renaming master/slave to parent/child

README.md

@@ -68,7 +68,7 @@ func prog(state overseer.State) {
 * The child process is provided with these files which is converted into a `Listener/s` for the `Program` to consume.
 * All child process pipes are connected back to the main process.
 * All signals received on the main process are forwarded through to the child process.
-* `Fetcher` runs in a goroutine and checks for updates at preconfigured interval. When `Fetcher` returns a valid binary stream (`io.Reader`), the master process saves it to a temporary location, verifies it, replaces the current binary and initiates a graceful restart.
+* `Fetcher` runs in a goroutine and checks for updates at pre-configured interval. When `Fetcher` returns a valid binary stream (`io.Reader`), the parent process saves it to a temporary location, verifies it, replaces the current binary and initiates a graceful restart.
 * The `fetcher.HTTP` accepts a `URL`, it polls this URL with HEAD requests and until it detects a change. On change, we `GET` the `URL` and stream it back out to `overseer`. See also `fetcher.S3`.
 * Once a binary is received, it is run with a simple echo token to confirm it is a `overseer` binary.
 * Except for scheduled restarts, the active child process exiting will cause the main process to exit with the same code. So, **`overseer` is not a process manager**.
@@ -150,7 +150,7 @@ func main() {
 
 ### Known issues
 
-* The master process's `overseer.Config` cannot be changed via an upgrade, the master process must be restarted.
+* The parent process's `overseer.Config` cannot be changed via an upgrade, the parent process must be restarted.
 	* Therefore, `Addresses` can only be changed by restarting the main process.
 * Currently shells out to `mv` for moving files because `mv` handles cross-partition moves unlike `os.Rename`.
 * Package `init()` functions will run twice on start, once in the main process and once in the child process.

example/go.sum

@@ -1,21 +1,10 @@
+github.com/StackExchange/wmi v0.0.0-20190523213315-cbe66965904d h1:G0m3OIz70MZUWq3EgK3CesDbo8upS2Vm9/P3FtgI+Jk=
 github.com/StackExchange/wmi v0.0.0-20190523213315-cbe66965904d/go.mod h1:3eOhrUMpNV+6aFIbp5/iudMxNCF27Vw2OZgy4xEx0Fg=
-github.com/aws/aws-sdk-go v1.29.34 h1:yrzwfDaZFe9oT4AmQeNNunSQA7c0m2chz0B43+bJ1ok=
-github.com/aws/aws-sdk-go v1.29.34/go.mod h1:1KvfttTE3SPKMpo8g2c6jL3ZKfXtFvKscTgahTma5Xg=
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-ole/go-ole v1.2.4 h1:nNBDSCOigTSiarFpYE9J/KtEA1IOW4CNeqT9TQDqCxI=
 github.com/go-ole/go-ole v1.2.4/go.mod h1:XCwSNxSkXRo4vlyPy93sltvi/qJq0jqQhjqQNIwKuxM=
-github.com/go-sql-driver/mysql v1.5.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
-github.com/jmespath/go-jmespath v0.0.0-20180206201540-c2b33e8439af h1:pmfjZENx5imkbgOkpRUYLnmbU7UEFbjtDA2hxJ1ichM=
-github.com/jmespath/go-jmespath v0.0.0-20180206201540-c2b33e8439af/go.mod h1:Nht3zPeWKUH0NzdCt2Blrr5ys8VGpn0CEB0cQHVjt7k=
-github.com/kardianos/osext v0.0.0-20190222173326-2bc1f35cddc0 h1:iQTw/8FWTuc7uiaSepXwyf3o52HaUYcV+Tu66S3F5GA=
-github.com/kardianos/osext v0.0.0-20190222173326-2bc1f35cddc0/go.mod h1:1NbS8ALrpOvjt0rHPNLyCIeMtbizbir8U//inJ+zuB8=
-github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
-github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/shirou/gopsutil v2.20.2+incompatible/go.mod h1:5b4v6he4MtMOwMlS0TUMTu2PcXUg8+E1lC7eC3UO/RA=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/net v0.0.0-20200202094626-16171245cfb2/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+github.com/jpillora/s3 v1.1.4 h1:YCCKDWzb/Ye9EBNd83ATRF/8wPEy0xd43Rezb6u6fzc=
+github.com/jpillora/s3 v1.1.4/go.mod h1:yedE603V+crlFi1Kl/5vZJaBu9pUzE9wvKegU/lF2zs=
+github.com/smartystreets/assertions v1.0.1 h1:voD4ITNjPL5jjBfgR/r8fPIIBrliWrWHeiJApdr3r4w=
+github.com/smartystreets/assertions v1.0.1/go.mod h1:kHHU4qYBaI3q23Pp3VPrmWhuIUrLW/7eUrw0BU5VaoM=
+github.com/smartystreets/gunit v1.1.3 h1:32x+htJCu3aMswhPw3teoJ+PnWPONqdNgaGs6Qt8ZaU=
+github.com/smartystreets/gunit v1.1.3/go.mod h1:EH5qMBab2UclzXUcpR8b93eHsIlp9u+pDQIRp5DZNzQ=

