[index] Allow TxIndex sync thread to be interrupted.

Author: Jim Posen

src/index/txindex.cpp

@@ -30,6 +30,12 @@ TxIndex::TxIndex(std::unique_ptr<TxIndexDB> db) :
     m_db(std::move(db)), m_synced(false), m_best_block_index(nullptr)
 {}
 
+TxIndex::~TxIndex()
+{
+    Interrupt();
+    Stop();
+}
+
 bool TxIndex::Init()
 {
     LOCK(cs_main);
@@ -76,6 +82,11 @@ void TxIndex::ThreadSync()
         int64_t last_log_time = 0;
         int64_t last_locator_write_time = 0;
         while (true) {
+            if (m_interrupt) {
+                WriteBestBlock(pindex);
+                return;
+            }
+
             {
                 LOCK(cs_main);
                 const CBlockIndex* pindex_next = NextSyncBlock(pindex);
@@ -222,6 +233,11 @@ bool TxIndex::FindTx(const uint256& txid, CDiskTxPos& pos) const
     return m_db->ReadTxPos(txid, pos);
 }
 
+void TxIndex::Interrupt()
+{
+    m_interrupt();
+}
+
 void TxIndex::Start()
 {
     // Need to register this ValidationInterface before running Init(), so that

src/index/txindex.h

@@ -6,6 +6,7 @@
 #define BITCOIN_INDEX_TXINDEX_H
 
 #include <primitives/block.h>
+#include <threadinterrupt.h>
 #include <txdb.h>
 #include <uint256.h>
 #include <validationinterface.h>
@@ -31,14 +32,16 @@ class TxIndex final : public CValidationInterface
     std::atomic<const CBlockIndex*> m_best_block_index;
 
     std::thread m_thread_sync;
+    CThreadInterrupt m_interrupt;
 
     /// Initialize internal state from the database and block index.
     bool Init();
 
     /// Sync the tx index with the block index starting from the current best
-    /// block. Intended to be run in its own thread, m_thread_sync. Once the
-    /// txindex gets in sync, the m_synced flag is set and the BlockConnected
-    /// ValidationInterface callback takes over and the sync thread exits.
+    /// block. Intended to be run in its own thread, m_thread_sync, and can be
+    /// interrupted with m_interrupt. Once the txindex gets in sync, the
+    /// m_synced flag is set and the BlockConnected ValidationInterface callback
+    /// takes over and the sync thread exits.
     void ThreadSync();
 
     /// Write update index entries for a newly connected block.
@@ -57,9 +60,14 @@ class TxIndex final : public CValidationInterface
     /// Constructs the TxIndex, which becomes available to be queried.
     explicit TxIndex(std::unique_ptr<TxIndexDB> db);
 
+    /// Destructor interrupts sync thread if running and blocks until it exits.
+    ~TxIndex();
+
     /// Look up the on-disk location of a transaction by hash.
     bool FindTx(const uint256& txid, CDiskTxPos& pos) const;
 
+    void Interrupt();
+
     /// Start initializes the sync state and registers the instance as a
     /// ValidationInterface so that it stays in sync with blockchain updates.
     void Start();

src/threadinterrupt.cpp

@@ -5,6 +5,8 @@
 
 #include <threadinterrupt.h>
 
+CThreadInterrupt::CThreadInterrupt() : flag(false) {}
+
 CThreadInterrupt::operator bool() const
 {
     return flag.load(std::memory_order_acquire);

src/threadinterrupt.h

@@ -18,6 +18,7 @@
 class CThreadInterrupt
 {
 public:
+    CThreadInterrupt();
     explicit operator bool() const;
     void operator()();
     void reset();