140 lines
2.7 KiB
Go
140 lines
2.7 KiB
Go
package gotelem
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import (
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"errors"
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"fmt"
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"sync"
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"golang.org/x/exp/slog"
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)
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type BrokerRequest struct {
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Source string // the name of the sender
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Msg Frame // the message to send
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}
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type BrokerClient struct {
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Name string // the name of the client
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Ch chan Frame // the channel to send frames to this client
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}
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type Broker struct {
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subs map[string]chan Frame
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publishCh chan BrokerRequest
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subsCh chan BrokerClient
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unsubCh chan BrokerClient
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}
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// Start runs the broker and sends messages to the subscribers (but not the sender)
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func (b *Broker) Start() {
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for {
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select {
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case newClient := <-b.subsCh:
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b.subs[newClient.Name] = newClient.Ch
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case req := <-b.publishCh:
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for name, ch := range b.subs {
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if name == req.Source {
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continue // don't send to ourselves.
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}
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// a kinda-inelegant non-blocking push.
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// if we can't do it, we just drop it. this should ideally never happen.
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select {
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case ch <- req.Msg:
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default:
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fmt.Printf("we dropped a packet to dest %s", name)
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}
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}
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case clientToRemove := <-b.unsubCh:
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close(b.subs[clientToRemove.Name])
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delete(b.subs, clientToRemove.Name)
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}
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}
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}
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func (b *Broker) Publish(name string, msg Frame) {
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breq := BrokerRequest{
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Source: name,
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Msg: msg,
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}
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b.publishCh <- breq
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}
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func (b *Broker) Subscribe(name string) <-chan Frame {
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ch := make(chan Frame, 3)
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bc := BrokerClient{
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Name: name,
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Ch: ch,
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}
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b.subsCh <- bc
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return ch
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}
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func (b *Broker) Unsubscribe(name string) {
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bc := BrokerClient{
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Name: name,
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}
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b.unsubCh <- bc
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}
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type JBroker struct {
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subs map[string] chan CANDumpEntry // contains the channel for each subsciber
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logger *slog.Logger
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lock sync.RWMutex
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bufsize int // size of chan buffer in elements.
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}
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func NewBroker(bufsize int, logger *slog.Logger) *JBroker {
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return &JBroker{
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subs: make(map[string]chan CANDumpEntry),
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logger: logger,
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bufsize: bufsize,
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}
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}
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func (b *JBroker) Subscribe(name string) (ch chan CANDumpEntry, err error) {
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// get rw lock.
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b.lock.Lock()
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defer b.lock.Unlock()
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_, ok := b.subs[name]
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if ok {
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return nil, errors.New("name already in use")
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}
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b.logger.Info("new subscriber", "name", name)
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ch = make(chan CANDumpEntry, b.bufsize)
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return
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}
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func (b *JBroker) Unsubscribe(name string) {
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// remove the channel from the map. We don't need to close it.
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b.lock.Lock()
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defer b.lock.Unlock()
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delete(b.subs, name)
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}
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func (b *JBroker) Publish(sender string, message CANDumpEntry) {
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b.lock.RLock()
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defer b.lock.RUnlock()
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for name, ch := range b.subs {
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if name == sender {
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continue
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}
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// non blocking send.
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select {
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case ch <- message:
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b.logger.Debug("sent message", "dest", name, "src", sender)
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default:
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b.logger.Warn("recipient buffer full", "dest", name)
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}
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}
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}
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