Improve elements memory usage

src/block_proof.cpp

@@ -13,7 +13,7 @@
 bool CheckChallenge(const CBlockHeader& block, const CBlockIndex& indexLast, const Consensus::Params& params)
 {
     if (g_signed_blocks) {
-        return block.proof.challenge == indexLast.proof.challenge;
+        return block.proof.challenge == indexLast.get_proof().challenge;
     } else {
         return block.nBits == GetNextWorkRequired(&indexLast, &block, params);
     }

src/chain.h

@@ -192,10 +192,51 @@ class CBlockIndex
     uint32_t nTime{0};
     uint32_t nBits{0};
     uint32_t nNonce{0};
-    CProof proof{};
+
+protected:
+    std::optional<CProof> proof{};
     // Dynamic federation fields
-    DynaFedParams dynafed_params{};
-    CScriptWitness m_signblock_witness{};
+    std::optional<DynaFedParams> m_dynafed_params{};
+    std::optional<CScriptWitness> m_signblock_witness{};
+
+    bool m_trimmed{false};
+
+    friend class CBlockTreeDB;
+
+public:
+
+    // Irrevocably remove blocksigning and dynafed-related stuff from this
+    // in-memory copy of the block header.
+    void trim() {
+        assert_untrimmed();
+        m_trimmed = true;
+        proof = std::nullopt;
+        m_dynafed_params = std::nullopt;
+        m_signblock_witness = std::nullopt;
+    }
+
+    bool trimmed() const {
+        return m_trimmed;
+    }
+
+    void assert_untrimmed() const {
+        assert(!m_trimmed);
+    }
+
+    const CProof& get_proof() const {
+        assert_untrimmed();
+        return proof.value();
+    }
+
+    const DynaFedParams& dynafed_params() const {
+        assert_untrimmed();
+        return m_dynafed_params.value();
+    }
+
+    const CScriptWitness& signblock_witness() const {
+        assert_untrimmed();
+        return m_signblock_witness.value();
+    }
 
     //! (memory only) Sequential id assigned to distinguish order in which blocks are received.
     int32_t nSequenceId{0};
@@ -214,7 +255,7 @@ class CBlockIndex
           nBits{block.nBits},
           nNonce{block.nNonce},
           proof{block.proof},
-          dynafed_params{block.m_dynafed_params},
+          m_dynafed_params{block.m_dynafed_params},
           m_signblock_witness{block.m_signblock_witness}
     {
     }
@@ -239,6 +280,7 @@ class CBlockIndex
 
     CBlockHeader GetBlockHeader() const
     {
+        assert_untrimmed();
         CBlockHeader block;
         block.nVersion       = nVersion;
         if (pprev)
@@ -250,9 +292,9 @@ class CBlockIndex
         }
         block.nBits          = nBits;
         block.nNonce         = nNonce;
-        block.proof          = proof;
-        block.m_dynafed_params  = dynafed_params;
-        block.m_signblock_witness = m_signblock_witness;
+        block.proof          = proof.value();
+        block.m_dynafed_params  = m_dynafed_params.value();
+        block.m_signblock_witness = m_signblock_witness.value();
         return block;
     }
 
@@ -366,12 +408,12 @@ class CDiskBlockIndex : public CBlockIndex
             nVersion = ~CBlockHeader::DYNAFED_HF_MASK & nVersion;
             return is_dyna;
         } else {
-            return !dynafed_params.IsNull();
+            return !dynafed_params().IsNull();
         }
     }
     bool RemoveDynaFedMaskOnSerialize(bool for_read) const {
         assert(!for_read);
-        return !dynafed_params.IsNull();
+        return !dynafed_params().IsNull();
     }
 
