Merge bitcoin/bitcoin#25487: [kernel 3b/n] Decouple `{Dump,Load}Mempool` from `ArgsManager`

cb3e9a1e3f8d72daaa361fc45dd853775e754b9d Move {Load,Dump}Mempool to kernel namespace (Carl Dong)
aa306765419f7dbea12b12e15553039835ba0e4d Move DEFAULT_PERSIST_MEMPOOL out of libbitcoinkernel (Carl Dong)
06b88ffb8ae7f2b2a93a32908cd80e77fafd270c LoadMempool: Pass in load_path, stop using gArgs (Carl Dong)
b857ac60d9a0433036519c26675378bbf56a1de1 test/fuzz: Invoke LoadMempool via CChainState (Carl Dong)
b3267258b052557fc136b9a4dcb754afb9219470 Move FopenFn to fsbridge namespace (Carl Dong)
ae1e8e37567fa603a5977d7d05105c682dd3f7db mempool: Use NodeClock+friends for LoadMempool (Carl Dong)
f9e8e5719f28d84f68f7d75e26c8e7fccac8e7d3 mempool: Improve comments for [GS]etLoadTried (Carl Dong)
813962da0b17b918941c6849996845e35d84a451 scripted-diff: Rename m_is_loaded -> m_load_tried (Carl Dong)
413f4bb52b72e082ad8716664ede48352b8e7e5a DumpMempool: Pass in dump_path, stop using gArgs (Carl Dong)
bd4407817e523e3c5b347bc6be25ed007cb27034 DumpMempool: Use std::chrono instead of weird int64_t arthmetics (Carl Dong)
c84390b741ab7b61c9f702d8b447c8cadc1257c8 test/mempool_persist: Test manual savemempool when -persistmempool=0 (Carl Dong)

Pull request description:

  This is part of the `libbitcoinkernel` project: #24303, https://github.com/bitcoin/bitcoin/projects/18

  -----

  This PR moves `{Dump,Load}Mempool` into its own `kernel/mempool_persist` module and introduces `ArgsManager` `node::` helpers in `node/mempool_persist_args`to remove the scattered calls to `GetBoolArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)`.

  More context can be gleaned from the commit messages.

  -----

  One thing I was reflecting on as I wrote this was that in the long run, I think we should probably invert the validation <-> mempool relationship. Instead of mempool not depending on validation, it might make more sense to have validation not depend on mempool. Not super urgent since `libbitcoinkernel` will include both validation and mempool, but perhaps something for the future.

ACKs for top commit:
  glozow:
    re ACK cb3e9a1e3f8d72daaa361fc45dd853775e754b9d via `git range-diff 7ae032e...cb3e9a1`
  MarcoFalke:
    ACK cb3e9a1e3f 🔒
  ryanofsky:
    Code review ACK cb3e9a1e3f8d72daaa361fc45dd853775e754b9d

Tree-SHA512: 979d7237c3abb5a1dd9b5ad3dbf3b954f906a6d8320ed7b923557f41a4472deccae3e8a6bca0018c8e7a3c4a93afecc502acd1e26756f2054f157f1c0edd939d

