From bcf33d786ca2c5518d0504e8034c0dba30705170 Mon Sep 17 00:00:00 2001
From: Adhiraj Singh <adhirajsingh1001@gmail.com>
Date: Fri, 25 Nov 2022 22:00:25 +0530
Subject: [PATCH] chore: log mutex deadlocks

---
 src/Utils/event-buffer.ts |  2 +-
 src/Utils/make-mutex.ts   | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/Utils/event-buffer.ts b/src/Utils/event-buffer.ts
index ea7803a..71c9385 100644
--- a/src/Utils/event-buffer.ts
+++ b/src/Utils/event-buffer.ts
@@ -21,7 +21,7 @@ const BUFFERABLE_EVENT = [
 	'groups.update',
 ] as const
 
-const BUFFER_TIMEOUT_MS = 30_000
+const BUFFER_TIMEOUT_MS = 60_000
 
 type BufferableEvent = typeof BUFFERABLE_EVENT[number]
 
diff --git a/src/Utils/make-mutex.ts b/src/Utils/make-mutex.ts
index d897903..1b1d70b 100644
--- a/src/Utils/make-mutex.ts
+++ b/src/Utils/make-mutex.ts
@@ -1,16 +1,35 @@
+import logger from './logger'
+
+const MUTEX_TIMEOUT_MS = 60_000
+
 export const makeMutex = () => {
 	let task = Promise.resolve() as Promise<any>
+
+	let taskTimeout: NodeJS.Timeout | undefined
+
 	return {
 		mutex<T>(code: () => Promise<T> | T): Promise<T> {
 			task = (async() => {
+				const stack = new Error('mutex start').stack
+				let waitOver = false
+				taskTimeout = setTimeout(() => {
+					logger.warn({ stack, waitOver }, 'possible mutex deadlock')
+				}, MUTEX_TIMEOUT_MS)
 				// wait for the previous task to complete
 				// if there is an error, we swallow so as to not block the queue
 				try {
 					await task
 				} catch{ }
 
-				// execute the current task
-				return code()
+				waitOver = true
+
+				try {
+					// execute the current task
+					const result = await code()
+					return result
+				} finally {
+					clearTimeout(taskTimeout)
+				}
 			})()
 			// we replace the existing task, appending the new piece of execution to it
 			// so the next task will have to wait for this one to finish