Merge pull request #1971 from kcalvinalvin/add-pruning

main, wire, blockchain, indexers, ffldb: Add pruning

blockchain/chain.go

@@ -115,6 +115,10 @@ type BlockChain struct {
 	// fields in this struct below this point.
 	chainLock sync.RWMutex
 
+	// pruneTarget is the size in bytes the database targets for when the node
+	// is pruned.
+	pruneTarget uint64
+
 	// These fields are related to the memory block index.  They both have
 	// their own locks, however they are often also protected by the chain
 	// lock to help prevent logic races when blocks are being processed.
@@ -600,6 +604,26 @@ func (b *BlockChain) connectBlock(node *blockNode, block *btcutil.Block,
 
 	// Atomically insert info into the database.
 	err = b.db.Update(func(dbTx database.Tx) error {
+		// If the pruneTarget isn't 0, we should attempt to delete older blocks
+		// from the database.
+		if b.pruneTarget != 0 {
+			// When the total block size is under the prune target, prune blocks is
+			// a no-op and the deleted hashes are nil.
+			deletedHashes, err := dbTx.PruneBlocks(b.pruneTarget)
+			if err != nil {
+				return err
+			}
+
+			// Only attempt to delete if we have any deleted blocks.
+			if len(deletedHashes) != 0 {
+				// Delete the spend journals of the pruned blocks.
+				err = dbPruneSpendJournalEntry(dbTx, deletedHashes)
+				if err != nil {
+					return err
+				}
+			}
+		}
+
 		// Update best block state.
 		err := dbPutBestState(dbTx, state, node.workSum)
 		if err != nil {
@@ -1702,6 +1726,11 @@ type Config struct {
 	// This field can be nil if the caller is not interested in using a
 	// signature cache.
 	HashCache *txscript.HashCache
+
+	// Prune specifies the target database usage (in bytes) the database
+	// will target for with block files.  Prune at 0 specifies that no
+	// blocks will be deleted.
+	Prune uint64
 }
 
 // New returns a BlockChain instance using the provided configuration details.
@@ -1757,6 +1786,7 @@ func New(config *Config) (*BlockChain, error) {
 		prevOrphans:         make(map[chainhash.Hash][]*orphanBlock),
 		warningCaches:       newThresholdCaches(vbNumBits),
 		deploymentCaches:    newThresholdCaches(chaincfg.DefinedDeployments),
+		pruneTarget:         config.Prune,
 	}
 
 	// Ensure all the deployments are synchronized with our clock if

blockchain/chainio.go

@@ -494,6 +494,21 @@ func dbRemoveSpendJournalEntry(dbTx database.Tx, blockHash *chainhash.Hash) erro
 	return spendBucket.Delete(blockHash[:])
 }
 
+// dbPruneSpendJournalEntry uses an existing database transaction to remove all
+// the spend journal entries for the pruned blocks.
+func dbPruneSpendJournalEntry(dbTx database.Tx, blockHashes []chainhash.Hash) error {
+	spendBucket := dbTx.Metadata().Bucket(spendJournalBucketName)
+
+	for _, blockHash := range blockHashes {
+		err := spendBucket.Delete(blockHash[:])
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // -----------------------------------------------------------------------------
 // The unspent transaction output (utxo) set consists of an entry for each
 // unspent output using a format that is optimized to reduce space using domain

blockchain/indexers/addrindex.go

@@ -991,3 +991,15 @@ func NewAddrIndex(db database.DB, chainParams *chaincfg.Params) *AddrIndex {
 func DropAddrIndex(db database.DB, interrupt <-chan struct{}) error {
 	return dropIndex(db, addrIndexKey, addrIndexName, interrupt)
 }
+
+// AddrIndexInitialized returns true if the address index has been created previously.
+func AddrIndexInitialized(db database.DB) bool {
+	var exists bool
+	db.View(func(dbTx database.Tx) error {
+		bucket := dbTx.Metadata().Bucket(addrIndexKey)
+		exists = bucket != nil
+		return nil
+	})
+
+	return exists
+}