     SERIALIZE_METHODS(CDiskBlockIndex, obj)
@@ -394,7 +436,7 @@ class CDiskBlockIndex : public CBlockIndex
             READWRITE(obj.nVersion);
         } else {
             int32_t nVersion = obj.nVersion;
-            if (!obj.dynafed_params.IsNull()) {
+            if (!obj.dynafed_params().IsNull()) {
                 nVersion |= CBlockHeader::DYNAFED_HF_MASK;
             }
             READWRITE(nVersion);
@@ -406,11 +448,14 @@ class CDiskBlockIndex : public CBlockIndex
         READWRITE(obj.nTime);
         // For compatibility with elements 0.14 based chains
         if (g_signed_blocks) {
+            SER_READ(obj, obj.m_dynafed_params = DynaFedParams());
+            SER_READ(obj, obj.m_signblock_witness = CScriptWitness());
+            SER_READ(obj, obj.proof = CProof());
             if (is_dyna) {
-                READWRITE(obj.dynafed_params);
-                READWRITE(obj.m_signblock_witness.stack);
+                READWRITE(obj.m_dynafed_params.value());
+                READWRITE(obj.m_signblock_witness.value().stack);
             } else {
-                READWRITE(obj.proof);
+                READWRITE(obj.proof.value());
             }
         } else {
             READWRITE(obj.nBits);
@@ -420,6 +465,7 @@ class CDiskBlockIndex : public CBlockIndex
 
     uint256 GetBlockHash() const
     {
+        assert_untrimmed();
         CBlockHeader block;
         block.nVersion        = nVersion;
         block.hashPrevBlock   = hashPrev;
@@ -430,8 +476,8 @@ class CDiskBlockIndex : public CBlockIndex
         }
         block.nBits           = nBits;
         block.nNonce          = nNonce;
-        block.proof           = proof;
-        block.m_dynafed_params   = dynafed_params;
+        block.proof           = proof.value();
+        block.m_dynafed_params   = m_dynafed_params.value();
         return block.GetHash();
     }
 

src/dynafed.cpp

@@ -15,7 +15,7 @@ bool NextBlockIsParameterTransition(const CBlockIndex* pindexPrev, const Consens
     for (int32_t height = next_height - 1; height >= (int32_t)(next_height - consensus.dynamic_epoch_length); --height) {
         const CBlockIndex* p_epoch_walk = pindexPrev->GetAncestor(height);
         assert(p_epoch_walk);
-        const DynaFedParamEntry& proposal = p_epoch_walk->dynafed_params.m_proposed;
+        const DynaFedParamEntry& proposal = p_epoch_walk->dynafed_params().m_proposed;
         const uint256 proposal_root = proposal.CalculateRoot();
         vote_tally[proposal_root]++;
         // Short-circuit once 4/5 threshold is reached
@@ -56,13 +56,13 @@ DynaFedParamEntry ComputeNextBlockFullCurrentParameters(const CBlockIndex* pinde
     // may be pre-dynafed params
     const CBlockIndex* p_epoch_start = pindexPrev->GetAncestor(epoch_start_height);
     assert(p_epoch_start);
-    if (p_epoch_start->dynafed_params.IsNull()) {
+    if (p_epoch_start->dynafed_params().IsNull()) {
         // We need to construct the "full" current parameters of pre-dynafed
         // consensus
 
         // Convert signblockscript to P2WSH
         uint256 signblock_witness_program;
-        CSHA256().Write(p_epoch_start->proof.challenge.data(), p_epoch_start->proof.challenge.size()).Finalize(signblock_witness_program.begin());
+        CSHA256().Write(p_epoch_start->get_proof().challenge.data(), p_epoch_start->get_proof().challenge.size()).Finalize(signblock_witness_program.begin());
         CScript p2wsh_signblock_script = CScript() << OP_0 << ToByteVector(signblock_witness_program);
 
         // Make P2SH-P2WSH-ness of non-dynafed fedpegscript explicit
@@ -75,7 +75,7 @@ DynaFedParamEntry ComputeNextBlockFullCurrentParameters(const CBlockIndex* pinde
         // Put them in winning proposal
         winning_proposal = DynaFedParamEntry(p2wsh_signblock_script, consensus.max_block_signature_size, sh_wsh_fedpeg_program, consensus.fedpegScript, consensus.first_extension_space);
     } else {
-        winning_proposal = p_epoch_start->dynafed_params.m_current;
+        winning_proposal = p_epoch_start->dynafed_params().m_current;
     }
     return winning_proposal;
 }
@@ -93,7 +93,7 @@ DynaFedParamEntry ComputeNextBlockCurrentParameters(const CBlockIndex* pindexPre
 
