From 4df56c77e380cdfec5e23862f7faa8bd843022e6 Mon Sep 17 00:00:00 2001
From: Matthew Holt <mholt@users.noreply.github.com>
Date: Wed, 13 May 2020 11:28:15 -0600
Subject: cmd: Add pidfile support (closes #3235)

---
 admin.go            | 23 ++++++++++++++++-------
 caddy.go            |  3 +++
 cmd/commandfuncs.go | 15 +++++++++++++++
 cmd/commands.go     |  6 ++++--
 4 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/admin.go b/admin.go
index 1d19066..e584a3b 100644
--- a/admin.go
+++ b/admin.go
@@ -21,6 +21,7 @@ import (
 	"expvar"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"net"
 	"net/http"
 	"net/http/pprof"
@@ -546,13 +547,6 @@ func handleUnload(w http.ResponseWriter, r *http.Request) error {
 			Err:  fmt.Errorf("method not allowed"),
 		}
 	}
-	currentCfgMu.RLock()
-	hasCfg := currentCfg != nil
-	currentCfgMu.RUnlock()
-	if !hasCfg {
-		Log().Named("admin.api").Info("nothing to unload")
-		return nil
-	}
 	Log().Named("admin.api").Info("unloading")
 	if err := stopAndCleanup(); err != nil {
 		Log().Named("admin.api").Error("error unloading", zap.Error(err))
@@ -801,12 +795,27 @@ var (
 	}
 )
 
+// PIDFile writes a pidfile to the file at filename. It
+// will get deleted before the process gracefully exits.
+func PIDFile(filename string) error {
+	pid := []byte(strconv.Itoa(os.Getpid()) + "\n")
+	err := ioutil.WriteFile(filename, pid, 0644)
+	if err != nil {
+		return err
+	}
+	pidfile = filename
+	return nil
+}
+
 // idRegexp is used to match ID fields and their associated values
 // in the config. It also matches adjacent commas so that syntax
 // can be preserved no matter where in the object the field appears.
 // It supports string and most numeric values.
 var idRegexp = regexp.MustCompile(`(?m),?\s*"` + idKey + `"\s*:\s*(-?[0-9]+(\.[0-9]+)?|(?U)".*")\s*,?`)
 
+// pidfile is the name of the pidfile, if any.
+var pidfile string
+
 const (
 	rawConfigKey = "config"
 	idKey        = "@id"
diff --git a/caddy.go b/caddy.go
index 1184bc9..0092641 100644
--- a/caddy.go
+++ b/caddy.go
@@ -470,6 +470,9 @@ func stopAndCleanup() error {
 		return err
 	}
 	certmagic.CleanUpOwnLocks()
+	if pidfile != "" {
+		os.Remove(pidfile)
+	}
 	return nil
 }
 
diff --git a/cmd/commandfuncs.go b/cmd/commandfuncs.go
index efdcfdc..f9e1033 100644
--- a/cmd/commandfuncs.go
+++ b/cmd/commandfuncs.go
@@ -41,6 +41,7 @@ import (
 func cmdStart(fl Flags) (int, error) {
 	startCmdConfigFlag := fl.String("config")
 	startCmdConfigAdapterFlag := fl.String("adapter")
+	startCmdPidfileFlag := fl.String("pidfile")
 	startCmdWatchFlag := fl.Bool("watch")
 
 	// open a listener to which the child process will connect when
@@ -71,6 +72,9 @@ func cmdStart(fl Flags) (int, error) {
 	if startCmdWatchFlag {
 		cmd.Args = append(cmd.Args, "--watch")
 	}
+	if startCmdPidfileFlag != "" {
+		cmd.Args = append(cmd.Args, "--pidfile", startCmdPidfileFlag)
+	}
 	stdinpipe, err := cmd.StdinPipe()
 	if err != nil {
 		return caddy.ExitCodeFailedStartup,
@@ -149,6 +153,7 @@ func cmdRun(fl Flags) (int, error) {
 	runCmdResumeFlag := fl.Bool("resume")
 	runCmdPrintEnvFlag := fl.Bool("environ")
 	runCmdWatchFlag := fl.Bool("watch")
+	runCmdPidfileFlag := fl.String("pidfile")
 	runCmdPingbackFlag := fl.String("pingback")
 
 	// if we are supposed to print the environment, do that first
@@ -225,6 +230,16 @@ func cmdRun(fl Flags) (int, error) {
 		go watchConfigFile(configFile, runCmdConfigAdapterFlag)
 	}
 
+	// create pidfile
+	if runCmdPidfileFlag != "" {
+		err := caddy.PIDFile(runCmdPidfileFlag)
+		if err != nil {
+			caddy.Log().Error("unable to write PID file",
+				zap.String("pidfile", runCmdPidfileFlag),
+				zap.Error(err))
+		}
+	}
+
 	// warn if the environment does not provide enough information about the disk
 	hasXDG := os.Getenv("XDG_DATA_HOME") != "" &&
 		os.Getenv("XDG_CONFIG_HOME") != "" &&
diff --git a/cmd/commands.go b/cmd/commands.go
index e02f6a0..5a40b1d 100644
--- a/cmd/commands.go
+++ b/cmd/commands.go
@@ -74,7 +74,7 @@ func init() {
 	RegisterCommand(Command{
 		Name:  "start",
 		Func:  cmdStart,
-		Usage: "[--config <path> [--adapter <name>]] [--watch]",
+		Usage: "[--config <path> [--adapter <name>]] [--watch] [--pidfile <file>]",
 		Short: "Starts the Caddy process in the background and then returns",
 		Long: `
 Starts the Caddy process, optionally bootstrapped with an initial config file.
@@ -87,6 +87,7 @@ using 'caddy run' instead to keep it in the foreground.`,
 			fs := flag.NewFlagSet("start", flag.ExitOnError)
 			fs.String("config", "", "Configuration file")
 			fs.String("adapter", "", "Name of config adapter to apply")
+			fs.String("pidfile", "", "Path of file to which to write process ID")
 			fs.Bool("watch", false, "Reload changed config file automatically")
 			return fs
 		}(),
@@ -95,7 +96,7 @@ using 'caddy run' instead to keep it in the foreground.`,
 	RegisterCommand(Command{
 		Name:  "run",
 		Func:  cmdRun,
-		Usage: "[--config <path> [--adapter <name>]] [--environ] [--watch]",
+		Usage: "[--config <path> [--adapter <name>]] [--environ] [--resume] [--watch] [--pidfile <fil>]",
 		Short: `Starts the Caddy process and blocks indefinitely`,
 		Long: `
 Starts the Caddy process, optionally bootstrapped with an initial config file,
@@ -132,6 +133,7 @@ development environment.`,
 			fs.Bool("environ", false, "Print environment")
 			fs.Bool("resume", false, "Use saved config, if any (and prefer over --config file)")
 			fs.Bool("watch", false, "Watch config file for changes and reload it automatically")
+			fs.String("pidfile", "", "Path of file to which to write process ID")
 			fs.String("pingback", "", "Echo confirmation bytes to this address on success")
 			return fs
 		}(),
-- 
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