overseer.go

@@ -14,8 +14,8 @@ import (
 )
 
 const (
-	envSlaveID        = "OVERSEER_SLAVE_ID"
-	envIsSlave        = "OVERSEER_IS_SLAVE"
+	envChildID        = "OVERSEER_CHILD_ID"
+	envIsChild        = "OVERSEER_IS_CHILD"
 	envNumFDs         = "OVERSEER_NUM_FDS"
 	envBinID          = "OVERSEER_BIN_ID"
 	envBinPath        = "OVERSEER_BIN_PATH"
@@ -136,7 +136,7 @@ func SanityCheck() {
 	}
 }
 
-//abstraction over master/slave
+//abstraction over parent/child
 var currentProcess interface {
 	triggerRestart()
 	run() error
@@ -153,11 +153,11 @@ func runErr(c *Config) error {
 	if sanityCheck() {
 		return nil
 	}
-	//run either in master or slave mode
-	if os.Getenv(envIsSlave) == "1" {
-		currentProcess = &slave{Config: c}
+	//run either in parent or child mode
+	if os.Getenv(envIsChild) == "1" {
+		currentProcess = &child{Config: c}
 	} else {
-		currentProcess = &master{Config: c}
+		currentProcess = &parent{Config: c}
 	}
 	return currentProcess.run()
 }

proc_slave.go → proc_child.go

@@ -29,7 +29,7 @@ type State struct {
 	StartedAt time.Time
 	//Listener is the first net.Listener in Listeners
 	Listener net.Listener
-	//Listeners are the set of acquired sockets by the master
+	//Listeners are the set of acquired sockets by the parent
 	//process. These are all passed into this program in the
 	//same order they are specified in Config.Addresses.
 	Listeners []net.Listener
@@ -44,19 +44,19 @@ type State struct {
 	BinPath string
 }
 
-//a overseer slave process
+//a overseer child process
 
-type slave struct {
+type child struct {
 	*Config
 	id         string
 	listeners  []*overseerListener
-	masterPid  int
-	masterProc *os.Process
+	parentPid  int
+	parentProc *os.Process
 	state      State
 }
 
-func (sp *slave) run() error {
-	sp.id = os.Getenv(envSlaveID)
+func (sp *child) run() error {
+	sp.id = os.Getenv(envChildID)
 	sp.debugf("run")
 	sp.state.Enabled = true
 	sp.state.ID = os.Getenv(envBinID)
@@ -78,7 +78,7 @@ func (sp *slave) run() error {
 	return nil
 }
 
-func (sp *slave) initFileDescriptors() error {
+func (sp *child) initFileDescriptors() error {
 	//inspect file descriptors
 	numFDs, err := strconv.Atoi(os.Getenv(envNumFDs))
 	if err != nil {
@@ -102,26 +102,26 @@ func (sp *slave) initFileDescriptors() error {
 	return nil
 }
 
