using SSE instead of socket IO

packages/api/package.json

@@ -35,6 +35,7 @@
     "express": "^4.17.1",
     "express-basic-auth": "^1.2.0",
     "express-fileupload": "^1.2.0",
+    "express-sse": "^0.5.3",
     "fs-extra": "^9.1.0",
     "fs-reverse": "^0.0.3",
     "get-port": "^5.1.1",

packages/api/src/main.js

@@ -4,7 +4,7 @@ const bodyParser = require('body-parser');
 const fileUpload = require('express-fileupload');
 const http = require('http');
 const cors = require('cors');
-const io = require('socket.io');
+// const io = require('socket.io');
 const fs = require('fs');
 const getPort = require('get-port');
 const childProcessChecker = require('./utility/childProcessChecker');
@@ -43,7 +43,11 @@ function start() {
   const app = express();
 
   const server = http.createServer(app);
-  socket.set(io(server));
+
+  // const sse = new SSE();
+  // app.get('/stream', sse.init);
+  // socket.set(sse);
+  // socket.set(io(server));
 
   if (process.env.LOGIN && process.env.PASSWORD) {
     app.use(
@@ -81,6 +85,30 @@ function start() {
   });
 
   app.use(cors());
+
+  app.get('/stream', async function (req, res) {
+    res.set({
+      'Cache-Control': 'no-cache',
+      'Content-Type': 'text/event-stream',
+      Connection: 'keep-alive',
+    });
+    res.flushHeaders();
+
+    // Tell the client to retry every 10 seconds if connectivity is lost
+    res.write('retry: 10000\n\n');
+    socket.set(res);
+
+    // let count = 0;
+
+    // while (true) {
+    //   await new Promise((resolve) => setTimeout(resolve, 1000));
+
+    //   console.log("Emit", ++count);
+    //   // Emit an SSE that contains the current 'count' as a string
+    //   res.write(`event: ping\ndata: ${JSON.stringify({ count })}\n\n`);
+    // }
+  });
+
   app.use(bodyParser.json({ limit: '50mb' }));
 
   app.use(

packages/api/src/utility/socket.js

@@ -1,19 +1,35 @@
-let socket = null;
+let res = null;
+let init = '';
 
 module.exports = {
   set(value) {
-    socket = value;
-  },
-  get() {
-    return socket;
+    res = value;
   },
+  // get() {
+  //   return socket;
+  // },
   emit(message, data) {
+    if (res) {
+      if (init) {
+        res.write(init);
+        init = '';
+      }
+      res.write(`event: ${message}\ndata: ${JSON.stringify(data == null ? null : data)}\n\n`);
+    } else {
+      init += res;
+    }
+
     // console.log('EMIT:', message, data);
-    socket.emit(message, data);
+    // socket.emit(message, data);
   },
   emitChanged(key) {
+    this.emit('clean-cache', key);
+    this.emit(key);
     // console.log('EMIT_CHANGED:', key);
-    socket.emit('clean-cache', key);
-    socket.emit(key);
+    // socket.emit('clean-cache', key);
+    // socket.emit(key);
+
+    // socket.send(key, 'clean-cache');
+    // socket.send(null, key);
   },
 };

packages/web/src/utility/api.ts

@@ -1,6 +1,16 @@
 import resolveApi, { resolveApiHeaders } from './resolveApi';
 import { writable } from 'svelte/store';
-import socket from './socket';
+import { cacheClean } from './cache';
+// import socket from './socket';
+
+let eventSource;
+
+function wantEventSource() {
+  if (!eventSource) {
+    eventSource = new EventSource(`${resolveApi()}/stream`);
+    eventSource.addEventListener('clean-cache', e => cacheClean(JSON.parse(e.data)));
+  }
+}
 
 export async function apiCall(route: string, args: {} = undefined) {
   const resp = await fetch(`${resolveApi()}/${route}`, {
@@ -15,16 +25,28 @@ export async function apiCall(route: string, args: {} = undefined) {
   return resp.json();
 }
 
+const apiHandlers = new WeakMap();
+
 export function apiOn(event: string, handler: Function) {
-  socket().on(event, handler);
+  wantEventSource();
+  if (!apiHandlers.has(handler)) {
+    const handlerProxy = e => {
+      // console.log('RECEIVED', e.type, JSON.parse(e.data));
+      handler(JSON.parse(e.data));
+    };
+    apiHandlers.set(handler, handlerProxy);
+  }
+
+  eventSource.addEventListener(event, apiHandlers.get(handler));
 }
 
 export function apiOff(event: string, handler: Function) {
-  socket().off(event, handler);
+  wantEventSource();
+  if (apiHandlers.has(handler)) {
+    eventSource.removeEventListener(event, apiHandlers.get(handler));
+  }
 }
 
-import _ from 'lodash';
-
 export function useApiCall(route, args, defaultValue) {
   const result = writable(defaultValue);
 

packages/web/src/utility/metadataLoaders.ts

@@ -2,7 +2,6 @@ import _ from 'lodash';
 import { cacheGet, cacheSet, getCachedPromise } from './cache';
 import stableStringify from 'json-stable-stringify';
 import { cacheClean } from './cache';
-import socket from './socket';
 import getAsArray from './getAsArray';
 import { DatabaseInfo } from 'dbgate-types';
 import { derived } from 'svelte/store';
@@ -194,11 +193,11 @@ function useCore(loader, args) {
         }
       }
 
-      if (reloadTrigger && !socket) {
-        console.error('Socket not available, reloadTrigger not planned');
-      }
+      // if (reloadTrigger && !socket) {
+      //   console.error('Socket not available, reloadTrigger not planned');
+      // }
       handleReload();
-      if (reloadTrigger && socket) {
+      if (reloadTrigger) {
         for (const item of getAsArray(reloadTrigger)) {
           apiOn(item, handleReload);
         }

packages/web/src/utility/socket.js

@@ -1,23 +0,0 @@
-import io from 'socket.io-client';
-import resolveApi from './resolveApi';
-import { cacheClean } from './cache';
-import { shouldWaitForElectronInitialize } from './getElectron';
-
-let socketInstance;
-
-function recreateSocket() {
-  if (shouldWaitForElectronInitialize()) return;
-
-  socketInstance = io(resolveApi());
-  socketInstance.on('clean-cache', reloadTrigger => cacheClean(reloadTrigger));
-}
-
-window['dbgate_recreateSocket'] = recreateSocket;
-
-recreateSocket();
-
-function socket() {
-  return socketInstance;
-}
-
-export default socket;

yarn.lock

@@ -4032,6 +4032,11 @@ express-fileupload@^1.2.0:
   dependencies:
     busboy "^0.3.1"
 
+express-sse@^0.5.3:
+  version "0.5.3"
+  resolved "https://registry.yarnpkg.com/express-sse/-/express-sse-0.5.3.tgz#6e6cb1a85ef7b6ec1eb658e37e923907c482bd31"
+  integrity sha512-DJF0nofFGq0IXJLGq95hfrryP3ZprVAVpyZUnmAk6QhHnm7zCzsHBNFP0i4FKFo2XjOf+JiYUKjT7jQhIeljpg==
+
 express@^4.17.1:
   version "4.17.1"
   resolved "https://registry.yarnpkg.com/express/-/express-4.17.1.tgz#4491fc38605cf51f8629d39c2b5d026f98a4c134"