blockchain/indexers/cfindex.go

@@ -355,3 +355,15 @@ func NewCfIndex(db database.DB, chainParams *chaincfg.Params) *CfIndex {
 func DropCfIndex(db database.DB, interrupt <-chan struct{}) error {
 	return dropIndex(db, cfIndexParentBucketKey, cfIndexName, interrupt)
 }
+
+// CfIndexInitialized returns true if the cfindex has been created previously.
+func CfIndexInitialized(db database.DB) bool {
+	var exists bool
+	db.View(func(dbTx database.Tx) error {
+		bucket := dbTx.Metadata().Bucket(cfIndexParentBucketKey)
+		exists = bucket != nil
+		return nil
+	})
+
+	return exists
+}

blockchain/indexers/txindex.go

@@ -481,3 +481,15 @@ func DropTxIndex(db database.DB, interrupt <-chan struct{}) error {
 
 	return dropIndex(db, txIndexKey, txIndexName, interrupt)
 }
+
+// TxIndexInitialized returns true if the tx index has been created previously.
+func TxIndexInitialized(db database.DB) bool {
+	var exists bool
+	db.View(func(dbTx database.Tx) error {
+		bucket := dbTx.Metadata().Bucket(txIndexKey)
+		exists = bucket != nil
+		return nil
+	})
+
+	return exists
+}

btcd.go

@@ -157,6 +157,88 @@ func btcdMain(serverChan chan<- *server) error {
 		return nil
 	}
 
+	// Check if the database had previously been pruned.  If it had been, it's
+	// not possible to newly generate the tx index and addr index.
+	var beenPruned bool
+	db.View(func(dbTx database.Tx) error {
+		beenPruned, err = dbTx.BeenPruned()
+		return err
+	})
+	if err != nil {
+		btcdLog.Errorf("%v", err)
+		return err
+	}
+	if beenPruned && cfg.Prune == 0 {
+		err = fmt.Errorf("--prune cannot be disabled as the node has been "+
+			"previously pruned. You must delete the files in the datadir: \"%s\" "+
+			"and sync from the beginning to disable pruning", cfg.DataDir)
+		btcdLog.Errorf("%v", err)
+		return err
+	}
+	if beenPruned && cfg.TxIndex {
+		err = fmt.Errorf("--txindex cannot be enabled as the node has been "+
+			"previously pruned. You must delete the files in the datadir: \"%s\" "+
+			"and sync from the beginning to enable the desired index", cfg.DataDir)
+		btcdLog.Errorf("%v", err)
+		return err
+	}
+	if beenPruned && cfg.AddrIndex {
+		err = fmt.Errorf("--addrindex cannot be enabled as the node has been "+
+			"previously pruned. You must delete the files in the datadir: \"%s\" "+
+			"and sync from the beginning to enable the desired index", cfg.DataDir)
+		btcdLog.Errorf("%v", err)
+		return err
+	}
+	// If we've previously been pruned and the cfindex isn't present, it means that the
+	// user wants to enable the cfindex after the node has already synced up and been
+	// pruned.
+	if beenPruned && !indexers.CfIndexInitialized(db) && !cfg.NoCFilters {
+		err = fmt.Errorf("compact filters cannot be enabled as the node has been "+
+			"previously pruned. You must delete the files in the datadir: \"%s\" "+
+			"and sync from the beginning to enable the desired index. You may "+
+			"use the --nocfilters flag to start the node up without the compact "+
+			"filters", cfg.DataDir)
+		btcdLog.Errorf("%v", err)
+		return err
+	}
+	// If the user wants to disable the cfindex and is pruned or has enabled pruning, force
+	// the user to either drop the cfindex manually or restart the node without the --nocfilters
+	// flag.
+	if (beenPruned || cfg.Prune != 0) && indexers.CfIndexInitialized(db) && cfg.NoCFilters {
+		err = fmt.Errorf("--nocfilters flag was given but the compact filters have " +
+			"previously been enabled on this node and the index data currently " +
+			"exists in the database. The node has also been previously pruned and " +
+			"the database would be left in an inconsistent state if the compact " +
+			"filters don't get indexed now. To disable compact filters, please drop the " +
+			"index completely with the --dropcfindex flag and restart the node. " +
+			"To keep the compact filters, restart the node without the --nocfilters " +
+			"flag")
+		btcdLog.Errorf("%v", err)
+		return err
+	}
+
+	// Enforce removal of txindex and addrindex if user requested pruning.
+	// This is to require explicit action from the user before removing
+	// indexes that won't be useful when block files are pruned.
+	//
+	// NOTE: The order is important here because dropping the tx index also
+	// drops the address index since it relies on it.  We explicitly make the
+	// user drop both indexes if --addrindex was enabled previously.
+	if cfg.Prune != 0 && indexers.AddrIndexInitialized(db) {
+		err = fmt.Errorf("--prune flag may not be given when the address index " +
+			"has been initialized. Please drop the address index with the " +
+			"--dropaddrindex flag before enabling pruning")
+		btcdLog.Errorf("%v", err)
+		return err
+	}
+	if cfg.Prune != 0 && indexers.TxIndexInitialized(db) {
+		err = fmt.Errorf("--prune flag may not be given when the transaction index " +
+			"has been initialized. Please drop the transaction index with the " +
+			"--droptxindex flag before enabling pruning")
+		btcdLog.Errorf("%v", err)
+		return err
+	}
+
 	// The config file is already created if it did not exist and the log
 	// file has already been opened by now so we only need to allow
 	// creating rpc cert and key files if they don't exist.

