Merge #15323: rpc: Expose g_is_mempool_loaded via getmempoolinfo

effe81f750 Move g_is_mempool_loaded into CTxMemPool::m_is_loaded (Ben Woosley)
bb8ae2c419 rpc: Expose g_is_mempool_loaded via getmempoolinfo and /rest/mempool/info.json (Ben Woosley)

Pull request description:

  And use it to fix a race condition in mempool_persist.py:
  https://travis-ci.org/Empact/bitcoin/jobs/487577243

  Since e.g. getrawmempool returns errors based on this status, this
  enables users to test it for readiness.

  Fixes #12863

ACKs for commit effe81:
  MarcoFalke:
    utACK effe81f750
  jnewbery:
    utACK effe81f7503d2ca3c88cfdea687f9f997f353e0d

Tree-SHA512: 74328b0c17a97efb8a000d4ee49b9a673c2b6dde7ea30c43a6a2eff961a233351c9471f9a42344412135786c02bdf2ee1b2526651bb8fed68bd94d2120c4ef86

8 files changed, 49 insertions, 27 deletions

diff --git a/doc/REST-interface.md b/doc/REST-interface.md
index 02a665008b..c96871ab5f 100644
--- a/doc/REST-interface.md
+++ b/doc/REST-interface.md
@@ -101,6 +101,7 @@ $ curl localhost:18332/rest/getutxos/checkmempool/b2cdfd7b89def827ff8af7cd9bff76
 
 Returns various information about the TX mempool.
 Only supports JSON as output format.
+* loaded : (boolean) if the mempool is fully loaded
 * size : (numeric) the number of transactions in the TX mempool
 * bytes : (numeric) size of the TX mempool in bytes
 * usage : (numeric) total TX mempool memory usage
diff --git a/src/init.cpp b/src/init.cpp
index 2272624f8a..92b3c9510a 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -241,8 +241,8 @@ void Shutdown(InitInterfaces& interfaces)
     g_txindex.reset();
     DestroyAllBlockFilterIndexes();
 
-    if (g_is_mempool_loaded && gArgs.GetArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
-        DumpMempool();
+    if (::mempool.IsLoaded() && gArgs.GetArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
+        DumpMempool(::mempool);
     }
 
     if (fFeeEstimatesInitialized)
@@ -735,9 +735,9 @@ static void ThreadImport(std::vector<fs::path> vImportFiles)
     }
     } // End scope of CImportingNow
     if (gArgs.GetArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
-        LoadMempool();
+        LoadMempool(::mempool);
     }
-    g_is_mempool_loaded = !ShutdownRequested();
+    ::mempool.SetIsLoaded(!ShutdownRequested());
 }
 
 /** Sanity checks
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 672fc69673..e3fab44719 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1491,6 +1491,7 @@ UniValue MempoolInfoToJSON(const CTxMemPool& pool)
     // Make sure this call is atomic in the pool.
     LOCK(pool.cs);
     UniValue ret(UniValue::VOBJ);
+    ret.pushKV("loaded", pool.IsLoaded());
     ret.pushKV("size", (int64_t)pool.size());
     ret.pushKV("bytes", (int64_t)pool.GetTotalTxSize());
     ret.pushKV("usage", (int64_t)pool.DynamicMemoryUsage());
@@ -1511,6 +1512,7 @@ static UniValue getmempoolinfo(const JSONRPCRequest& request)
                 {},
                 RPCResult{
             "{\n"
+            "  \"loaded\": true|false         (boolean) True if the mempool is fully loaded\n"
             "  \"size\": xxxxx,               (numeric) Current tx count\n"
             "  \"bytes\": xxxxx,              (numeric) Sum of all virtual transaction sizes as defined in BIP 141. Differs from actual serialized size because witness data is discounted\n"
             "  \"usage\": xxxxx,              (numeric) Total memory usage for the mempool\n"
@@ -2061,11 +2063,11 @@ static UniValue savemempool(const JSONRPCRequest& request)
             }.ToString());
     }
 
-    if (!g_is_mempool_loaded) {
+    if (!::mempool.IsLoaded()) {
         throw JSONRPCError(RPC_MISC_ERROR, "The mempool was not loaded yet");
     }
 
-    if (!DumpMempool()) {
+    if (!DumpMempool(::mempool)) {
         throw JSONRPCError(RPC_MISC_ERROR, "Unable to dump mempool to disk");
     }
 
