Fix empty toplevel batch bug and add step batch description

Author: jcwilk

lib/simplekiq.rb

@@ -7,6 +7,7 @@
 require "simplekiq/orchestration"
 require "simplekiq/orchestration_job"
 require "simplekiq/batching_job"
+require "simplekiq/batch_tracker_job"
 
 module Simplekiq
   class << self

lib/simplekiq/batch_tracker_job.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+# This job serves two purposes:
+# * TODO: It provides a convenient way to track top-level orchestration batches
+# * The top-level orchestration batch would otherwise be empty (aside from
+#   child-batches) and all sidekiq-pro batches must have at least 1 job
+
+module Simplekiq
+  class BatchTrackerJob
+    include Sidekiq::Worker
+
+    def perform(klass_name, bid, args)
+      # In the future, this will likely surface the toplevel batch to a callback method on the
+      # orchestration job. We're holding off on this until we have time to design a comprehensive
+      # plan for providing simplekiq-wide instrumentation, ideally while being backwards compatible
+      # for in-flight orchestrations.
+
+      # For now, it's just satisfying the all-batches-must-have-jobs limitation in sidekiq-pro
+      # described at the head of the file.
+    end
+  end
+end

lib/simplekiq/orchestration_executor.rb

@@ -12,6 +12,10 @@ def self.execute(args:, job:, workflow:)
       orchestration_batch.description = "#{job.class.name} Simplekiq orchestration"
       Simplekiq.auto_define_callbacks(orchestration_batch, args: args, job: job)
 
+      orchestration_batch.jobs do
+        Simplekiq::BatchTrackerJob.perform_async(job.class.name, orchestration_batch.bid, args)
+      end
+
       new.run_step(orchestration_batch, workflow, 0)
     end
 
@@ -20,12 +24,14 @@ def run_step(orchestration_batch, workflow, step)
       # This will never be empty because Orchestration#serialized_workflow skips inserting
       # a new step for in_parallel if there were no inner jobs specified.
 
+      next_step = step + 1
       orchestration_batch.jobs do
         step_batch = Sidekiq::Batch.new
+        step_batch.description = "Simplekiq orchestrated step #{next_step}"
         step_batch.on(
           "success",
           self.class,
-          {"orchestration_workflow" => workflow, "step" => step + 1}
+          {"orchestration_workflow" => workflow, "step" => next_step}
         )
 
         step_batch.jobs do

spec/orchestration_executor_spec.rb

@@ -23,11 +23,15 @@ def execute
       described_class.execute(args: ["some", "args"], job: job, workflow: workflow)
     end
 
-    it "kicks off the first step with a new batch" do
-      batch_double = instance_double(Sidekiq::Batch)
+    it "kicks off the first step with a new batch with the empty tracking batch inside it" do
+      batch_double = instance_double(Sidekiq::Batch, bid: 42)
       allow(Sidekiq::Batch).to receive(:new).and_return(batch_double)
       expect(batch_double).to receive(:description=).with("FakeOrchestration Simplekiq orchestration")
       expect(batch_double).to receive(:on).with("success", FakeOrchestration, "args" => ["some", "args"])
+      expect(batch_double).to receive(:jobs) do |&block|
+        expect(Simplekiq::BatchTrackerJob).to receive(:perform_async)
+        block.call
+      end
 
       instance = instance_double(Simplekiq::OrchestrationExecutor)
       allow(Simplekiq::OrchestrationExecutor).to receive(:new).and_return(instance)
@@ -69,6 +73,7 @@ def execute
         block.call
         batch_stack.shift
       end
+
       expect(step_batch).to receive(:jobs) do |&block|
         expect(batch_stack).to eq ["orchestration"]
         batch_stack.push("step")
@@ -86,6 +91,7 @@ def execute
         "orchestration_workflow" => workflow,
         "step" => 1
       })
+      expect(step_batch).to receive(:description=).with("Simplekiq orchestrated step 1")
 
       instance.run_step(orchestration_batch, workflow, 0)
     end