From f0d5e3addd803d7bb60e53bebec5a6d583e0e5da Mon Sep 17 00:00:00 2001
From: hghaf099 <83242695+hghaf099@users.noreply.github.com>
Date: Mon, 4 Oct 2021 15:56:47 -0400
Subject: [PATCH] Fix a Deadlock on HA leadership transfer (#12691) (#12721)

* Fix a Deadlock on HA leadership transfer when standby
was actively forwarding a request
fixes GH #12601

* adding the changelog
---
 changelog/12691.txt         | 3 +++
 vault/request_forwarding.go | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 changelog/12691.txt

diff --git a/changelog/12691.txt b/changelog/12691.txt
new file mode 100644
index 0000000000000..2a8efdc8001d6
--- /dev/null
+++ b/changelog/12691.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+core: Fix a deadlock on HA leadership transfer
+```
diff --git a/vault/request_forwarding.go b/vault/request_forwarding.go
index c76fbaa4e5133..f6f01cbc07ee5 100644
--- a/vault/request_forwarding.go
+++ b/vault/request_forwarding.go
@@ -329,6 +329,9 @@ func (c *Core) clearForwardingClients() {
 // ForwardRequest forwards a given request to the active node and returns the
 // response.
 func (c *Core) ForwardRequest(req *http.Request) (int, http.Header, []byte, error) {
+	// checking if the node is perfStandby here to avoid a deadlock between
+	// Core.stateLock and Core.requestForwardingConnectionLock
+	isPerfStandby := c.PerfStandby()
 	c.requestForwardingConnectionLock.RLock()
 	defer c.requestForwardingConnectionLock.RUnlock()
 
@@ -369,7 +372,7 @@ func (c *Core) ForwardRequest(req *http.Request) (int, http.Header, []byte, erro
 	// If we are a perf standby and the request was forwarded to the active node
 	// we should attempt to wait for the WAL to ship to offer best effort read after
 	// write guarantees
-	if c.PerfStandby() && resp.LastRemoteWal > 0 {
+	if isPerfStandby && resp.LastRemoteWal > 0 {
 		WaitUntilWALShipped(req.Context(), c, resp.LastRemoteWal)
 	}