From 093be9a2996dbca5f9d0f3f6459941e16fb56bcb Mon Sep 17 00:00:00 2001
From: Michael Vines <mvines@gmail.com>
Date: Fri, 15 May 2020 09:02:48 -0700
Subject: [PATCH] Forge a confirmed root before halting for RPC inspection
 (#10061)

(cherry picked from commit 1da16679203c55ba4b1d9eea0c566db69f948f1a)
---
 core/src/commitment.rs | 1 -
 core/src/validator.rs  | 7 +++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/core/src/commitment.rs b/core/src/commitment.rs
index 427a7b64d36d1e..7de5d07376f0a5 100644
--- a/core/src/commitment.rs
+++ b/core/src/commitment.rs
@@ -180,7 +180,6 @@ impl BlockCommitmentCache {
         }
     }
 
-    #[cfg(test)]
     pub(crate) fn set_get_largest_confirmed_root(&mut self, root: Slot) {
         self.largest_confirmed_root = root;
     }
diff --git a/core/src/validator.rs b/core/src/validator.rs
index bdca14705a5c61..471c485406437c 100644
--- a/core/src/validator.rs
+++ b/core/src/validator.rs
@@ -318,6 +318,13 @@ impl Validator {
         );
 
         if config.dev_halt_at_slot.is_some() {
+            // Simulate a confirmed root to avoid RPC errors with CommitmentmentConfig::max() and
+            // to ensure RPC endpoints like getConfirmedBlock, which require a confirmed root, work
+            block_commitment_cache
+                .write()
+                .unwrap()
+                .set_get_largest_confirmed_root(bank_forks.read().unwrap().root());
+
             // Park with the RPC service running, ready for inspection!
             warn!("Validator halted");
             std::thread::park();