2 files changed, 217 insertions, 0 deletions

diff --git a/src/kernel/mempool_persist.cpp b/src/kernel/mempool_persist.cpp
new file mode 100644
index 0000000000..1a1cf2bbdc
--- /dev/null
+++ b/src/kernel/mempool_persist.cpp
@@ -0,0 +1,189 @@
+// 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 <kernel/mempool_persist.h>
+
+#include <clientversion.h>
+#include <consensus/amount.h>
+#include <fs.h>
+#include <logging.h>
+#include <primitives/transaction.h>
+#include <serialize.h>
+#include <shutdown.h>
+#include <streams.h>
+#include <sync.h>
+#include <txmempool.h>
+#include <uint256.h>
+#include <util/system.h>
+#include <util/time.h>
+#include <validation.h>
+
+#include <chrono>
+#include <cstdint>
+#include <cstdio>
+#include <exception>
+#include <functional>
+#include <map>
+#include <memory>
+#include <set>
+#include <stdexcept>
+#include <utility>
+#include <vector>
+
+using fsbridge::FopenFn;
+
+namespace kernel {
+
+static const uint64_t MEMPOOL_DUMP_VERSION = 1;
+
+bool LoadMempool(CTxMemPool& pool, const fs::path& load_path, CChainState& active_chainstate, FopenFn mockable_fopen_function)
+{
+    if (load_path.empty()) return false;
+
+    FILE* filestr{mockable_fopen_function(load_path, "rb")};
+    CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
+    if (file.IsNull()) {
+        LogPrintf("Failed to open mempool file from disk. Continuing anyway.\n");
+        return false;
+    }
+
+    int64_t count = 0;
+    int64_t expired = 0;
+    int64_t failed = 0;
+    int64_t already_there = 0;
+    int64_t unbroadcast = 0;
+    auto now = NodeClock::now();
+
+    try {
+        uint64_t version;
+        file >> version;
+        if (version != MEMPOOL_DUMP_VERSION) {
+            return false;
+        }
+        uint64_t num;
+        file >> num;
+        while (num) {
+            --num;
+            CTransactionRef tx;
+            int64_t nTime;
+            int64_t nFeeDelta;
+            file >> tx;
+            file >> nTime;
+            file >> nFeeDelta;
+
+            CAmount amountdelta = nFeeDelta;
+            if (amountdelta) {
+                pool.PrioritiseTransaction(tx->GetHash(), amountdelta);
+            }
+            if (nTime > TicksSinceEpoch<std::chrono::seconds>(now - pool.m_expiry)) {
+                LOCK(cs_main);
+                const auto& accepted = AcceptToMemoryPool(active_chainstate, tx, nTime, /*bypass_limits=*/false, /*test_accept=*/false);
+                if (accepted.m_result_type == MempoolAcceptResult::ResultType::VALID) {
+                    ++count;
+                } else {
+                    // mempool may contain the transaction already, e.g. from
+                    // wallet(s) having loaded it while we were processing
+                    // mempool transactions; consider these as valid, instead of
+                    // failed, but mark them as 'already there'
+                    if (pool.exists(GenTxid::Txid(tx->GetHash()))) {
+                        ++already_there;
+                    } else {
+                        ++failed;
+                    }
+                }
+            } else {
+                ++expired;
+            }
+            if (ShutdownRequested())
+                return false;
+        }
+        std::map<uint256, CAmount> mapDeltas;
+        file >> mapDeltas;
+
+        for (const auto& i : mapDeltas) {
+            pool.PrioritiseTransaction(i.first, i.second);
+        }
+
+        std::set<uint256> unbroadcast_txids;
+        file >> unbroadcast_txids;
+        unbroadcast = unbroadcast_txids.size();
+        for (const auto& txid : unbroadcast_txids) {
+            // Ensure transactions were accepted to mempool then add to
+            // unbroadcast set.
+            if (pool.get(txid) != nullptr) pool.AddUnbroadcastTx(txid);
+        }
+    } catch (const std::exception& e) {
+        LogPrintf("Failed to deserialize mempool data on disk: %s. Continuing anyway.\n", e.what());
+        return false;
+    }
+
+    LogPrintf("Imported mempool transactions from disk: %i succeeded, %i failed, %i expired, %i already there, %i waiting for initial broadcast\n", count, failed, expired, already_there, unbroadcast);
+    return true;
+}
+
+bool DumpMempool(const CTxMemPool& pool, const fs::path& dump_path, FopenFn mockable_fopen_function, bool skip_file_commit)
+{
+    auto start = SteadyClock::now();
+
+    std::map<uint256, CAmount> mapDeltas;
+    std::vector<TxMempoolInfo> vinfo;
+    std::set<uint256> unbroadcast_txids;
+
+    static Mutex dump_mutex;
+    LOCK(dump_mutex);
+
+    {
+        LOCK(pool.cs);
+        for (const auto &i : pool.mapDeltas) {
+            mapDeltas[i.first] = i.second;
+        }
+        vinfo = pool.infoAll();
+        unbroadcast_txids = pool.GetUnbroadcastTxs();
+    }
+
+    auto mid = SteadyClock::now();
+
+    try {
+        FILE* filestr{mockable_fopen_function(dump_path + ".new", "wb")};
+        if (!filestr) {
+            return false;
+        }
+
+        CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
+
+        uint64_t version = MEMPOOL_DUMP_VERSION;
+        file << version;
+
+        file << (uint64_t)vinfo.size();
+        for (const auto& i : vinfo) {
+            file << *(i.tx);
+            file << int64_t{count_seconds(i.m_time)};
+            file << int64_t{i.nFeeDelta};
+            mapDeltas.erase(i.tx->GetHash());
+        }
+
+        file << mapDeltas;
+
+        LogPrintf("Writing %d unbroadcast transactions to disk.\n", unbroadcast_txids.size());
+        file << unbroadcast_txids;
+
+        if (!skip_file_commit && !FileCommit(file.Get()))
+            throw std::runtime_error("FileCommit failed");
+        file.fclose();
+        if (!RenameOver(dump_path + ".new", dump_path)) {
+            throw std::runtime_error("Rename failed");
+        }
+        auto last = SteadyClock::now();
+
+        LogPrintf("Dumped mempool: %gs to copy, %gs to dump\n",
+                  Ticks<SecondsDouble>(mid - start),
+                  Ticks<SecondsDouble>(last - mid));
+    } catch (const std::exception& e) {
+        LogPrintf("Failed to dump mempool: %s. Continuing anyway.\n", e.what());
+        return false;
+    }
+    return true;
+}
+
+} // namespace kernel
diff --git a/src/kernel/mempool_persist.h b/src/kernel/mempool_persist.h
new file mode 100644
index 0000000000..9a15ec6dca
--- /dev/null
+++ b/src/kernel/mempool_persist.h
@@ -0,0 +1,28 @@
+// 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_KERNEL_MEMPOOL_PERSIST_H
+#define BITCOIN_KERNEL_MEMPOOL_PERSIST_H
+
+#include <fs.h>
+
+class CChainState;
+class CTxMemPool;
+
+namespace kernel {
+
+/** Dump the mempool to disk. */
+bool DumpMempool(const CTxMemPool& pool, const fs::path& dump_path,
+                 fsbridge::FopenFn mockable_fopen_function = fsbridge::fopen,
+                 bool skip_file_commit = false);
+
+/** Load the mempool from disk. */
+bool LoadMempool(CTxMemPool& pool, const fs::path& load_path,
+                 CChainState& active_chainstate,
+                 fsbridge::FopenFn mockable_fopen_function = fsbridge::fopen);
+
+} // namespace kernel
+
+
+#endif // BITCOIN_KERNEL_MEMPOOL_PERSIST_H