Merge #16908: txmempool: Make entry time type-safe (std::chrono)

faec689bed txmempool: Make entry time type-safe (std::chrono) (MarcoFalke)
faaa1f01da util: Add count_seconds time helper (MarcoFalke)
1111170f2f test: mempool entry time is persisted (MarcoFalke)

Pull request description:

  This changes the type of the entry time of txs into the mempool from `int64_t` to `std::chrono::seconds`.

  The benefits:
  * Documents the type for developers
  * Type violations result in compile errors
  * After compilation, the two are equivalent (at no run time cost)

ACKs for top commit:
  ajtowns:
    utACK faec689bed
  laanwj:
    ACK faec689bed

Tree-SHA512: d958e058755d1a1d54cef536a8b30a11cc502b7df0d6ecf84a0ab1d38bc8105a67668a99cd5087a444f6de2421238111c5fca133cdf8e2e2273cb12cb6957845

src/net.h

@@ -761,7 +761,7 @@ public:
         // Used for BIP35 mempool sending
         bool fSendMempool GUARDED_BY(cs_tx_inventory){false};
         // Last time a "MEMPOOL" request was serviced.
-        std::atomic<int64_t> timeLastMempoolReq{0};
+        std::atomic<std::chrono::seconds> m_last_mempool_req{std::chrono::seconds{0}};
         int64_t nNextInvSend{0};
 
         CCriticalSection cs_feeFilter;

src/net_processing.cpp

@@ -1541,11 +1541,11 @@ void static ProcessGetData(CNode* pfrom, const CChainParams& chainparams, CConnm
             if (mi != mapRelay.end()) {
                 connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *mi->second));
                 push = true;
-            } else if (pfrom->m_tx_relay->timeLastMempoolReq) {
+            } else if (pfrom->m_tx_relay->m_last_mempool_req.load().count()) {
                 auto txinfo = mempool.info(inv.hash);
                 // To protect privacy, do not answer getdata using the mempool when
                 // that TX couldn't have been INVed in reply to a MEMPOOL request.
-                if (txinfo.tx && txinfo.nTime <= pfrom->m_tx_relay->timeLastMempoolReq) {
+                if (txinfo.tx && txinfo.m_time <= pfrom->m_tx_relay->m_last_mempool_req.load()) {
                     connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *txinfo.tx));
                     push = true;
                 }
@@ -3873,7 +3873,7 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
                             vInv.clear();
                         }
                     }
-                    pto->m_tx_relay->timeLastMempoolReq = GetTime();
+                    pto->m_tx_relay->m_last_mempool_req = GetTime<std::chrono::seconds>();
                 }
 
                 // Determine transactions to relay

src/rpc/blockchain.cpp

@@ -418,7 +418,7 @@ static void entryToJSON(const CTxMemPool& pool, UniValue& info, const CTxMemPool
     info.pushKV("weight", (int)e.GetTxWeight());
     info.pushKV("fee", ValueFromAmount(e.GetFee()));
     info.pushKV("modifiedfee", ValueFromAmount(e.GetModifiedFee()));
-    info.pushKV("time", e.GetTime());
+    info.pushKV("time", count_seconds(e.GetTime()));
     info.pushKV("height", (int)e.GetHeight());
     info.pushKV("descendantcount", e.GetCountWithDescendants());
     info.pushKV("descendantsize", e.GetSizeWithDescendants());

src/txmempool.cpp

@@ -917,7 +917,8 @@ void CTxMemPool::RemoveStaged(setEntries &stage, bool updateDescendants, MemPool
     }
 }
 
-int CTxMemPool::Expire(int64_t time) {
+int CTxMemPool::Expire(std::chrono::seconds time)
+{
     AssertLockHeld(cs);
     indexed_transaction_set::index<entry_time>::type::iterator it = mapTx.get<entry_time>().begin();
     setEntries toremove;

src/txmempool.h

@@ -102,7 +102,7 @@ public:
     const CAmount& GetFee() const { return nFee; }
     size_t GetTxSize() const;
     size_t GetTxWeight() const { return nTxWeight; }
-    int64_t GetTime() const { return nTime; }
+    std::chrono::seconds GetTime() const { return std::chrono::seconds{nTime}; }
     unsigned int GetHeight() const { return entryHeight; }
     int64_t GetSigOpCost() const { return sigOpCost; }
     int64_t GetModifiedFee() const { return nFee + feeDelta; }
@@ -332,7 +332,7 @@ struct TxMempoolInfo
     CTransactionRef tx;
 
     /** Time the transaction entered the mempool. */
-    int64_t nTime;
+    std::chrono::seconds m_time;
 
     /** Feerate of the transaction. */
     CFeeRate feeRate;
@@ -657,7 +657,7 @@ public:
     void TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpendsRemaining = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /** Expire all transaction (and their dependencies) in the mempool older than time. Return the number of removed transactions. */
-    int Expire(int64_t time) EXCLUSIVE_LOCKS_REQUIRED(cs);
+    int Expire(std::chrono::seconds time) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
      * Calculate the ancestor and descendant count for the given transaction.

src/util/time.h

@@ -10,6 +10,14 @@
 #include <string>
 #include <chrono>
 
+/**
+ * Helper to count the seconds of a duration.
+ *
+ * All durations should be using std::chrono and calling this should generally be avoided in code. Though, it is still
+ * preferred to an inline t.count() to protect against a reliance on the exact type of t.
+ */
+inline int64_t count_seconds(std::chrono::seconds t) { return t.count(); }
+
 /**
  * DEPRECATED
  * Use either GetSystemTimeInSeconds (not mockable) or GetTime<T> (mockable)

src/validation.cpp

@@ -314,10 +314,10 @@ bool CheckSequenceLocks(const CTxMemPool& pool, const CTransaction& tx, int flag
 // Returns the script flags which should be checked for a given block
 static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& chainparams);
 
