allocrunner: automatically stop batch types allocations. (#26)

Previously, when running batch type jobs (batch/sysbatch), the
allocs would run until the user initiated shutdown. This is not
how batch workloads run and caused load testing problems as nodes
would fill with running workload. This problem can be overcome by
using the "real" allocrunner, but adds resource overhead on the
nodesim process.

Automatically stopping batch workload mimics real work and allows
us to use the simulated allocrunner for a lighter overhead. This
means benchmarking can be cheaper and easier to run.

Author: jrasell

allocrunnersim/allocrunnersim.go

@@ -174,6 +174,24 @@ func (ar *simulatedAllocRunner) Run() {
 	ar.allocStateLock.Unlock()
 
 	ar.updateAllocAndSendUpdate(taskStates)
+
+	// Who wants to live forever?
+	//
+	// Batch and sysbatch jobs certainly don't, so after a little pause to
+	// simulate the allocation has done something, we stop it. This is useful
+	// for load testing, as we can continually dispatch jobs, without nodes
+	// becoming resource exhausted and still use the lighter-weight simulated
+	// alloc-runner.
+	//
+	// Other job types which are meant to run forever, must be stopped by a
+	// user initiated command.
+	switch ar.alloc.Job.Type {
+	case structs.JobTypeBatch, structs.JobTypeSysBatch:
+		go func() {
+			time.Sleep(5 * time.Second)
+			ar.stopAll()
+		}()
+	}
 }
 
 // updateAllocAndSendUpdate is a small helper that builds a new allocation