Allow to specify total memory on agent configuration

Allow to set the total memory of an agent in its configuration file. This
can be used in case the automatic detection doesn't work or in specific
environments when memory overcommit (using swap for example) can be
desirable.

client/config/config.go

@@ -91,6 +91,10 @@ type Config struct {
 	// dynamically. It should be given as Cores * MHz (2 Cores * 2 Ghz = 4000)
 	CpuCompute int
 
+	// MemoryMB is the default node total memory if it cannot be determined
+	// dynamically.
+	MemoryMB int
+
 	// MaxKillTimeout allows capping the user-specifiable KillTimeout. If the
 	// task's KillTimeout is greater than the MaxKillTimeout, MaxKillTimeout is
 	// used.

client/fingerprint/memory.go

@@ -24,19 +24,28 @@ func NewMemoryFingerprint(logger *log.Logger) Fingerprint {
 }
 
 func (f *MemoryFingerprint) Fingerprint(cfg *config.Config, node *structs.Node) (bool, error) {
-	memInfo, err := mem.VirtualMemory()
-	if err != nil {
-		f.logger.Printf("[WARN] Error reading memory information: %s", err)
-		return false, err
-	}
+	var totalMemory int
+
+	if cfg.MemoryMB != 0 {
+		totalMemory = cfg.MemoryMB
+	} else {
+		memInfo, err := mem.VirtualMemory()
+		if err != nil {
+			f.logger.Printf("[WARN] Error reading memory information: %s", err)
+			return false, err
+		}
 
-	if memInfo.Total > 0 {
-		node.Attributes["memory.totalbytes"] = fmt.Sprintf("%d", memInfo.Total)
+		if memInfo.Total > 0 {
+			node.Attributes["memory.totalbytes"] = fmt.Sprintf("%d", memInfo.Total)
+			totalMemory = int(memInfo.Total / 1024 / 1024)
+		}
+	}
 
+	if totalMemory > 0 {
 		if node.Resources == nil {
 			node.Resources = &structs.Resources{}
 		}
-		node.Resources.MemoryMB = int(memInfo.Total / 1024 / 1024)
+		node.Resources.MemoryMB = totalMemory
 	}
 
 	return true, nil

command/agent/agent.go

@@ -333,6 +333,9 @@ func (a *Agent) clientConfig() (*clientconfig.Config, error) {
 	if a.config.Client.CpuCompute != 0 {
 		conf.CpuCompute = a.config.Client.CpuCompute
 	}
+	if a.config.Client.MemoryMB != 0 {
+		conf.MemoryMB = a.config.Client.MemoryMB
+	}
 	if a.config.Client.MaxKillTimeout != "" {
 		dur, err := time.ParseDuration(a.config.Client.MaxKillTimeout)
 		if err != nil {

command/agent/config-test-fixtures/basic.hcl

@@ -40,6 +40,7 @@ client {
 	network_interface = "eth0"
 	network_speed = 100
 	cpu_total_compute = 4444
+	total_memory = 5555
 	reserved {
 		cpu = 10
 		memory = 10

command/agent/config.go

@@ -175,6 +175,9 @@ type ClientConfig struct {
 	// CpuCompute is used to override any detected or default total CPU compute.
 	CpuCompute int `mapstructure:"cpu_total_compute"`
 
+	// MemoryMB is used to override any detected or default total memory.
+	MemoryMB int `mapstructure:"total_memory"`
+
 	// MaxKillTimeout allows capping the user-specifiable KillTimeout.
 	MaxKillTimeout string `mapstructure:"max_kill_timeout"`
 
@@ -1079,6 +1082,9 @@ func (a *ClientConfig) Merge(b *ClientConfig) *ClientConfig {
 	if b.CpuCompute != 0 {
 		result.CpuCompute = b.CpuCompute
 	}
+	if b.MemoryMB != 0 {
+		result.MemoryMB = b.MemoryMB
+	}
 	if b.MaxKillTimeout != "" {
 		result.MaxKillTimeout = b.MaxKillTimeout
 	}

command/agent/config_parse.go

@@ -355,6 +355,7 @@ func parseClient(result **ClientConfig, list *ast.ObjectList) error {
 		"chroot_env",
 		"network_interface",
 		"network_speed",
+		"total_memory",
 		"cpu_total_compute",
 		"max_kill_timeout",
 		"client_max_port",

command/agent/config_parse_test.go

@@ -64,6 +64,7 @@ func TestConfig_Parse(t *testing.T) {
 					NetworkInterface: "eth0",
 					NetworkSpeed:     100,
 					CpuCompute:       4444,
+					MemoryMB:         5555,
 					MaxKillTimeout:   "10s",
 					ClientMinPort:    1000,
 					ClientMaxPort:    2000,

command/agent/config_test.go

@@ -84,6 +84,7 @@ func TestConfig_Merge(t *testing.T) {
 			},
 			NetworkSpeed:   100,
 			CpuCompute:     100,
+			MemoryMB:       200,
 			MaxKillTimeout: "20s",
 			ClientMaxPort:  19996,
 			Reserved: &Resources{
@@ -227,6 +228,7 @@ func TestConfig_Merge(t *testing.T) {
 			ClientMinPort:  22000,
 			NetworkSpeed:   105,
 			CpuCompute:     105,
+			MemoryMB:       205,
 			MaxKillTimeout: "50s",
 			Reserved: &Resources{
 				CPU:                 15,