From c539b8ee46baa69911c53ef852f8a26474cf79ab Mon Sep 17 00:00:00 2001
From: Prakhar Pratyush <prakhar@zulip.com>
Date: Sun, 19 Nov 2023 12:02:48 +0530
Subject: [PATCH] watchdog: Handle exception in `callback`.

Earlier, in the 'check_for_unsuspend' function, we didn't
handle the exception, if any, during callback execution,
resulting in 'watchdog_time' not always being updated.

This commit handles the exception using the try/catch block.

Fixes #27723.
---
 web/src/watchdog.ts        | 14 +++++++++++++-
 web/tests/watchdog.test.js | 15 +++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/web/src/watchdog.ts b/web/src/watchdog.ts
index eeff824ba1..07082fa0fa 100644
--- a/web/src/watchdog.ts
+++ b/web/src/watchdog.ts
@@ -1,3 +1,5 @@
+import * as blueslip from "./blueslip";
+
 const unsuspend_callbacks: (() => void)[] = [];
 let watchdog_time = Date.now();
 
@@ -35,7 +37,17 @@ export function check_for_unsuspend(): void {
         // Our app's JS wasn't running, which probably means the machine was
         // asleep.
         for (const callback of unsuspend_callbacks) {
-            callback();
+            try {
+                callback();
+            } catch (error) {
+                blueslip.error(
+                    `Error while executing callback '${
+                        callback.name || "Anonymous function"
+                    }' from unsuspend_callbacks.`,
+                    undefined,
+                    error,
+                );
+            }
         }
     }
     watchdog_time = new_time;
diff --git a/web/tests/watchdog.test.js b/web/tests/watchdog.test.js
index 662d26127c..4257bf6d56 100644
--- a/web/tests/watchdog.test.js
+++ b/web/tests/watchdog.test.js
@@ -6,6 +6,7 @@ const MockDate = require("mockdate");
 
 const {set_global, zrequire} = require("./lib/namespace");
 const {run_test} = require("./lib/test");
+const blueslip = require("./lib/zblueslip");
 
 let time = 0;
 let checker;
@@ -58,6 +59,20 @@ run_test("basics", () => {
     advance_secs(21);
     watchdog.check_for_unsuspend();
     assert.equal(num_times_called_back, 1);
+
+    // Error while executing callback
+    num_times_called_back = 0;
+    advance_secs(21);
+    watchdog.on_unsuspend(() => {
+        num_times_called_back += 1;
+        throw new Error("Some error while executing");
+    });
+    blueslip.expect(
+        "error",
+        `Error while executing callback 'Anonymous function' from unsuspend_callbacks.`,
+    );
+    watchdog.check_for_unsuspend();
+    assert.equal(num_times_called_back, 2);
 });
 
 run_test("suspect_offline", () => {