fix(realtime): Connect concurrency

Previously, an event could call for a reconnect
while the previous one was waiting before
creating  a new socket. This would create
a two socket in a row.

This change adds a protection against concurrency
when creating a socket.

packages/cozy-realtime/src/CozyRealtime.js

@@ -100,8 +100,19 @@ class CozyRealtime {
    */
   async connect() {
     logger.info('connecting…')
-    await this.retryManager.waitBeforeNextAttempt()
-    this.createSocket()
+    // avoid multiple concurrent calls to connect, keeps the first one
+    if (this.waitingForConnect) {
+      logger.debug('Pending reconnection, skipping reconnect')
+      return
+    }
+    logger.debug('No pending reconnection, will reconnect')
+    try {
+      this.waitingForConnect = true
+      await this.retryManager.waitBeforeNextAttempt()
+      this.createSocket()
+    } finally {
+      this.waitingForConnect = false
+    }
   }
 
   /**
@@ -618,6 +629,7 @@ class CozyRealtime {
    * @private
    */
   onOnline() {
+    logger.info('reconnect because receiving an online event')
     this.reconnect()
   }
 

packages/cozy-realtime/src/CozyRealtime.spec.js

@@ -608,5 +608,31 @@ describe('CozyRealtime', () => {
         server.stop(done)
       })
     })
+
+    describe('connection concurrency', () => {
+      it('should not start two concurrent connections', async done => {
+        const server = createSocketServer()
+        const realtime = createRealtime()
+        const handler = jest.fn()
+        realtime.subscribe(event, type, undefined, handler)
+        await realtime.waitForSocketReady()
+
+        // makes the reconnect wait
+        realtime.retryManager.onFailure()
+        realtime.retryManager.onFailure()
+        realtime.retryManager.onFailure()
+        realtime.retryManager.onFailure()
+        realtime.retryManager.onFailure()
+        realtime.onOnline()
+        await sleep(25)
+
+        // reconnect before the previous connection finishes to wait
+        realtime.onOnline()
+        await realtime.waitForSocketReady()
+
+        expect(server.onconnect).toHaveBeenCalledTimes(2)
+        server.stop(done)
+      })
+    })
   })
 })

packages/cozy-realtime/src/RetryManager.js

@@ -1,5 +1,7 @@
 import MicroEE from 'microee'
 
+import logger from './logger'
+
 import {
   maxWaitBetweenRetries as defaultMaxWaitBetweenRetries,
   baseWaitAfterFirstFailure as defaultBaseWaitAfterFirstFailure,
@@ -109,6 +111,7 @@ class RetryManager {
    * @param {object} error
    */
   onFailure(error) {
+    logger.debug('failure, increase the failure counter of the retry manager')
     this.clearSuccessWatcher()
     this.increaseFailureCounter()
     this.emit('failure', error)
@@ -128,6 +131,7 @@ class RetryManager {
    * Reset failures counters (do not wait before trying to connect next time)
    */
   reset() {
+    logger.debug('reset the retry manager')
     this.clearSuccessWatcher()
     this.retries = 0
     this.wait = 0
@@ -155,6 +159,7 @@ class RetryManager {
    * Wait an amount of time before the next attempt (if needed)
    */
   async waitBeforeNextAttempt() {
+    logger.debug('waitBeforeNextAttempt', this.wait)
     if (this.wait) {
       await new Promise(resolve => {
         global.setTimeout(resolve, this.wait)