Make sure the library compiles for windows

systemd sockets are not applicable for windows. However compilation
should not fail on windows

README.md

@@ -1,4 +1,4 @@
-Create http server listening on unix sockets or systemd socket activated fds
+Create http server listening on unix sockets and systemd socket activated fds
 
 ## Quick Usage
 
@@ -17,36 +17,52 @@ Just replace `http.ListenAndServe` with `anyhttp.ListenAndServe`.
 
 Syntax
 
-    unix/<path to socket>
+    unix?path=<socket_path>&mode=<socket file mode>&remove_existing=<true|false>
 
 Examples
 
-    unix/relative/path.sock
-    unix//var/run/app/absolutepath.sock
+    unix?path=relative/path.sock
+    unix?path=/var/run/app/absolutepath.sock
+    unix?path=/run/app.sock&mode=600&remove_existing=false
+
+| option          | description                                    | default  |
+|-----------------|------------------------------------------------|----------|
+| path            | path to unix socket                            | Required |
+| mode            | socket file mode                               | 666      |
+| remove_existing | Whether to remove existing socket file or fail | true     |
 
 ### Systemd Socket activated fd:
 
 Syntax
 
-    sysd/fdidx/<fd index starting at 0>
-    sysd/fdname/<fd name set using FileDescriptorName socket setting >
+    sysd?idx=<fd index>&name=<fd name>&check_pid=<true|false>&unset_env=<true|false>&idle_timeout=<duration>
+
+Only one of `idx` or `name` has to be set
 
 Examples:
-    
+
     # First (or only) socket fd passed to app
-    sysd/fdidx/0
+    sysd?idx=0
 
     # Socket with FileDescriptorName
-    sysd/fdname/myapp
+    sysd?name=myapp
 
-    # Using default name
-    sysd/fdname/myapp.socket
+    # Using default name and auto shutdown if no requests received in last 30 minutes
+    sysd?name=myapp.socket&idle_timeout=30m
 
-### TCP port
+| option       | description                                                                                | default          |
+|--------------|--------------------------------------------------------------------------------------------|------------------|
+| name         | Name configured via FileDescriptorName or socket file name                                 | Required         |
+| idx          | FD Index. Actual fd num will be 3 + idx                                                    | Required         |
+| idle_timeout | time to wait before shutdown. [syntax][0]                                                  | no auto shutdown |
+| check_pid    | Check process PID matches LISTEN_PID                                                       | true             |
+| unset_env    | Unsets the LISTEN\* environment variables, so they don't get passed to any child processes | true             |
 
-If the address is a number less than 65536, it is assumed as a port and passed as `http.ListenAndServe(":<port>",...)`
+### TCP
 
-Anything else is directly passed to `http.ListenAndServe` as well. Below examples should work
+If the address is not one of above, it is assumed to be tcp and passed to `http.ListenAndServe`.
+
+Examples:
 
     :http
     :8888
@@ -59,4 +75,6 @@ https://pkg.go.dev/go.balki.me/anyhttp
 ### Related links
 
   * https://gist.github.com/teknoraver/5ffacb8757330715bcbcc90e6d46ac74#file-unixhttpd-go
-  * https://github.com/coreos/go-systemd/tree/main/activation
+  * https://github.com/coreos/go-systemd/tree/main/activation
+
+[0]: https://pkg.go.dev/time#ParseDuration

anyhttp.go

@@ -2,16 +2,34 @@
 package anyhttp
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io/fs"
 	"net"
 	"net/http"
+	"net/url"
 	"os"
 	"strconv"
 	"strings"
 	"sync"
-	"syscall"
+	"time"
+
+	"go.balki.me/anyhttp/idle"
+)
+
+// AddressType of the address passed
+type AddressType string
+
+var (
+	// UnixSocket - address is a unix socket, e.g. unix?path=/run/foo.sock
+	UnixSocket AddressType = "UnixSocket"
+	// SystemdFD - address is a systemd fd, e.g. sysd?name=myapp.socket
+	SystemdFD AddressType = "SystemdFD"
+	// TCP - address is a TCP address, e.g. :1234
+	TCP AddressType = "TCP"
+	// Unknown - address is not recognized
+	Unknown AddressType = "Unknown"
 )
 
