From e65d393f481681eb9069be28da51621c92b0bee4 Mon Sep 17 00:00:00 2001
From: ArtificialPB <matej@kriptal.io>
Date: Sat, 14 Dec 2024 13:52:06 +0100
Subject: [PATCH] perf(providers): re-check the event queue while holding the
 lock in `BlockingSubscriptionStream`

this avoids awaiting in case the condition signal was missed
---
 .../kotlin/io/ethers/providers/SubscriptionStream.kt   | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/ethers-providers/src/main/kotlin/io/ethers/providers/SubscriptionStream.kt b/ethers-providers/src/main/kotlin/io/ethers/providers/SubscriptionStream.kt
index 55e6768..71bbc0c 100644
--- a/ethers-providers/src/main/kotlin/io/ethers/providers/SubscriptionStream.kt
+++ b/ethers-providers/src/main/kotlin/io/ethers/providers/SubscriptionStream.kt
@@ -106,7 +106,15 @@ class BlockingSubscriptionStream<T> private constructor(
 
                     // if no next element, wait until next event to avoid CPU cycle burning
                     if (next == null) {
-                        lock.withLock { newEventCondition.await() }
+                        lock.withLock {
+                            // re-check the queue, as it might have been modified by the time we got the lock, and the
+                            // signalling of the condition might have been missed
+                            next = eventQueue.poll()
+
+                            if (next == null) {
+                                newEventCondition.await()
+                            }
+                        }
                     }
                 }