From 4235b32a5c72154badebabe1f930be0e1f126007 Mon Sep 17 00:00:00 2001
From: Michael Schurter <mschurter@hashicorp.com>
Date: Wed, 19 Dec 2018 12:26:57 -0800
Subject: [PATCH] test: fix race in eval broker update chan

Similar to previous commits the delayed eval update chan was set and
access from different goroutines causing a race. Passing the chan on the
stack resolves the race.

Race output from `go test -race -run 'Server_RPC$'` in nomad/

```
==================
WARNING: DATA RACE
Write at 0x00c000339150 by goroutine 63:
  github.com/hashicorp/nomad/nomad.(*EvalBroker).flush()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/eval_broker.go:708
+0x3dc
  github.com/hashicorp/nomad/nomad.(*EvalBroker).SetEnabled()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/eval_broker.go:174
+0xc4
  github.com/hashicorp/nomad/nomad.(*Server).revokeLeadership()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/leader.go:718
+0x1fd
  github.com/hashicorp/nomad/nomad.(*Server).leaderLoop()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/leader.go:122
+0x95d
  github.com/hashicorp/nomad/nomad.(*Server).monitorLeadership.func1()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/leader.go:72
+0x6c

Previous read at 0x00c000339150 by goroutine 73:
  github.com/hashicorp/nomad/nomad.(*EvalBroker).runDelayedEvalsWatcher()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/eval_broker.go:771
+0x176

Goroutine 63 (running) created at:
  github.com/hashicorp/nomad/nomad.(*Server).monitorLeadership()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/leader.go:70
+0x269

Goroutine 73 (running) created at:
  github.com/hashicorp/nomad/nomad.(*EvalBroker).SetEnabled()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/eval_broker.go:170
+0x173
  github.com/hashicorp/nomad/nomad.(*Server).establishLeadership()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/leader.go:207
+0x355
  github.com/hashicorp/nomad/nomad.(*Server).leaderLoop()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/leader.go:117
+0x82e
  github.com/hashicorp/nomad/nomad.(*Server).monitorLeadership.func1()
      /home/schmichael/go/src/github.com/hashicorp/nomad/nomad/leader.go:72
+0x6c
==================
```
---
 nomad/eval_broker.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/nomad/eval_broker.go b/nomad/eval_broker.go
index e507a060c..d3dfdc61e 100644
--- a/nomad/eval_broker.go
+++ b/nomad/eval_broker.go
@@ -10,7 +10,7 @@ import (
 
 	"context"
 
-	"github.com/armon/go-metrics"
+	metrics "github.com/armon/go-metrics"
 	"github.com/hashicorp/nomad/helper/uuid"
 	"github.com/hashicorp/nomad/lib/delayheap"
 	"github.com/hashicorp/nomad/nomad/structs"
@@ -167,7 +167,7 @@ func (b *EvalBroker) SetEnabled(enabled bool) {
 		// start the go routine for delayed evals
 		ctx, cancel := context.WithCancel(context.Background())
 		b.delayedEvalCancelFunc = cancel
-		go b.runDelayedEvalsWatcher(ctx)
+		go b.runDelayedEvalsWatcher(ctx, b.delayedEvalsUpdateCh)
 	}
 	b.l.Unlock()
 	if !enabled {
@@ -741,7 +741,7 @@ func (d *evalWrapper) Namespace() string {
 
 // runDelayedEvalsWatcher is a long-lived function that waits till a time deadline is met for
 // pending evaluations before enqueuing them
-func (b *EvalBroker) runDelayedEvalsWatcher(ctx context.Context) {
+func (b *EvalBroker) runDelayedEvalsWatcher(ctx context.Context, updateCh <-chan struct{}) {
 	var timerChannel <-chan time.Time
 	var delayTimer *time.Timer
 	for {
@@ -768,7 +768,7 @@ func (b *EvalBroker) runDelayedEvalsWatcher(ctx context.Context) {
 			b.stats.TotalWaiting -= 1
 			b.enqueueLocked(eval, eval.Type)
 			b.l.Unlock()
-		case <-b.delayedEvalsUpdateCh:
+		case <-updateCh:
 			continue
 		}
 	}