 // UnixSocketConfig has the configuration for Unix socket
@@ -83,6 +101,8 @@ type SysdConfig struct {
 	CheckPID bool
 	// Unsets the LISTEN* environment variables, so they don't get passed to any child processes
 	UnsetEnv bool
+	// Shutdown http server if no requests received for below timeout
+	IdleTimeout *time.Duration
 }
 
 // DefaultSysdConfig has the default values for SysdConfig
@@ -129,16 +149,6 @@ func (u *UnixSocketConfig) GetListener() (net.Listener, error) {
 // StartFD is the starting file descriptor number
 const StartFD = 3
 
-func makeFdListener(fd int, name string) (net.Listener, error) {
-	fdFile := os.NewFile(uintptr(fd), name)
-	l, err := net.FileListener(fdFile)
-	if err != nil {
-		return nil, err
-	}
-	syscall.CloseOnExec(fd)
-	return l, nil
-}
-
 // GetListener returns the FileListener created with socketed activated fd
 func (s *SysdConfig) GetListener() (net.Listener, error) {
 
@@ -182,59 +192,86 @@ func (s *SysdConfig) GetListener() (net.Listener, error) {
 	return nil, errors.New("neither FDIndex nor FDName set")
 }
 
-// UnknownAddress Error is returned when address does not match any known syntax
-type UnknownAddress struct{}
+// GetListener is low level function for use with non-http servers. e.g. tcp, smtp
+// Caller should handle idle timeout if needed
+func GetListener(addr string) (net.Listener, AddressType, any /* cfg */, error) {
 
-func (u UnknownAddress) Error() string {
-	return "unknown address"
+	addrType, unixSocketConfig, sysdConfig, perr := parseAddress(addr)
+	if perr != nil {
+		return nil, Unknown, nil, perr
+	}
+	if unixSocketConfig != nil {
+		listener, err := unixSocketConfig.GetListener()
+		if err != nil {
+			return nil, Unknown, nil, err
+		}
+		return listener, addrType, unixSocketConfig, nil
+	} else if sysdConfig != nil {
+		listener, err := sysdConfig.GetListener()
+		if err != nil {
+			return nil, Unknown, nil, err
+		}
+		return listener, addrType, sysdConfig, nil
+	}
+	if addr == "" {
+		addr = ":http"
+	}
+	listener, err := net.Listen("tcp", addr)
+	return listener, TCP, nil, err
 }
 
-// GetListener gets a unix or systemd socket listener
-func GetListener(addr string) (net.Listener, error) {
-	if strings.HasPrefix(addr, "unix/") {
-		usc := NewUnixSocketConfig(strings.TrimPrefix(addr, "unix/"))
-		return usc.GetListener()
-	}
+type ServerCtx struct {
+	AddressType      AddressType
+	Listener         net.Listener
+	Server           *http.Server
+	Idler            idle.Idler
+	Done             <-chan error
+	UnixSocketConfig *UnixSocketConfig
+	SysdConfig       *SysdConfig
+}
 
-	if strings.HasPrefix(addr, "sysd/fdidx/") {
-		idx, err := strconv.Atoi(strings.TrimPrefix(addr, "sysd/fdidx/"))
-		if err != nil {
-			return nil, fmt.Errorf("invalid fdidx, addr:%q err: %w", addr, err)
-		}
-		sysdc := NewSysDConfigWithFDIdx(idx)
-		return sysdc.GetListener()
-	}
+func (s *ServerCtx) Wait() error {
+	return <-s.Done
+}
 
