micro/router/default.go

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package router
import (
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"errors"
"fmt"
"math"
"sort"
"strings"
"sync"
"time"
"github.com/google/uuid"
"github.com/micro/go-micro/v2/registry"
"github.com/micro/go-micro/v2/util/log"
)
var (
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// AdvertiseEventsTick is time interval in which the router advertises route updates
AdvertiseEventsTick = 10 * time.Second
// DefaultAdvertTTL is default advertisement TTL
DefaultAdvertTTL = 2 * time.Minute
// AdvertSuppress is advert suppression threshold
AdvertSuppress = 200.0
// AdvertRecover is advert recovery threshold
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AdvertRecover = 20.0
// Penalty for routes processed multiple times
Penalty = 100.0
// PenaltyHalfLife is the time the advert penalty decays to half its value
PenaltyHalfLife = 30.0
// MaxSuppressTime defines time after which the suppressed advert is deleted
MaxSuppressTime = 90 * time.Second
// PenaltyDecay is a coefficient which controls the speed the advert penalty decays
PenaltyDecay = math.Log(2) / PenaltyHalfLife
)
// router implements default router
type router struct {
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sync.RWMutex
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running bool
table *table
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options Options
exit chan bool
eventChan chan *Event
// advert subscribers
sub sync.RWMutex
subscribers map[string]chan *Advert
}
// newRouter creates new router and returns it
func newRouter(opts ...Option) Router {
// get default options
options := DefaultOptions()
// apply requested options
for _, o := range opts {
o(&options)
}
return &router{
options: options,
table: newTable(),
subscribers: make(map[string]chan *Advert),
}
}
// Init initializes router with given options
func (r *router) Init(opts ...Option) error {
r.Lock()
defer r.Unlock()
for _, o := range opts {
o(&r.options)
}
return nil
}
// Options returns router options
func (r *router) Options() Options {
r.RLock()
defer r.RUnlock()
options := r.options
return options
}
// Table returns routing table
func (r *router) Table() Table {
return r.table
}
// manageRoute applies action on a given route
func (r *router) manageRoute(route Route, action string) error {
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switch action {
case "create":
if err := r.table.Create(route); err != nil && err != ErrDuplicateRoute {
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return fmt.Errorf("failed adding route for service %s: %s", route.Service, err)
}
case "delete":
if err := r.table.Delete(route); err != nil && err != ErrRouteNotFound {
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return fmt.Errorf("failed deleting route for service %s: %s", route.Service, err)
}
case "update":
if err := r.table.Update(route); err != nil {
return fmt.Errorf("failed updating route for service %s: %s", route.Service, err)
}
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default:
return fmt.Errorf("failed to manage route for service %s: unknown action %s", route.Service, action)
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}
return nil
}
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// manageServiceRoutes applies action to all routes of the service.
// It returns error of the action fails with error.
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func (r *router) manageRoutes(service *registry.Service, action string) error {
// action is the routing table action
action = strings.ToLower(action)
// take route action on each service node
for _, node := range service.Nodes {
route := Route{
Service: service.Name,
Address: node.Address,
Gateway: "",
Network: r.options.Network,
Router: r.options.Id,
Link: DefaultLink,
Metric: DefaultLocalMetric,
}
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if err := r.manageRoute(route, action); err != nil {
return err
}
}
return nil
}
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// manageRegistryRoutes applies action to all routes of each service found in the registry.
// It returns error if either the services failed to be listed or the routing table action fails.
func (r *router) manageRegistryRoutes(reg registry.Registry, action string) error {
services, err := reg.ListServices()
if err != nil {
return fmt.Errorf("failed listing services: %v", err)
}
// add each service node as a separate route
for _, service := range services {
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// get the service to retrieve all its info
srvs, err := reg.GetService(service.Name)
if err != nil {
continue
}
// manage the routes for all returned services
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for _, srv := range srvs {
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if err := r.manageRoutes(srv, action); err != nil {
return err
}
}
}
return nil
}
// watchRegistry watches registry and updates routing table based on the received events.
