Restart HeartbeatProcess on transient pipe errors

When the monitor subprocess exits unexpectedly (e.g. due to a transient
network/Redis error), @pipe.write raises IOError or Errno::EPIPE. With
abort_on_exception=true on the heartbeat thread, this killed the entire
worker mid-run, causing tests to be skipped.

HeartbeatProcess#tick! now catches these errors, restarts the subprocess
via a new restart! method, and retries up to MAX_RESTART_ATTEMPTS (3)
consecutive failures before re-raising. The counter resets on each
successful tick so transient errors don't exhaust the budget permanently.

Also adds mocha as a dev dependency and a dedicated test file covering
retry, restart, max-attempts, and counter-reset behaviour.

Author: ianks

ruby/Gemfile.lock

@@ -43,6 +43,8 @@ GEM
       builder
       minitest (>= 5.0)
       ruby-progressbar
+    mocha (3.1.0)
+      ruby2_keywords (>= 0.0.5)
     msgpack (1.8.0)
     parallel (1.27.0)
     parser (3.3.10.2)
@@ -86,6 +88,7 @@ GEM
       parser (>= 3.3.7.2)
       prism (~> 1.7)
     ruby-progressbar (1.13.0)
+    ruby2_keywords (0.0.5)
     securerandom (0.4.1)
     simplecov (0.22.0)
       docile (~> 1.1)
@@ -112,6 +115,7 @@ DEPENDENCIES
   ci-queue!
   minitest (~> 5.11)
   minitest-reporters (~> 1.1)
+  mocha
   msgpack
   rake
   redis

ruby/ci-queue.gemspec

@@ -40,6 +40,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'redis'
   spec.add_development_dependency 'simplecov', '~> 0.12'
   spec.add_development_dependency 'minitest-reporters', '~> 1.1'
+  spec.add_development_dependency 'mocha'
 
   spec.add_development_dependency 'rexml'
   spec.add_development_dependency 'snappy'

ruby/lib/ci/queue/redis/base.rb

@@ -264,6 +264,8 @@ def resolve_lua_includes(script, root)
         end
 
         class HeartbeatProcess
+          MAX_RESTART_ATTEMPTS = 3
+
           def initialize(redis_url, zset_key, owners_key, leases_key)
             @redis_url = redis_url
             @zset_key = zset_key
@@ -313,10 +315,28 @@ def shutdown!
 
           def tick!(id, lease)
             send_message(:tick!, id: id, lease: lease.to_s)
+            @restart_attempts = 0
+          rescue IOError, Errno::EPIPE => error
+            @restart_attempts = (@restart_attempts || 0) + 1
+            raise if @restart_attempts > MAX_RESTART_ATTEMPTS
+
+            restart!
+            retry
           end
 
           private
 
+          def restart!
+            @pipe.close rescue nil
+            begin
+              Process.kill(:TERM, @pid)
+              Process.waitpid2(@pid)
+            rescue Errno::ESRCH, Errno::ECHILD
+              nil
+            end
+            boot!
+          end
+
           def send_message(*message)
             payload = message.to_json
             @pipe.write([payload.bytesize].pack("L").b, payload)

ruby/test/ci/queue/redis/heartbeat_process_test.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+require 'test_helper'
+
+class CI::Queue::Redis::Base::HeartbeatProcessTest < Minitest::Test
+  MAX = CI::Queue::Redis::Base::HeartbeatProcess::MAX_RESTART_ATTEMPTS
+
+  def setup
+    @hp = CI::Queue::Redis::Base::HeartbeatProcess.new(
+      'redis://localhost:6379/0',
+      'zset', 'owners', 'leases'
+    )
+    # boot! and restart! must not spawn real processes
+    @hp.stubs(:boot!)
+    @hp.stubs(:restart!)
+  end
+
+  def test_tick_retries_after_pipe_ioerror
+    @hp.expects(:send_message).twice.raises(IOError, "closed stream").then.returns(nil)
+
+    @hp.tick!("test_id", "lease_id")
+  end
+
+  def test_tick_retries_after_epipe
+    @hp.expects(:send_message).twice.raises(Errno::EPIPE).then.returns(nil)
+
+    @hp.tick!("test_id", "lease_id")
+  end
+
+  def test_tick_calls_restart_on_pipe_error
+    @hp.stubs(:send_message).raises(IOError, "closed stream").then.returns(nil)
+    @hp.expects(:restart!).once
+
+    @hp.tick!("test_id", "lease_id")
+  end
+
+  def test_tick_raises_after_max_restart_attempts
+    @hp.stubs(:send_message).raises(IOError, "closed stream")
+
+    assert_raises(IOError) do
+      (MAX + 1).times { @hp.tick!("test_id", "lease_id") }
+    end
+  end
+
+  def test_restart_counter_resets_after_success
+    # Build a sequence: [raise, return] * (MAX+1).
+    # Without @restart_attempts = 0 on success, the (MAX+1)th failure would exceed MAX and raise.
+    stub = @hp.stubs(:send_message)
+    (MAX + 1).times do |i|
+      stub = stub.raises(IOError, "closed stream").then.returns(nil)
+      stub = stub.then unless i == MAX
+    end
+
+    (MAX + 1).times { @hp.tick!("test_id", "lease_id") }
+  end
+end

ruby/test/test_helper.rb

@@ -9,6 +9,7 @@
 require 'ci/queue/redis'
 require 'minitest/queue'
 require 'minitest/autorun'
+require 'mocha/minitest'
 
 Minitest::Reporters.use!([Minitest::Reporters::SpecReporter.new])