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server.go
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server.go
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// Package p9 adds a shutdown method to a [p9.Server].
package p9
import (
"context"
"errors"
"io"
"math/rand"
"net"
"sync"
"sync/atomic"
"time"
"github.com/djdv/go-filesystem-utils/internal/generic"
"github.com/hugelgupf/p9/p9"
manet "github.com/multiformats/go-multiaddr/net"
"github.com/u-root/uio/ulog"
)
type (
// NOTE: unfortunately we need to mock all the upstream options
// if we want to hijack the logger for our own use.
// ServerOpt is an optional config for a new server.
ServerOpt func(s *Server) p9.ServerOpt
// Server adds Close and Shutdown methods
// similar to [net/http.Server], for a [p9.Server].
Server struct {
shutdown atomic.Bool
log ulog.Logger
server *p9.Server
listeners listenerMap
connections connectionMap
idleDuration time.Duration
mu sync.Mutex
listenersWg sync.WaitGroup
}
// TrackedIO exposes metrics around an IO interface.
TrackedIO interface {
LastRead() time.Time
LastWrite() time.Time
io.ReadWriteCloser
}
trackedReads interface {
io.ReadCloser
LastRead() time.Time
}
trackedWrites interface {
io.WriteCloser
LastWrite() time.Time
}
trackedIOpair struct {
trackedReads
trackedWrites
}
postCloseFunc = func()
trackedReadCloser struct {
trackedReads
postCloseFn postCloseFunc
}
trackedWriteCloser struct {
trackedWrites
postCloseFn postCloseFunc
}
// The same notes in [net/http]'s pkg apply to us.
// Specifically; interfaces as keys will panic
// if the underlying type is unhashable;
// thus the pointer-to-interface.
listenerMap map[*manet.Listener]struct{}
connectionMap map[*trackedIOpair]struct{}
manetConn = manet.Conn
// TrackedConn records metrics
// of a network connection.
TrackedConn struct {
read, wrote *atomic.Pointer[time.Time]
manetConn
}
trackedReader struct {
last *atomic.Pointer[time.Time]
io.ReadCloser
}
trackedWriter struct {
last *atomic.Pointer[time.Time]
io.WriteCloser
}
// onceCloseListener wraps a net.Listener, protecting it from
// multiple Close calls. (Specifically in Serve; Close; Shutdown)
onceCloseListener struct {
manet.Listener
*onceCloser
}
// onceCloseIO wraps an [io.ReadWriteCloser],
// protecting it from multiple Close calls.
// This is necessary before passing to
// [p9.Server.Handle] (which implicitly calls close
// on both its arguments).
onceCloseIO struct {
io.ReadWriteCloser
*onceCloser
}
onceCloseTrackedIO struct {
TrackedIO
*onceCloser
}
onceCloser struct {
error
sync.Once
}
)
// ErrServerClosed may be returned by [Server.Serve] methods
// after [Server.Shutdown] or [Server.Close] is called.
const ErrServerClosed generic.ConstError = "p9: Server closed"
// NewServer wraps the
// [p9.NewServer] constructor.
func NewServer(attacher p9.Attacher, options ...ServerOpt) *Server {
const defaultIdleDuration = 30 * time.Second
var (
passthrough []p9.ServerOpt
srv = Server{
log: ulog.Null,
idleDuration: defaultIdleDuration,
}
)
for _, applyAndUnwrap := range options {
if relayedOpt := applyAndUnwrap(&srv); relayedOpt != nil {
passthrough = append(passthrough, relayedOpt)
}
}
srv.server = p9.NewServer(attacher, passthrough...)
return &srv
}
// WithServerLogger overrides the default logger for the server.
func WithServerLogger(l ulog.Logger) ServerOpt {
return func(s *Server) p9.ServerOpt {
s.log = l
return p9.WithServerLogger(l)
}
}
// WithIdleDuration sets the duration used by the server
// when evaluating connection idleness.
// If the time since the last connection operation
// exceeds the duration, it will be considered idle.
func WithIdleDuration(d time.Duration) ServerOpt {
return func(s *Server) p9.ServerOpt {
s.idleDuration = d
return nil
}
}
// Handle handles a single connection.
// If [TrackedIO] is passed in for either or both
// of the transmit and receive parameters, they will be
// asserted and re-used. This allows the [Server] and caller
// to share metrics without requiring extra overhead.
func (srv *Server) Handle(t io.ReadCloser, r io.WriteCloser) error {
var (
trackedT, trackedR = makeTrackedIO(t, r)
connection = &trackedIOpair{
trackedReads: trackedT,
trackedWrites: trackedR,
}
connections = srv.getConnections()
closedRead, closedWrite bool
deleteFn = func() {
srv.mu.Lock()
defer srv.mu.Unlock()
delete(connections, connection)
}
cleanupT = trackedReadCloser{
trackedReads: trackedT,
postCloseFn: func() {
closedRead = true
if closedWrite {
deleteFn()
}
},
}
cleanupR = trackedWriteCloser{
trackedWrites: trackedR,
postCloseFn: func() {
closedWrite = true
if closedRead {
deleteFn()
}
},
}
)
srv.mu.Lock()
connections[connection] = struct{}{}
srv.mu.Unlock()
// HACK: Despite having valid value methods,
// we pass an address because the 9P server
// uses the `%p` verb in its log's format string.