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index daac24cc40..90b28227a0 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -1091,4 +1091,16 @@ void CTxMemPool::GetTransactionAncestry(const uint256& txid, size_t& ancestors,
     }
 }
 
+bool CTxMemPool::IsLoaded() const
+{
+    LOCK(cs);
+    return m_is_loaded;
+}
+
+void CTxMemPool::SetIsLoaded(bool loaded)
+{
+    LOCK(cs);
+    m_is_loaded = loaded;
+}
+
 SaltedTxidHasher::SaltedTxidHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}
diff --git a/src/txmempool.h b/src/txmempool.h
index a8a0f7fa45..3ada47a28e 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -455,6 +455,8 @@ private:
 
     void trackPackageRemoved(const CFeeRate& rate) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
+    bool m_is_loaded GUARDED_BY(cs){false};
+
 public:
 
     static const int ROLLING_FEE_HALFLIFE = 60 * 60 * 12; // public only for testing
@@ -672,6 +674,12 @@ public:
      */
     void GetTransactionAncestry(const uint256& txid, size_t& ancestors, size_t& descendants) const;
 
+    /** @returns true if the mempool is fully loaded */
+    bool IsLoaded() const;
+
+    /** Sets the current loaded state */
+    void SetIsLoaded(bool loaded);
+
     unsigned long size() const
     {
         LOCK(cs);
diff --git a/src/validation.cpp b/src/validation.cpp
index d8c8e638ce..1da79e09f6 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -256,7 +256,6 @@ CFeeRate minRelayTxFee = CFeeRate(DEFAULT_MIN_RELAY_TX_FEE);
 
 CBlockPolicyEstimator feeEstimator;
 CTxMemPool mempool(&feeEstimator);
-std::atomic_bool g_is_mempool_loaded{false};
 
 /** Constant stuff for coinbase transactions we create: */
 CScript COINBASE_FLAGS;
@@ -4735,7 +4734,7 @@ int VersionBitsTipStateSinceHeight(const Consensus::Params& params, Consensus::D
 
 static const uint64_t MEMPOOL_DUMP_VERSION = 1;
 
-bool LoadMempool()
+bool LoadMempool(CTxMemPool& pool)
 {
     const CChainParams& chainparams = Params();
     int64_t nExpiryTimeout = gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60;
@@ -4770,12 +4769,12 @@ bool LoadMempool()
 
             CAmount amountdelta = nFeeDelta;
             if (amountdelta) {
-                mempool.PrioritiseTransaction(tx->GetHash(), amountdelta);
+                pool.PrioritiseTransaction(tx->GetHash(), amountdelta);
             }
             CValidationState state;
             if (nTime + nExpiryTimeout > nNow) {
                 LOCK(cs_main);
-                AcceptToMemoryPoolWithTime(chainparams, mempool, state, tx, nullptr /* pfMissingInputs */, nTime,
+                AcceptToMemoryPoolWithTime(chainparams, pool, state, tx, nullptr /* pfMissingInputs */, nTime,
                                            nullptr /* plTxnReplaced */, false /* bypass_limits */, 0 /* nAbsurdFee */,
                                            false /* test_accept */);
                 if (state.IsValid()) {
@@ -4785,7 +4784,7 @@ bool LoadMempool()
                     // 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 (mempool.exists(tx->GetHash())) {
+                    if (pool.exists(tx->GetHash())) {
                         ++already_there;
                     } else {
                         ++failed;
@@ -4801,7 +4800,7 @@ bool LoadMempool()
         file >> mapDeltas;
 
         for (const auto& i : mapDeltas) {
-            mempool.PrioritiseTransaction(i.first, i.second);
+            pool.PrioritiseTransaction(i.first, i.second);
         }
     } catch (const std::exception& e) {
         LogPrintf("Failed to deserialize mempool data on disk: %s. Continuing anyway.\n", e.what());
@@ -4812,7 +4811,7 @@ bool LoadMempool()
     return true;
 }
 
-bool DumpMempool()
+bool DumpMempool(const CTxMemPool& pool)
 {
     int64_t start = GetTimeMicros();
 
@@ -4823,11 +4822,11 @@ bool DumpMempool()
     LOCK(dump_mutex);
 