config.go

@@ -66,6 +66,7 @@ const (
 	sampleConfigFilename         = "sample-btcd.conf"
 	defaultTxIndex               = false
 	defaultAddrIndex             = false
+	pruneMinSize                 = 1536
 )
 
 var (
@@ -146,6 +147,7 @@ type config struct {
 	Proxy                string        `long:"proxy" description:"Connect via SOCKS5 proxy (eg. 127.0.0.1:9050)"`
 	ProxyPass            string        `long:"proxypass" default-mask:"-" description:"Password for proxy server"`
 	ProxyUser            string        `long:"proxyuser" description:"Username for proxy server"`
+	Prune                uint64        `long:"prune" description:"Prune already validated blocks from the database. Must specify a target size in MiB (minimum value of 1536, default value of 0 will disable pruning)"`
 	RegressionTest       bool          `long:"regtest" description:"Use the regression test network"`
 	RejectNonStd         bool          `long:"rejectnonstd" description:"Reject non-standard transactions regardless of the default settings for the active network."`
 	RejectReplacement    bool          `long:"rejectreplacement" description:"Reject transactions that attempt to replace existing transactions within the mempool through the Replace-By-Fee (RBF) signaling policy."`
@@ -1137,6 +1139,30 @@ func loadConfig() (*config, []string, error) {
 		}
 	}
 
+	if cfg.Prune != 0 && cfg.Prune < pruneMinSize {
+		err := fmt.Errorf("%s: the minimum value for --prune is %d. Got %d",
+			funcName, pruneMinSize, cfg.Prune)
+		fmt.Fprintln(os.Stderr, err)
+		fmt.Fprintln(os.Stderr, usageMessage)
+		return nil, nil, err
+	}
+
+	if cfg.Prune != 0 && cfg.TxIndex {
+		err := fmt.Errorf("%s: the --prune and --txindex options may "+
+			"not be activated at the same time", funcName)
+		fmt.Fprintln(os.Stderr, err)
+		fmt.Fprintln(os.Stderr, usageMessage)
+		return nil, nil, err
+	}
+
+	if cfg.Prune != 0 && cfg.AddrIndex {
+		err := fmt.Errorf("%s: the --prune and --addrindex options may "+
+			"not be activated at the same time", funcName)
+		fmt.Fprintln(os.Stderr, err)
+		fmt.Fprintln(os.Stderr, usageMessage)
+		return nil, nil, err
+	}
+
 	// Warn about missing config file only after all other configuration is
 	// done.  This prevents the warning on help messages and invalid
 	// options.  Note this should go directly before the return.

database/ffldb/blockio.go

@@ -15,6 +15,9 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
 	"sync"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
@@ -23,6 +26,10 @@ import (
 )
 
 const (
+	// blockFileExtension is the extension that's used to store the block
+	// files on the disk.
+	blockFileExtension = ".fdb"
+
 	// The Bitcoin protocol encodes block height as int32, so max number of
 	// blocks is 2^31.  Max block size per the protocol is 32MiB per block.
 	// So the theoretical max at the time this comment was written is 64PiB
@@ -32,7 +39,7 @@ const (
 	// 512MiB each for a total of ~476.84PiB (roughly 7.4 times the current
 	// theoretical max), so there is room for the max block size to grow in
 	// the future.
-	blockFilenameTemplate = "%09d.fdb"
+	blockFilenameTemplate = "%09d" + blockFileExtension
 
