From 4acae51c42c1aba57ca3a7c4b33dec4bbc5a8ff7 Mon Sep 17 00:00:00 2001
From: Stefan Kaes <stefan.kaes@xing.com>
Date: Thu, 20 Jul 2023 09:01:30 +0200
Subject: [PATCH] rescue IO::TimeoutError raised by Ruby since 3.2.0 on
 blocking reads/writes

One scenario in which this happens is when a firewall silently drops
connections between clients and memcached instances.

With this patch the client reopens the connection and the request succeeds.
Without it, IO:TimeoutError is raised for the application to handle which
deviates from Dalli behavior under Ruby 3.1 and earlier.
---
 lib/dalli/protocol.rb                    | 9 +++++++++
 lib/dalli/protocol/base.rb               | 2 +-
 lib/dalli/protocol/connection_manager.rb | 6 +++---
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/lib/dalli/protocol.rb b/lib/dalli/protocol.rb
index 1a7bac17..ef7983b1 100644
--- a/lib/dalli/protocol.rb
+++ b/lib/dalli/protocol.rb
@@ -4,5 +4,14 @@ module Dalli
   module Protocol
     # Preserved for backwards compatibility.  Should be removed in 4.0
     NOT_FOUND = ::Dalli::NOT_FOUND
+
+    # Ruby 3.2 raises IO::TimeoutError on blocking reads/writes, but
+    # it is not defined in earlier Ruby versions.
+    require 'timeout'
+    if defined?(IO::TimeoutError)
+      TIMEOUT_ERRORS = [Timeout::Error, IO::TimeoutError]
+    else
+      TIMEOUT_ERRORS = [Timeout::Error]
+    end
   end
 end
diff --git a/lib/dalli/protocol/base.rb b/lib/dalli/protocol/base.rb
index f5cffb6c..74274f80 100644
--- a/lib/dalli/protocol/base.rb
+++ b/lib/dalli/protocol/base.rb
@@ -106,7 +106,7 @@ def pipeline_next_responses
         end
 
         values
-      rescue SystemCallError, Timeout::Error, EOFError => e
+      rescue SystemCallError, *TIMEOUT_ERRORS, EOFError => e
         @connection_manager.error_on_request!(e)
       end
 
diff --git a/lib/dalli/protocol/connection_manager.rb b/lib/dalli/protocol/connection_manager.rb
index 0f5a01b6..27b514ce 100644
--- a/lib/dalli/protocol/connection_manager.rb
+++ b/lib/dalli/protocol/connection_manager.rb
@@ -150,19 +150,19 @@ def read_line
         data = @sock.gets("\r\n")
         error_on_request!('EOF in read_line') if data.nil?
         data
-      rescue SystemCallError, Timeout::Error, EOFError => e
+      rescue SystemCallError, *TIMEOUT_ERRORS, EOFError => e
         error_on_request!(e)
       end
 
       def read(count)
         @sock.readfull(count)
-      rescue SystemCallError, Timeout::Error, EOFError => e
+      rescue SystemCallError, *TIMEOUT_ERRORS, EOFError => e
         error_on_request!(e)
       end
 
       def write(bytes)
         @sock.write(bytes)
-      rescue SystemCallError, Timeout::Error => e
+      rescue SystemCallError, *TIMEOUT_ERRORS => e
         error_on_request!(e)
       end