client: scan for drivers

client/client.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/hashicorp/nomad/client/driver"
 	"github.com/hashicorp/nomad/client/fingerprint"
 	"github.com/hashicorp/nomad/nomad"
 	"github.com/hashicorp/nomad/nomad/structs"
@@ -99,6 +100,11 @@ func NewClient(config *Config) (*Client, error) {
 	if err := c.fingerprint(); err != nil {
 		return nil, fmt.Errorf("fingerprinting failed: %v", err)
 	}
+
+	// Scan for drivers
+	if err := c.setupDrivers(); err != nil {
+		return nil, fmt.Errorf("driver setup failed: %v", err)
+	}
 	return c, nil
 }
 
@@ -239,3 +245,23 @@ func (c *Client) fingerprint() error {
 	c.logger.Printf("[DEBUG] client: applied fingerprints %v", applied)
 	return nil
 }
+
+// setupDrivers is used to find the available drivers
+func (c *Client) setupDrivers() error {
+	var avail []string
+	for name := range driver.BuiltinDrivers {
+		d, err := driver.NewDriver(name, c.logger)
+		if err != nil {
+			return err
+		}
+		applies, err := d.Fingerprint(c.config.Node)
+		if err != nil {
+			return err
+		}
+		if applies {
+			avail = append(avail, name)
+		}
+	}
+	c.logger.Printf("[DEBUG] client: available drivers %v", avail)
+	return nil
+}

client/client_test.go

@@ -126,3 +126,14 @@ func TestClient_Fingerprint(t *testing.T) {
 		t.Fatalf("missing arch")
 	}
 }
+
+func TestClient_Drivers(t *testing.T) {
+	c := testClient(t, nil)
+	defer c.Shutdown()
+
+	// Ensure os and arch are always present
+	node := c.Node()
+	if node.Attributes["driver.exec"] == "" {
+		t.Fatalf("missing exec driver")
+	}
+}

client/driver/exec.go

@@ -21,7 +21,8 @@ func NewExecDriver(logger *log.Logger) Driver {
 	return d
 }
 
-func (d *ExecDriver) Fingerprint(*structs.Node) (bool, error) {
+func (d *ExecDriver) Fingerprint(node *structs.Node) (bool, error) {
 	// We can always do a fork/exec
+	node.Attributes["driver.exec"] = "1"
 	return true, nil
 }

client/driver/exec_test.go

@@ -4,6 +4,8 @@ import (
 	"log"
 	"os"
 	"testing"
+
+	"github.com/hashicorp/nomad/nomad/structs"
 )
 
 func testLogger() *log.Logger {
@@ -12,11 +14,17 @@ func testLogger() *log.Logger {
 
 func TestExecDriver_Fingerprint(t *testing.T) {
 	d := NewExecDriver(testLogger())
-	apply, err := d.Fingerprint(nil)
+	node := &structs.Node{
+		Attributes: make(map[string]string),
+	}
+	apply, err := d.Fingerprint(node)
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}
 	if !apply {
 		t.Fatalf("should apply")
 	}
+	if node.Attributes["driver.exec"] == "" {
+		t.Fatalf("missing driver")
+	}
 }