-static void LimitMempoolSize(CTxMemPool& pool, size_t limit, unsigned long age)
+static void LimitMempoolSize(CTxMemPool& pool, size_t limit, std::chrono::seconds age)
     EXCLUSIVE_LOCKS_REQUIRED(pool.cs, ::cs_main)
 {
-    int expired = pool.Expire(GetTime() - age);
+    int expired = pool.Expire(GetTime<std::chrono::seconds>() - age);
     if (expired != 0) {
         LogPrint(BCLog::MEMPOOL, "Expired %i transactions from the memory pool\n", expired);
     }
@@ -389,7 +389,7 @@ static void UpdateMempoolForReorg(DisconnectedBlockTransactions& disconnectpool,
     // We also need to remove any now-immature transactions
     mempool.removeForReorg(&::ChainstateActive().CoinsTip(), ::ChainActive().Tip()->nHeight + 1, STANDARD_LOCKTIME_VERIFY_FLAGS);
     // Re-limit mempool size, in case we added any transactions
-    LimitMempoolSize(mempool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
+    LimitMempoolSize(mempool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, std::chrono::hours{gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
 }
 
 // Used to avoid mempool polluting consensus critical paths if CCoinsViewMempool
@@ -1011,7 +1011,7 @@ bool MemPoolAccept::Finalize(ATMPArgs& args, Workspace& ws)
 
     // trim mempool and check if tx was trimmed
     if (!bypass_limits) {
-        LimitMempoolSize(m_pool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
+        LimitMempoolSize(m_pool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, std::chrono::hours{gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
         if (!m_pool.exists(hash))
             return state.Invalid(ValidationInvalidReason::TX_MEMPOOL_POLICY, false, REJECT_INSUFFICIENTFEE, "mempool full");
     }
@@ -5041,8 +5041,8 @@ bool DumpMempool(const CTxMemPool& pool)
         file << (uint64_t)vinfo.size();
         for (const auto& i : vinfo) {
             file << *(i.tx);
-            file << (int64_t)i.nTime;
-            file << (int64_t)i.nFeeDelta;
+            file << int64_t{count_seconds(i.m_time)};
+            file << int64_t{i.nFeeDelta};
             mapDeltas.erase(i.tx->GetHash());
         }
 

test/functional/mempool_persist.py

@@ -37,9 +37,15 @@ Test is as follows:
 """
 from decimal import Decimal
 import os
+import time
 
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, assert_raises_rpc_error, wait_until
+from test_framework.util import (
+    assert_equal,
+    assert_greater_than_or_equal,
+    assert_raises_rpc_error,
+    wait_until,
+)
 
 
 class MempoolPersistTest(BitcoinTestFramework):
@@ -51,18 +57,13 @@ class MempoolPersistTest(BitcoinTestFramework):
         self.skip_if_no_wallet()
 
     def run_test(self):
-        chain_height = self.nodes[0].getblockcount()
-        assert_equal(chain_height, 200)
-
-        self.log.debug("Mine a single block to get out of IBD")
-        self.nodes[0].generate(1)
-        self.sync_all()
-
         self.log.debug("Send 5 transactions from node2 (to its own address)")
+        tx_creation_time_lower = int(time.time())
         for i in range(5):
             last_txid = self.nodes[2].sendtoaddress(self.nodes[2].getnewaddress(), Decimal("10"))
         node2_balance = self.nodes[2].getbalance()
         self.sync_all()
+        tx_creation_time_higher = int(time.time())
 
         self.log.debug("Verify that node0 and node1 have 5 transactions in their mempools")
         assert_equal(len(self.nodes[0].getrawmempool()), 5)
@@ -75,6 +76,10 @@ class MempoolPersistTest(BitcoinTestFramework):
         fees = self.nodes[0].getmempoolentry(txid=last_txid)['fees']
         assert_equal(fees['base'] + Decimal('0.00001000'), fees['modified'])
 
+        tx_creation_time = self.nodes[0].getmempoolentry(txid=last_txid)['time']
+        assert_greater_than_or_equal(tx_creation_time, tx_creation_time_lower)
+        assert_greater_than_or_equal(tx_creation_time_higher, tx_creation_time)
+
         self.log.debug("Stop-start the nodes. Verify that node0 has the transactions in its mempool and node1 does not. Verify that node2 calculates its balance correctly after loading wallet transactions.")
         self.stop_nodes()
         # Give this node a head-start, so we can be "extra-sure" that it didn't load anything later
@@ -93,6 +98,9 @@ class MempoolPersistTest(BitcoinTestFramework):
         fees = self.nodes[0].getmempoolentry(txid=last_txid)['fees']
         assert_equal(fees['base'] + Decimal('0.00001000'), fees['modified'])
 
+        self.log.debug('Verify time is loaded correctly')
+        assert_equal(tx_creation_time, self.nodes[0].getmempoolentry(txid=last_txid)['time'])
+
         # Verify accounting of mempool transactions after restart is correct
         self.nodes[2].syncwithvalidationinterfacequeue()  # Flush mempool to wallet
         assert_equal(node2_balance, self.nodes[2].getbalance())