From 3969958f2c66fe76d0110386b7c0691dc8a12b48 Mon Sep 17 00:00:00 2001
From: Eddy Ashton <edashton@microsoft.com>
Date: Thu, 6 Mar 2025 13:58:57 +0000
Subject: [PATCH 1/4] Protect access to strategies collection

---
 include/ccf/indexing/indexer_interface.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/ccf/indexing/indexer_interface.h b/include/ccf/indexing/indexer_interface.h
index add86f3963d3..08474072ba21 100644
--- a/include/ccf/indexing/indexer_interface.h
+++ b/include/ccf/indexing/indexer_interface.h
@@ -4,6 +4,7 @@
 
 #include "ccf/indexing/strategy.h"
 #include "ccf/node_subsystem_interface.h"
+#include "ccf/pal/locking.h"
 
 #include <map>
 #include <memory>
@@ -19,6 +20,7 @@ namespace ccf::indexing
   class IndexingStrategies : public ccf::AbstractNodeSubSystem
   {
   protected:
+    ccf::pal::Mutex lock;
     std::set<StrategyPtr> strategies;
 
   public:
@@ -36,11 +38,13 @@ namespace ccf::indexing
         throw std::logic_error("Tried to install null strategy");
       }
 
+      std::lock_guard<ccf::pal::Mutex> guard(lock);
       return strategies.insert(strategy).second;
     }
 
     void uninstall_strategy(const StrategyPtr& strategy)
     {
+      std::lock_guard<ccf::pal::Mutex> guard(lock);
       if (strategy == nullptr || strategies.find(strategy) == strategies.end())
       {
         throw std::logic_error("Strategy doesn't exist");
@@ -51,6 +55,7 @@ namespace ccf::indexing
 
     nlohmann::json describe() const
     {
+      std::lock_guard<ccf::pal::Mutex> guard(lock);
       auto j = nlohmann::json::array();
 
       for (const auto& strategy : strategies)

From a57bfef95926e24138ce1061138f8bdacf0eb5f4 Mon Sep 17 00:00:00 2001
From: Eddy Ashton <edashton@microsoft.com>
Date: Thu, 6 Mar 2025 14:00:29 +0000
Subject: [PATCH 2/4] Lock in derived class

---
 src/indexing/indexer.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/indexing/indexer.h b/src/indexing/indexer.h
index a98e583495b5..bf1b6dff2064 100644
--- a/src/indexing/indexer.h
+++ b/src/indexing/indexer.h
@@ -68,6 +68,9 @@ namespace ccf::indexing
       update_commit(newly_committed);
 
       std::optional<ccf::SeqNo> min_requested = std::nullopt;
+
+      std::lock_guard<ccf::pal::Mutex> guard(lock);
+
       for (auto& strategy : strategies)
       {
         strategy->tick();

From 9c27e034fb9e47a6a627b3fb31b562be1a6465cc Mon Sep 17 00:00:00 2001
From: Eddy Ashton <edashton@microsoft.com>
Date: Thu, 6 Mar 2025 14:01:10 +0000
Subject: [PATCH 3/4] Lock max_requested_seqno in LazyStrategy

---
 include/ccf/indexing/strategy.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/ccf/indexing/strategy.h b/include/ccf/indexing/strategy.h
index 1d29483adb64..5f8c95f9b5a8 100644
--- a/include/ccf/indexing/strategy.h
+++ b/include/ccf/indexing/strategy.h
@@ -3,6 +3,7 @@
 #pragma once
 
 #include "ccf/kv/read_only_store.h"
+#include "ccf/pal/locking.h"
 #include "ccf/tx_id.h"
 
 #include <optional>
@@ -68,6 +69,7 @@ namespace ccf::indexing
   class LazyStrategy : public Base
   {
   protected:
+    ccf::pal::Mutex lock;
     ccf::SeqNo max_requested_seqno = 0;
 
   public:
@@ -78,6 +80,7 @@ namespace ccf::indexing
       const auto base = Base::next_requested();
       if (base.has_value())
       {
+        std::lock_guard<ccf::pal::Mutex> guard(lock);
         if (*base <= max_requested_seqno)
         {
           return base;
@@ -89,6 +92,7 @@ namespace ccf::indexing
 
     void extend_index_to(ccf::TxID to_txid)
     {
+      std::lock_guard<ccf::pal::Mutex> guard(lock);
       if (to_txid.seqno > max_requested_seqno)
       {
         max_requested_seqno = to_txid.seqno;

From 3789b440a4e671690bbf6a8f8e712817de3ac7a8 Mon Sep 17 00:00:00 2001
From: Eddy Ashton <edashton@microsoft.com>
Date: Mon, 10 Mar 2025 10:03:47 +0000
Subject: [PATCH 4/4] Hmm

---
 include/ccf/indexing/indexer_interface.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/ccf/indexing/indexer_interface.h b/include/ccf/indexing/indexer_interface.h
index 08474072ba21..58cb70f75afa 100644
--- a/include/ccf/indexing/indexer_interface.h
+++ b/include/ccf/indexing/indexer_interface.h
@@ -53,7 +53,7 @@ namespace ccf::indexing
       strategies.erase(strategy);
     }
 
-    nlohmann::json describe() const
+    nlohmann::json describe()
     {
       std::lock_guard<ccf::pal::Mutex> guard(lock);
       auto j = nlohmann::json::array();