-	if strings.HasPrefix(addr, "sysd/fdname/") {
-		sysdc := NewSysDConfigWithFDName(strings.TrimPrefix(addr, "sysd/fdname/"))
-		return sysdc.GetListener()
-	}
+func (s *ServerCtx) Addr() net.Addr {
+	return s.Listener.Addr()
+}
 
-	return nil, UnknownAddress{}
+func (s *ServerCtx) Shutdown(ctx context.Context) error {
+	err := s.Server.Shutdown(ctx)
+	if err != nil {
+		return err
+	}
+	return <-s.Done
+}
+
+// ServeTLS creates and serves a HTTPS server.
+func ServeTLS(addr string, h http.Handler, certFile string, keyFile string) (*ServerCtx, error) {
+	return serve(addr, h, certFile, keyFile)
+}
+
+// Serve creates and serves a HTTP server.
+func Serve(addr string, h http.Handler) (*ServerCtx, error) {
+	return serve(addr, h, "", "")
 }
 
 // ListenAndServe is the drop-in replacement for `http.ListenAndServe`.
 // Supports unix and systemd sockets in addition
 func ListenAndServe(addr string, h http.Handler) error {
-
-	listener, err := GetListener(addr)
-	if _, isUnknown := err.(UnknownAddress); err != nil && !isUnknown {
+	ctx, err := Serve(addr, h)
+	if err != nil {
 		return err
 	}
+	return ctx.Wait()
+}
 
-	if listener != nil {
-		return http.Serve(listener, h)
+func ListenAndServeTLS(addr string, certFile string, keyFile string, h http.Handler) error {
+	ctx, err := ServeTLS(addr, h, certFile, keyFile)
+	if err != nil {
+		return err
 	}
-
-	if port, err := strconv.Atoi(addr); err == nil {
-		if port > 0 && port < 65536 {
-
-			return http.ListenAndServe(fmt.Sprintf(":%v", port), h)
-		}
-		return fmt.Errorf("invalid port: %v", port)
-	}
-
-	return http.ListenAndServe(addr, h)
+	return ctx.Wait()
 }
 
