initial fetch: Add a timeout to abort.

Using `INITIAL_FETCH_ABORT` and `promiseTimeout`, which we set up in
the last few commits, abort and go to the accounts screen if the
initial fetch is taking too long.

Fixes: zulip#4165

src/message/fetchActions.js

@@ -30,7 +30,8 @@ import {
 } from '../actionConstants';
 import { FIRST_UNREAD_ANCHOR, LAST_MESSAGE_ANCHOR } from '../anchor';
 import { ALL_PRIVATE_NARROW } from '../utils/narrow';
-import { BackoffMachine } from '../utils/async';
+import { BackoffMachine, promiseTimeout, TimeoutError } from '../utils/async';
+import * as logging from '../utils/logging';
 import { initNotifications } from '../notification/notificationActions';
 import { addToOutbox, sendOutbox } from '../outbox/outboxActions';
 import { realmInit } from '../realm/realmActions';
@@ -128,8 +129,6 @@ const initialFetchComplete = (): Action => ({
   type: INITIAL_FETCH_COMPLETE,
 });
 
-// This will be used in an upcoming commit.
-/* eslint-disable-next-line no-unused-vars */
 const initialFetchAbort = (): Action => ({
   type: INITIAL_FETCH_ABORT,
 });
@@ -236,13 +235,21 @@ const fetchTopMostNarrow = () => async (dispatch: Dispatch, getState: GetState)
  * handled further up in the call stack.
  */
 export async function tryFetch<T>(func: () => Promise<T>): Promise<T> {
+  const MAX_TIME_MS: number = 60000;
   const backoffMachine = new BackoffMachine();
+
+  const timeAtStart = Date.now();
   // eslint-disable-next-line no-constant-condition
   while (true) {
+    const msElapsed = Date.now() - timeAtStart;
+    // If the first attempt had a 60-second timeout, but it took 3
+    // seconds, then the second attempt should have a 57-second
+    // timeout. Etc.
+    const timeLimitMs = MAX_TIME_MS - msElapsed;
     try {
-      return await func();
+      return await promiseTimeout(func(), timeLimitMs);
     } catch (e) {
-      if (isClientError(e)) {
+      if (isClientError(e) || e instanceof TimeoutError) {
         throw e;
       }
       await backoffMachine.wait();
@@ -294,9 +301,15 @@ export const doInitialFetch = () => async (dispatch: Dispatch, getState: GetStat
       tryFetch(() => api.getServerSettings(auth.realm)),
     ]);
   } catch (e) {
-    // This should only happen on a 4xx HTTP status, which should only
-    // happen when `auth` is no longer valid.  No use retrying; just log out.
-    dispatch(logout());
+    if (isClientError(e)) {
+      dispatch(logout());
+    } else if (e instanceof TimeoutError) {
+      dispatch(initialFetchAbort());
+    } else {
+      logging.warn(e, {
+        message: 'Unexpected error during initial fetch and serverSettings fetch.',
+      });
+    }
     return;
   }