return srv.server.Handle(&cleanupT, &cleanupR)
}
func makeTrackedIO(rc io.ReadCloser, wc io.WriteCloser) (trackedReads, trackedWrites) {
var (
trackedR, rOk = rc.(trackedReads)
trackedW, wOK = wc.(trackedWrites)
needTimestamp = !rOk || !wOK
stamp *time.Time
)
if needTimestamp {
now := time.Now()
stamp = &now
}
if !rOk {
var (
ptr atomic.Pointer[time.Time]
tracked = trackedReader{
last: &ptr,
ReadCloser: rc,
}
)
ptr.Store(stamp)
trackedR = tracked
}
if !wOK {
var (
ptr atomic.Pointer[time.Time]
tracked = trackedWriter{
last: &ptr,
WriteCloser: wc,
}
)
ptr.Store(stamp)
trackedW = tracked
}
return trackedR, trackedW
}
func (srv *Server) getConnections() connectionMap {
if connections := srv.connections; connections != nil {
return connections
}
connections := make(connectionMap)
srv.connections = connections
return connections
}
// Serve handles requests from the listener.
//
// The passed listener _must_ be created in packet mode.
func (srv *Server) Serve(listener manet.Listener) error {
listener = onceCloseListener{
Listener: listener,
onceCloser: new(onceCloser),
}
trackToken, err := srv.trackListener(listener)
if err != nil {
return err
}
defer srv.dropListener(trackToken)
var (
handleFn = srv.Handle
handleConn = func(t io.ReadCloser, r io.WriteCloser) {
// If a connection fails, we'll just alert the operator.
// No need to accumulate these, nor take the whole server down.
if err := handleFn(t, r); err != nil &&
err != io.EOF {
if srv.shuttingDown() &&
errors.Is(err, net.ErrClosed) {
return // Shutdown expected, drop error.
}
srv.log.Printf("connection handler encountered an error: %s\n", err)
}
}
)
for {
connection, err := listener.Accept()
if err != nil {
if srv.shuttingDown() {
return errors.Join(ErrServerClosed, listener.Close())
}
return errors.Join(err, listener.Close())
}
go handleConn(splitConn(connection))
}
}
func splitConn(connection manet.Conn) (io.ReadCloser, io.WriteCloser) {
if tracked, ok := connection.(TrackedIO); ok {
closeConnOnce := onceCloseTrackedIO{
TrackedIO: tracked,
onceCloser: new(onceCloser),
}
return closeConnOnce, closeConnOnce
}
closeConnOnce := onceCloseIO{
ReadWriteCloser: connection,
onceCloser: new(onceCloser),
}
return closeConnOnce, closeConnOnce
}
func (srv *Server) shuttingDown() bool {
return srv.shutdown.Load()
}
func (srv *Server) trackListener(listener manet.Listener) (*manet.Listener, error) {
srv.mu.Lock()
defer srv.mu.Unlock()
if srv.shuttingDown() {
return nil, ErrServerClosed
}
var (
listeners = srv.listeners
lPtr = &listener
)
if listeners == nil {
listeners = make(listenerMap, 1)
srv.listeners = listeners
}
listeners[lPtr] = struct{}{}
srv.listenersWg.Add(1)
return lPtr, nil
}
func (srv *Server) dropListener(listener *manet.Listener) {
srv.mu.Lock()
defer srv.mu.Unlock()
delete(srv.listeners, listener)
srv.listenersWg.Done()
}
// Close requests the server to stop serving immediately.
// Listeners and connections associated with the server
// become closed by this call.
func (srv *Server) Close() error {
srv.shutdown.Store(true)
srv.mu.Lock()
defer srv.mu.Unlock()
err := srv.closeListenersLocked()
// NOTE: refer to [net/http.Server]
// implementation for lock sequence explanation.
srv.mu.Unlock()
srv.listenersWg.Wait()
srv.mu.Lock()
return errors.Join(err, srv.closeAllConns())
}
func (srv *Server) closeListenersLocked() error {
var errs []error
for listener := range srv.listeners {
if err := (*listener).Close(); err != nil {
errs = append(errs, err)
}
}
return errors.Join(errs...)
}
// Shutdown requests the server to stop accepting new request
// and eventually close.
// Listeners associated with the server become closed immediately,
// and connections become closed when they are considered idle.
// If the context is done, connections become closed immediately.
func (srv *Server) Shutdown(ctx context.Context) error {
srv.shutdown.Store(true)
srv.mu.Lock()
var errs []error
if err := srv.closeListenersLocked(); err != nil {
errs = append(errs, err)
}
// NOTE: refer to [net/http.Server]
// implementation for lock sequence explanation.
srv.mu.Unlock()
srv.listenersWg.Wait()
var (
nextPollInterval = makeJitterFunc(time.Millisecond)
timer = time.NewTimer(nextPollInterval())
)
defer timer.Stop()
for {
idle, err := srv.closeIdleConns()
if err != nil {
errs = append(errs, err)
}
if idle {
return errors.Join(errs...)
