Merge pull request #663 from evoskuil/master

Refactor prune() to be backup/restore safe.

Author: evoskuil

include/bitcoin/database/impl/primitives/arraymap.ipp

@@ -50,17 +50,21 @@ bool CLASS::close() NOEXCEPT
 }
 
 TEMPLATE
-bool CLASS::reset() NOEXCEPT
+bool CLASS::clear() NOEXCEPT
 {
-    Link count{};
-    return head_.clear() && head_.get_body_count(count) &&
-        body_.truncate(count);
+    // Head is nullified and its body reference is zeroized. Body memory
+    // recovery requires truncate/unload/load, which should be preceded by a
+    // snapshot as all existing snapshots will be invalidated by the truncate.
+    // An intervening snapshot will capture the zero count body reference (and
+    // null head links) and will therefore be recoverable whether or not the
+    // truncation succeeds.
+    return head_.clear();
 }
 
 TEMPLATE
-bool CLASS::backup() NOEXCEPT
+bool CLASS::backup(bool prune) NOEXCEPT
 {
-    return head_.set_body_count(body_.count());
+    return head_.set_body_count(prune ? Link{ 0 } : body_.count());
 }
 
 TEMPLATE

include/bitcoin/database/impl/primitives/hashmap.ipp

@@ -51,7 +51,7 @@ bool CLASS::close() NOEXCEPT
 }
 
 TEMPLATE
-bool CLASS::backup() NOEXCEPT
+bool CLASS::backup(bool) NOEXCEPT
 {
     return head_.set_body_count(body_.count());
 }

include/bitcoin/database/impl/primitives/nomap.ipp

@@ -49,7 +49,7 @@ bool CLASS::close() NOEXCEPT
 }
 
 TEMPLATE
-bool CLASS::backup() NOEXCEPT
+bool CLASS::backup(bool) NOEXCEPT
 {
     return head_.set_body_count(manager_.count());
 }

include/bitcoin/database/impl/store.ipp

@@ -429,59 +429,59 @@ code CLASS::prune(const event_handler& handler) NOEXCEPT
     }
 
     code ec{ error::success };
-    const auto prune = [&handler](code& ec, auto& storage, table_t table) NOEXCEPT
-    {
-        if (!ec)
-        {
-            handler(event_t::prune_table, table);
-            if (!storage.reset())
-                ec = error::prune_table;
-        }
-    };
-
-    const auto unload = [&handler](code& ec, auto& storage, table_t table) NOEXCEPT
-    {
-        if (!ec)
-        {
-            handler(event_t::unload_file, table);
-            ec = storage.unload();
-        }
-    };
-
-    const auto load = [&handler](code& ec, auto& storage, table_t table) NOEXCEPT
-    {
-        if (!ec)
-        {
-            handler(event_t::load_file, table);
-            ec = storage.load();
-        }
-    };
 
     // Prevouts resettable if all candidates confirmed (fork is candidate top).
-    if (query<CLASS>{ *this }.is_coalesced())
+    if (!query<CLASS>{ *this }.is_coalesced())
     {
-        // zeroize table head, set body logical size to zero.
-        prune(ec, prevout, table_t::prevout_table);
-
-        // unmap body, setting mapped size to logical size (zero).
-        unload(ec, prevout_body_, table_t::prevout_body);
-
-        // map body, making table usable again.
-        load(ec, prevout_body_, table_t::prevout_body);
+        ec = error::not_coalesced;
     }
     else
     {
-        ec = error::not_coalesced;
+        // nullify table head, set reference body count to zero.
+        handler(event_t::prune_table, table_t::prevout_head);
+        if (!prevout.clear())
+        {
+            ec = error::prune_table;
+        }
+        else
+        {
+            // Snapshot with nullified head and zero body count.
+            // The 'prune' parameter signals to not reset body count.
+            ec = snapshot(handler, true);
+
+            if (!ec)
+            {
+                // zeroize table body, set logical body count to zero.
+                handler(event_t::prune_table, table_t::prevout_body);
+                if (!prevout_body_.truncate(zero))
+                {
+                    ec = error::prune_table;
+                }
+                else
+                {
+                    // unmap body, setting mapped size to logical size (zero).
+                    handler(event_t::unload_file, table_t::prevout_body);
+                    ec = prevout_body_.unload();
+
+                    if (!ec)
+                    {
+                        // map body, making table usable again.
+                        handler(event_t::load_file, table_t::prevout_body);
+                        ec = prevout_body_.load();
+                    }
+                }
+            }
+        }
     }
 
     transactor_mutex_.unlock();
     return ec;
 }
 
 TEMPLATE
-code CLASS::snapshot(const event_handler& handler) NOEXCEPT
+code CLASS::snapshot(const event_handler& handler, bool prune) NOEXCEPT
 {
-    while (!transactor_mutex_.try_lock_for(std::chrono::seconds(1)))
+    while (!prune && !transactor_mutex_.try_lock_for(std::chrono::seconds(1)))
     {
         handler(event_t::wait_lock, table_t::store);
     }
@@ -511,16 +511,16 @@ code CLASS::snapshot(const event_handler& handler) NOEXCEPT
     flush(ec, strong_tx_body_, table_t::strong_tx_body);
 
     flush(ec, duplicate_body_, table_t::duplicate_body);
-    flush(ec, prevout_body_, table_t::prevout_body);
+    if (!prune) flush(ec, prevout_body_, table_t::prevout_body);
     flush(ec, validated_bk_body_, table_t::validated_bk_body);
     flush(ec, validated_tx_body_, table_t::validated_tx_body);
 
     flush(ec, address_body_, table_t::address_body);
     flush(ec, filter_bk_body_, table_t::filter_bk_body);
     flush(ec, filter_tx_body_, table_t::filter_tx_body);
 