 // UnsetSystemdListenVars unsets the LISTEN* environment variables so they are not passed to any child processes
@@ -243,3 +280,150 @@ func UnsetSystemdListenVars() {
 	_ = os.Unsetenv("LISTEN_FDS")
 	_ = os.Unsetenv("LISTEN_FDNAMES")
 }
+
+func parseAddress(addr string) (addrType AddressType, usc *UnixSocketConfig, sysc *SysdConfig, err error) {
+	usc = nil
+	sysc = nil
+	err = nil
+	u, err := url.Parse(addr)
+	if err != nil {
+		return TCP, nil, nil, nil
+	}
+	if u.Path == "unix" {
+		duc := DefaultUnixSocketConfig
+		usc = &duc
+		addrType = UnixSocket
+		for key, val := range u.Query() {
+			if len(val) != 1 {
+				err = fmt.Errorf("unix socket address error. Multiple %v found: %v", key, val)
+				return
+			}
+			if key == "path" {
+				usc.SocketPath = val[0]
+			} else if key == "mode" {
+				if _, serr := fmt.Sscanf(val[0], "%o", &usc.SocketMode); serr != nil {
+					err = fmt.Errorf("unix socket address error. Bad mode: %v, err: %w", val, serr)
+					return
+				}
+			} else if key == "remove_existing" {
+				if removeExisting, berr := strconv.ParseBool(val[0]); berr == nil {
+					usc.RemoveExisting = removeExisting
+				} else {
+					err = fmt.Errorf("unix socket address error. Bad remove_existing: %v, err: %w", val, berr)
+					return
+				}
+			} else {
+				err = fmt.Errorf("unix socket address error. Bad option; key: %v, val: %v", key, val)
+				return
+			}
+		}
+		if usc.SocketPath == "" {
+			err = fmt.Errorf("unix socket address error. Missing path; addr: %v", addr)
+			return
+		}
+	} else if u.Path == "sysd" {
+		dsc := DefaultSysdConfig
+		sysc = &dsc
+		addrType = SystemdFD
+		for key, val := range u.Query() {
+			if len(val) != 1 {
+				err = fmt.Errorf("systemd socket fd address error. Multiple %v found: %v", key, val)
+				return
+			}
+			if key == "name" {
+				sysc.FDName = &val[0]
+			} else if key == "idx" {
+				if idx, ierr := strconv.Atoi(val[0]); ierr == nil {
+					sysc.FDIndex = &idx
+				} else {
+					err = fmt.Errorf("systemd socket fd address error. Bad idx: %v, err: %w", val, ierr)
+					return
+				}
+			} else if key == "check_pid" {
+				if checkPID, berr := strconv.ParseBool(val[0]); berr == nil {
+					sysc.CheckPID = checkPID
+				} else {
+					err = fmt.Errorf("systemd socket fd address error. Bad check_pid: %v, err: %w", val, berr)
+					return
+				}
+			} else if key == "unset_env" {
+				if unsetEnv, berr := strconv.ParseBool(val[0]); berr == nil {
+					sysc.UnsetEnv = unsetEnv
+				} else {
+					err = fmt.Errorf("systemd socket fd address error. Bad unset_env: %v, err: %w", val, berr)
+					return
+				}
+			} else if key == "idle_timeout" {
+				if timeout, terr := time.ParseDuration(val[0]); terr == nil {
+					sysc.IdleTimeout = &timeout
+				} else {
+					err = fmt.Errorf("systemd socket fd address error. Bad idle_timeout: %v, err: %w", val, terr)
+					return
+				}
+			} else {
+				err = fmt.Errorf("systemd socket fd address error. Bad option; key: %v, val: %v", key, val)
+				return
+			}
+		}
+		if (sysc.FDIndex == nil) == (sysc.FDName == nil) {
+			err = fmt.Errorf("systemd socket fd address error. Exactly only one of name and idx has to be set. name: %v, idx: %v", sysc.FDName, sysc.FDIndex)
+			return
+		}
+	} else {
+		// Just assume as TCP address
+		return TCP, nil, nil, nil
+	}
+	return
+}
+
+func serve(addr string, h http.Handler, certFile string, keyFile string) (*ServerCtx, error) {
+
+	serveFn := func() func(ctx *ServerCtx) error {
+		if certFile != "" {
+			return func(ctx *ServerCtx) error {
+				return ctx.Server.ServeTLS(ctx.Listener, certFile, keyFile)
+			}
+		}
+		return func(ctx *ServerCtx) error {
+			return ctx.Server.Serve(ctx.Listener)
+		}
+	}()
+	var ctx ServerCtx
+	var err error
+	var cfg any
+
+	ctx.Listener, ctx.AddressType, cfg, err = GetListener(addr)
+	if err != nil {
+		return nil, err
+	}
+	switch ctx.AddressType {
+	case UnixSocket:
+		ctx.UnixSocketConfig = cfg.(*UnixSocketConfig)
+	case SystemdFD:
+		ctx.SysdConfig = cfg.(*SysdConfig)
+	}
+	errChan := make(chan error)
+	ctx.Done = errChan
+	if ctx.AddressType == SystemdFD && ctx.SysdConfig.IdleTimeout != nil {
+		ctx.Idler = idle.CreateIdler(*ctx.SysdConfig.IdleTimeout)
+		ctx.Server = &http.Server{Handler: idle.WrapIdlerHandler(ctx.Idler, h)}
+		waitErrChan := make(chan error)
+		go func() {
+			waitErrChan <- serveFn(&ctx)
+		}()
+		go func() {
+			select {
+			case err := <-waitErrChan:
+				errChan <- err
+			case <-ctx.Idler.Chan():
+				errChan <- ctx.Server.Shutdown(context.TODO())
+			}
+		}()
+	} else {
+		ctx.Server = &http.Server{Handler: h}
+		go func() {
+			errChan <- serveFn(&ctx)
+		}()
+	}
+	return &ctx, nil
+}

