refactor, txdb: Add CoinsViewOptions struct

Add CoinsViewOptions struct to remove ArgsManager uses from txdb.

To reduce size of this commit, this moves references to gArgs variable out of
txdb.cpp to calling code in validation.cpp. But these moves are temporary. The
gArgs references in validation.cpp are moved out to calling code in init.cpp in
later commits.

This commit does not change behavior.

8 files changed, 72 insertions, 40 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 6d5f2eebd3..7b9ffe427d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -204,6 +204,7 @@ BITCOIN_CORE_H = \
   node/chainstate.h \
   node/chainstatemanager_args.h \
   node/coin.h \
+  node/coins_view_args.h \
   node/connection_types.h \
   node/context.h \
   node/database_args.h \
@@ -389,6 +390,7 @@ libbitcoin_node_a_SOURCES = \
   node/chainstate.cpp \
   node/chainstatemanager_args.cpp \
   node/coin.cpp \
+  node/coins_view_args.cpp \
   node/connection_types.cpp \
   node/context.cpp \
   node/database_args.cpp \
diff --git a/src/node/coins_view_args.cpp b/src/node/coins_view_args.cpp
new file mode 100644
index 0000000000..67c9b8dbac
--- /dev/null
+++ b/src/node/coins_view_args.cpp
@@ -0,0 +1,16 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <node/coins_view_args.h>
+
+#include <txdb.h>
+#include <util/system.h>
+
+namespace node {
+void ReadCoinsViewArgs(const ArgsManager& args, CoinsViewOptions& options)
+{
+    if (auto value = args.GetIntArg("-dbbatchsize")) options.batch_write_bytes = *value;
+    if (auto value = args.GetIntArg("-dbcrashratio")) options.simulate_crash_ratio = *value;
+}
+} // namespace node
diff --git a/src/node/coins_view_args.h b/src/node/coins_view_args.h
new file mode 100644
index 0000000000..71a7a671fd
--- /dev/null
+++ b/src/node/coins_view_args.h
@@ -0,0 +1,15 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_NODE_COINS_VIEW_ARGS_H
+#define BITCOIN_NODE_COINS_VIEW_ARGS_H
+
+class ArgsManager;
+struct CoinsViewOptions;
+
+namespace node {
+void ReadCoinsViewArgs(const ArgsManager& args, CoinsViewOptions& options);
+} // namespace node
+
+#endif // BITCOIN_NODE_COINS_VIEW_ARGS_H
diff --git a/src/test/coins_tests.cpp b/src/test/coins_tests.cpp
index 55ecd41af1..eb33e0028e 100644
--- a/src/test/coins_tests.cpp
+++ b/src/test/coins_tests.cpp
@@ -278,7 +278,7 @@ BOOST_AUTO_TEST_CASE(coins_cache_simulation_test)
     CCoinsViewTest base;
     SimulationTest(&base, false);
 
-    CCoinsViewDB db_base{"test", /*nCacheSize=*/1 << 23, /*fMemory=*/true, /*fWipe=*/false};
+    CCoinsViewDB db_base{{.path = "test", .cache_bytes = 1 << 23, .memory_only = true}, {}};
     SimulationTest(&db_base, true);
 }
 
@@ -1064,7 +1064,7 @@ void TestFlushBehavior(
 BOOST_AUTO_TEST_CASE(ccoins_flush_behavior)
 {
     // Create two in-memory caches atop a leveldb view.
-    CCoinsViewDB base{"test", /*nCacheSize=*/ 1 << 23, /*fMemory=*/ true, /*fWipe=*/ false};
+    CCoinsViewDB base{{.path = "test", .cache_bytes = 1 << 23, .memory_only = true}, {}};
     std::vector<std::unique_ptr<CCoinsViewCacheTest>> caches;
     caches.push_back(std::make_unique<CCoinsViewCacheTest>(&base));
     caches.push_back(std::make_unique<CCoinsViewCacheTest>(caches.back().get()));
diff --git a/src/txdb.cpp b/src/txdb.cpp
index 697eaa926d..5803bc7b31 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -71,32 +71,22 @@ struct CoinEntry {
 
 } // namespace
 
-CCoinsViewDB::CCoinsViewDB(fs::path ldb_path, size_t nCacheSize, bool fMemory, bool fWipe) :
-    m_db{std::make_unique<CDBWrapper>(DBParams{
-        .path = ldb_path,
-        .cache_bytes = nCacheSize,
-        .memory_only = fMemory,
-        .wipe_data = fWipe,
-        .obfuscate = true,
-        .options = [] { DBOptions options; node::ReadDatabaseArgs(gArgs, options); return options; }()})},
-    m_ldb_path(ldb_path),
-    m_is_memory(fMemory) { }
+CCoinsViewDB::CCoinsViewDB(DBParams db_params, CoinsViewOptions options) :
+    m_db_params{std::move(db_params)},
+    m_options{std::move(options)},
+    m_db{std::make_unique<CDBWrapper>(m_db_params)} { }
 
 void CCoinsViewDB::ResizeCache(size_t new_cache_size)
 {
     // We can't do this operation with an in-memory DB since we'll lose all the coins upon
     // reset.
-    if (!m_is_memory) {
+    if (!m_db_params.memory_only) {
         // Have to do a reset first to get the original `m_db` state to release its
         // filesystem lock.
         m_db.reset();
-        m_db = std::make_unique<CDBWrapper>(DBParams{
-            .path = m_ldb_path,
-            .cache_bytes = new_cache_size,
-            .memory_only = m_is_memory,
-            .wipe_data = false,
-            .obfuscate = true,
-            .options = [] { DBOptions options; node::ReadDatabaseArgs(gArgs, options); return options; }()});
+        m_db_params.cache_bytes = new_cache_size;
+        m_db_params.wipe_data = false;
+        m_db = std::make_unique<CDBWrapper>(m_db_params);
     }
 }
 
