Add caller_id to the context for cron workers

This always sets the caller_id to "Cronjob" for these workers, this
would otherwise be nil.

Sometimes we do call the cron worker from somewhere else, in this case
we don't want to overwrite the caller id.

app/workers/concerns/cronjob_queue.rb

@@ -10,4 +10,14 @@ module CronjobQueue
     sidekiq_options retry: false
     worker_context project: nil, namespace: nil, user: nil
   end
+
+  class_methods do
+    # Cronjobs never get scheduled with arguments, so this is safe to
+    # override
+    def context_for_arguments(_args)
+      return if Gitlab::ApplicationContext.current_context_include?('meta.caller_id')
+
+      Gitlab::ApplicationContext.new(caller_id: "Cronjob")
+    end
+  end
 end

lib/gitlab/application_context.rb

@@ -25,6 +25,10 @@ module Gitlab
       Labkit::Context.push(application_context.to_lazy_hash)
     end
 
+    def self.current_context_include?(attribute_name)
+      Labkit::Context.current.to_h.include?(Labkit::Context.log_key(attribute_name))
+    end
+
     def initialize(**args)
       unknown_attributes = args.keys - APPLICATION_ATTRIBUTES.map(&:name)
       raise ArgumentError, "#{unknown_attributes} are not known keys" if unknown_attributes.any?

spec/lib/gitlab/application_context_spec.rb

@@ -42,6 +42,18 @@ describe Gitlab::ApplicationContext do
     end
   end
 
+  describe '.current_context_include?' do
+    it 'returns true if the key was present in the context' do
+      described_class.with_context(caller_id: "Hello") do
+        expect(described_class.current_context_include?(:caller_id)).to be(true)
+      end
+    end
+
+    it 'returns false if the key was not present in the current context' do
+      expect(described_class.current_context_include?(:caller_id)).to be(false)
+    end
+  end
+
   describe '#to_lazy_hash' do
     let(:user) { build(:user) }
     let(:project) { build(:project) }

spec/workers/concerns/cronjob_queue_spec.rb

@@ -14,6 +14,10 @@ describe CronjobQueue do
     end
   end
 
+  before do
+    stub_const("DummyWorker", worker)
+  end
+
   it 'sets the queue name of a worker' do
     expect(worker.sidekiq_options['queue'].to_s).to eq('cronjob:dummy')
   end
@@ -29,4 +33,22 @@ describe CronjobQueue do
     expect(worker_context[:root_namespace]).to be_nil
     expect(worker_context[:project]).to be_nil
   end
+
+  it 'gets scheduled with caller_id set to Cronjob' do
+    worker.perform_async
+
+    job = worker.jobs.last
+
+    expect(job).to include('meta.caller_id' => 'Cronjob')
+  end
+
+  it 'does not set the caller_id if there was already one in the context' do
+    Gitlab::ApplicationContext.with_context(caller_id: 'already set') do
+      worker.perform_async
+    end
+
+    job = worker.jobs.last
+
+    expect(job).to include('meta.caller_id' => 'already set')
+  end
 end