anyhttp_test.go

@@ -0,0 +1,158 @@
+package anyhttp
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+	"time"
+)
+
+func Test_parseAddress(t *testing.T) {
+	tests := []struct {
+		name string // description of this test case
+		// Named input parameters for target function.
+		addr         string
+		wantAddrType AddressType
+		wantUsc      *UnixSocketConfig
+		wantSysc     *SysdConfig
+		wantErr      bool
+	}{
+		{
+			name:         "tcp port",
+			addr:         ":8080",
+			wantAddrType: TCP,
+			wantUsc:      nil,
+			wantSysc:     nil,
+			wantErr:      false,
+		},
+		{
+			name:         "unix address",
+			addr:         "unix?path=/run/foo.sock&mode=660",
+			wantAddrType: UnixSocket,
+			wantUsc: &UnixSocketConfig{
+				SocketPath:     "/run/foo.sock",
+				SocketMode:     0660,
+				RemoveExisting: true,
+			},
+			wantSysc: nil,
+			wantErr:  false,
+		},
+		{
+			name:         "systemd address",
+			addr:         "sysd?name=foo.socket",
+			wantAddrType: SystemdFD,
+			wantUsc:      nil,
+			wantSysc: &SysdConfig{
+				FDIndex:     nil,
+				FDName:      ptr("foo.socket"),
+				CheckPID:    true,
+				UnsetEnv:    true,
+				IdleTimeout: nil,
+			},
+			wantErr: false,
+		},
+		{
+			name:         "systemd address with index",
+			addr:         "sysd?idx=0&idle_timeout=30m",
+			wantAddrType: SystemdFD,
+			wantUsc:      nil,
+			wantSysc: &SysdConfig{
+				FDIndex:     ptr(0),
+				FDName:      nil,
+				CheckPID:    true,
+				UnsetEnv:    true,
+				IdleTimeout: ptr(30 * time.Minute),
+			},
+			wantErr: false,
+		},
+		{
+			name:         "systemd address. Bad example",
+			addr:         "sysd?idx=0&idle_timeout=30m&name=foo",
+			wantAddrType: SystemdFD,
+			wantUsc:      nil,
+			wantSysc:     nil,
+			wantErr:      true,
+		},
+		{
+			name:         "systemd address with check_pid and unset_env",
+			addr:         "sysd?idx=0&check_pid=false&unset_env=f",
+			wantAddrType: SystemdFD,
+			wantUsc:      nil,
+			wantSysc: &SysdConfig{
+				FDIndex:     ptr(0),
+				FDName:      nil,
+				CheckPID:    false,
+				UnsetEnv:    false,
+				IdleTimeout: nil,
+			},
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotAddrType, gotUsc, gotSysc, gotErr := parseAddress(tt.addr)
+			if gotErr != nil {
+				if !tt.wantErr {
+					t.Errorf("parseAddress() failed: %v", gotErr)
+				}
+				return
+			}
+			if tt.wantErr {
+				t.Fatal("parseAddress() succeeded unexpectedly")
+			}
+
+			if gotAddrType != tt.wantAddrType {
+				t.Errorf("parseAddress() addrType = %v, want %v", gotAddrType, tt.wantAddrType)
+			}
+
+			if !check(gotUsc, tt.wantUsc) {
+				t.Errorf("parseAddress() Usc = %v, want %v", gotUsc, tt.wantUsc)
+			}
+			if !check(gotSysc, tt.wantSysc) {
+				if (gotSysc == nil || tt.wantSysc == nil) ||
+					!(check(gotSysc.FDIndex, tt.wantSysc.FDIndex) &&
+						check(gotSysc.FDName, tt.wantSysc.FDName) &&
+						check(gotSysc.IdleTimeout, tt.wantSysc.IdleTimeout)) {
+					t.Errorf("parseAddress() Sysc = %v, want %v", asJSON(gotSysc), asJSON(tt.wantSysc))
+				}
+			}
+		})
+	}
+}
+
+func TestServe(t *testing.T) {
+	ctx, err := Serve("unix?path=/tmp/foo.sock", nil)
+	if err != nil {
+		t.Fatal()
+	}
+	if ctx.AddressType != UnixSocket {
+		t.Errorf("Serve() ServerCtx = %v, want %v", ctx.AddressType, UnixSocket)
+	}
+	ctx.Shutdown(context.TODO())
+}
+
+// Helpers
+
+// print value instead of pointer
+func asJSON[T any](val T) string {
+	op, err := json.Marshal(val)
+	if err != nil {
+		return err.Error()
+	}
+	return string(op)
+}
+
+func ptr[T any](val T) *T {
+	return &val
+}
+
+// nil safe equal check
+func check[T comparable](got, want *T) bool {
+	if (got == nil) != (want == nil) {
+		return false
+	}
+	if got == nil {
+		return true
+	}
+	return *got == *want
+}