// It returns error if either the registry watcher fails with error or if the routing table update fails.
func (r *router) watchRegistry(w registry.Watcher) error {
exit := make(chan bool)
defer func() {
close(exit)
}()
go func() {
defer w.Stop()
select {
case <-exit:
return
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case <-r.exit:
return
}
}()
for {
res, err := w.Next()
if err != nil {
if err != registry.ErrWatcherStopped {
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return err
}
break
}
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if err := r.manageRoutes(res.Service, res.Action); err != nil {
return err
}
}
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return nil
}
// watchTable watches routing table entries and either adds or deletes locally registered service to/from network registry
// It returns error if the locally registered services either fails to be added/deleted to/from network registry.
func (r *router) watchTable(w Watcher) error {
exit := make(chan bool)
defer func() {
close(exit)
}()
// wait in the background for the router to stop
// when the router stops, stop the watcher and exit
go func() {
defer w.Stop()
select {
case <-r.exit:
return
case <-exit:
return
}
}()
for {
event, err := w.Next()
if err != nil {
if err != ErrWatcherStopped {
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return err
}
break
}
select {
case <-r.exit:
close(r.eventChan)
return nil
case r.eventChan <- event:
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// process event
}
}
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return nil
}
// publishAdvert publishes router advert to advert channel
func (r *router) publishAdvert(advType AdvertType, events []*Event) {
a := &Advert{
Id: r.options.Id,
Type: advType,
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TTL: DefaultAdvertTTL,
Timestamp: time.Now(),
Events: events,
}
r.sub.RLock()
for _, sub := range r.subscribers {
// now send the message
select {
case sub <- a:
case <-r.exit:
r.sub.RUnlock()
return
}
}
r.sub.RUnlock()
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}
// advert contains a route event to be advertised
type advert struct {
// event received from routing table
event *Event
// lastSeen records the time of the last advert update
lastSeen time.Time
// penalty is current advert penalty
penalty float64
// isSuppressed flags the advert suppression
isSuppressed bool
// suppressTime records the time interval the advert has been suppressed for
suppressTime time.Time
}
// adverts maintains a map of router adverts
type adverts map[uint64]*advert
// process processes advert
// It updates advert timestamp, increments its penalty and
// marks upresses or recovers it if it reaches configured thresholds
func (m adverts) process(a *advert) error {
// lookup advert in adverts
hash := a.event.Route.Hash()
a, ok := m[hash]
if !ok {
return fmt.Errorf("advert not found")
}
// decay the event penalty
delta := time.Since(a.lastSeen).Seconds()
// decay advert penalty
a.penalty = a.penalty * math.Exp(-delta*PenaltyDecay)
service := a.event.Route.Service
address := a.event.Route.Address
// suppress/recover the event based on its penalty level
switch {
case a.penalty > AdvertSuppress && !a.isSuppressed:
log.Debugf("Router suppressing advert %d %.2f for route %s %s", hash, a.penalty, service, address)
a.isSuppressed = true
a.suppressTime = time.Now()
case a.penalty < AdvertRecover && a.isSuppressed:
log.Debugf("Router recovering advert %d %.2f for route %s %s", hash, a.penalty, service, address)
a.isSuppressed = false
}
// if suppressed, checked how long has it been suppressed for
if a.isSuppressed {
// max suppression time threshold has been reached, delete the advert
if time.Since(a.suppressTime) > MaxSuppressTime {
delete(m, hash)
return nil
}
}
return nil
}
// advertiseEvents advertises routing table events
// It suppresses unhealthy flapping events and advertises healthy events upstream.
