Add 'pid_file' config option (#3321)

* add pid_file config option

* address review feedback

* address review comments

command/server.go

@@ -660,6 +660,18 @@ CLUSTER_SYNTHESIS_COMPLETE:
 	// Release the log gate.
 	c.logGate.Flush()
 
+	// Write out the PID to the file now that server has successfully started
+	if err := c.storePidFile(config.PidFile); err != nil {
+		c.Ui.Output(fmt.Sprintf("Error storing PID: %v", err))
+		return 1
+	}
+
+	defer func() {
+		if err := c.removePidFile(config.PidFile); err != nil {
+			c.Ui.Output(fmt.Sprintf("Error deleting the PID file: %v", err))
+		}
+	}()
+
 	// Wait for shutdown
 	shutdownTriggered := false
 
@@ -1226,6 +1238,37 @@ func (c *ServerCommand) AutocompleteFlags() complete.Flags {
 	}
 }
 
+// storePidFile is used to write out our PID to a file if necessary
+func (c *ServerCommand) storePidFile(pidPath string) error {
+	// Quit fast if no pidfile
+	if pidPath == "" {
+		return nil
+	}
+
+	// Open the PID file
+	pidFile, err := os.OpenFile(pidPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
+	if err != nil {
+		return fmt.Errorf("could not open pid file: %v", err)
+	}
+	defer pidFile.Close()
+
+	// Write out the PID
+	pid := os.Getpid()
+	_, err = pidFile.WriteString(fmt.Sprintf("%d", pid))
+	if err != nil {
+		return fmt.Errorf("could not write to pid file: %v", err)
+	}
+	return nil
+}
+
+// removePidFile is used to cleanup the PID file if necessary
+func (c *ServerCommand) removePidFile(pidPath string) error {
+	if pidPath == "" {
+		return nil
+	}
+	return os.Remove(pidPath)
+}
+
 // MakeShutdownCh returns a channel that can be used for shutdown
 // notifications for commands. This channel will send a message for every
 // SIGINT or SIGTERM received.

command/server/config.go

@@ -47,6 +47,7 @@ type Config struct {
 
 	PluginDirectory string `hcl:"plugin_directory"`
 
+	PidFile              string      `hcl:"pid_file"`
 	EnableRawEndpoint    bool        `hcl:"-"`
 	EnableRawEndpointRaw interface{} `hcl:"raw_storage_endpoint"`
 }
@@ -302,6 +303,11 @@ func (c *Config) Merge(c2 *Config) *Config {
 		result.PluginDirectory = c2.PluginDirectory
 	}
 
+	result.PidFile = c.PidFile
+	if c2.PidFile != "" {
+		result.PidFile = c2.PidFile
+	}
+
 	return result
 }
 
@@ -399,6 +405,7 @@ func ParseConfig(d string, logger log.Logger) (*Config, error) {
 		"cluster_name",
 		"cluster_cipher_suites",
 		"plugin_directory",
+		"pid_file",
 		"raw_storage_endpoint",
 	}
 	if err := checkHCLKeys(list, valid); err != nil {

command/server/config_test.go

@@ -70,6 +70,8 @@ func TestLoadConfigFile(t *testing.T) {
 		DefaultLeaseTTL:    10 * time.Hour,
 		DefaultLeaseTTLRaw: "10h",
 		ClusterName:        "testcluster",
+
+		PidFile: "./pidfile",
 	}
 	if !reflect.DeepEqual(config, expected) {
 		t.Fatalf("expected \n\n%#v\n\n to be \n\n%#v\n\n", config, expected)
@@ -123,16 +125,16 @@ func TestLoadConfigFile_json(t *testing.T) {
 			CirconusBrokerSelectTag:            "",
 		},
 
-		MaxLeaseTTL:        10 * time.Hour,
-		MaxLeaseTTLRaw:     "10h",
-		DefaultLeaseTTL:    10 * time.Hour,
-		DefaultLeaseTTLRaw: "10h",
-		ClusterName:        "testcluster",
-		DisableCacheRaw:    interface{}(nil),
-		DisableMlockRaw:    interface{}(nil),
-		EnableUI:           true,
-		EnableUIRaw:        true,
-
+		MaxLeaseTTL:          10 * time.Hour,
+		MaxLeaseTTLRaw:       "10h",
+		DefaultLeaseTTL:      10 * time.Hour,
+		DefaultLeaseTTLRaw:   "10h",
+		ClusterName:          "testcluster",
+		DisableCacheRaw:      interface{}(nil),
+		DisableMlockRaw:      interface{}(nil),
+		EnableUI:             true,
+		EnableUIRaw:          true,
+		PidFile:              "./pidfile",
 		EnableRawEndpoint:    true,
 		EnableRawEndpointRaw: true,
 	}

command/server/test-fixtures/config.hcl

@@ -28,4 +28,5 @@ telemetry {
 max_lease_ttl = "10h"
 default_lease_ttl = "10h"
 cluster_name = "testcluster"
-raw_storage_endpoint = true
+pid_file = "./pidfile"
+raw_storage_endpoint = true

command/server/test-fixtures/config.hcl.json

@@ -18,5 +18,6 @@
 	"default_lease_ttl": "10h",
 	"cluster_name":"testcluster",
 	"ui":true,
+	"pid_file":"./pidfile",
 	"raw_storage_endpoint":true
 }

website/source/docs/configuration/index.html.md

@@ -109,6 +109,9 @@ to specify where the configuration is.
   the standard Vault API address will automatically redirect there. This can also
   be provided via the environment variable `VAULT_UI`.
 
+- `pid_file` `(string: "")` - Path to the file in which the Vault server's
+  Process ID (PID) should be stored.
+
 [storage-backend]: /docs/configuration/storage/index.html
 [listener]: /docs/configuration/listener/index.html
 [telemetry]: /docs/configuration/telemetry.html