 	// maxOpenFiles is the max number of open files to maintain in the
 	// open blocks cache.  Note that this does not include the current
@@ -713,36 +720,57 @@ func (s *blockStore) handleRollback(oldBlockFileNum, oldBlockOffset uint32) {
 }
 
 // scanBlockFiles searches the database directory for all flat block files to
-// find the end of the most recent file.  This position is considered the
-// current write cursor which is also stored in the metadata.  Thus, it is used
-// to detect unexpected shutdowns in the middle of writes so the block files
-// can be reconciled.
-func scanBlockFiles(dbPath string) (int, uint32) {
-	lastFile := -1
-	fileLen := uint32(0)
-	for i := 0; ; i++ {
-		filePath := blockFilePath(dbPath, uint32(i))
-		st, err := os.Stat(filePath)
-		if err != nil {
-			break
-		}
-		lastFile = i
+// find the first file, last file, and the end of the most recent file.  The
+// position at the last file is considered the current write cursor which is
+// also stored in the metadata.  Thus, it is used to detect unexpected shutdowns
+// in the middle of writes so the block files can be reconciled.
+func scanBlockFiles(dbPath string) (int, int, uint32, error) {
+	firstFile, lastFile, lastFileLen, err := int(-1), int(-1), uint32(0), error(nil)
 
-		fileLen = uint32(st.Size())
+	files, err := filepath.Glob(filepath.Join(dbPath, "*"+blockFileExtension))
+	if err != nil {
+		return 0, 0, 0, err
+	}
+	sort.Strings(files)
+
+	// Return early if there's no block files.
+	if len(files) == 0 {
+		return firstFile, lastFile, lastFileLen, nil
 	}
 
-	log.Tracef("Scan found latest block file #%d with length %d", lastFile,
-		fileLen)
-	return lastFile, fileLen
+	// Grab the first and last file's number.
+	firstFile, err = strconv.Atoi(strings.TrimSuffix(filepath.Base(files[0]), blockFileExtension))
+	if err != nil {
+		return 0, 0, 0, fmt.Errorf("scanBlockFiles error: %v", err)
+	}
+	lastFile, err = strconv.Atoi(strings.TrimSuffix(filepath.Base(files[len(files)-1]), blockFileExtension))
+	if err != nil {
+		return 0, 0, 0, fmt.Errorf("scanBlockFiles error: %v", err)
+	}
+
+	// Get the last file's length.
+	filePath := blockFilePath(dbPath, uint32(lastFile))
+	st, err := os.Stat(filePath)
+	if err != nil {
+		return 0, 0, 0, err
+	}
+	lastFileLen = uint32(st.Size())
+
+	log.Tracef("Scan found latest block file #%d with length %d", lastFile, lastFileLen)
+
+	return firstFile, lastFile, lastFileLen, err
 }
 
 // newBlockStore returns a new block store with the current block file number
 // and offset set and all fields initialized.
-func newBlockStore(basePath string, network wire.BitcoinNet) *blockStore {
+func newBlockStore(basePath string, network wire.BitcoinNet) (*blockStore, error) {
 	// Look for the end of the latest block to file to determine what the
 	// write cursor position is from the viewpoing of the block files on
 	// disk.
-	fileNum, fileOff := scanBlockFiles(basePath)
+	_, fileNum, fileOff, err := scanBlockFiles(basePath)
+	if err != nil {
+		return nil, err
+	}
 	if fileNum == -1 {
 		fileNum = 0
 		fileOff = 0
@@ -765,5 +793,5 @@ func newBlockStore(basePath string, network wire.BitcoinNet) *blockStore {
 	store.openFileFunc = store.openFile
 	store.openWriteFileFunc = store.openWriteFile
 	store.deleteFileFunc = store.deleteFile
-	return store
+	return store, nil
 }

database/ffldb/db.go

@@ -1669,6 +1669,116 @@ func (tx *transaction) writePendingAndCommit() error {
 	return tx.db.cache.commitTx(tx)
 }
 