func (r *router) advertiseEvents() error {
// ticker to periodically scan event for advertising
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ticker := time.NewTicker(AdvertiseEventsTick)
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defer ticker.Stop()
// adverts is a map of advert events
adverts := make(adverts)
// routing table watcher
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w, err := r.Watch()
if err != nil {
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return err
}
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defer w.Stop()
go func() {
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var err error
for {
select {
case <-r.exit:
return
default:
if w == nil {
// routing table watcher
w, err = r.Watch()
if err != nil {
log.Logf("Error creating watcher: %v", err)
time.Sleep(time.Second)
continue
}
}
if err := r.watchTable(w); err != nil {
log.Logf("Error watching table: %v", err)
time.Sleep(time.Second)
}
// reset
w.Stop()
w = nil
}
}
}()
for {
select {
case <-ticker.C:
// If we're not advertising any events then sip processing them entirely
if r.options.Advertise == AdvertiseNone {
continue
}
var events []*Event
// collect all events which are not flapping
for key, advert := range adverts {
// process the advert
if err := adverts.process(advert); err != nil {
log.Debugf("Router failed processing advert %d: %v", key, err)
continue
}
// if suppressed go to the next advert
if advert.isSuppressed {
continue
}
// if we only advertise local routes skip processing anything not link local
if r.options.Advertise == AdvertiseLocal && advert.event.Route.Link != "local" {
continue
}
// copy the event and append
e := new(Event)
// this is ok, because router.Event only contains builtin types
// and no references so this creates a deep copy of struct Event
*e = *(advert.event)
events = append(events, e)
// delete the advert from adverts
delete(adverts, key)
}
// advertise events to subscribers
if len(events) > 0 {
log.Debugf("Router publishing %d events", len(events))
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go r.publishAdvert(RouteUpdate, events)
}
case e := <-r.eventChan:
// if event is nil, continue
if e == nil {
continue
}
// If we're not advertising any events then skip processing them entirely
if r.options.Advertise == AdvertiseNone {
continue
}
// if we only advertise local routes skip processing anything not link local
if r.options.Advertise == AdvertiseLocal && e.Route.Link != "local" {
continue
}
now := time.Now()
log.Debugf("Router processing table event %s for service %s %s", e.Type, e.Route.Service, e.Route.Address)
// check if we have already registered the route
hash := e.Route.Hash()
a, ok := adverts[hash]
if !ok {
a = &advert{
event: e,
penalty: Penalty,
lastSeen: now,
}
adverts[hash] = a
continue
}
// override the route event only if the previous event was different
if a.event.Type != e.Type {
a.event = e
}
// process the advert
if err := adverts.process(a); err != nil {
log.Debugf("Router error processing advert %d: %v", hash, err)
continue
}
// update event penalty and timestamp
a.lastSeen = now
// increment the penalty
a.penalty += Penalty
log.Debugf("Router advert %d for route %s %s event penalty: %f", hash, a.event.Route.Service, a.event.Route.Address, a.penalty)
case <-r.exit:
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w.Stop()
return nil
}
}
}
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// drain all the events, only called on Stop
func (r *router) drain() {
for {
select {
case <-r.eventChan:
default:
return
}
}
}
// Start starts the router
func (r *router) Start() error {
r.Lock()
defer r.Unlock()
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if r.running {
return nil
}
// add all local service routes into the routing table
if err := r.manageRegistryRoutes(r.options.Registry, "create"); err != nil {
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return fmt.Errorf("failed adding registry routes: %s", err)
}
// add default gateway into routing table
if r.options.Gateway != "" {
// note, the only non-default value is the gateway
route := Route{
Service: "*",
Address: "*",
Gateway: r.options.Gateway,
Network: "*",
Router: r.options.Id,
Link: DefaultLink,
Metric: DefaultLocalMetric,
}
if err := r.table.Create(route); err != nil {
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return fmt.Errorf("failed adding default gateway route: %s", err)
}
}
// create error and exit channels
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r.exit = make(chan bool)
// registry watcher
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w, err := r.options.Registry.Watch()
if err != nil {
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return fmt.Errorf("failed creating registry watcher: %v", err)
}
go func() {
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var err error
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for {
select {
case <-r.exit:
w.Stop()
return
default:
if w == nil {
w, err = r.options.Registry.Watch()
if err != nil {
log.Logf("failed creating registry watcher: %v", err)
time.Sleep(time.Second)
continue
}
}
if err := r.watchRegistry(w); err != nil {
log.Logf("Error watching the registry: %v", err)
time.Sleep(time.Second)
}
w.Stop()
w = nil
}
}
}()
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r.running = true
return nil
}
// Advertise stars advertising the routes to the network and returns the advertisements channel to consume from.
