Merge pull request #1190 from gwillen/fix-elements-memory-usage

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 @@ public:
     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 @@ public:
           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 @@ public:
 
     CBlockHeader GetBlockHeader() const
     {
+        assert_untrimmed();
         CBlockHeader block;
         block.nVersion       = nVersion;
         if (pprev)
@@ -250,9 +292,9 @@ public:
         }
         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 @@ public:
             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 @@ public:
             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);
@@ -404,13 +446,19 @@ public:
         READWRITE(obj.hashPrev);
         READWRITE(obj.hashMerkleRoot);
         READWRITE(obj.nTime);
+
+        // Allocate objects in the optional<> fields when reading, since READWRITE will not do this
+        SER_READ(obj, obj.m_dynafed_params = DynaFedParams());
+        SER_READ(obj, obj.m_signblock_witness = CScriptWitness());
+        SER_READ(obj, obj.proof = CProof());
+
         // For compatibility with elements 0.14 based chains
         if (g_signed_blocks) {
             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 +468,7 @@ public:
 
     uint256 GetBlockHash() const
     {
+        assert_untrimmed();
         CBlockHeader block;
         block.nVersion        = nVersion;
         block.hashPrevBlock   = hashPrev;
@@ -430,8 +479,8 @@ public:
         }
         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 (by default older than 2 epochs), 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 +980,26 @@ bool AppInitParameterInteraction(const ArgsManager& args)
         fPruneMode = true;
     }
 
+    uint32_t epoch_length = chainparams.GetConsensus().dynamic_epoch_length;
+    if (epoch_length == std::numeric_limits<uint32_t>::max()) {
+        // That's the default value, for non-dynafed chains and some tests. Pick a more sensible default here.
+        epoch_length = 20160;
+    }
+
+    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.
+
+        nMustKeepFullHeaders = (chainparams.GetConsensus().total_valid_epochs + 2) * 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 = epoch_length * 2;
+
     nConnectTimeout = args.GetArg("-timeout", DEFAULT_CONNECT_TIMEOUT);
     if (nConnectTimeout <= 0) {
         nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
@@ -1690,7 +1711,7 @@ 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 +1723,11 @@ 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/net_processing.cpp

@@ -48,7 +48,7 @@ static constexpr auto UNCONDITIONAL_RELAY_DELAY = 2min;
 /** Headers download timeout.
  *  Timeout = base + per_header * (expected number of headers) */
 static constexpr auto HEADERS_DOWNLOAD_TIMEOUT_BASE = 15min;
-static constexpr auto HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER = 1ms;
+static constexpr auto HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER = 2ms;
 /** Protect at least this many outbound peers from disconnection due to slow/
  * behind headers chain.
  */
@@ -910,6 +910,10 @@ bool PeerManagerImpl::TipMayBeStale()
 
 bool PeerManagerImpl::CanDirectFetch()
 {
+    if(!m_chainman.ActiveChain().Tip()) {
+        LogPrint(BCLog::NET, "Tried to call CanDirectFetch with no currently-active chain.\n");
+        return false;
+    }
     return m_chainman.ActiveChain().Tip()->GetBlockTime() > GetAdjustedTime() - m_chainparams.GetConsensus().nPowTargetSpacing * 20;
 }
 
@@ -2007,6 +2011,36 @@ void PeerManagerImpl::ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
         return;
     }
 
