From 29911b6e76a81a0e52473fb3bc9a8c81ad99328e Mon Sep 17 00:00:00 2001
From: BrandonCheng0121 <brandon_cheng@accton.com>
Date: Thu, 25 Jun 2026 16:07:13 +0800
Subject: [PATCH] [Accton][wedge800cact] Fix warmboot
 VerifyHostToQueueMappingClassID failure

Regarding the T1 warmboot.AgentQueuePerHostL2Test.VerifyHostToQueueMappingClassID failure,
the issue is a warmboot stats race condition.
The test gets stale cached ACL stats within milliseconds of warmboot completing because the background stats thread only updates every 1 second.

Solution:
Explicitly call updateStats() in SwSwitch::initialConfigApplied() after warmboot completes to immediately sync hardware stats to software cache.
---
 fboss/agent/SwSwitch.cpp                           | 14 ++++++++++++++
 .../agent_hw_tests/AgentQueuePerHostL2Tests.cpp    |  6 ++++++
 2 files changed, 20 insertions(+)

diff --git a/fboss/agent/SwSwitch.cpp b/fboss/agent/SwSwitch.cpp
index 706777ee77f21..7d89057be8b0d 100644
--- a/fboss/agent/SwSwitch.cpp
+++ b/fboss/agent/SwSwitch.cpp
@@ -1649,6 +1649,20 @@ void SwSwitch::initialConfigApplied(
   sendNeighborSolicitationForConfiguredInterfaces("warm boot");
   sendArpRequestForConfiguredInterfaces("warm boot");
 
+  // After warmboot completes, immediately synchronize hardware stats to
+  // software cache (hwSwitchStats_). This ensures that tests reading stats
+  // immediately after warmboot get correct values instead of stale cached
+  // data. The background stats thread normally updates cache every 1 second,
+  // but tests may read stats within milliseconds of warmboot completing.
+
+  try {
+    XLOG(DBG2) << "Warm boot: synchronizing hardware stats to software cache";
+    updateStats();
+    XLOG(DBG2) << "Warm boot: stats synchronization completed";
+  } catch (const std::exception& ex) {
+    XLOG(ERR) << "Warm boot: stats synchronization failed: " << ex.what();
+  }
+
   if (flags_ & SwitchFlags::PUBLISH_STATS) {
     stats()->switchConfiguredMs(
         duration_cast<std::chrono::milliseconds>(
diff --git a/fboss/agent/test/agent_hw_tests/AgentQueuePerHostL2Tests.cpp b/fboss/agent/test/agent_hw_tests/AgentQueuePerHostL2Tests.cpp
index e1a3bac626964..a5041b4f873f6 100644
--- a/fboss/agent/test/agent_hw_tests/AgentQueuePerHostL2Tests.cpp
+++ b/fboss/agent/test/agent_hw_tests/AgentQueuePerHostL2Tests.cpp
@@ -47,6 +47,8 @@ class AgentQueuePerHostL2Test : public AgentHwTest {
     auto ttlCounterName = utility::getQueuePerHostTtlCounterName();
 
     auto statBefore = utility::getAclInOutPackets(getSw(), ttlCounterName);
+    XLOG(DBG2) << "ACL counter '" << ttlCounterName
+               << "' statBefore = " << statBefore;
 
     std::map<int, int64_t> beforeQueueOutPkts;
     for (const auto& queueId : utility::kQueuePerhostQueueIds()) {
@@ -132,6 +134,10 @@ class AgentQueuePerHostL2Test : public AgentHwTest {
         auto statAfter =
             utility::getAclInOutPackets(this->getSw(), ttlCounterName);
 
+        XLOG(DBG2) << "ACL counter '" << ttlCounterName
+                   << "' statBefore = " << statBefore
+                   << ", statAfter = " << statAfter
+                   << ", delta = " << (statAfter - statBefore);
         /*
          * counts ttl >= 128 packet only
          * but L2 traffic (so TTL is not decremented, and thus looped back