// If the router is already advertising it returns the channel to consume from.
// It returns error if either the router is not running or if the routing table fails to list the routes to advertise.
func (r *router) Advertise() (<-chan *Advert, error) {
r.Lock()
defer r.Unlock()
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if !r.running {
return nil, errors.New("not running")
}
// already advertising
if r.eventChan != nil {
advertChan := make(chan *Advert, 128)
r.subscribers[uuid.New().String()] = advertChan
return advertChan, nil
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}
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// list all the routes and pack them into even slice to advertise
events, err := r.flushRouteEvents(Create)
if err != nil {
return nil, fmt.Errorf("failed to flush routes: %s", err)
}
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// create event channels
r.eventChan = make(chan *Event)
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// create advert channel
advertChan := make(chan *Advert, 128)
r.subscribers[uuid.New().String()] = advertChan
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// advertise your presence
go r.publishAdvert(Announce, events)
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go func() {
select {
case <-r.exit:
return
default:
if err := r.advertiseEvents(); err != nil {
log.Logf("Error adveritising events: %v", err)
}
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}
}()
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return advertChan, nil
}
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// Process updates the routing table using the advertised values
func (r *router) Process(a *Advert) error {
// NOTE: event sorting might not be necessary
// copy update events intp new slices
events := make([]*Event, len(a.Events))
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copy(events, a.Events)
// sort events by timestamp
sort.Slice(events, func(i, j int) bool {
return events[i].Timestamp.Before(events[j].Timestamp)
})
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log.Tracef("Router %s processing advert from: %s", r.options.Id, a.Id)
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for _, event := range events {
// skip if the router is the origin of this route
if event.Route.Router == r.options.Id {
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log.Tracef("Router skipping processing its own route: %s", r.options.Id)
continue
}
// create a copy of the route
route := event.Route
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action := event.Type
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log.Tracef("Router %s applying %s from router %s for service %s %s", r.options.Id, action, route.Router, route.Service, route.Address)
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if err := r.manageRoute(route, action.String()); err != nil {
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return fmt.Errorf("failed applying action %s to routing table: %s", action, err)
}
}
return nil
}
// flushRouteEvents returns a slice of events, one per each route in the routing table
func (r *router) flushRouteEvents(evType EventType) ([]*Event, error) {
// get a list of routes for each service in our routing table
// for the configured advertising strategy
q := []QueryOption{
QueryStrategy(r.options.Advertise),
}
routes, err := r.Table().Query(q...)
if err != nil && err != ErrRouteNotFound {
return nil, err
}
log.Debugf("Router advertising %d routes with strategy %s", len(routes), r.options.Advertise)
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// build a list of events to advertise
events := make([]*Event, len(routes))
var i int
for _, route := range routes {
event := &Event{
Type: evType,
Timestamp: time.Now(),
Route: route,
}
events[i] = event
i++
}
return events, nil
}
// Lookup routes in the routing table
func (r *router) Lookup(q ...QueryOption) ([]Route, error) {
return r.table.Query(q...)
}
// Watch routes
func (r *router) Watch(opts ...WatchOption) (Watcher, error) {
return r.table.Watch(opts...)
}
// Stop stops the router
func (r *router) Stop() error {
r.Lock()
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defer r.Unlock()
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select {
case <-r.exit:
return nil
default:
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close(r.exit)
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// extract the events
r.drain()
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// close advert subscribers
for id, sub := range r.subscribers {
// close the channel
close(sub)
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// delete the subscriber
r.sub.Lock()
delete(r.subscribers, id)
r.sub.Unlock()
}
}
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// remove event chan
r.eventChan = nil
return nil
}
// String prints debugging information about router
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func (r *router) String() string {
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return "registry"
}