(PUP-12061) Handle changing splay in puppet.conf

Previously, enabling or disabling splay in puppet.conf did not work if the
agent was already running periodically.

If the agent was started with splay disabled, then enabling it would cause a
NoMethodError, when trying to call Puppet::Scheduler::Job#splay_limit

If the agent was started with splay enabled, then disabling it would have no
effect, since we never recalculated the splay limit.

To handle these cases, always create a SplayJob for the agent_run job and set
its splay_limit to either the limit or 0, depending on whether splay is enabled
or not. Setting a splay_limit to 0 causes the splay to also be set to 0 because
rand(1) always returns 0.

lib/puppet/daemon.rb

@@ -157,7 +157,9 @@ def remove_pidfile
 
   # Loop forever running events - or, at least, until we exit.
   def run_event_loop
-    agent_run = Puppet::Scheduler.create_job(Puppet[:runinterval], Puppet[:splay], Puppet[:splaylimit]) do |job|
+    splaylimit = Puppet[:splay] ? Puppet[:splaylimit] : 0
+
+    agent_run = Puppet::Scheduler.create_job(Puppet[:runinterval], true, splaylimit) do |job|
       if job.splay != 0
         Puppet.info "Running agent every #{job.run_interval} seconds with splay #{job.splay} of #{job.splay_limit} seconds"
       else
@@ -171,7 +173,7 @@ def run_event_loop
     reparse_run = Puppet::Scheduler.create_job(Puppet[:filetimeout]) do
       Puppet.settings.reparse_config_files
       agent_run.run_interval = Puppet[:runinterval]
-      agent_run.splay_limit = Puppet[:splaylimit] if Puppet[:splay]
+      agent_run.splay_limit = Puppet[:splay] ? Puppet[:splaylimit] : 0
       if Puppet[:filetimeout] == 0
         reparse_run.disable
       else

spec/unit/daemon_spec.rb

@@ -85,7 +85,7 @@ def run_loop(jobs)
 
     it "does not splay the agent run by default" do
       daemon.start
-      expect(agent_run).to be_an_instance_of(Puppet::Scheduler::Job)
+      expect(agent_run.splay).to eq(0)
     end
 
     describe "and calculating splay" do
@@ -115,6 +115,26 @@ def run_loop(jobs)
 
         expect(agent_run.splay).to eq(init_splay)
       end
+
+      it "recalculates when splay is enabled later" do
+        Puppet[:splay] = false
+        daemon.start
+
+        Puppet[:splay] = true
+        allow(agent_run).to receive(:rand).and_return(999)
+        reparse_run.run(Time.now)
+
+        expect(agent_run.splay).to eq(999)
+      end
+
+      it "sets splay to 0 when splay is disabled" do
+        daemon.start
+
+        Puppet[:splay] = false
+        reparse_run.run(Time.now)
+
+        expect(agent_run.splay).to eq(0)
+      end
     end
   end