examples/idle_server_shutdown/main.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"context"
+	"net/http"
+	"time"
+
+	"go.balki.me/anyhttp/idle"
+)
+
+func main() {
+	idler := idle.CreateIdler(10 * time.Second)
+
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		idler.Tick()
+		w.Write([]byte("Hey there!\n"))
+	})
+
+	http.HandleFunc("/job", func(w http.ResponseWriter, r *http.Request) {
+		go func() {
+			idler.Enter()
+			defer idler.Exit()
+
+			time.Sleep(15 * time.Second)
+		}()
+		w.Write([]byte("Job scheduled\n"))
+	})
+
+	server := http.Server{
+		Addr: ":8888",
+	}
+	go server.ListenAndServe()
+	idler.Wait()
+	server.Shutdown(context.TODO())
+}

examples/simple/main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net/http"
+	"os"
+	"time"
+
+	"go.balki.me/anyhttp"
+)
+
+func main() {
+
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("hello\n"))
+	})
+	//log.Println("Got error: ", anyhttp.ListenAndServe(os.Args[1], nil))
+	ctx, err := anyhttp.Serve(os.Args[1], nil)
+	log.Printf("Got ctx: %v\n,  err: %v", ctx, err)
+	log.Println(ctx.Addr())
+	if err != nil {
+		return
+	}
+	select {
+	case doneErr := <-ctx.Done:
+		log.Println(doneErr)
+	case <-time.After(1 * time.Minute):
+		log.Println("Awake")
+		ctx.Shutdown(context.TODO())
+	}
+}

fd_unix.go

@@ -0,0 +1,19 @@
+//go:build unix
+
+package anyhttp
+
+import (
+	"net"
+	"os"
+	"syscall"
+)
+
+func makeFdListener(fd int, name string) (net.Listener, error) {
+	fdFile := os.NewFile(uintptr(fd), name)
+	l, err := net.FileListener(fdFile)
+	if err != nil {
+		return nil, err
+	}
+	syscall.CloseOnExec(fd)
+	return l, nil
+}

fd_windows.go

@@ -0,0 +1,10 @@
+package anyhttp
+
+import (
+	"errors"
+	"net"
+)
+
+func makeFdListener(fd int, name string) (net.Listener, error) {
+	return nil, errors.New("windows not supported")
+}

