micro/network/router/default_router.go

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package router
import (
"fmt"
"strings"
"sync"
"github.com/micro/go-micro/registry"
"github.com/olekukonko/tablewriter"
)
// router provides default router implementation
type router struct {
opts Options
exit chan struct{}
wg *sync.WaitGroup
}
// newRouter creates new router and returns it
func newRouter(opts ...Option) Router {
// TODO: we need to add default GW entry here
// Should default GW be part of router options?
// get default options
options := DefaultOptions()
// apply requested options
for _, o := range opts {
o(&options)
}
return &router{
opts: options,
exit: make(chan struct{}),
wg: &sync.WaitGroup{},
}
}
// Init initializes router with given options
func (r *router) Init(opts ...Option) error {
for _, o := range opts {
o(&r.opts)
}
return nil
}
// Options returns router options
func (r *router) Options() Options {
return r.opts
}
// ID returns router ID
func (r *router) ID() string {
return r.opts.ID
}
// Table returns routing table
func (r *router) Table() Table {
return r.opts.Table
}
// Address returns router's bind address
func (r *router) Address() string {
return r.opts.Address
}
// Network returns the address router advertises to the network
func (r *router) Network() string {
return r.opts.Network
}
// Advertise advertises the routes to the network. It is a blocking function.
// It returns error if any of the launched goroutines fail with error.
func (r *router) Advertise() error {
// add local service routes into the routing table
if err := r.addServiceRoutes(r.opts.Registry, "local", DefaultLocalMetric); err != nil {
return fmt.Errorf("failed adding routes: %v", err)
}
localWatcher, err := r.opts.Registry.Watch()
if err != nil {
return fmt.Errorf("failed to create registry watcher: %v", err)
}
// error channel collecting goroutine errors
errChan := make(chan error, 1)
r.wg.Add(1)
go func() {
defer r.wg.Done()
// watch local registry and register routes in routine table
errChan <- r.manageServiceRoutes(localWatcher, DefaultLocalMetric)
}()
return <-errChan
}
// addServiceRoutes adds all services in given registry to the routing table.
// NOTE: this is a one-off operation done when bootstrapping the routing table
// It returns error if either the services failed to be listed or
// if the routes could not be added to the routing table.
func (r *router) addServiceRoutes(reg registry.Registry, network string, metric int) error {
services, err := reg.ListServices()
if err != nil {
return fmt.Errorf("failed to list 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
}
// create a flat slide of nodes
var nodes []*registry.Node
for _, s := range srvs {
nodes = append(nodes, s.Nodes...)
}
// range over the flat slice of nodes
for _, node := range nodes {
gw := node.Address
if node.Port > 0 {
gw = fmt.Sprintf("%s:%d", node.Address, node.Port)
}
route := Route{
Destination: service.Name,
Gateway: gw,
Router: r.opts.Address,
Network: r.opts.Network,
Metric: metric,
}
if err := r.opts.Table.Add(route); err != nil && err != ErrDuplicateRoute {
return fmt.Errorf("error adding route for service %s: %s", service.Name, err)
}
}
}
return nil
}
// manageServiceRoutes watches services in given registry and updates the routing table accordingly.
// It returns error if the service registry watcher has stopped or if the routing table failed to be updated.
func (r *router) manageServiceRoutes(w registry.Watcher, metric int) error {
// wait in the background for the router to stop
// when the router stops, stop the watcher and exit
r.wg.Add(1)
go func() {
defer r.wg.Done()
<-r.exit
w.Stop()
}()
var watchErr error
for {
res, err := w.Next()
if err == registry.ErrWatcherStopped {
break
}
if err != nil {
watchErr = err
break
}
route := Route{
Destination: res.Service.Name,
Router: r.opts.Address,
Network: r.opts.Network,
Metric: metric,
}
switch res.Action {
case "create":
// only return error if the route is not duplicate, but something else has failed
if err := r.opts.Table.Add(route); err != nil && err != ErrDuplicateRoute {
return fmt.Errorf("failed to add route for service %v: %s", res.Service.Name, err)
}
case "delete":
// only return error if the route is not in the table, but something else has failed
if err := r.opts.Table.Delete(route); err != nil && err != ErrRouteNotFound {
return fmt.Errorf("failed to delete route for service %v: %s", res.Service.Name, err)
}
}
}
return watchErr
}
// Stop stops the router
func (r *router) Stop() error {
// notify all goroutines to finish
close(r.exit)
// wait for all goroutines to finish
r.wg.Wait()
return nil
}
// String prints debugging information about router
func (r *router) String() string {
sb := &strings.Builder{}
table := tablewriter.NewWriter(sb)
table.SetHeader([]string{"ID", "Address", "Network", "Table"})
data := []string{
r.opts.ID,
r.opts.Address,
r.opts.Network,
fmt.Sprintf("%d", r.opts.Table.Size()),
}
table.Append(data)
// render table into sb
table.Render()
return sb.String()
}