From dbfd5dc8e61d6a6c6340605efcb70c77432e1d58 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Thu, 20 Jun 2019 14:39:05 +0100
Subject: [PATCH] Connection backoff

---
 packages/driver-websocket/package.json |  1 +
 packages/driver-websocket/src/index.js | 47 +++++++++++++++++++++-----
 2 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/packages/driver-websocket/package.json b/packages/driver-websocket/package.json
index 207d996..79866c7 100644
--- a/packages/driver-websocket/package.json
+++ b/packages/driver-websocket/package.json
@@ -21,6 +21,7 @@
   "dependencies": {
     "@syndicate-lang/core": "^0.2.7",
     "@syndicate-lang/driver-timer": "^0.2.7",
+    "debug": "^4.1.1",
     "isomorphic-ws": "^4.0.1",
     "ws": "^6.1.2"
   }
diff --git a/packages/driver-websocket/src/index.js b/packages/driver-websocket/src/index.js
index 97693f0..1e0c0fd 100644
--- a/packages/driver-websocket/src/index.js
+++ b/packages/driver-websocket/src/index.js
@@ -18,6 +18,7 @@
 
 import { currentFacet, Bytes, Observe, Dataspace } from "@syndicate-lang/core";
 const { sleep } = activate require("@syndicate-lang/driver-timer");
+const debugFactory = require('debug');
 
 const _WebSocket = require('isomorphic-ws');
 
@@ -32,26 +33,56 @@ Object.assign(module.exports, {
 spawn named 'WebSocketFactory' {
   during Observe(WebSocket($id, $url, $options)) spawn named ['WebSocket', id, url] {
     const facet = currentFacet();
+    const debug = debugFactory('syndicate/driver-websocket:' + (id && id.toString()));
 
     let finish = Dataspace.backgroundTask();
     on stop finish();
 
+    const DEFAULT_RECONNECT_DELAY = 1000; // milliseconds
+    const MAX_RECONNECT_DELAY = 30000; // milliseconds
+
     let ws = null;
     field this.connected = false;
+    field this.reconnectDelay = DEFAULT_RECONNECT_DELAY;
+
+    const guard = (context, f) => {
+      try {
+        f()
+      } catch (e) {
+        // Swallow e, which will be some kind of websocket-related exception.
+        debug('exception in actor '+facet.actor.toString()+' during '+context+':', e.message);
+        facet.stop();
+      }
+    };
 
     const connect = () => {
       disconnect();
-      console.log('WebSocket', id, url, 'connecting');
+      debug(url, 'connecting');
       ws = new _WebSocket(url, [], options.toJS());
 
       ws.onerror = Dataspace.wrapExternal((e) => {
-        console.error('WebSocket', id, url, e);
+        debug(url, e.message);
         disconnect();
-        sleep(1000, connect);
+        if (this.reconnectDelay !== DEFAULT_RECONNECT_DELAY) {
+          debug('Will reconnect in '+Math.floor(this.reconnectDelay)+' milliseconds');
+        }
+        sleep(Math.floor(this.reconnectDelay), connect);
+        this.reconnectDelay = this.reconnectDelay * 1.618 + (Math.random() * 1000);
+        this.reconnectDelay =
+          this.reconnectDelay > MAX_RECONNECT_DELAY
+          ? MAX_RECONNECT_DELAY + (Math.random() * 1000)
+          : this.reconnectDelay;
       });
 
-      ws.onopen = Dataspace.wrapExternal(() => { this.connected = true; });
-      ws.onclose = Dataspace.wrapExternal(() => { if (this.connected) { connect(); }});
+      ws.onopen = Dataspace.wrapExternal(() => {
+        this.connected = true;
+        this.reconnectDelay = DEFAULT_RECONNECT_DELAY;
+      });
+      ws.onclose = Dataspace.wrapExternal(() => {
+        if (this.connected) {
+          connect();
+        }
+      });
       ws.onmessage = Dataspace.wrapExternal((data) => {
         if (typeof Blob !== 'undefined' && data.data instanceof Blob) {
           var reader = new FileReader();
@@ -67,8 +98,8 @@ spawn named 'WebSocketFactory' {
 
     const disconnect = () => {
       if (ws) {
-        console.log('WebSocket', id, url, 'disconnecting');
-        try { ws.close(); } catch (_e) {}
+        debug(url, 'disconnecting');
+        guard('close', () => ws.close());
         ws = null;
       }
       this.connected = false;
@@ -81,7 +112,7 @@ spawn named 'WebSocketFactory' {
 
     on message DataOut(id, $data) {
       if (this.connected) {
-        ws.send(Bytes.toIO(data));
+        guard('send', () => ws.send(Bytes.toIO(data)));
       }
     }
   }