-func (sp *slave) watchSignal() {
+func (sp *child) watchSignal() {
 	signals := make(chan os.Signal)
 	signal.Notify(signals, sp.Config.RestartSignal)
 	go func() {
 		<-signals
 		signal.Stop(signals)
 		sp.debugf("graceful shutdown requested")
-		//master wants to restart,
+		//parent wants to restart,
 		close(sp.state.GracefulShutdown)
-		//release any sockets and notify master
+		//release any sockets and notify parent
 		if len(sp.listeners) > 0 {
 			//perform graceful shutdown
 			for _, l := range sp.listeners {
 				l.release(sp.Config.TerminateTimeout)
 			}
-			//signal release of held sockets, allows master to start
+			//signal release of held sockets, allows parent to start
 			//a new process before this child has actually exited.
 			//early restarts not supported with restarts disabled.
 			if !sp.NoRestart {
-				sp.masterProc.Signal(SIGUSR1)
+				sp.parentProc.Signal(SIGUSR1)
 			}
 			//listeners should be waiting on connections to close...
 		}
@@ -134,20 +134,20 @@ func (sp *slave) watchSignal() {
 	}()
 }
 
-func (sp *slave) triggerRestart() {
-	if err := sp.masterProc.Signal(sp.Config.RestartSignal); err != nil {
+func (sp *child) triggerRestart() {
+	if err := sp.parentProc.Signal(sp.Config.RestartSignal); err != nil {
 		os.Exit(1)
 	}
 }
 
-func (sp *slave) debugf(f string, args ...interface{}) {
+func (sp *child) debugf(f string, args ...interface{}) {
 	if sp.Config.Debug {
-		log.Printf("[overseer slave#"+sp.id+"] "+f, args...)
+		log.Printf("[overseer child#"+sp.id+"] "+f, args...)
 	}
 }
 
-func (sp *slave) warnf(f string, args ...interface{}) {
+func (sp *child) warnf(f string, args ...interface{}) {
 	if sp.Config.Debug || !sp.Config.NoWarn {
-		log.Printf("[overseer slave#"+sp.id+"] "+f, args...)
+		log.Printf("[overseer child#"+sp.id+"] "+f, args...)
 	}
 }

proc_child_others.go

@@ -0,0 +1,30 @@
+// +build !windows
+
+package overseer
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+	"time"
+)
+
+func (sp *child) watchParent() error {
+	sp.parentPid = os.Getppid()
+	proc, err := os.FindProcess(sp.parentPid)
+	if err != nil {
+		return fmt.Errorf("parent process: %s", err)
+	}
+	sp.parentProc = proc
+	go func() {
+		//send signal 0 to parent process forever
+		for {
+			//should not error as long as the process is alive
+			if err := sp.parentProc.Signal(syscall.Signal(0)); err != nil {
+				os.Exit(1)
+			}
+			time.Sleep(2 * time.Second)
+		}
+	}()
+	return nil
+}

proc_slave_windows.go → proc_child_windows.go

@@ -5,9 +5,10 @@ package overseer
 import (
 	"context"
 	"fmt"
-	"github.com/StackExchange/wmi"
 	"os"
 	"time"
+
+	"github.com/StackExchange/wmi"
 )
 
 var (
@@ -53,18 +54,18 @@ type Win32_Process struct {
 	WorkingSetSize        uint64
 }
 
-func (sp *slave) watchParent() error {
-	sp.masterPid = os.Getppid()
-	proc, err := os.FindProcess(sp.masterPid)
+func (cp *child) watchParent() error {
+	cp.parentPid = os.Getppid()
+	proc, err := os.FindProcess(cp.parentPid)
 	if err != nil {
-		return fmt.Errorf("master process: %s", err)
+		return fmt.Errorf("parent process: %s", err)
 	}
-	sp.masterProc = proc
+	cp.parentProc = proc
 	go func() {
-		//send signal 0 to master process forever
+		//send signal 0 to parent process forever
 		for {
 			//should not error as long as the process is alive
-			if _, err := GetWin32Proc(int32(sp.masterPid)); err != nil {
+			if _, err := GetWin32Proc(int32(cp.parentPid)); err != nil {
 				os.Exit(1)
 			}
 			time.Sleep(2 * time.Second)