+    // If we are already too far ahead of where we want to be on headers, discard
+    //   the received headers. We can still get ahead by up to a single maximum-sized
+    //   headers message here, but never further, so that's fine.
+    if (pindexBestHeader) {
+        uint64_t headers_ahead = pindexBestHeader->nHeight - m_chainman.ActiveHeight();
+        bool too_far_ahead = fTrimHeaders && (headers_ahead >= nHeaderDownloadBuffer);
+        if (too_far_ahead) {
+            LOCK(cs_main);
+            CNodeState *nodestate = State(pfrom.GetId());
+            if ((nodestate->pindexBestKnownBlock == nullptr) ||
+                (nodestate->pindexBestKnownBlock->nHeight < m_chainman.ActiveHeight())) {
+                // Our notion of what blocks a peer has available is based on its pindexBestKnownBlock,
+                // which is based on headers recieved from it. If we don't have one, or it's too old,
+                // then we can never get blocks from this peer until we accept headers from it first.
+                LogPrint(BCLog::NET, "NOT discarding headers from peer=%d, to update its block availability. (current best header %d, active chain height %d)\n", pfrom.GetId(), pindexBestHeader->nHeight, m_chainman.ActiveHeight());
+            } else {
+                LogPrint(BCLog::NET, "Discarding received headers and pausing header sync from peer=%d, because we are too far ahead of block sync. (%d > %d)\n", pfrom.GetId(), pindexBestHeader->nHeight, m_chainman.ActiveHeight());
+                if (nodestate->fSyncStarted) {
+                    // Cancel sync from this node, so we don't penalize it later.
+                    // This will cause us to automatically start syncing from a different node (or restart syncing from the same node) later,
+                    //   if we still need to sync headers.
+                    nSyncStarted--;
+                    nodestate->fSyncStarted = false;
+                    nodestate->m_headers_sync_timeout = 0us;
+                }
+                return;
+            }
+        }
+    }
+
     bool received_new_header = false;
     const CBlockIndex *pindexLast = nullptr;
     {
@@ -2084,14 +2118,29 @@ void PeerManagerImpl::ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
             nodestate->m_last_block_announcement = GetTime();
         }
 
-        if (nCount == MAX_HEADERS_RESULTS && !all_duplicate) {
-            // Headers message had its maximum size; the peer may have more headers.
-            // TODO: optimize: if pindexLast is an ancestor of m_chainman.ActiveChain().Tip or pindexBestHeader, continue
-            // from there instead.
-            // HOWEVER, if all headers we got this time were duplicates that we already had, don't ask for any more.
-            LogPrint(BCLog::NET, "more getheaders (%d) to end to peer=%d (startheight:%d)\n",
-                                 pindexLast->nHeight, pfrom.GetId(), peer.m_starting_height);
-            m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETHEADERS, m_chainman.ActiveChain().GetLocator(pindexLast), uint256()));
+        // If a peer gives us as many headers as possible, this is implicitly a signal that the
+        //   peer has more headers to send us. In Bitcoin Core, the node always asks for more
+        //   headers at this point. Our logic is slightly more complex, to work around an apparent
+        //   bug in the Bitcoin Core state machine, where we can end up downloading headers from
+        ///  lots of peers at the same time by accident.
+        if (nCount == MAX_HEADERS_RESULTS) {
+            if (all_duplicate && !nodestate->fSyncStarted) {
+                // In this case two things are true:
+                // 1) This node's most recent batch of headers only included ones we already had.
+                // 2) We don't have this node marked as a peer to header-sync from.
+                // This happens when some exogenous event, like an INV of a new block, causes us
+                //   to ask a peer for an unbounded number of headers, when we're already in the
+                //   process of downloading the headers from a different peer.
+                // In this case the right thing to do is simply stop syncing headers from this
+                //   peer; it's redundant. Here we do nothing; since we don't ask the peer for
+                //   more headers, it will stop sending them.
+            } else {
+                // TODO: optimize: if pindexLast is an ancestor of m_chainman.ActiveChain().Tip or pindexBestHeader, continue
+                // from there instead.
+                LogPrint(BCLog::NET, "more getheaders (%d) to end to peer=%d (startheight:%d)\n",
+                                    pindexLast->nHeight, pfrom.GetId(), peer.m_starting_height);
+                m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::GETHEADERS, m_chainman.ActiveChain().GetLocator(pindexLast), uint256()));
+            }
         }
 
