BUGFIX: work correctly if process forks

lib/scheduler/defer.rb

@@ -3,11 +3,10 @@ module Scheduler
     def initialize
       @async = Rails.env != "test"
       @queue = Queue.new
-      @thread = Thread.new {
-        while true
-          do_work
-        end
-      }
+      @mutex = Mutex.new
+      @thread = nil
+      start_thread
+
     end
 
     # for test
@@ -17,6 +16,7 @@ module Scheduler
 
     def later(&blk)
       if @async
+        start_thread unless @thread.alive?
         @queue << [RailsMultisite::ConnectionManagement.current_db, blk]
       else
         blk.call
@@ -27,8 +27,24 @@ module Scheduler
       @thread.kill
     end
 
+    # test only
+    def stopped?
+      !@thread.alive?
+    end
+
     private
 
+    def start_thread
+      @mutex.synchronize do
+        return if @thread && @thread.alive?
+        @thread = Thread.new {
+          while true
+            do_work
+          end
+        }
+      end
+    end
+
     def do_work
       db, job = @queue.deq
       RailsMultisite::ConnectionManagement.establish_connection(db: db)

spec/components/scheduler/defer_spec.rb

@@ -23,6 +23,26 @@ describe Scheduler::Defer do
     @defer.stop!
   end
 
+  it "recovers from a crash / fork" do
+    s = nil
+    @defer.stop!
+    wait_for(10) do
+      @defer.stopped?
+    end
+    # hack allow thread to die
+    sleep 0.005
+
+    @defer.later do
+      s = "good"
+    end
+
+    wait_for(10) do
+      s == "good"
+    end
+
+    s.should == "good"
+  end
+
   it "can queue jobs properly" do
     s = nil