refactor: move code for fetching an available port to the ports plugin

Also translate the code to golang.

docs/appendices/0.31.0-migration-guide.md

@@ -8,6 +8,7 @@
 - Users no longer need to clear the `source-image` git property when transitioning from image-based deploys (`git:from-image` and `git:load-image`) to other deployment methods (git push, `git:from-archive`, `git:sync`).
 - For deploys via the `git:from-image` and `git:load-image` commands, the `CHECKS` file is now extracted from the configured `WORKDIR` property of the image. For all other deploys - git push, `git:from-archive`, `git:sync` - will have the `CHECKS` extracted directly from the source code. The filename in both cases is `CHECKS` and cannot be modified.
 - The `common#get_app_raw_tcp_ports()` function has been deprecated and will be removed in the next release. Users should avoid interacting with this function for dockerfile ports and instead use the `ports-get` plugin trigger for fetching ports for an app.
+- The `common#get_available_port()` function has been deprecated and will be removed in the next release. Users should avoid interacting with this function and instead use the `ports-get-available` plugin trigger for fetching an available port.
 
 ## Deprecations
 

docs/development/plugin-triggers.md

@@ -1288,6 +1288,21 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 # TODO
 ```
 
+### `ports-get-available`
+
+- Description: Prints out an available port greater than 1024
+- Invoked by: Various networking plugins
+- Arguments `$APP`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+# TODO
+```
+
 ### `post-app-clone`
 
 - Description: Allows you to run commands after an app was cloned.

plugins/20_events/ports-get-available

@@ -0,0 +1 @@
+hook

plugins/common/functions

@@ -699,15 +699,8 @@ docker_cleanup() {
 
 get_available_port() {
   declare desc="returns first currently unused port > 1024"
-  while true; do
-    local port=$(shuf -i 1025-65535 -n 1)
-    if ! nc -z 0.0.0.0 "$port"; then
-      echo "$port"
-      return 0
-    else
-      continue
-    fi
-  done
+  dokku_log_warn "Deprecated: please use the 'ports-get-available' plugin trigger instead"
+  plugn trigger ports-get-available
 }
 
 dokku_auth() {

plugins/ports/Makefile

@@ -1,5 +1,5 @@
 SUBCOMMANDS = subcommands/list subcommands/add subcommands/clear subcommands/remove subcommands/set subcommands/report
-TRIGGERS = triggers/ports-clear triggers/ports-dockerfile-raw-tcp-ports triggers/ports-get triggers/post-certs-remove triggers/post-certs-update triggers/report
+TRIGGERS = triggers/ports-clear triggers/ports-dockerfile-raw-tcp-ports triggers/ports-get triggers/ports-get-available triggers/post-certs-remove triggers/post-certs-update triggers/report
 BUILD = commands subcommands triggers
 PLUGIN_NAME = ports
 

plugins/ports/functions.go

@@ -3,6 +3,7 @@ package ports
 import (
 	"errors"
 	"fmt"
+	"net"
 	"os"
 	"sort"
 	"strconv"
@@ -38,6 +39,26 @@ func filterAppPortMaps(appName string, scheme string, hostPort int) []PortMap {
 	return filteredPortMaps
 }
 
+func getAvailablePort() int {
+	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
+	if err != nil {
+		return 0
+	}
+
+	for {
+		l, err := net.ListenTCP("tcp", addr)
+		if err != nil {
+			return 0
+		}
+		defer l.Close()
+
+		port := l.Addr().(*net.TCPAddr).Port
+		if port >= 1025 && port <= 65535 {
+			return port
+		}
+	}
+}
+
 func getDockerfileRawTCPPorts(appName string) []int {
 	b, _ := common.PlugnTriggerOutput("config-get", []string{appName, "DOKKU_DOCKERFILE_PORTS"}...)
 	dockerfilePorts := strings.TrimSpace(string(b[:]))

plugins/ports/proxy-configure-ports

@@ -8,7 +8,7 @@ trigger-ports-proxy-configure-ports() {
   declare desc="ports proxy-configure-ports plugin trigger"
   declare trigger="proxy-configure-ports"
   declare APP="$1"
-  local RAW_TCP_PORTS="$(get_app_raw_tcp_ports "$APP")"
+  local RAW_TCP_PORTS="$(plugn trigger ports-dockerfile-raw-tcp-ports "$APP" | xargs)"
   local DOKKU_PROXY_PORT=$(config_get "$APP" DOKKU_PROXY_PORT)
   local DOKKU_PROXY_SSL_PORT=$(config_get "$APP" DOKKU_PROXY_SSL_PORT)
   local DOKKU_PROXY_PORT_MAP=$(config_get "$APP" DOKKU_PROXY_PORT_MAP)
@@ -20,7 +20,7 @@ trigger-ports-proxy-configure-ports() {
   if [[ -z "$DOKKU_PROXY_PORT" ]] && [[ -z "$RAW_TCP_PORTS" ]]; then
     if [[ "$IS_APP_VHOST_ENABLED" == "false" ]]; then
       dokku_log_info1 "No port set, setting to random open high port"
-      local PROXY_PORT=$(get_available_port)
+      local PROXY_PORT=$(plugn trigger ports-get-available)
     else
       local PROXY_PORT=$(config_get --global DOKKU_PROXY_PORT)
       PROXY_PORT=${PROXY_PORT:=80}
@@ -33,7 +33,7 @@ trigger-ports-proxy-configure-ports() {
       PROXY_SSL_PORT=${PROXY_SSL_PORT:=443}
       if [[ -z "$RAW_TCP_PORTS" ]] && [[ "$IS_APP_VHOST_ENABLED" == "false" ]]; then
         dokku_log_info1 "No ssl port set, setting to random open high port"
-        PROXY_SSL_PORT=$(get_available_port)
+        PROXY_SSL_PORT=$(plugn trigger ports-get-available)
       fi
       DOKKU_QUIET_OUTPUT=1 config_set --no-restart "$APP" DOKKU_PROXY_SSL_PORT="$PROXY_SSL_PORT"
     fi

plugins/ports/src/triggers/triggers.go

@@ -18,15 +18,17 @@ func main() {
 
 	var err error
 	switch trigger {
-	case "ports-get":
-		appName := flag.Arg(0)
-		err = ports.TriggerPortsGet(appName)
 	case "ports-clear":
 		appName := flag.Arg(0)
 		err = ports.TriggerPortsClear(appName)
 	case "ports-dockerfile-raw-tcp-ports":
 		appName := flag.Arg(0)
 		err = ports.TriggerPortsDockerfileRawTCPPorts(appName)
+	case "ports-get":
+		appName := flag.Arg(0)
+		err = ports.TriggerPortsGet(appName)
+	case "ports-get-available":
+		err = ports.TriggerPortsGetAvailable()
 	case "post-certs-remove":
 		appName := flag.Arg(0)
 		err = ports.TriggerPostCertsRemove(appName)

plugins/ports/triggers.go

@@ -35,6 +35,16 @@ func TriggerPortsGet(appName string) error {
 	return nil
 }
 
+// TriggerPortsGetAvailable prints out an available port greater than 1024
+func TriggerPortsGetAvailable() error {
+	port := getAvailablePort()
+	if port > 0 {
+		common.Log(fmt.Sprint(port))
+	}
+
+	return nil
+}
+
 // TriggerPostCertsRemove unsets port config vars after SSL cert is added
 func TriggerPostCertsRemove(appName string) error {
 	keys := []string{"DOKKU_PROXY_SSL_PORT"}