From 060e8e3b0f5d2145fcdf9b7dcb935be72a98ff23 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Pit-Claudel?= <clement.pit-claudel@epfl.ch>
Date: Sun, 22 Dec 2024 21:59:20 +0100
Subject: [PATCH] client: Automatically reconnect if websocket connection drops
---
.../webapp/client/StateMachineClientApp.scala | 54 ++++++++++++++++---
.../cs214/webapp/server/web/ServerApp.scala | 2 +-
2 files changed, 47 insertions(+), 9 deletions(-)
diff --git a/js/src/main/scala/cs214/webapp/client/StateMachineClientApp.scala b/js/src/main/scala/cs214/webapp/client/StateMachineClientApp.scala
index 5c59937..3155739 100644
--- a/js/src/main/scala/cs214/webapp/client/StateMachineClientApp.scala
+++ b/js/src/main/scala/cs214/webapp/client/StateMachineClientApp.scala
@@ -9,23 +9,61 @@ import org.scalajs.dom
type Target = dom.Element
+private class WebSocket(endpoint: String):
+ var socket: Option[dom.WebSocket] = None
+
+ val MIN_DELAY_MS = 10d
+ val MAX_DELAY_MS = 5000d
+ var reconnect_delay_ms = MIN_DELAY_MS
+
+ private var listeners: List[String => Unit] = Nil
+ def addListener(listener: String => Unit) =
+ listeners = listener :: listeners
+
+ def send(str: String) = socket match
+ case Some(s) => s.send(str)
+ case None => dom.window.alert("Disconnected!")
+
+ private def onmessage(event: dom.MessageEvent) =
+ listeners.foreach(_(event.data.toString))
+
+ private def reconnect(): Unit =
+ println("[ws] Attempting to connect")
+ val _socket = dom.WebSocket(endpoint)
+
+ def onopen(event: dom.Event) =
+ reconnect_delay_ms = MIN_DELAY_MS
+ println("[ws] WebSocket connection opened")
+ def onclose(event: dom.CloseEvent) =
+ if socket == Some(_socket) then socket = None
+ println(s"[ws] WebSocket connection closed (${event.code}): ${event.reason}")
+ if event.code != 1000 then // Normal closure
+ dom.window.setTimeout(() => reconnect(), reconnect_delay_ms)
+ reconnect_delay_ms = math.min(1.5 * reconnect_delay_ms, MAX_DELAY_MS)
+ def onerror(event: dom.Event) =
+ println(s"[ws] WebSocket error")
+ _socket.close(3000) // Lowest custom error code
+
+ _socket.onopen = evt => onopen(evt)
+ _socket.onclose = evt => onclose(evt)
+ _socket.onerror = evt => onerror(evt)
+ _socket.onmessage = msg => onmessage(msg)
+ socket = Some(_socket)
+
+ reconnect()
+
abstract class WSClientApp extends ClientApp:
WebClient.register(this)
protected def init(userId: UserId, sendMessage: ujson.Value => Unit, target: Target): ClientAppInstance
def init(instanceId: InstanceId, userId: UserId, endpoint: String, target: Target): ClientAppInstance =
- val socket = new dom.WebSocket(endpoint)
- socket.onopen = (event: dom.Event) => println("WebSocket connection opened")
- socket.onclose = (event: dom.CloseEvent) => println(s"WebSocket connection closed: ${event.reason}")
- socket.onerror = (event: dom.Event) => println(s"WebSocket error: ${event.`type`}")
-
+ val socket = WebSocket(endpoint)
val sendMessage = (js: ujson.Value) => socket.send(js.toString)
val client = init(userId, sendMessage, target)
- socket.onmessage = msg =>
- val js = ujson.read(msg.data.toString)
+ socket.addListener: msg =>
+ val js = ujson.read(msg)
client.onMessage(SocketResponseWire.decode(js).flatten)
-
client
/** Instance of a client-side state machine application.
diff --git a/jvm/src/main/scala/cs214/webapp/server/web/ServerApp.scala b/jvm/src/main/scala/cs214/webapp/server/web/ServerApp.scala
index c468c3d..78d9022 100644
--- a/jvm/src/main/scala/cs214/webapp/server/web/ServerApp.scala
+++ b/jvm/src/main/scala/cs214/webapp/server/web/ServerApp.scala
@@ -100,7 +100,7 @@ private[web] abstract class ServerApp:
for channels <- channels.values
channel <- channels
do
- channel.send(cask.Ws.Close())
+ channel.send(cask.Ws.Close(cask.Ws.Close.NormalClosure, "Shutdown"))
/** Sends a message to a specific client. */
private def send(userId: UserId)(message: ujson.Value): Unit = instanceLock.synchronized:
--
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