     // Return appropriate format based on epoch age or if we *just* activated
     // dynafed via BIP9
-    if (epoch_age == 0 || pindexPrev->dynafed_params.IsNull()) {
+    if (epoch_age == 0 || pindexPrev->dynafed_params().IsNull()) {
         return entry;
     } else {
         return DynaFedParamEntry(entry.m_signblockscript, entry.m_signblock_witness_limit, entry.CalculateExtraRoot());

src/init.cpp

@@ -425,6 +425,7 @@ void SetupServerArgs(ArgsManager& argsman)
     hidden_args.emplace_back("-sysperms");
 #endif
     argsman.AddArg("-txindex", strprintf("Maintain a full transaction index, used by the getrawtransaction rpc call (default: %u)", DEFAULT_TXINDEX), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
+    argsman.AddArg("-trim_headers", strprintf("Trim old headers in memory, removing blocksigning and dynafed-related fields. Saves memory, but blocks us from serving blocks or headers to peers, and removes trimmed fields from some JSON RPC outputs. (default: false)"), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-blockfilterindex=<type>",
                  strprintf("Maintain an index of compact filters by block (default: %s, values: %s).", DEFAULT_BLOCKFILTERINDEX, ListBlockFilterTypes()) +
                  " If <type> is not supplied or if <type> = 1, indexes for all known types are enabled.",
@@ -979,6 +980,23 @@ bool AppInitParameterInteraction(const ArgsManager& args)
         fPruneMode = true;
     }
 
+    if (args.IsArgSet("-trim_headers")) {
+        LogPrintf("Configured for header-trimming mode. This will reduce memory usage substantially, but we will be unable to serve as a full P2P peer, and certain header fields may be missing from JSON RPC output.\n");
+        fTrimHeaders = true;
+        // This calculation is driven by GetValidFedpegScripts in pegins.cpp, which walks the chain
+        //   back to current epoch start, and then an additional total_valid_epochs on top of that.
+        //   We add one epoch here for the current partial epoch, and then another one for good luck.
+        // NB: If we're non-dynafed, then:
+        //   - total_valid_epochs = 1
+        //   - dynamic_epoch_length = std::numeric_limits<uint32_t>::max()
+        //   So this will work out to an unhelpfully-large number. XXX: Is this a problem?
+        nMustKeepFullHeaders = (chainparams.GetConsensus().total_valid_epochs + 2) * (chainparams.GetConsensus().dynamic_epoch_length);
+        // This is the number of headers we can have in flight downloading at a time, beyond the
+        //   set of blocks we've already validated. Capping this is necessary to keep memory usage
+        //   bounded during IBD.
+    }
+    nHeaderDownloadBuffer = chainparams.GetConsensus().dynamic_epoch_length * 2;
+
     nConnectTimeout = args.GetArg("-timeout", DEFAULT_CONNECT_TIMEOUT);
     if (nConnectTimeout <= 0) {
         nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
@@ -1690,7 +1708,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
     // if pruning, unset the service bit and perform the initial blockstore prune
     // after any wallet rescanning has taken place.
-    if (fPruneMode) {
+    if (fPruneMode || fTrimHeaders) {
         LogPrintf("Unsetting NODE_NETWORK on prune mode\n");
         nLocalServices = ServiceFlags(nLocalServices & ~NODE_NETWORK);
         if (!fReindex) {
@@ -1702,6 +1720,11 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         }
     }
 
+    if (fTrimHeaders) {
+        LogPrintf("Unsetting NODE_NETWORK_LIMITED on header trim mode\n");
+        nLocalServices = ServiceFlags(nLocalServices & ~NODE_NETWORK_LIMITED);
+    }
+
     if (DeploymentEnabled(chainparams.GetConsensus(), Consensus::DEPLOYMENT_SEGWIT)) {
         // Advertise witness capabilities.
         // The option to not set NODE_WITNESS is only used in the tests and should be removed.

