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online_status_tracker.go
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online_status_tracker.go
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// Copyright 2019 Keybase Inc. All rights reserved.
// Use of this source code is governed by a BSD
// license that can be found in the LICENSE file.
package libkbfs
import (
"fmt"
"sync"
"time"
"github.com/keybase/client/go/logger"
"github.com/keybase/client/go/protocol/keybase1"
"golang.org/x/net/context"
)
type onlineStatusTracker struct {
cancel func()
config Config
onChange func()
log logger.Logger
lock sync.RWMutex
currentStatus keybase1.KbfsOnlineStatus
userIsLooking map[string]bool
userIn chan struct{}
userOut chan struct{}
wg *sync.WaitGroup
}
const ostTryingStateTimeout = 4 * time.Second
type ostState int
const (
_ ostState = iota
// We are connected to the mdserver, and user is looking at the Fs tab.
ostOnlineUserIn
// We are connected to the mdserver, and user is not looking at the Fs tab.
ostOnlineUserOut
// User is looking at the Fs tab. We are not connected to the mdserver, but
// we are showing a "trying" state in GUI. This usually lasts for
// ostTryingStateTimeout.
ostTryingUserIn
// User is not looking at the Fs tab. We are not connected to the mdserver,
// but we are telling GUI a "trying" state.
ostTryingUserOut
// User is looking at the Fs tab. We are disconnected from the mdserver and
// are telling GUI so.
ostOfflineUserIn
// User is not looking at the Fs tab. We are disconnected from the mdserver
// and are telling GUI so.
//
// Note that we can only go to ostOfflineUserOut from ostOfflineUserIn, but
// not from any other state. This is because when user is out we don't fast
// forward. Even if user has got good connection, we might still show as
// offline until user navigates into the Fs tab which triggers a fast
// forward and get us connected. If we were to show this state, user would
// see an offline screen flash for a second before actually getting
// connected every time they come back to the Fs tab with a previous bad
// (or lack of) connection, or even from backgrounded app. So instead, in
// this case we just use the trying state which shows a slim (less
// invasive) banner saying we are trying to reconnect. On the other hand,
// if user has seen the transition into offline, and user has remained
// disconnected, it'd be weird for them to see a "trying" state every time
// they switch away and back into the Fs tab. So in this case just keep the
// offline state, which is what ostOfflineUserOut is for.
ostOfflineUserOut
)
func (s ostState) String() string {
switch s {
case ostOnlineUserIn:
return "online-userIn"
case ostOnlineUserOut:
return "online-userOut"
case ostTryingUserIn:
return "trying-userIn"
case ostTryingUserOut:
return "trying-userOut"
case ostOfflineUserIn:
return "offline-userIn"
case ostOfflineUserOut:
return "offline-userOut"
default:
panic("unknown state")
}
}
func (s ostState) getOnlineStatus() keybase1.KbfsOnlineStatus {
switch s {
case ostOnlineUserIn:
return keybase1.KbfsOnlineStatus_ONLINE
case ostOnlineUserOut:
return keybase1.KbfsOnlineStatus_ONLINE
case ostTryingUserIn:
return keybase1.KbfsOnlineStatus_TRYING
case ostTryingUserOut:
return keybase1.KbfsOnlineStatus_TRYING
case ostOfflineUserIn:
return keybase1.KbfsOnlineStatus_OFFLINE
case ostOfflineUserOut:
return keybase1.KbfsOnlineStatus_OFFLINE
default:
panic("unknown state")
}
}
// ostSideEffect is a type for side effects that happens as a result of
// transitions happening inside the FSM. These side effects describe what
// should happen, but the FSM doesn't directly do them. The caller of outFsm
// should make sure those actions are carried out.
type ostSideEffect int
const (
// ostResetTimer describes a side effect where the timer for transitioning
// from a "trying" state into a "offline" state should be reset and
// started.
ostResetTimer ostSideEffect = iota
// ostStopTimer describes a side effect where the timer for transitioning
// from a "trying" state into a "offline" state should be stopped.
ostStopTimer
// ostFastForward describes a side effect where we should fast forward the
// reconnecting backoff timer and attempt to connect to the mdserver right
// away.