         // If this set of headers is valid and ends in a block with at least as
@@ -3133,10 +3182,17 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
         LogPrint(BCLog::NET, "getheaders %d to %s from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.IsNull() ? "end" : hashStop.ToString(), pfrom.GetId());
         for (; pindex; pindex = m_chainman.ActiveChain().Next(pindex))
         {
+            if (pindex->trimmed()) {
+                // For simplicity, if any of the headers they're asking for are trimmed,
+                //   just drop the request.
+                LogPrint(BCLog::NET, "%s: ignoring getheaders from peer=%i which would return at least one trimmed header\n", __func__, pfrom.GetId());
+                return;
+            }
             vHeaders.push_back(pindex->GetBlockHeader());
             if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop)
                 break;
         }
+
         // pindex can be nullptr either if we sent m_chainman.ActiveChain().Tip() OR
         // if our peer has m_chainman.ActiveChain().Tip() (and thus we are sending an empty
         // headers message). In both cases it's safe to update
@@ -4476,7 +4532,10 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
         if (pindexBestHeader == nullptr)
             pindexBestHeader = m_chainman.ActiveChain().Tip();
         bool fFetch = state.fPreferredDownload || (nPreferredDownload == 0 && !pto->fClient && !pto->IsAddrFetchConn()); // Download if this is a nice peer, or we have no nice peers and this one might do.
-        if (!state.fSyncStarted && !pto->fClient && !fImporting && !fReindex) {
+        uint64_t headers_ahead = pindexBestHeader->nHeight - m_chainman.ActiveHeight();
+        // ELEMENTS: Only download if our headers aren't "too far ahead" of our blocks.
+        bool got_enough_headers = fTrimHeaders && (headers_ahead >= nHeaderDownloadBuffer);
+        if (!state.fSyncStarted && !pto->fClient && !fImporting && !fReindex && !got_enough_headers) {
             // Only actively request headers from a single peer, unless we're close to today.
             if ((nSyncStarted == 0 && fFetch) || pindexBestHeader->GetBlockTime() > GetAdjustedTime() - 24 * 60 * 60) {
                 state.fSyncStarted = true;

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;
@@ -409,6 +412,17 @@ bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus
     return true;
 }
 
+bool ReadBlockHeaderFromDisk(CBlockHeader& header, const CBlockIndex* pindex, const Consensus::Params& consensusParams)
+{
+    // Not very efficient: read a block and throw away all but the header.
+    CBlock tmp;
+    if (!ReadBlockFromDisk(tmp, pindex, consensusParams)) {
+        return false;
+    }
+    header = tmp.GetBlockHeader();
+    return true;
+}
+
 bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const FlatFilePos& pos, const CMessageHeader::MessageStartChars& message_start)
 {
     FlatFilePos hpos = pos;

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. */
+// NOTE: 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);
@@ -71,6 +78,8 @@ bool ReadBlockFromDisk(CBlock& block, const FlatFilePos& pos, const Consensus::P
 bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams);
 bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const FlatFilePos& pos, const CMessageHeader::MessageStartChars& message_start);
 bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CBlockIndex* pindex, const CMessageHeader::MessageStartChars& message_start);
+// ELEMENTS:
+bool ReadBlockHeaderFromDisk(class CBlockHeader& header, const CBlockIndex* pindex, const Consensus::Params& consensusParams);
 
 bool UndoReadFromDisk(CBlockUndo& blockundo, const CBlockIndex* pindex);
 bool WriteUndoDataForBlock(const CBlockUndo& blockundo, BlockValidationState& state, CBlockIndex* pindex, const CChainParams& chainparams);

