From 0965847026f42141f2a4914063fcfc06795fc41a Mon Sep 17 00:00:00 2001
From: boyska <piuttosto@logorroici.org>
Date: Mon, 24 Jul 2017 00:04:46 +0200
Subject: [PATCH] FIX remove workers (concurrently)

---
 uiserver/server.go | 57 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 46 insertions(+), 11 deletions(-)

diff --git a/uiserver/server.go b/uiserver/server.go
index 28b9a94..0d0fc86 100644
--- a/uiserver/server.go
+++ b/uiserver/server.go
@@ -4,7 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net"
-	"os"
+	"sync"
 )
 
 // Worker handles a single connection, providing updates to the clients
@@ -53,10 +53,11 @@ func (w *Worker) Work() {
 // the API is designed so to make it possible to attach it to multiple
 // listeners, despite this is NOT possible at the moment
 type NetUI struct {
-	Object  interface{}
-	workers []Worker
-	sock    *net.Listener
-	exit    chan interface{}
+	Object       interface{}
+	workers      []Worker
+	workersMutex sync.Mutex
+	sock         *net.Listener
+	exit         chan interface{}
 }
 
 // protocolHello is the hello message that the server will give to clients
@@ -77,14 +78,19 @@ func NewNetUI(obj interface{}) NetUI {
 
 // Update sends the new state to every connected client
 func (n *NetUI) Update() {
+	todelete := make([]Worker, 0)
+	n.workersMutex.Lock()
 	for _, w := range n.workers {
 		select {
 		case w.Update <- n.Object:
 		default:
-			fmt.Fprintln(os.Stderr, "error pushing message to worker on", w.Conn.RemoteAddr())
-			// TODO: shall we remove w from the pool on first error?
+			todelete = append(todelete, w)
 		}
 	}
+	n.workersMutex.Unlock()
+	for _, w := range todelete {
+		n.removeWorker(w)
+	}
 }
 
 // Close shuts the TCPserver down synchronously
@@ -92,10 +98,39 @@ func (n *NetUI) Close() {
 	if n.sock != nil {
 		(*n.sock).Close()
 	}
-	for _, w := range n.workers {
-		close(w.Exit)
-		close(w.Update)
+	// for _, w := range n.workers {
+	// 	close(w.Exit)
+	// 	close(w.Update)
+	// }
+}
+
+func (n *NetUI) removeWorker(worker Worker) error {
+	n.workersMutex.Lock()
+	err := n.removeWorkerNoLock(worker)
+	n.workersMutex.Unlock()
+	return err
+}
+func (n *NetUI) removeWorkerNoLock(worker Worker) error {
+	fmt.Println("avevo una lista lunga", len(n.workers))
+	i := -1
+	for pos, w := range n.workers {
+		if worker == w {
+			i = pos
+			break
+		}
 	}
+	if i == -1 {
+		return fmt.Errorf("No such worker")
+	}
+	n.workers[i] = n.workers[0]
+	n.workers = n.workers[1:]
+	fmt.Println("ora ho una lista lunga", len(n.workers))
+	return nil
+}
+func (n *NetUI) addWorker(connworker Worker) {
+	n.workersMutex.Lock()
+	n.workers = append(n.workers, connworker)
+	n.workersMutex.Unlock()
 }
 
 // Run does the heavy work, and is blocking. It expects a Listener (typically
@@ -123,7 +158,7 @@ func (n *NetUI) Run(sock net.Listener) error {
 		}
 		connworker := NewWorker(conn)
 		connworker.Update <- n.Object
-		n.workers = append(n.workers, connworker)
+		n.addWorker(connworker)
 		go connworker.Work()
 	}
 }