micro/router/default.go
ben-toogood deea8fecf4
router/registry: add fallback if routes aren't found in the cache (#1758)
* router/registry: add fallback if routes aren't found in the cache

* router: fix rlock bug

* router/registry: pass fetchRoutes into the table, not the router
2020-06-30 09:53:49 +01:00

712 lines
16 KiB
Go

package router
import (
"errors"
"fmt"
"sort"
"strings"
"sync"
"time"
"github.com/google/uuid"
"github.com/micro/go-micro/v2/logger"
"github.com/micro/go-micro/v2/registry"
)
var (
// AdvertiseEventsTick is time interval in which the router advertises route updates
AdvertiseEventsTick = 10 * time.Second
// DefaultAdvertTTL is default advertisement TTL
DefaultAdvertTTL = 2 * time.Minute
)
// router implements default router
type router struct {
sync.RWMutex
running bool
table *table
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)
}
// construct the router
r := &router{
options: options,
subscribers: make(map[string]chan *Advert),
}
// create the new table, passing the fetchRoute method in as a fallback if
// the table doesn't contain the result for a query.
r.table = newTable(r.fetchRoutes)
// start the router and return
r.start()
return r
}
// Init initializes router with given options
func (r *router) Init(opts ...Option) error {
// stop the router before we initialize
if err := r.Close(); err != nil {
return err
}
r.Lock()
defer r.Unlock()
for _, o := range opts {
o(&r.options)
}
// restart the router
if err := r.start(); err != nil {
return err
}
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 {
switch action {
case "create":
if err := r.table.Create(route); err != nil && err != ErrDuplicateRoute {
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 {
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)
}
default:
return fmt.Errorf("failed to manage route for service %s: unknown action %s", route.Service, action)
}
return nil
}
// manageServiceRoutes applies action to all routes of the service.
// It returns error of the action fails with error.
func (r *router) manageRoutes(service *registry.Service, action, network 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: network,
Router: r.options.Id,
Link: DefaultLink,
Metric: DefaultLocalMetric,
}
if err := r.manageRoute(route, action); err != nil {
return err
}
}
return nil
}
// 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(registry.ListDomain(registry.WildcardDomain))
if err != nil {
return fmt.Errorf("failed listing services: %v", err)
}
// add each service node as a separate route
for _, service := range services {
// get the services domain from metadata. Fallback to wildcard.
var domain string
if service.Metadata != nil && len(service.Metadata["domain"]) > 0 {
domain = service.Metadata["domain"]
} else {
domain = registry.WildcardDomain
}
// get the service to retrieve all its info
srvs, err := reg.GetService(service.Name, registry.GetDomain(domain))
if err != nil {
continue
}
// manage the routes for all returned services
for _, srv := range srvs {
if err := r.manageRoutes(srv, action, domain); err != nil {
return err
}
}
}
return nil
}
// fetchRoutes retrieves all the routes for a given service and creates them in the routing table
func (r *router) fetchRoutes(service string) error {
services, err := r.options.Registry.GetService(service, registry.GetDomain(registry.WildcardDomain))
if err != nil {
return fmt.Errorf("failed getting services: %v", err)
}
for _, srv := range services {
var domain string
if srv.Metadata != nil && len(srv.Metadata["domain"]) > 0 {
domain = srv.Metadata["domain"]
} else {
domain = registry.WildcardDomain
}
if err := r.manageRoutes(srv, "create", domain); 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
case <-r.exit:
return
}
}()
for {
res, err := w.Next()
if err != nil {
if err != registry.ErrWatcherStopped {
return err
}
break
}
if res.Service == nil {
continue
}
// get the services domain from metadata. Fallback to wildcard.
var domain string
if res.Service.Metadata != nil && len(res.Service.Metadata["domain"]) > 0 {
domain = res.Service.Metadata["domain"]
} else {
domain = registry.WildcardDomain
}
if err := r.manageRoutes(res.Service, res.Action, domain); err != nil {
return err
}
}
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 {
return err
}
break
}
select {
case <-r.exit:
close(r.eventChan)
return nil
case r.eventChan <- event:
// process event
}
}
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,
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()
}
// adverts maintains a map of router adverts
type adverts map[uint64]*Event
// 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
ticker := time.NewTicker(AdvertiseEventsTick)
defer ticker.Stop()
// adverts is a map of advert events
adverts := make(adverts)
// routing table watcher
w, err := r.Watch()
if err != nil {
return err
}
defer w.Stop()
go func() {
var err error
for {
select {
case <-r.exit:
return
default:
if w == nil {