}
select {
case <-ctx.Done():
srv.mu.Lock()
defer srv.mu.Unlock()
errs = append([]error{ctx.Err()}, errs...)
if err := srv.closeAllConns(); err != nil {
errs = append(errs, err)
}
return errors.Join(errs...)
case <-timer.C:
timer.Reset(nextPollInterval())
}
}
}
func makeJitterFunc(initial time.Duration) func() time.Duration {
// Adapted from an inlined [net/http] closure.
const pollIntervalMax = 500 * time.Millisecond
return func() time.Duration {
// Add 10% jitter.
interval := initial +
time.Duration(rand.Intn(int(initial/10)))
// Double and clamp for next time.
initial *= 2
if initial > pollIntervalMax {
initial = pollIntervalMax
}
return interval
}
}
func (srv *Server) closeIdleConns() (allIdle bool, err error) {
srv.mu.Lock()
defer srv.mu.Unlock()
var (
errs []error
threshold = srv.idleDuration
)
allIdle = true
for connection := range srv.connections {
var (
lastActive = lastActive(connection)
isIdle = time.Since(lastActive) >= threshold
)
if !isIdle {
allIdle = false
continue
}
if err := connection.Close(); err != nil {
errs = append(errs, err)
}
delete(srv.connections, connection)
}
return allIdle, errors.Join(errs...)
}
func (srv *Server) closeAllConns() error {
var errs []error
for connection := range srv.connections {
if err := (*connection).Close(); err != nil {
errs = append(errs, err)
}
}
return errors.Join(errs...)
}
// NewTrackedConn wraps conn, providing operation metrics.
func NewTrackedConn(conn manet.Conn) TrackedConn {
var (
now = time.Now()
nowAddr = &now
read, wrote atomic.Pointer[time.Time]
tracked = TrackedConn{
read: &read,
wrote: &wrote,
manetConn: conn,
}
)
read.Store(nowAddr)
wrote.Store(nowAddr)
return tracked
}
// Read performs a read operation and updates the
// operation timestamp if successful.
func (tc TrackedConn) Read(b []byte) (int, error) {
return trackRead(tc.manetConn, tc.read, b)
}
// LastRead returns the timestamp of the last successful read.
func (tc TrackedConn) LastRead() time.Time {
return *tc.read.Load()
}
// Write performs a write operation and updates the
// operation timestamp if successful.
func (tc TrackedConn) Write(b []byte) (int, error) {
return trackWrite(tc.manetConn, tc.wrote, b)
}
// LastWrite returns the timestamp of the last successful write.
func (tc TrackedConn) LastWrite() time.Time {
return *tc.wrote.Load()
}
// Close closes the connection.
func (tc TrackedConn) Close() error {
return tc.manetConn.Close()
}
func (tr trackedReader) Read(b []byte) (int, error) {
return trackRead(tr.ReadCloser, tr.last, b)
}
func (tr trackedReader) LastRead() time.Time {
return *tr.last.Load()
}
func (tw trackedWriter) Write(b []byte) (int, error) {
return trackWrite(tw.WriteCloser, tw.last, b)
}
func (tw trackedWriter) LastWrite() time.Time {
return *tw.last.Load()
}
func (ol onceCloseListener) Close() error {
ol.Once.Do(func() { ol.error = ol.Listener.Close() })
return ol.error
}
func (oc onceCloseIO) Close() error {
oc.Once.Do(func() { oc.error = oc.ReadWriteCloser.Close() })
return oc.error
}
func (oc onceCloseTrackedIO) Close() error {
oc.Once.Do(func() { oc.error = oc.TrackedIO.Close() })
return oc.error
}
func trackRead(r io.Reader, stamp *atomic.Pointer[time.Time], b []byte) (int, error) {
read, err := r.Read(b)
if err != nil {
return read, err
}
now := time.Now()
stamp.Store(&now)
return read, nil
}
func trackWrite(w io.Writer, stamp *atomic.Pointer[time.Time], b []byte) (int, error) {
wrote, err := w.Write(b)
if err != nil {
return wrote, err
}
now := time.Now()
stamp.Store(&now)
return wrote, nil
}
func lastActive(tio TrackedIO) time.Time {
var (
read = tio.LastRead()
write = tio.LastWrite()
)
if read.After(write) {
return read
}
return write
}
func (ct *trackedIOpair) Close() error {
return errors.Join(
ct.trackedReads.Close(),
ct.trackedWrites.Close(),
)
}
func (trc trackedReadCloser) Close() error {
err := trc.trackedReads.Close()
trc.postCloseFn()
return err
}
func (twc trackedWriteCloser) Close() error {
err := twc.trackedWrites.Close()
twc.postCloseFn()
return err
}