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/rest.cpp

@@ -221,7 +221,13 @@ static bool rest_headers(const std::any& context,
     case RetFormat::BINARY: {
         CDataStream ssHeader(SER_NETWORK, PROTOCOL_VERSION);
         for (const CBlockIndex *pindex : headers) {
-            ssHeader << pindex->GetBlockHeader();
+            if (pindex->trimmed()) {
+                CBlockHeader tmp;
+                ReadBlockHeaderFromDisk(tmp, pindex, Params().GetConsensus());
+                ssHeader << tmp;
+            } else {
+                ssHeader << pindex->GetBlockHeader();
+            }
         }
 
         std::string binaryHeader = ssHeader.str();
@@ -233,7 +239,14 @@ static bool rest_headers(const std::any& context,
     case RetFormat::HEX: {
         CDataStream ssHeader(SER_NETWORK, PROTOCOL_VERSION);
         for (const CBlockIndex *pindex : headers) {
-            ssHeader << pindex->GetBlockHeader();
+            if (pindex->trimmed()) {
+                CBlockHeader tmp;
+                ReadBlockHeaderFromDisk(tmp, pindex, Params().GetConsensus());
+                ssHeader << tmp;
+
+            } else {
+                ssHeader << pindex->GetBlockHeader();
+            }
         }
 
         std::string strHex = HexStr(ssHeader) + "\n";

src/rpc/blockchain.cpp

@@ -248,13 +248,26 @@ 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()) {
+            if (blockindex->trimmed()) {
+                result.pushKV("signblock_witness_asm", "<trimmed>");
+                result.pushKV("signblock_witness_hex", "<trimmed>");
+                result.pushKV("signblock_challenge", "<trimmed>");
+                result.pushKV("warning", "Fields missing due to -trim_headers flag.");
+            } else {
+                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));
+            if (blockindex->trimmed()) {
+                result.pushKV("signblock_witness_hex", "<trimmed>");
+                result.pushKV("dynamic_parameters", "<trimmed>");
+                result.pushKV("warning", "Fields missing due to -trim_headers flag.");
+            } else {
+                result.pushKV("signblock_witness_hex", EncodeHexScriptWitness(blockindex->signblock_witness()));
+                result.pushKV("dynamic_parameters", dynaParamsToJSON(blockindex->dynafed_params()));
+            }
         }
     }
     result.pushKV("nTx", (uint64_t)blockindex->nTx);
@@ -267,7 +280,13 @@ UniValue blockheaderToJSON(const CBlockIndex* tip, const CBlockIndex* blockindex
 
 UniValue blockToJSON(const CBlock& block, const CBlockIndex* tip, const CBlockIndex* blockindex, bool txDetails)
 {
-    UniValue result = blockheaderToJSON(tip, blockindex);
+    UniValue result;
+    if (blockindex->trimmed()) {
+        CBlockIndex tmp = CBlockIndex(block.GetBlockHeader());
+        result = blockheaderToJSON(tip, &tmp);
+    } else {
+        result = blockheaderToJSON(tip, blockindex);
+    }
 
     result.pushKV("strippedsize", (int)::GetSerializeSize(block, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS));
     result.pushKV("size", (int)::GetSerializeSize(block, PROTOCOL_VERSION));
@@ -969,7 +988,13 @@ static RPCHelpMan getblockheader()
     if (!fVerbose)
     {
         CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION);
-        ssBlock << pblockindex->GetBlockHeader();
+        if (pblockindex->trimmed()) {
+            CBlockHeader tmp;
+            ReadBlockHeaderFromDisk(tmp, pblockindex, Params().GetConsensus());
+            ssBlock << tmp;
+        } else {
+            ssBlock << pblockindex->GetBlockHeader();
+        }
         std::string strHex = HexStr(ssBlock);
         return strHex;
     }

src/txdb.cpp

@@ -307,12 +307,50 @@ bool CBlockTreeDB::WritePAKList(const std::vector<std::vector<unsigned char> >&
         return Write(std::make_pair(DB_PAK, uint256S("1")), offline_list) && Write(std::make_pair(DB_PAK, uint256S("2")), online_list) && Write(std::make_pair(DB_PAK, uint256S("3")), reject);
 }
 