idle/idle.go

@@ -0,0 +1,127 @@
+// Package idle helps to gracefully shutdown idle (typically http) servers
+package idle
+
+import (
+	"fmt"
+	"net/http"
+	"sync/atomic"
+	"time"
+)
+
+var (
+	// For simple servers without backgroud jobs, global singleton for simpler API
+	// Enter/Exit worn't work for global idler as Enter may be called before Wait, use CreateIdler in those cases
+	gIdler atomic.Pointer[idler]
+)
+
+// Wait waits till the server is idle and returns. i.e. no Ticks in last <timeout> duration
+func Wait(timeout time.Duration) error {
+	i := CreateIdler(timeout).(*idler)
+	ok := gIdler.CompareAndSwap(nil, i)
+	if !ok {
+		return fmt.Errorf("idler already waiting")
+	}
+	i.Wait()
+	return nil
+}
+
+// Tick records the current time. This will make the server not idle until next Tick or timeout
+func Tick() {
+	i := gIdler.Load()
+	if i != nil {
+		i.Tick()
+	}
+}
+
+// WrapHandler calls Tick() before processing passing request to http.Handler
+func WrapHandler(h http.Handler) http.Handler {
+	if h == nil {
+		h = http.DefaultServeMux
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		Tick()
+		h.ServeHTTP(w, r)
+	})
+}
+
+// WrapIdlerHandler calls idler.Tick() before processing passing request to http.Handler
+func WrapIdlerHandler(i Idler, h http.Handler) http.Handler {
+	if h == nil {
+		h = http.DefaultServeMux
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		i.Tick()
+		h.ServeHTTP(w, r)
+	})
+}
+
+// Idler helps manage idle servers
+type Idler interface {
+	// Tick records the current time. This will make the server not idle until next Tick or timeout
+	Tick()
+
+	// Wait waits till the server is idle and returns. i.e. no Ticks in last <timeout> duration
+	Wait()
+
+	// For long running background jobs, use Enter to record start time. Wait will not return while there are active jobs running
+	Enter()
+
+	// Exit records end of a background job
+	Exit()
+
+	// Get the channel to wait yourself
+	Chan() <-chan struct{}
+}
+
+type idler struct {
+	lastTick atomic.Pointer[time.Time]
+	c        chan struct{}
+	active   atomic.Int64
+}
+
+func (i *idler) Enter() {
+	i.active.Add(1)
+}
+
+func (i *idler) Exit() {
+	i.Tick()
+	i.active.Add(-1)
+}
+
+// CreateIdler creates an Idler with given timeout
+func CreateIdler(timeout time.Duration) Idler {
+	i := &idler{}
+	i.c = make(chan struct{})
+	i.Tick()
+	go func() {
+		for {
+			if i.active.Load() != 0 {
+				time.Sleep(timeout)
+				continue
+			}
+			t := *i.lastTick.Load()
+			now := time.Now()
+			dur := t.Add(timeout).Sub(now)
+			if dur == dur.Abs() {
+				time.Sleep(dur)
+				continue
+			}
+			break
+		}
+		close(i.c)
+	}()
+	return i
+}
+
+func (i *idler) Tick() {
+	now := time.Now()
+	i.lastTick.Store(&now)
+}
+
+func (i *idler) Wait() {
+	<-i.c
+}
+
+func (i *idler) Chan() <-chan struct{} {
+	return i.c
+}

idle/idle_test.go

@@ -0,0 +1,34 @@
+package idle
+
+import (
+	"testing"
+	"time"
+)
+
+func TestIdlerChan(_ *testing.T) {
+	i := CreateIdler(10 * time.Millisecond)
+	<-i.Chan()
+}
+
+func TestGlobalIdler(t *testing.T) {
+	err := Wait(10 * time.Millisecond)
+	if err != nil {
+		t.Fatalf("idle.Wait failed, %v", err)
+	}
+	err = Wait(10 * time.Millisecond)
+	if err == nil {
+		t.Fatal("idle.Wait should fail when called second time")
+	}
+}
+
+func TestIdlerEnterExit(t *testing.T) {
+	i := CreateIdler(10 * time.Millisecond).(*idler)
+	i.Enter()
+	if i.active.Load() != 1 {
+		t.FailNow()
+	}
+	i.Exit()
+	if i.active.Load() != 0 {
+		t.FailNow()
+	}
+}