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/spec/cable/server_spec.cr b/spec/cable/server_spec.cr
index a505ec0..4572be8 100644
--- a/spec/cable/server_spec.cr
+++ b/spec/cable/server_spec.cr
@@ -18,6 +18,25 @@ describe Cable::Server do
     end
   end
 
+  describe "#shutdown" do
+    it "closes the fiber_channel so the subscribed messages fiber doesn't leak" do
+      Cable.reset_server
+      Cable.temp_config(backend_class: Cable::DevBackend) do
+        server = Cable.server
+        server.fiber_channel.closed?.should be_false
+
+        server.shutdown
+
+        server.fiber_channel.closed?.should be_true
+        # Sending to the closed channel must raise rather than silently leak.
+        expect_raises(::Channel::ClosedError) do
+          server.fiber_channel.send({"foo", "bar"})
+        end
+      end
+      Cable.reset_server
+    end
+  end
+
   describe "#active_connections_for" do
     it "accurately returns active connections for a specificic token" do
       Cable.reset_server
diff --git a/src/cable/server.cr b/src/cable/server.cr
index 2e35744..4710286 100644
--- a/src/cable/server.cr
+++ b/src/cable/server.cr
@@ -195,6 +195,9 @@ module Cable
       connections_to_close.each do |connection|
         connection.close
       end
+      # Close the channel so the `process_subscribed_messages` fiber stops
+      # blocking on `receive` and exits cleanly instead of leaking across restarts.
+      fiber_channel.close
     end
 
     def restart?
@@ -210,7 +213,7 @@ module Cable
     private def process_subscribed_messages
       server = self
       spawn(name: "Cable::Server - process_subscribed_messages") do
-        while received = fiber_channel.receive
+        while received = fiber_channel.receive?
           channel, message = received
           if channel.starts_with?("cable_internal")
             identifier = channel.split('/').last