From 32d1d12528d06025abb786ac6e33e862f24513e3 Mon Sep 17 00:00:00 2001
From: Jan Kattelans <jan@kattelans.dev>
Date: Thu, 1 Oct 2026 08:47:23 +0200
Subject: [PATCH] Ignore already-closed channels when shutting down publisher
 pools

A confirm timeout closes the channel and resets the confirms pool while
the channel is still checked out. On checkin the pool's shutdown block
closed it again, raising Bunny::ChannelAlreadyClosed. That masked the
PublishConfirmationTimeout, and the retry handler then retried it as a
connection error, risking a duplicate message.

Side effects:
- Confirm timeouts and nacks reach the caller and are not retried.
- A pool reset by another thread no longer makes a successful publish
  raise on checkin.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 CHANGELOG.md                             |  6 ++++
 Gemfile.lock                             |  4 +--
 lib/ears/publisher_channel_pool.rb       | 12 ++++++--
 lib/ears/version.rb                      |  2 +-
 spec/ears/publisher_channel_pool_spec.rb | 36 ++++++++++++++++++++++++
 5 files changed, 54 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 98154a8..474c6ce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## 0.26.1 (2026-10-01)
+
+### Fixed
+
+- Resetting a publisher channel pool while a closed channel is checked out no longer raises `Bunny::ChannelAlreadyClosed` on checkin. Previously this masked the original error (e.g. `PublishConfirmationTimeout`) and caused it to be retried as a connection error, which could duplicate a message.
+
 ## 0.26.0 (2026-06-01)
 
 - Upgrade `connection_pool` dependency to `~> 3.0`
diff --git a/Gemfile.lock b/Gemfile.lock
index b9382d3..08a8330 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    ears (0.26.0)
+    ears (0.26.1)
       bunny (>= 3.0.0)
       connection_pool (~> 3.0)
       json (>= 2.9.0)
@@ -102,7 +102,7 @@ CHECKSUMS
   bunny (3.3.0) sha256=85ef5562ec2b24f542e8fad69c4302d30d966fb79ff803dc9d0c398a4054672a
   connection_pool (3.0.2) sha256=33fff5ba71a12d2aa26cb72b1db8bba2a1a01823559fb01d29eb74c286e62e0a
   diff-lcs (1.6.2) sha256=9ae0d2cba7d4df3075fe8cd8602a8604993efc0dfa934cff568969efb1909962
-  ears (0.26.0)
+  ears (0.26.1)
   json (2.21.2) sha256=1f1d3b7cf2b3ba1a69beca0bb6db13d5438b80bff3cd54cdaaa620b9b07c1c6a
   language_server-protocol (3.17.0.6) sha256=5ef2c0c138f8267e1bc631d3328347d354f96724b0af22f2c79516120443b7f0
   lint_roller (1.1.0) sha256=2c0c845b632a7d172cb849cc90c1bce937a28c5c8ccccb50dfd46a485003cc87
diff --git a/lib/ears/publisher_channel_pool.rb b/lib/ears/publisher_channel_pool.rb
index 3bcb368..44171a9 100644
--- a/lib/ears/publisher_channel_pool.rb
+++ b/lib/ears/publisher_channel_pool.rb
@@ -34,8 +34,8 @@ def reset!
         @confirms_pool = nil
         @creator_pid = nil
 
-        std_pool&.shutdown(&:close)
-        cnf_pool&.shutdown(&:close)
+        std_pool&.shutdown { |channel| close_channel(channel) }
+        cnf_pool&.shutdown { |channel| close_channel(channel) }
         nil
       end
 
@@ -47,7 +47,7 @@ def reset_confirms_pool!
         cnf_pool = @confirms_pool
         @confirms_pool = nil
 
-        cnf_pool&.shutdown(&:close)
+        cnf_pool&.shutdown { |channel| close_channel(channel) }
         nil
       end
 
@@ -112,6 +112,12 @@ def validate_channel_health!(channel, confirms)
               'Channel is closed'
       end
 
+      def close_channel(channel)
+        channel.close
+      rescue Bunny::ChannelAlreadyClosed
+        nil
+      end
+
       def cleanup_closed_channel(channel)
         return unless channel.respond_to?(:close)
 
diff --git a/lib/ears/version.rb b/lib/ears/version.rb
index 9aba081..876a131 100644
--- a/lib/ears/version.rb
+++ b/lib/ears/version.rb
@@ -1,3 +1,3 @@
 module Ears
-  VERSION = '0.26.0'
+  VERSION = '0.26.1'
 end
diff --git a/spec/ears/publisher_channel_pool_spec.rb b/spec/ears/publisher_channel_pool_spec.rb
index 74beb5d..0db3801 100644
--- a/spec/ears/publisher_channel_pool_spec.rb
+++ b/spec/ears/publisher_channel_pool_spec.rb
@@ -84,6 +84,42 @@
       end
     end
 
+    context 'when the pool is reset while its channel is checked out and closed' do
+      let(:mock_channel) do
+        instance_double(Bunny::Channel, confirm_select: nil)
+      end
+
+      before do
+        allow(mock_channel).to receive(:open?).and_return(true, false)
+        allow(mock_channel).to receive(:close).and_raise(
+          Bunny::ChannelAlreadyClosed.new(
+            'cannot use a closed channel!',
+            mock_channel,
+          ),
+        )
+      end
+
+      it 'returns the result of the block' do
+        result =
+          described_class.with_channel(confirms: true) do
+            described_class.reset_confirms_pool!
+            :published
+          end
+
+        expect(result).to eq(:published)
+      end
+
+      it 'raises the error from the block' do
+        expect {
+          described_class.with_channel(confirms: true) do
+            described_class.reset_confirms_pool!
+            raise Ears::PublishConfirmationTimeout,
+                  'Confirmation timeout after 5.0s'
+          end
+        }.to raise_error(Ears::PublishConfirmationTimeout)
+      end
+    end
+
     context 'with confirms: false (default)' do
       it 'yields a channel from the standard pool' do
         allow(ConnectionPool).to receive(:new).and_return(mock_standard_pool)