rescue IO::TimeoutError raised by Ruby since 3.2.0 on blocking reads/…

…writes (#973)

* 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.

* trying to make Rubocop happy

* Shift require to address lint

* Add changelog entry

---------

Co-authored-by: Stefan Kaes <[email protected]>

CHANGELOG.md

@@ -4,6 +4,7 @@ Dalli Changelog
 Unreleased
 ==========
 
+- Rescue IO::TimeoutError raised by Ruby since 3.2.0 on blocking reads/writes (skaes)
 
 3.2.5
 ==========

lib/dalli/protocol.rb

@@ -1,8 +1,19 @@
 # frozen_string_literal: true
 
+require 'timeout'
+
 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.
+    TIMEOUT_ERRORS =
+      if defined?(IO::TimeoutError)
+        [Timeout::Error, IO::TimeoutError]
+      else
+        [Timeout::Error]
+      end
   end
 end

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
 

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