allow nomad to schedule based on the status of a client driver health check

Slight updates for go style

client/client.go

@@ -1006,15 +1006,15 @@ func (c *Client) updateNodeFromFingerprint(response *cstructs.FingerprintRespons
 		c.config.Node.Resources.Merge(response.Resources)
 	}
 
-	for name, new_val := range response.Drivers {
-		old_val := c.config.Node.Drivers[name]
-		if new_val.Equals(old_val) {
+	for name, newVal := range response.Drivers {
+		oldVal := c.config.Node.Drivers[name]
+		if newVal.Equals(oldVal) {
 			continue
 		}
-		if old_val == nil {
-			c.config.Node.Drivers[name] = new_val
+		if oldVal == nil {
+			c.config.Node.Drivers[name] = newVal
 		} else {
-			c.config.Node.Drivers[name].MergeFingerprintInfo(new_val)
+			c.config.Node.Drivers[name].MergeFingerprintInfo(newVal)
 		}
 	}
 	if nodeHasChanged {
@@ -1031,16 +1031,16 @@ func (c *Client) updateNodeFromHealthCheck(response *cstructs.HealthCheckRespons
 	nodeHasChanged := false
 
 	// update the node with the latest driver health information
-	for name, new_val := range response.Drivers {
-		old_val := c.config.Node.Drivers[name]
-		if new_val.Equals(old_val) {
+	for name, newVal := range response.Drivers {
+		oldVal := c.config.Node.Drivers[name]
+		if newVal.Equals(oldVal) {
 			continue
 		}
 		nodeHasChanged = true
-		if old_val == nil {
-			c.config.Node.Drivers[name] = new_val
+		if oldVal == nil {
+			c.config.Node.Drivers[name] = newVal
 		} else {
-			c.config.Node.Drivers[name].MergeHealthCheck(new_val)
+			c.config.Node.Drivers[name].MergeHealthCheck(newVal)
 		}
 	}
 

nomad/mock/mock.go

@@ -46,6 +46,7 @@ func Node() *structs.Node {
 				},
 			},
 		},
+		Drivers: make(map[string]*structs.DriverInfo),
 		Links: map[string]string{
 			"consul": "foobar.dc1",
 		},

scheduler/feasible.go

@@ -129,21 +129,37 @@ func (c *DriverChecker) Feasible(option *structs.Node) bool {
 func (c *DriverChecker) hasDrivers(option *structs.Node) bool {
 	for driver := range c.drivers {
 		driverStr := fmt.Sprintf("driver.%s", driver)
-		value, ok := option.Attributes[driverStr]
-		if !ok {
-			return false
-		}
 
-		enabled, err := strconv.ParseBool(value)
-		if err != nil {
-			c.ctx.Logger().
-				Printf("[WARN] scheduler.DriverChecker: node %v has invalid driver setting %v: %v",
-					option.ID, driverStr, value)
-			return false
-		}
+		// TODO this is a compatibility mechanism- as of Nomad 0.8, nodes have a
+		// DriverInfo that corresponds with every driver. As a Nomad server might
+		// be on a later version than a Nomad client, we need to check for
+		// compatibility here to verify the client supports this.
+		if option.Drivers != nil {
+			driverInfo := option.Drivers[driverStr]
+			if driverInfo == nil {
+				c.ctx.Logger().
+					Printf("[WARN] scheduler.DriverChecker: node %v has no driver info set for %v",
+						option.ID, driverStr)
+				return false
+			}
+			return driverInfo.Detected && driverInfo.Healthy
+		} else {
+			value, ok := option.Attributes[driverStr]
+			if !ok {
+				return false
+			}
 
-		if !enabled {
-			return false
+			enabled, err := strconv.ParseBool(value)
+			if err != nil {
+				c.ctx.Logger().
+					Printf("[WARN] scheduler.DriverChecker: node %v has invalid driver setting %v: %v",
+						option.ID, driverStr, value)
+				return false
+			}
+
+			if !enabled {
+				return false
+			}
 		}
 	}
 	return true

scheduler/feasible_test.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"reflect"
 	"testing"
+	"time"
 
 	"github.com/hashicorp/nomad/helper/uuid"
 	"github.com/hashicorp/nomad/nomad/mock"
@@ -125,6 +126,65 @@ func TestDriverChecker(t *testing.T) {
 	}
 }
 
+func TestDriverChecker_HealthChecks(t *testing.T) {
+	_, ctx := testContext(t)
+	nodes := []*structs.Node{
+		mock.Node(),
+		mock.Node(),
+		mock.Node(),
+	}
+	nodes[0].Attributes["driver.foo"] = "1"
+	nodes[0].Drivers["driver.foo"] = &structs.DriverInfo{
+		Detected:          true,
+		Healthy:           true,
+		HealthDescription: "running",
+		UpdateTime:        time.Now(),
+	}
+	nodes[1].Attributes["driver.bar"] = "1"
+	nodes[1].Drivers["driver.bar"] = &structs.DriverInfo{
+		Detected:          true,
+		Healthy:           false,
+		HealthDescription: "not running",
+		UpdateTime:        time.Now(),
+	}
+	nodes[2].Attributes["driver.baz"] = "0"
+	nodes[2].Drivers["driver.baz"] = &structs.DriverInfo{
+		Detected:          false,
+		Healthy:           false,
+		HealthDescription: "not running",
+		UpdateTime:        time.Now(),
+	}
+
+	testDrivers := []string{"foo", "bar", "baz"}
+	cases := []struct {
+		Node   *structs.Node
+		Result bool
+	}{
+		{
+			Node:   nodes[0],
+			Result: true,
+		},
+		{
+			Node:   nodes[1],
+			Result: false,
+		},
+		{
+			Node:   nodes[2],
+			Result: false,
+		},
+	}
+
+	for i, c := range cases {
+		drivers := map[string]struct{}{
+			testDrivers[i]: {},
+		}
+		checker := NewDriverChecker(ctx, drivers)
+		if act := checker.Feasible(c.Node); act != c.Result {
+			t.Fatalf("case(%d) failed: got %v; want %v", i, act, c.Result)
+		}
+	}
+}
+
 func TestConstraintChecker(t *testing.T) {
 	_, ctx := testContext(t)
 	nodes := []*structs.Node{