@@ -127,8 +117,6 @@ bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, boo
     CDBBatch batch(*m_db);
     size_t count = 0;
     size_t changed = 0;
-    size_t batch_size = (size_t)gArgs.GetIntArg("-dbbatchsize", nDefaultDbBatchSize);
-    int crash_simulate = gArgs.GetIntArg("-dbcrashratio", 0);
     assert(!hashBlock.IsNull());
 
     uint256 old_tip = GetBestBlock();
@@ -159,13 +147,13 @@ bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, boo
         }
         count++;
         it = erase ? mapCoins.erase(it) : std::next(it);
-        if (batch.SizeEstimate() > batch_size) {
+        if (batch.SizeEstimate() > m_options.batch_write_bytes) {
             LogPrint(BCLog::COINDB, "Writing partial batch of %.2f MiB\n", batch.SizeEstimate() * (1.0 / 1048576.0));
             m_db->WriteBatch(batch);
             batch.Clear();
-            if (crash_simulate) {
+            if (m_options.simulate_crash_ratio) {
                 static FastRandomContext rng;
-                if (rng.randrange(crash_simulate) == 0) {
+                if (rng.randrange(m_options.simulate_crash_ratio) == 0) {
                     LogPrintf("Simulating a crash. Goodbye.\n");
                     _Exit(0);
                 }
diff --git a/src/txdb.h b/src/txdb.h
index e3422846c0..bfbfab57a4 100644
--- a/src/txdb.h
+++ b/src/txdb.h
@@ -45,18 +45,24 @@ static const int64_t max_filter_index_cache = 1024;
 //! Max memory allocated to coin DB specific cache (MiB)
 static const int64_t nMaxCoinsDBCache = 8;
 
+//! User-controlled performance and debug options.
+struct CoinsViewOptions {
+    //! Maximum database write batch size in bytes.
+    size_t batch_write_bytes = nDefaultDbBatchSize;
+    //! If non-zero, randomly exit when the database is flushed with (1/ratio)
+    //! probability.
+    int simulate_crash_ratio = 0;
+};
+
 /** CCoinsView backed by the coin database (chainstate/) */
 class CCoinsViewDB final : public CCoinsView
 {
 protected:
+    DBParams m_db_params;
+    CoinsViewOptions m_options;
     std::unique_ptr<CDBWrapper> m_db;
-    fs::path m_ldb_path;
-    bool m_is_memory;
 public:
-    /**
-     * @param[in] ldb_path    Location in the filesystem where leveldb data will be stored.
-     */
-    explicit CCoinsViewDB(fs::path ldb_path, size_t nCacheSize, bool fMemory, bool fWipe);
+    explicit CCoinsViewDB(DBParams db_params, CoinsViewOptions options);
 
     bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
     bool HaveCoin(const COutPoint &outpoint) const override;
diff --git a/src/validation.cpp b/src/validation.cpp
index f0ffb748dd..971eb346a4 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -28,6 +28,8 @@
 #include <node/blockstorage.h>
 #include <node/interface_ui.h>
 #include <node/utxo_snapshot.h>
+#include <node/coins_view_args.h>
+#include <node/database_args.h>
 #include <policy/policy.h>
 #include <policy/rbf.h>
 #include <policy/settings.h>
@@ -1511,13 +1513,9 @@ CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams)
     return nSubsidy;
 }
 
-CoinsViews::CoinsViews(
-    fs::path ldb_name,
-    size_t cache_size_bytes,
-    bool in_memory,
-    bool should_wipe) : m_dbview(
-                            gArgs.GetDataDirNet() / ldb_name, cache_size_bytes, in_memory, should_wipe),
-                        m_catcherview(&m_dbview) {}
+CoinsViews::CoinsViews(DBParams db_params, CoinsViewOptions options)
+    : m_dbview{std::move(db_params), std::move(options)},
+      m_catcherview(&m_dbview) {}
 
 void CoinsViews::InitCache()
 {
@@ -1546,7 +1544,14 @@ void Chainstate::InitCoinsDB(
     }
 
     m_coins_views = std::make_unique<CoinsViews>(
-        leveldb_name, cache_size_bytes, in_memory, should_wipe);
+        DBParams{
+            .path = gArgs.GetDataDirNet() / leveldb_name,
+            .cache_bytes = cache_size_bytes,
+            .memory_only = in_memory,
+            .wipe_data = should_wipe,
+            .obfuscate = true,
+            .options = [] { DBOptions options; node::ReadDatabaseArgs(gArgs, options); return options; }()},
+        [] { CoinsViewOptions options; node::ReadCoinsViewArgs(gArgs, options); return options; }());
 }
 
 void Chainstate::InitCoinsCache(size_t cache_size_bytes)
diff --git a/src/validation.h b/src/validation.h
index 7170467b00..13a59d32dd 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -408,7 +408,7 @@ public:
     //! state to disk, which should not be done until the health of the database is verified.
     //!
     //! All arguments forwarded onto CCoinsViewDB.
-    CoinsViews(fs::path ldb_name, size_t cache_size_bytes, bool in_memory, bool should_wipe);
+    CoinsViews(DBParams db_params, CoinsViewOptions options);
 
     //! Initialize the CCoinsViewCache member.
     void InitCache() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);