     {
-        LOCK(mempool.cs);
-        for (const auto &i : mempool.mapDeltas) {
+        LOCK(pool.cs);
+        for (const auto &i : pool.mapDeltas) {
             mapDeltas[i.first] = i.second;
         }
-        vinfo = mempool.infoAll();
+        vinfo = pool.infoAll();
     }
 
     int64_t mid = GetTimeMicros();
diff --git a/src/validation.h b/src/validation.h
index 61a7a270fc..7ab6adaf33 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -142,7 +142,6 @@ extern CScript COINBASE_FLAGS;
 extern CCriticalSection cs_main;
 extern CBlockPolicyEstimator feeEstimator;
 extern CTxMemPool mempool;
-extern std::atomic_bool g_is_mempool_loaded;
 typedef std::unordered_map<uint256, CBlockIndex*, BlockHasher> BlockMap;
 extern BlockMap& mapBlockIndex GUARDED_BY(cs_main);
 extern Mutex g_best_block_mutex;
@@ -474,10 +473,10 @@ static const unsigned int REJECT_HIGHFEE = 0x100;
 CBlockFileInfo* GetBlockFileInfo(size_t n);
 
 /** Dump the mempool to disk. */
-bool DumpMempool();
+bool DumpMempool(const CTxMemPool& pool);
 
 /** Load the mempool from disk. */
-bool LoadMempool();
+bool LoadMempool(CTxMemPool& pool);
 
 //! Check whether the block associated with this index entry is pruned or not.
 inline bool IsBlockPruned(const CBlockIndex* pblockindex)
diff --git a/test/functional/mempool_persist.py b/test/functional/mempool_persist.py
index d74d4eaaf1..bb0169ee52 100755
--- a/test/functional/mempool_persist.py
+++ b/test/functional/mempool_persist.py
@@ -37,7 +37,6 @@ 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
@@ -83,9 +82,10 @@ class MempoolPersistTest(BitcoinTestFramework):
         self.start_node(1, extra_args=["-persistmempool=0"])
         self.start_node(0)
         self.start_node(2)
-        # Give bitcoind a second to reload the mempool
-        wait_until(lambda: len(self.nodes[0].getrawmempool()) == 5, timeout=1)
-        wait_until(lambda: len(self.nodes[2].getrawmempool()) == 5, timeout=1)
+        wait_until(lambda: self.nodes[0].getmempoolinfo()["loaded"], timeout=1)
+        wait_until(lambda: self.nodes[2].getmempoolinfo()["loaded"], timeout=1)
+        assert_equal(len(self.nodes[0].getrawmempool()), 5)
+        assert_equal(len(self.nodes[2].getrawmempool()), 5)
         # The others have loaded their mempool. If node_1 loaded anything, we'd probably notice by now:
         assert_equal(len(self.nodes[1].getrawmempool()), 0)
 
@@ -100,14 +100,14 @@ class MempoolPersistTest(BitcoinTestFramework):
         self.log.debug("Stop-start node0 with -persistmempool=0. Verify that it doesn't load its mempool.dat file.")
         self.stop_nodes()
         self.start_node(0, extra_args=["-persistmempool=0"])
-        # Give bitcoind a second to reload the mempool
-        time.sleep(1)
+        wait_until(lambda: self.nodes[0].getmempoolinfo()["loaded"])
         assert_equal(len(self.nodes[0].getrawmempool()), 0)
 
         self.log.debug("Stop-start node0. Verify that it has the transactions in its mempool.")
         self.stop_nodes()
         self.start_node(0)
-        wait_until(lambda: len(self.nodes[0].getrawmempool()) == 5)
+        wait_until(lambda: self.nodes[0].getmempoolinfo()["loaded"])
+        assert_equal(len(self.nodes[0].getrawmempool()), 5)
 
         mempooldat0 = os.path.join(self.nodes[0].datadir, 'regtest', 'mempool.dat')
         mempooldat1 = os.path.join(self.nodes[1].datadir, 'regtest', 'mempool.dat')
@@ -120,7 +120,8 @@ class MempoolPersistTest(BitcoinTestFramework):
         os.rename(mempooldat0, mempooldat1)
         self.stop_nodes()
         self.start_node(1, extra_args=[])
-        wait_until(lambda: len(self.nodes[1].getrawmempool()) == 5)
+        wait_until(lambda: self.nodes[1].getmempoolinfo()["loaded"])
+        assert_equal(len(self.nodes[1].getrawmempool()), 5)
 
         self.log.debug("Prevent bitcoind from writing mempool.dat to disk. Verify that `savemempool` fails")
         # to test the exception we are creating a tmp folder called mempool.dat.new