-bool CBlockTreeDB::LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex)
+/** Note that we only get a conservative (lower) estimate of the max header height here,
+ * obtained by sampling the first 10,000 headers on disk (which are in random order) and
+ * taking the highest block we see. */
+bool CBlockTreeDB::WalkBlockIndexGutsForMaxHeight(int* nHeight) {
+    std::unique_ptr<CDBIterator> pcursor(NewIterator());
+    *nHeight = 0;
+    int i = 0;
+    pcursor->Seek(std::make_pair(DB_BLOCK_INDEX, uint256()));
+    while (pcursor->Valid()) {
+        if (ShutdownRequested()) return false;
+        std::pair<uint8_t, uint256> key;
+        if (pcursor->GetKey(key) && key.first == DB_BLOCK_INDEX) {
+            i++;
+            if (i > 10'000) {
+                // Under the (accurate) assumption that the headers on disk are effectively in random height order,
+                //   we have a good-enough (conservative) estimate of the max height very quickly, and don't need to
+                //   waste more time. Shortcutting like this will cause us to keep a few extra headers, which is fine.
+                break;
+            }
+            CDiskBlockIndex diskindex;
+            if (pcursor->GetValue(diskindex)) {
+                if (diskindex.nHeight > *nHeight) {
+                    *nHeight = diskindex.nHeight;
+                }
+                pcursor->Next();
+            } else {
+                return error("%s: failed to read value", __func__);
+            }
+        } else {
+            break;
+        }
+    }
+    return true;
+}
+
+bool CBlockTreeDB::LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex, int trimBelowHeight)
 {
     std::unique_ptr<CDBIterator> pcursor(NewIterator());
 
     pcursor->Seek(std::make_pair(DB_BLOCK_INDEX, uint256()));
 
+    int n_untrimmed = 0;
+    int n_total = 0;
+
     // Load m_block_index
     while (pcursor->Valid()) {
         if (ShutdownRequested()) return false;
@@ -332,19 +370,27 @@ bool CBlockTreeDB::LoadBlockIndexGuts(const Consensus::Params& consensusParams,
                 pindexNew->nTime          = diskindex.nTime;
                 pindexNew->nBits          = diskindex.nBits;
                 pindexNew->nNonce         = diskindex.nNonce;
-                pindexNew->proof          = diskindex.proof;
                 pindexNew->nStatus        = diskindex.nStatus;
                 pindexNew->nTx            = diskindex.nTx;
-                pindexNew->dynafed_params       = diskindex.dynafed_params;
-                pindexNew->m_signblock_witness = diskindex.m_signblock_witness;
 
-                const uint256 block_hash = pindexNew->GetBlockHash();
-                // Only validate one of every 1000 block header for sanity check
-                if (pindexNew->nHeight % 1000 == 0 &&
-                        block_hash != consensusParams.hashGenesisBlock &&
-                        !CheckProof(pindexNew->GetBlockHeader(), consensusParams)) {
-                    return error("%s: CheckProof: %s, %s", __func__, block_hash.ToString(), pindexNew->ToString());
+                n_total++;
+                if (diskindex.nHeight >= trimBelowHeight) {
+                    n_untrimmed++;
+                    pindexNew->proof               = diskindex.proof;
+                    pindexNew->m_dynafed_params    = diskindex.m_dynafed_params;
+                    pindexNew->m_signblock_witness = diskindex.m_signblock_witness;
+
+                    const uint256 block_hash = pindexNew->GetBlockHash();
+                    // Only validate one of every 1000 block header for sanity check
+                    if (pindexNew->nHeight % 1000 == 0 &&
+                            block_hash != consensusParams.hashGenesisBlock &&
+                            !CheckProof(pindexNew->GetBlockHeader(), consensusParams)) {
+                        return error("%s: CheckProof: %s, %s", __func__, block_hash.ToString(), pindexNew->ToString());
+                    }
+                } else {
+                    pindexNew->m_trimmed = true;
                 }
+
                 pcursor->Next();
             } else {
                 return error("%s: failed to read value", __func__);
@@ -354,6 +400,7 @@ bool CBlockTreeDB::LoadBlockIndexGuts(const Consensus::Params& consensusParams,
         }
     }
 
