136 lines
2.8 KiB
Go
136 lines
2.8 KiB
Go
package router
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import (
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"errors"
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"strings"
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"github.com/olekukonko/tablewriter"
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)
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var (
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// ErrWatcherStopped is returned when routing table watcher has been stopped
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ErrWatcherStopped = errors.New("watcher stopped")
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)
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// EventType defines routing table event
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type EventType int
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const (
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// CreateEvent is emitted when new route has been created
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CreateEvent EventType = iota
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// DeleteEvent is emitted when an existing route has been deleted
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DeleteEvent
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// UpdateEvent is emitted when a routing table has been updated
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UpdateEvent
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)
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// String returns string representation of the event
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func (et EventType) String() string {
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switch et {
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case CreateEvent:
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return "CREATE"
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case DeleteEvent:
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return "DELETE"
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case UpdateEvent:
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return "UPDATE"
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default:
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return "UNKNOWN"
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}
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}
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// Event is returned by a call to Next on the watcher.
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type Event struct {
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// Type defines type of event
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Type EventType
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// Route is table rout
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Route Route
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}
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// WatchOption is used to define what routes to watch in the table
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type WatchOption func(*WatchOptions)
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// Watcher defines routing table watcher interface
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// Watcher returns updates to the routing table
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type Watcher interface {
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// Next is a blocking call that returns watch result
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Next() (*Event, error)
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// Chan returns event channel
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Chan() (<-chan *Event, error)
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// Stop stops watcher
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Stop()
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}
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// WatchOptions are table watcher options
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type WatchOptions struct {
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// Specify destination address to watch
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Destination string
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}
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// WatchDestination sets what destination to watch
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// Destination is usually microservice name
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func WatchDestination(d string) WatchOption {
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return func(o *WatchOptions) {
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o.Destination = d
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}
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}
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type tableWatcher struct {
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opts WatchOptions
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resChan chan *Event
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done chan struct{}
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}
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// Next returns the next noticed action taken on table
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// TODO: this needs to be thought through properly; we only allow watching particular route destination for now
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func (w *tableWatcher) Next() (*Event, error) {
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for {
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select {
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case res := <-w.resChan:
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switch w.opts.Destination {
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case "*", "":
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return res, nil
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default:
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if w.opts.Destination == res.Route.Destination {
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return res, nil
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}
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continue
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}
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case <-w.done:
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return nil, ErrWatcherStopped
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}
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}
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}
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// Chan returns watcher events channel
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func (w *tableWatcher) Chan() (<-chan *Event, error) {
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return w.resChan, nil
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}
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// Stop stops routing table watcher
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func (w *tableWatcher) Stop() {
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select {
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case <-w.done:
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return
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default:
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close(w.done)
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}
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}
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// String prints debug information
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func (w *tableWatcher) String() string {
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sb := &strings.Builder{}
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table := tablewriter.NewWriter(sb)
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table.SetHeader([]string{"Destination"})
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data := []string{
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w.opts.Destination,
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}
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table.Append(data)
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// render table into sb
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table.Render()
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return sb.String()
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}
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