ostFastForward
)
func ostFsm(
ctx context.Context,
wg *sync.WaitGroup,
log logger.Logger,
initialState ostState,
// sideEffects carries events about side effects caused by the FSM
// transitions. Caller should handle these effects and make things actually
// happen.
sideEffects chan<- ostSideEffect,
// onlineStatusUpdates carries a special side effect for the caller to know
// when the onlineStatus changes.
onlineStatusUpdates chan<- keybase1.KbfsOnlineStatus,
// userIn is used to signify the FSM that user has just started looking at
// the Fs tab.
userIn <-chan struct{},
// userOut is used to signify the FSM that user has just switched away from
// the Fs tab.
userOut <-chan struct{},
// tryingTimerUp is used to signify the FSM that the timer for
// transitioning from a "trying" state to "offline" state is up.
tryingTimerUp <-chan struct{},
// connected is used to signify the FSM that we've just connected to the
// mdserver.
connected <-chan struct{},
// disconnected is used to signify the FSM that we've just lost connection to
// the mdserver.
disconnected <-chan struct{},
) {
defer wg.Done()
select {
case <-ctx.Done():
return
default:
}
log.CDebugf(ctx, "ostFsm initialState=%s", initialState)
state := initialState
for {
previousState := state
switch state {
case ostOnlineUserIn:
select {
case <-userIn:
case <-userOut:
state = ostOnlineUserOut
case <-tryingTimerUp:
case <-connected:
case <-disconnected:
state = ostTryingUserIn
sideEffects <- ostFastForward
sideEffects <- ostResetTimer
case <-ctx.Done():
return
}
case ostOnlineUserOut:
select {
case <-userIn:
state = ostOnlineUserIn
case <-userOut:
case <-tryingTimerUp:
case <-connected:
case <-disconnected:
state = ostTryingUserOut
// Don't start a timer as we don't want to transition into
// offline from trying when user is out. See comment for
// ostOfflineUserOut above.
case <-ctx.Done():
return
}
case ostTryingUserIn:
select {
case <-userIn:
case <-userOut:
state = ostTryingUserOut
// Stop the timer as we don't transition into offline when
// user is not looking.
sideEffects <- ostStopTimer
case <-tryingTimerUp:
state = ostOfflineUserIn
case <-connected:
state = ostOnlineUserIn
case <-disconnected:
case <-ctx.Done():
return
}
case ostTryingUserOut:
select {
case <-userIn:
state = ostTryingUserIn
sideEffects <- ostFastForward
sideEffects <- ostResetTimer
case <-userOut:
case <-tryingTimerUp:
// Don't transition into ostOfflineUserOut. See comment for
// offlienUserOut above.
case <-connected:
state = ostOnlineUserOut
case <-disconnected:
case <-ctx.Done():
return
}
case ostOfflineUserIn:
select {
case <-userIn:
case <-userOut:
state = ostOfflineUserOut
case <-tryingTimerUp:
case <-connected:
state = ostOnlineUserIn
case <-disconnected:
case <-ctx.Done():
return
}
case ostOfflineUserOut:
select {
case <-userIn:
state = ostOfflineUserIn
// Trigger fast forward but don't transition into "trying", to
// avoid flip-flopping.
sideEffects <- ostFastForward
case <-userOut:
case <-tryingTimerUp:
case <-connected:
state = ostOnlineUserOut
case <-disconnected:
case <-ctx.Done():
return
}
}
if previousState != state {
log.CDebugf(ctx, "ostFsm state=%s", state)
onlineStatus := state.getOnlineStatus()
if previousState.getOnlineStatus() != onlineStatus {
select {
case onlineStatusUpdates <- onlineStatus:
case <-ctx.Done():
return
}
}
}
}
}
func (ost *onlineStatusTracker) updateOnlineStatus(onlineStatus keybase1.KbfsOnlineStatus) {
ost.lock.Lock()
ost.currentStatus = onlineStatus
ost.lock.Unlock()
ost.onChange()
}
func (ost *onlineStatusTracker) run(ctx context.Context) {
defer ost.wg.Done()
for ost.config.KBFSOps() == nil {
time.Sleep(100 * time.Millisecond)
}
tryingStateTimer := time.NewTimer(time.Hour)
tryingStateTimer.Stop()
sideEffects := make(chan ostSideEffect)
onlineStatusUpdates := make(chan keybase1.KbfsOnlineStatus)
tryingTimerUp := make(chan struct{})
connected := make(chan struct{})
disconnected := make(chan struct{})
serviceErrors, invalidateChan := ost.config.KBFSOps().
