Merge #16355: refactor: move CCoinsViewErrorCatcher out of init.cpp

4f050b91c706181084b9288b8a87b7b637e4e4f7 move-onlyish: move CCoinsViewErrorCatcher out of init.cpp (James O'Beirne)

Pull request description:

  This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11):

  Parent PR: #15606
  Issue: #15605
  Specification: https://github.com/jamesob/assumeutxo-docs/tree/2019-04-proposal/proposal

  ---

  This change moves `CCoinsViewErrorCatcher` out of `init` and into `coins` so that it can later be included in [a `CoinsView` instance](https://github.com/bitcoin/bitcoin/pull/15606/commits/91284964ef34b90ee6c626137973d2c15e7b25da#diff-349fbb003d5ae550a2e8fa658e475880R504) under `CChainState`.

  Instead of hardcoding read failure behavior that has knowledge of qt, it accepts error callbacks via `AddReadErrCallback()`.

ACKs for top commit:
  dongcarl:
    re-ACK 4f050b91c706181084b9288b8a87b7b637e4e4f7
  ryanofsky:
    utACK 4f050b91c706181084b9288b8a87b7b637e4e4f7. Only change since last review is fixing const.

Tree-SHA512: eaba21606d15d2b8d0e3db7cec57779ce181af953db1ef4af80a0bc1dfb57923d0befde9d61b7be55c32224744f7fb6bd47d4e4c72f3ccfe6eaf0f4ae3765c17

3 files changed, 48 insertions, 25 deletions

diff --git a/src/coins.cpp b/src/coins.cpp
index 3ef9e0463c..6b85edd01a 100644
--- a/src/coins.cpp
+++ b/src/coins.cpp
@@ -5,6 +5,7 @@
 #include <coins.h>
 
 #include <consensus/consensus.h>
+#include <logging.h>
 #include <random.h>
 #include <version.h>
 
@@ -258,3 +259,19 @@ const Coin& AccessByTxid(const CCoinsViewCache& view, const uint256& txid)
     }
     return coinEmpty;
 }
+
+bool CCoinsViewErrorCatcher::GetCoin(const COutPoint &outpoint, Coin &coin) const {
+    try {
+        return CCoinsViewBacked::GetCoin(outpoint, coin);
+    } catch(const std::runtime_error& e) {
+        for (auto f : m_err_callbacks) {
+            f();
+        }
+        LogPrintf("Error reading from database: %s\n", e.what());
+        // Starting the shutdown sequence and returning false to the caller would be
+        // interpreted as 'entry not found' (as opposed to unable to read data), and
+        // could lead to invalid interpretation. Just exit immediately, as we can't
+        // continue anyway, and all writes should be atomic.
+        std::abort();
+    }
+}
diff --git a/src/coins.h b/src/coins.h
index 482e233e8c..dca1beabb6 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -17,6 +17,7 @@
 #include <assert.h>
 #include <stdint.h>
 
+#include <functional>
 #include <unordered_map>
 
 /**
@@ -315,4 +316,28 @@ void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool
 //! lookups to database, so it should be used with care.
 const Coin& AccessByTxid(const CCoinsViewCache& cache, const uint256& txid);
 
+/**
+ * This is a minimally invasive approach to shutdown on LevelDB read errors from the
+ * chainstate, while keeping user interface out of the common library, which is shared
+ * between bitcoind, and bitcoin-qt and non-server tools.
+ *
+ * Writes do not need similar protection, as failure to write is handled by the caller.
+*/
+class CCoinsViewErrorCatcher final : public CCoinsViewBacked
+{
+public:
+    explicit CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
+
+    void AddReadErrCallback(std::function<void()> f) {
+        m_err_callbacks.emplace_back(std::move(f));
+    }
+
+    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
+
+private:
+    /** A list of callbacks to execute upon leveldb read error. */
+    std::vector<std::function<void()>> m_err_callbacks;
+
+};
+
 #endif // BITCOIN_COINS_H
diff --git a/src/init.cpp b/src/init.cpp
index 26b2f9d6c2..068b05286c 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -15,6 +15,7 @@
 #include <blockfilter.h>
 #include <chain.h>
 #include <chainparams.h>
+#include <coins.h>
 #include <compat/sanity.h>
 #include <consensus/validation.h>
 #include <fs.h>
@@ -146,31 +147,6 @@ NODISCARD static bool CreatePidFile()
 // shutdown thing.
 //
 
-/**
- * This is a minimally invasive approach to shutdown on LevelDB read errors from the
- * chainstate, while keeping user interface out of the common library, which is shared
- * between bitcoind, and bitcoin-qt and non-server tools.
-*/
-class CCoinsViewErrorCatcher final : public CCoinsViewBacked
-{
-public:
-    explicit CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
-    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override {
-        try {
-            return CCoinsViewBacked::GetCoin(outpoint, coin);
-        } catch(const std::runtime_error& e) {
-            uiInterface.ThreadSafeMessageBox(_("Error reading from database, shutting down."), "", CClientUIInterface::MSG_ERROR);
-            LogPrintf("Error reading from database: %s\n", e.what());
-            // Starting the shutdown sequence and returning false to the caller would be
-            // interpreted as 'entry not found' (as opposed to unable to read data), and
-            // could lead to invalid interpretation. Just exit immediately, as we can't
-            // continue anyway, and all writes should be atomic.
-            abort();
-        }
-    }
-    // Writes do not need similar protection, as failure to write is handled by the caller.
-};
-
 static std::unique_ptr<CCoinsViewErrorCatcher> pcoinscatcher;
 static std::unique_ptr<ECCVerifyHandle> globalVerifyHandle;
 
@@ -1544,6 +1520,11 @@ bool AppInitMain(InitInterfaces& interfaces)
 
                 pcoinsdbview.reset(new CCoinsViewDB(nCoinDBCache, false, fReset || fReindexChainState));
                 pcoinscatcher.reset(new CCoinsViewErrorCatcher(pcoinsdbview.get()));
+                pcoinscatcher->AddReadErrCallback([]() {
+                    uiInterface.ThreadSafeMessageBox(
+                        _("Error reading from database, shutting down."),
+                        "", CClientUIInterface::MSG_ERROR);
+                });
 
                 // If necessary, upgrade from older database format.
                 // This is a no-op if we cleared the coinsviewdb with -reindex or -reindex-chainstate