+// PruneBlocks deletes the block files until it reaches the target size
+// (specified in bytes).  Throws an error if the target size is below
+// the maximum size of a single block file.
+//
+// This function is part of the database.Tx interface implementation.
+func (tx *transaction) PruneBlocks(targetSize uint64) ([]chainhash.Hash, error) {
+	// Ensure transaction state is valid.
+	if err := tx.checkClosed(); err != nil {
+		return nil, err
+	}
+
+	// Ensure the transaction is writable.
+	if !tx.writable {
+		str := "prune blocks requires a writable database transaction"
+		return nil, makeDbErr(database.ErrTxNotWritable, str, nil)
+	}
+
+	// Make a local alias for the maxBlockFileSize.
+	maxSize := uint64(tx.db.store.maxBlockFileSize)
+	if targetSize < maxSize {
+		return nil, fmt.Errorf("got target size of %d but it must be greater "+
+			"than %d, the max size of a single block file",
+			targetSize, maxSize)
+	}
+
+	first, last, lastFileSize, err := scanBlockFiles(tx.db.store.basePath)
+	if err != nil {
+		return nil, err
+	}
+
+	// If we have no files on disk or just a single file on disk, return early.
+	if first == last {
+		return nil, nil
+	}
+
+	// Last file number minus the first file number gives us the count of files
+	// on disk minus 1.  We don't want to count the last file since we can't assume
+	// that it is of max size.
+	maxSizeFileCount := last - first
+
+	// If the total size of block files are under the target, return early and
+	// don't prune.
+	totalSize := uint64(lastFileSize) + (maxSize * uint64(maxSizeFileCount))
+	if totalSize <= targetSize {
+		return nil, nil
+	}
+
+	log.Tracef("Using %d more bytes than the target of %d MiB. Pruning files...",
+		totalSize-targetSize,
+		targetSize/(1024*1024))
+
+	deletedFiles := make(map[uint32]struct{})
+
+	// We use < not <= so that the last file is never deleted.  There are other checks in place
+	// but setting it to < here doesn't hurt.
+	for i := uint32(first); i < uint32(last); i++ {
+		err = tx.db.store.deleteFileFunc(i)
+		if err != nil {
+			return nil, fmt.Errorf("PruneBlocks: Failed to delete block file "+
+				"number %d: %v", i, err)
+		}
+
+		// Add the file index to the deleted files map so that we can later
+		// delete the block location index.
+		deletedFiles[i] = struct{}{}
+
+		// If we're already at or below the target usage, break and don't
+		// try to delete more files.
+		totalSize -= maxSize
+		if totalSize <= targetSize {
+			break
+		}
+	}
+
+	// Delete the indexed block locations for the files that we've just deleted.
+	var deletedBlockHashes []chainhash.Hash
+	cursor := tx.blockIdxBucket.Cursor()
+	for ok := cursor.First(); ok; ok = cursor.Next() {
+		loc := deserializeBlockLoc(cursor.Value())
+
+		_, found := deletedFiles[loc.blockFileNum]
+		if found {
+			deletedBlockHashes = append(deletedBlockHashes, *(*chainhash.Hash)(cursor.Key()))
+			err := cursor.Delete()
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	log.Tracef("Finished pruning. Database now at %d bytes", totalSize)
+
+	return deletedBlockHashes, nil
+}
+
+// BeenPruned returns if the block storage has ever been pruned.
+//
+// This function is part of the database.Tx interface implementation.
+func (tx *transaction) BeenPruned() (bool, error) {
+	first, last, _, err := scanBlockFiles(tx.db.store.basePath)
+	if err != nil {
+		return false, err
+	}
+
+	// If the database is pruned, then the first .fdb will not be there.
+	// We also check that there isn't just 1 file on disk or if there are
+	// no files on disk by checking if first != last.
+	return first != 0 && (first != last), nil
+}
+
 // Commit commits all changes that have been made to the root metadata bucket
 // and all of its sub-buckets to the database cache which is periodically synced
 // to persistent storage.  In addition, it commits all new blocks directly to
@@ -2016,7 +2126,10 @@ func openDB(dbPath string, network wire.BitcoinNet, create bool) (database.DB, e
 	// according to the data that is actually on disk.  Also create the
 	// database cache which wraps the underlying leveldb database to provide
 	// write caching.
-	store := newBlockStore(dbPath, network)
+	store, err := newBlockStore(dbPath, network)
+	if err != nil {
+		return nil, convertErr(err.Error(), err)
+	}
 	cache := newDbCache(ldb, store, defaultCacheSize, defaultFlushSecs)
 	pdb := &db{store: store, cache: cache}
 

database/ffldb/driver_test.go

@@ -5,6 +5,7 @@
 package ffldb_test
 
 import (
+	"bytes"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -13,6 +14,7 @@ import (
 