StatusOfServices()
initialState := ostOfflineUserOut
if serviceErrors[MDServiceName] == nil {
initialState = ostOnlineUserOut
}
ost.wg.Add(1)
go ostFsm(ctx, ost.wg, ost.log,
initialState, sideEffects, onlineStatusUpdates,
ost.userIn, ost.userOut, tryingTimerUp, connected, disconnected)
ost.wg.Add(1)
// mdserver connection status watch routine
go func() {
defer ost.wg.Done()
invalidateChan := invalidateChan
var serviceErrors map[string]error
for {
select {
case <-invalidateChan:
serviceErrors, invalidateChan = ost.config.KBFSOps().
StatusOfServices()
if serviceErrors[MDServiceName] == nil {
connected <- struct{}{}
} else {
disconnected <- struct{}{}
}
case <-ctx.Done():
return
}
}
}()
for {
select {
case <-tryingStateTimer.C:
tryingTimerUp <- struct{}{}
case sideEffect := <-sideEffects:
switch sideEffect {
case ostResetTimer:
if !tryingStateTimer.Stop() {
select {
case <-tryingStateTimer.C:
default:
}
}
tryingStateTimer.Reset(ostTryingStateTimeout)
case ostStopTimer:
if !tryingStateTimer.Stop() {
<-tryingStateTimer.C
select {
case <-tryingStateTimer.C:
default:
}
}
case ostFastForward:
// This requires holding a lock and may block sometimes.
go ost.config.MDServer().FastForwardBackoff()
default:
panic(fmt.Sprintf("unknown side effect %d", sideEffect))
}
case onlineStatus := <-onlineStatusUpdates:
ost.updateOnlineStatus(onlineStatus)
ost.log.CDebugf(ctx, "ost onlineStatus=%d", onlineStatus)
case <-ctx.Done():
return
}
}
}
func (ost *onlineStatusTracker) userInOut(clientID string, clientIsIn bool) {
ost.lock.Lock()
wasIn := len(ost.userIsLooking) != 0
if clientIsIn {
ost.userIsLooking[clientID] = true
} else {
delete(ost.userIsLooking, clientID)
}
isIn := len(ost.userIsLooking) != 0
ost.lock.Unlock()
if wasIn && !isIn {
ost.userOut <- struct{}{}
}
if !wasIn && isIn {
ost.userIn <- struct{}{}
}
}
// UserIn tells the onlineStatusTracker that user is looking at the Fs tab in
// GUI. When user is looking at the Fs tab, the underlying RPC fast forwards
// any backoff timer for reconnecting to the mdserver.
func (ost *onlineStatusTracker) UserIn(ctx context.Context, clientID string) {
ost.userInOut(clientID, true)
ost.log.CDebugf(ctx, "UserIn clientID=%s", clientID)
}
// UserOut tells the onlineStatusTracker that user is not looking at the Fs
// tab in GUI anymore. GUI.
func (ost *onlineStatusTracker) UserOut(ctx context.Context, clientID string) {
ost.userInOut(clientID, false)
ost.log.CDebugf(ctx, "UserOut clientID=%s", clientID)
}
// GetOnlineStatus implements the OnlineStatusTracker interface.
func (ost *onlineStatusTracker) GetOnlineStatus() keybase1.KbfsOnlineStatus {
ost.lock.RLock()
defer ost.lock.RUnlock()
return ost.currentStatus
}
func newOnlineStatusTracker(
config Config, onChange func()) *onlineStatusTracker {
ctx, cancel := context.WithCancel(context.Background())
ost := &onlineStatusTracker{
cancel: cancel,
config: config,
onChange: onChange,
currentStatus: keybase1.KbfsOnlineStatus_ONLINE,
log: config.MakeLogger("onlineStatusTracker"),
userIsLooking: make(map[string]bool),
userIn: make(chan struct{}),
userOut: make(chan struct{}),
wg: &sync.WaitGroup{},
}
ost.wg.Add(1)
go ost.run(ctx)
return ost
}
func (ost *onlineStatusTracker) shutdown() {
ost.cancel()
ost.wg.Wait()
}