// routing table watcher
w, err = r.Watch()
if err != nil {
if logger.V(logger.ErrorLevel, logger.DefaultLogger) {
logger.Errorf("Error creating watcher: %v", err)
}
time.Sleep(time.Second)
continue
}
}
if err := r.watchTable(w); err != nil {
if logger.V(logger.ErrorLevel, logger.DefaultLogger) {
logger.Errorf("Error watching table: %v", err)
}
time.Sleep(time.Second)
}
if w != nil {
// 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, event := range adverts {
// if we only advertise local routes skip processing anything not link local
if r.options.Advertise == AdvertiseLocal && 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 = *event
events = append(events, e)
// delete the advert from adverts
delete(adverts, key)
}
// advertise events to subscribers
if len(events) > 0 {
if logger.V(logger.DebugLevel, logger.DefaultLogger) {
logger.Debugf("Router publishing %d events", len(events))
}
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
}
if logger.V(logger.DebugLevel, logger.DefaultLogger) {
logger.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()
ev, ok := adverts[hash]
if !ok {
ev = e
adverts[hash] = e
continue
}
// override the route event only if the previous event was different
if ev.Type != e.Type {
ev = e
}
case <-r.exit:
if w != nil {
w.Stop()
}
return nil
}
}
}
// drain all the events, only called on Stop
func (r *router) drain() {
for {
select {
case <-r.eventChan:
default:
return
}
}
}
// start the router. Should be called under lock.
func (r *router) start() error {
if r.running {
return nil
}
// add all local service routes into the routing table
if err := r.manageRegistryRoutes(r.options.Registry, "create"); err != nil {
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 {
return fmt.Errorf("failed adding default gateway route: %s", err)
}
}
// create error and exit channels
r.exit = make(chan bool)
// registry watcher
w, err := r.options.Registry.Watch(registry.WatchDomain(registry.WildcardDomain))
if err != nil {
return fmt.Errorf("failed creating registry watcher: %v", err)
}
go func() {
var err error
for {
select {
case <-r.exit:
if w != nil {
w.Stop()
}
return
default:
if w == nil {
w, err = r.options.Registry.Watch()
if err != nil {
if logger.V(logger.ErrorLevel, logger.DefaultLogger) {
logger.Errorf("failed creating registry watcher: %v", err)
}
time.Sleep(time.Second)
continue
}
}
if err := r.watchRegistry(w); err != nil {
if logger.V(logger.ErrorLevel, logger.DefaultLogger) {
logger.Errorf("Error watching the registry: %v", err)
}
time.Sleep(time.Second)
}
if w != nil {
w.Stop()
w = nil
}
}
}
}()
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()
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
}
// 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)
}
// create event channels
r.eventChan = make(chan *Event)
// create advert channel
advertChan := make(chan *Advert, 128)
r.subscribers[uuid.New().String()] = advertChan
// advertise your presence
go r.publishAdvert(Announce, events)
go func() {
select {
case <-r.exit:
return
default:
if err := r.advertiseEvents(); err != nil {
if logger.V(logger.ErrorLevel, logger.DefaultLogger) {
logger.Errorf("Error adveritising events: %v", err)
}
}
}
}()
return advertChan, nil
}
// 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))
copy(events, a.Events)
// sort events by timestamp
sort.Slice(events, func(i, j int) bool {
return events[i].Timestamp.Before(events[j].Timestamp)
})
if logger.V(logger.TraceLevel, logger.DefaultLogger) {
logger.Tracef("Router %s processing advert from: %s", r.options.Id, a.Id)
}
for _, event := range events {
// skip if the router is the origin of this route
if event.Route.Router == r.options.Id {
if logger.V(logger.TraceLevel, logger.DefaultLogger) {
logger.Tracef("Router skipping processing its own route: %s", r.options.Id)
}
continue
}
// create a copy of the route
route := event.Route
action := event.Type
if logger.V(logger.TraceLevel, logger.DefaultLogger) {
logger.Tracef("Router %s applying %s from router %s for service %s %s", r.options.Id, action, route.Router, route.Service, route.Address)
}
if err := r.manageRoute(route, action.String()); err != nil {
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
}
if logger.V(logger.DebugLevel, logger.DefaultLogger) {
logger.Debugf("Router advertising %d routes with strategy %s", len(routes), r.options.Advertise)
}
// 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...)
}
// Close the router
func (r *router) Close() error {
r.Lock()
defer r.Unlock()
select {
case <-r.exit:
return nil
default:
close(r.exit)
// extract the events
r.drain()
r.sub.Lock()
// close advert subscribers
for id, sub := range r.subscribers {
// close the channel
close(sub)
// delete the subscriber
delete(r.subscribers, id)
}
r.sub.Unlock()
}
// remove event chan
r.eventChan = nil
r.running = false
return nil
}
// String prints debugging information about router
func (r *router) String() string {
return "registry"
}