-    if (!ec) ec = backup(handler);
-    transactor_mutex_.unlock();
+    if (!ec) ec = backup(handler, prune);
+    if (!prune) transactor_mutex_.unlock();
     return ec;
 }
 
@@ -863,16 +863,16 @@ code CLASS::unload_close(const event_handler& handler) NOEXCEPT
 }
 
 TEMPLATE
-code CLASS::backup(const event_handler& handler) NOEXCEPT
+code CLASS::backup(const event_handler& handler, bool prune) NOEXCEPT
 {
     code ec{ error::success };
     const auto backup = [&handler](code& ec, auto& storage,
-        table_t table) NOEXCEPT
+        table_t table, bool prune=false) NOEXCEPT
     {
         if (!ec)
         {
             handler(event_t::backup_table, table);
-            if (!storage.backup())
+            if (!storage.backup(prune))
                 ec = error::backup_table;
         }
     };
@@ -891,7 +891,7 @@ code CLASS::backup(const event_handler& handler) NOEXCEPT
     backup(ec, strong_tx, table_t::strong_tx_table);
 
     backup(ec, duplicate, table_t::duplicate_table);
-    backup(ec, prevout, table_t::prevout_table);
+    backup(ec, prevout, table_t::prevout_table, prune);
     backup(ec, validated_bk, table_t::validated_bk_table);
     backup(ec, validated_tx, table_t::validated_tx_table);
 

include/bitcoin/database/primitives/arraymap.hpp

@@ -50,8 +50,8 @@ class arraymap
 
     bool create() NOEXCEPT;
     bool close() NOEXCEPT;
-    bool reset() NOEXCEPT;
-    bool backup() NOEXCEPT;
+    bool clear() NOEXCEPT;
+    bool backup(bool prune=false) NOEXCEPT;
     bool restore() NOEXCEPT;
     bool verify() const NOEXCEPT;
 

include/bitcoin/database/primitives/hashmap.hpp

@@ -54,7 +54,7 @@ class hashmap
 
     bool create() NOEXCEPT;
     bool close() NOEXCEPT;
-    bool backup() NOEXCEPT;
+    bool backup(bool=false) NOEXCEPT;
     bool restore() NOEXCEPT;
     bool verify() const NOEXCEPT;
 

include/bitcoin/database/primitives/nomap.hpp

@@ -46,7 +46,7 @@ class nomap
 
     bool create() NOEXCEPT;
     bool close() NOEXCEPT;
-    bool backup() NOEXCEPT;
+    bool backup(bool=false) NOEXCEPT;
     bool restore() NOEXCEPT;
     bool verify() const NOEXCEPT;
 

include/bitcoin/database/store.hpp

@@ -67,7 +67,7 @@ class store
     code prune(const event_handler& handler) NOEXCEPT;
 
     /// Snapshot the set of tables (from loaded, leaves loaded).
-    code snapshot(const event_handler& handler) NOEXCEPT;
+    code snapshot(const event_handler& handler, bool prune=false) NOEXCEPT;
 
     /// Restore the most recent snapshot (from closed, leaves loaded).
     code restore(const event_handler& handler) NOEXCEPT;
@@ -125,7 +125,7 @@ class store
 protected:
     code open_load(const event_handler& handler) NOEXCEPT;
     code unload_close(const event_handler& handler) NOEXCEPT;
-    code backup(const event_handler& handler) NOEXCEPT;
+    code backup(const event_handler& handler, bool prune=false) NOEXCEPT;
     code dump(const std::filesystem::path& folder,
         const event_handler& handler) NOEXCEPT;
 

test/primitives/arraymap.cpp

@@ -834,16 +834,17 @@ BOOST_AUTO_TEST_CASE(arraymap__record_body_count__nine_close__nine)
     BOOST_REQUIRE(!instance.get_fault());
 }
 
+// Close resets the cleared body count.
 BOOST_AUTO_TEST_CASE(arraymap__reset__nine_close__zero)
 {
     data_chunk head(initial_head_size, 0xff);
     auto body = base16_chunk("112233441122334411223344112233441122334411223344112233441122334411223344");
     test::chunk_storage head_store{ head };
     test::chunk_storage body_store{ body };
     record_table instance{ head_store, body_store, initial_buckets };
-    BOOST_REQUIRE(instance.reset());
+    BOOST_REQUIRE(instance.clear());
     BOOST_REQUIRE(instance.close());
-    BOOST_REQUIRE_EQUAL(head_store.buffer(), base16_chunk("000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"));
+    BOOST_REQUIRE_EQUAL(head_store.buffer(), base16_chunk("090000ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"));
     BOOST_REQUIRE(!instance.get_fault());
 }