+    LogPrintf("LoadBlockIndexGuts: loaded %d total / %d untrimmed (fully in-memory) headers\n", n_total, n_untrimmed);
     return true;
 }
 

src/txdb.h

@@ -85,8 +85,9 @@ public:
     void ReadReindexing(bool &fReindexing);
     bool WriteFlag(const std::string &name, bool fValue);
     bool ReadFlag(const std::string &name, bool &fValue);
-    bool LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex);
+    bool LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex, int trimBelowHeight);
     // ELEMENTS:
+    bool WalkBlockIndexGutsForMaxHeight(int* nHeight);
     bool ReadPAKList(std::vector<std::vector<unsigned char> >& offline_list, std::vector<std::vector<unsigned char> >& online_list, bool& reject);
     bool WritePAKList(const std::vector<std::vector<unsigned char> >& offline_list, const std::vector<std::vector<unsigned char> >& online_list, bool reject);
 };

src/validation.cpp

@@ -76,7 +76,7 @@ static const unsigned int EXTRA_DESCENDANT_TX_SIZE_LIMIT = 10000;
 /** Maximum kilobytes for transactions to store for processing during reorg */
 static const unsigned int MAX_DISCONNECTED_TX_POOL_SIZE = 20000;
 /** Time to wait between writing blocks/block index to disk. */
-static constexpr std::chrono::hours DATABASE_WRITE_INTERVAL{1};
+static constexpr std::chrono::minutes DATABASE_WRITE_INTERVAL{5};
 /** Time to wait between flushing chainstate to disk. */
 static constexpr std::chrono::hours DATABASE_FLUSH_INTERVAL{24};
 /** Maximum age of our tip for us to be considered current for fee estimation */
@@ -2346,6 +2346,7 @@ bool CChainState::FlushStateToDisk(
                 }
                 std::vector<const CBlockIndex*> vBlocks;
                 vBlocks.reserve(setDirtyBlockIndex.size());
+                std::set<CBlockIndex*> setTrimmableBlockIndex(setDirtyBlockIndex);
                 for (std::set<CBlockIndex*>::iterator it = setDirtyBlockIndex.begin(); it != setDirtyBlockIndex.end(); ) {
                     vBlocks.push_back(*it);
                     setDirtyBlockIndex.erase(it++);
@@ -2353,6 +2354,32 @@ bool CChainState::FlushStateToDisk(
                 if (!pblocktree->WriteBatchSync(vFiles, nLastBlockFile, vBlocks)) {
                     return AbortNode(state, "Failed to write to block index database");
                 }
+
+                if (fTrimHeaders) {
+                    LogPrintf("Flushing block index, trimming headers, setTrimmableBlockIndex.size(): %d\n", setTrimmableBlockIndex.size());
+                    int trim_height = m_chain.Height() - nMustKeepFullHeaders;
+                    int min_height = std::numeric_limits<int>::max();
+                    CBlockIndex* min_index = nullptr;
+                    for (std::set<CBlockIndex*>::iterator it = setTrimmableBlockIndex.begin(); it != setTrimmableBlockIndex.end(); it++) {
+                        (*it)->assert_untrimmed();
+                        if ((*it)->nHeight < trim_height) {
+                            (*it)->trim();
+                            if ((*it)->nHeight < min_height) {
+                                min_height = (*it)->nHeight;
+                                min_index = *it;
+                            }
+                        }
+                    }
+
+                    // Handle any remaining untrimmed blocks that were too recent for trimming last time we flushed.
+                    if (min_index) {
+                        min_index = min_index->pprev;
+                        while (min_index && !min_index->trimmed()) {
+                            min_index->trim();
+                            min_index = min_index->pprev;
+                        }
+                    }
+                }
             }
             // Finally remove any pruned files
             if (fFlushForPrune) {
@@ -2464,13 +2491,13 @@ void CChainState::UpdateTip(const CBlockIndex* pindexNew)
       !warning_messages.empty() ? strprintf(" warning='%s'", warning_messages.original) : "");
 