src/miner.cpp

@@ -29,7 +29,7 @@
 
 void ResetChallenge(CBlockHeader& block, const CBlockIndex& indexLast, const Consensus::Params& params)
 {
-    block.proof.challenge = indexLast.proof.challenge;
+    block.proof.challenge = indexLast.get_proof().challenge;
 }
 
 void ResetProof(CBlockHeader& block)

src/node/blockstorage.cpp

@@ -25,6 +25,9 @@ std::atomic_bool fReindex(false);
 bool fHavePruned = false;
 bool fPruneMode = false;
 uint64_t nPruneTarget = 0;
+bool fTrimHeaders = false;
+uint64_t nMustKeepFullHeaders = std::numeric_limits<uint64_t>::max();
+uint64_t nHeaderDownloadBuffer = std::numeric_limits<uint64_t>::max();
 
 // TODO make namespace {
 RecursiveMutex cs_LastBlockFile;

src/node/blockstorage.h

@@ -44,6 +44,13 @@ extern bool fHavePruned;
 extern bool fPruneMode;
 /** Number of MiB of block files that we're trying to stay below. */
 extern uint64_t nPruneTarget;
+/** True if we're running in -trim_headers mode. */
+extern bool fTrimHeaders;
+/** Minimum number of full untrimmed headers to keep, for blocks we have. */
+extern uint64_t nMustKeepFullHeaders;
+/** Target number of headers to download beyond the blocks we have. */
+// XXX: this currently only operates when in header trim mode, but it's really independent of that.
+extern uint64_t nHeaderDownloadBuffer;
 
 //! Check whether the block associated with this index entry is pruned or not.
 bool IsBlockPruned(const CBlockIndex* pblockindex);

src/pegins.cpp

@@ -487,8 +487,8 @@ std::vector<std::pair<CScript, CScript>> GetValidFedpegScripts(const CBlockIndex
             break;
         }
 
-        if (!p_epoch_start->dynafed_params.IsNull()) {
-            fedpegscripts.push_back(std::make_pair(p_epoch_start->dynafed_params.m_current.m_fedpeg_program, p_epoch_start->dynafed_params.m_current.m_fedpegscript));
+        if (!p_epoch_start->dynafed_params().IsNull()) {
+            fedpegscripts.push_back(std::make_pair(p_epoch_start->dynafed_params().m_current.m_fedpeg_program, p_epoch_start->dynafed_params().m_current.m_fedpegscript));
         } else {
             fedpegscripts.push_back(std::make_pair(GetScriptForDestination(ScriptHash(GetScriptForDestination(WitnessV0ScriptHash(params.fedpegScript)))), params.fedpegScript));
         }

src/rpc/blockchain.cpp

@@ -248,13 +248,13 @@ UniValue blockheaderToJSON(const CBlockIndex* tip, const CBlockIndex* blockindex
         result.pushKV("difficulty", GetDifficulty(blockindex));
         result.pushKV("chainwork", blockindex->nChainWork.GetHex());
     } else {
-        if (blockindex->dynafed_params.IsNull()) {
-            result.pushKV("signblock_witness_asm", ScriptToAsmStr(blockindex->proof.solution));
-            result.pushKV("signblock_witness_hex", HexStr(blockindex->proof.solution));
-            result.pushKV("signblock_challenge", HexStr(blockindex->proof.challenge));
+        if (blockindex->dynafed_params().IsNull()) {
+            result.pushKV("signblock_witness_asm", ScriptToAsmStr(blockindex->get_proof().solution));
+            result.pushKV("signblock_witness_hex", HexStr(blockindex->get_proof().solution));
+            result.pushKV("signblock_challenge", HexStr(blockindex->get_proof().challenge));
         } else {
-            result.pushKV("signblock_witness_hex", EncodeHexScriptWitness(blockindex->m_signblock_witness));
-            result.pushKV("dynamic_parameters", dynaParamsToJSON(blockindex->dynafed_params));
+            result.pushKV("signblock_witness_hex", EncodeHexScriptWitness(blockindex->signblock_witness()));
+            result.pushKV("dynamic_parameters", dynaParamsToJSON(blockindex->dynafed_params()));
         }
     }
     result.pushKV("nTx", (uint64_t)blockindex->nTx);