     // Do some logging if dynafed parameters changed.
-    if (pindexNew->pprev && !pindexNew->dynafed_params.IsNull()) {
+    if (pindexNew->pprev && !pindexNew->dynafed_params().IsNull()) {
         int height = pindexNew->nHeight;
         uint256 hash = pindexNew->GetBlockHash();
-        uint256 root = pindexNew->dynafed_params.m_current.CalculateRoot();
-        if (pindexNew->pprev->dynafed_params.IsNull()) {
+        uint256 root = pindexNew->dynafed_params().m_current.CalculateRoot();
+        if (pindexNew->pprev->dynafed_params().IsNull()) {
             LogPrintf("Dynafed activated in block %d:%s: %s\n", height, hash.GetHex(), root.GetHex());
-        } else if (root != pindexNew->pprev->dynafed_params.m_current.CalculateRoot()) {
+        } else if (root != pindexNew->pprev->dynafed_params().m_current.CalculateRoot()) {
             LogPrintf("New dynafed parameters activated in block %d:%s: %s\n", height, hash.GetHex(), root.GetHex());
         }
     }
@@ -4110,7 +4137,19 @@ bool BlockManager::LoadBlockIndex(
     CBlockTreeDB& blocktree,
     std::set<CBlockIndex*, CBlockIndexWorkComparator>& block_index_candidates)
 {
-    if (!blocktree.LoadBlockIndexGuts(consensus_params, [this](const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main) { return this->InsertBlockIndex(hash); }))
+    int trim_below_height = 0;
+    if (fTrimHeaders) {
+        int max_height = 0;
+        if (!blocktree.WalkBlockIndexGutsForMaxHeight(&max_height)) {
+            LogPrintf("LoadBlockIndex: Failed to WalkBlockIndexGutsForMaxHeight.\n");
+            return false;
+        }
+
+        int must_keep_headers = (consensus_params.total_valid_epochs + 2) * consensus_params.dynamic_epoch_length;
+        int extra_headers_buffer = consensus_params.dynamic_epoch_length * 2; // XXX arbitrary
+        trim_below_height = max_height - must_keep_headers - extra_headers_buffer;
+    }
+    if (!blocktree.LoadBlockIndexGuts(consensus_params, [this](const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main) { return this->InsertBlockIndex(hash); }, trim_below_height))
         return false;
 
     // Calculate nChainWork

src/validation.h

@@ -649,6 +649,7 @@ public:
     //! @returns A reference to the in-memory cache of the UTXO set.
     CCoinsViewCache& CoinsTip() EXCLUSIVE_LOCKS_REQUIRED(cs_main)
     {
+        assert(m_coins_views);
         assert(m_coins_views->m_cacheview);
         return *m_coins_views->m_cacheview.get();
     }

test/lint/lint-locale-dependence.sh

@@ -40,9 +40,11 @@ export LC_ALL=C
 KNOWN_VIOLATIONS=(
     "src/bitcoin-tx.cpp.*stoul"
     "src/bitcoin-tx.cpp.*trim_right"
+    "src/chain.h.*trim"
     "src/dbwrapper.cpp.*stoul"
     "src/dbwrapper.cpp:.*vsnprintf"
     "src/httprpc.cpp.*trim"
+    "src/init.cpp.*trim"
     "src/node/blockstorage.cpp:.*atoi"
     "src/qt/rpcconsole.cpp:.*atoi"
     "src/rest.cpp:.*strtol"