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/btcsuite/btcd/chaincfg"
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/database"
 	"github.com/btcsuite/btcd/database/ffldb"
 )
@@ -253,6 +255,166 @@ func TestPersistence(t *testing.T) {
 	}
 }
 
+// TestPrune tests that the older .fdb files are deleted with a call to prune.
+func TestPrune(t *testing.T) {
+	t.Parallel()
+
+	// Create a new database to run tests against.
+	dbPath := t.TempDir()
+	db, err := database.Create(dbType, dbPath, blockDataNet)
+	if err != nil {
+		t.Errorf("Failed to create test database (%s) %v", dbType, err)
+		return
+	}
+	defer db.Close()
+
+	blockFileSize := uint64(2048)
+
+	testfn := func(t *testing.T, db database.DB) {
+		// Load the test blocks and save in the test context for use throughout
+		// the tests.
+		blocks, err := loadBlocks(t, blockDataFile, blockDataNet)
+		if err != nil {
+			t.Errorf("loadBlocks: Unexpected error: %v", err)
+			return
+		}
+		err = db.Update(func(tx database.Tx) error {
+			for i, block := range blocks {
+				err := tx.StoreBlock(block)
+				if err != nil {
+					return fmt.Errorf("StoreBlock #%d: unexpected error: "+
+						"%v", i, err)
+				}
+			}
+			return nil
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		blockHashMap := make(map[chainhash.Hash][]byte, len(blocks))
+		for _, block := range blocks {
+			bytes, err := block.Bytes()
+			if err != nil {
+				t.Fatal(err)
+			}
+			blockHashMap[*block.Hash()] = bytes
+		}
+
+		err = db.Update(func(tx database.Tx) error {
+			_, err := tx.PruneBlocks(1024)
+			if err == nil {
+				return fmt.Errorf("Expected an error when attempting to prune" +
+					"below the maxFileSize")
+			}
+
+			_, err = tx.PruneBlocks(0)
+			if err == nil {
+				return fmt.Errorf("Expected an error when attempting to prune" +
+					"below the maxFileSize")
+			}
+
+			return nil
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		err = db.View(func(tx database.Tx) error {
+			pruned, err := tx.BeenPruned()
+			if err != nil {
+				return err
+			}
+
+			if pruned {
+				err = fmt.Errorf("The database hasn't been pruned but " +
+					"BeenPruned returned true")
+			}
+			return err
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var deletedBlocks []chainhash.Hash
+
+		// This should leave 3 files on disk.
+		err = db.Update(func(tx database.Tx) error {
+			deletedBlocks, err = tx.PruneBlocks(blockFileSize * 3)
+			return err
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// The only error we can get is a bad pattern error.  Since we're hardcoding
+		// the pattern, we should not have an error at runtime.
+		files, _ := filepath.Glob(filepath.Join(dbPath, "*.fdb"))
+		if len(files) != 3 {
+			t.Fatalf("Expected to find %d files but got %d",
+				3, len(files))
+		}
+
+		err = db.View(func(tx database.Tx) error {
+			pruned, err := tx.BeenPruned()
+			if err != nil {
+				return err
+			}
+
+			if !pruned {
+				err = fmt.Errorf("The database has been pruned but " +
+					"BeenPruned returned false")
+			}
+			return err
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// Check that all the blocks that say were deleted are deleted from the
+		// block index bucket as well.
+		err = db.View(func(tx database.Tx) error {
+			for _, deletedBlock := range deletedBlocks {
+				_, err := tx.FetchBlock(&deletedBlock)
+				if dbErr, ok := err.(database.Error); !ok ||
+					dbErr.ErrorCode != database.ErrBlockNotFound {
+
+					return fmt.Errorf("Expected ErrBlockNotFound "+
+						"but got %v", dbErr)
+				}
+			}
+
+			return nil
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// Check that the not deleted blocks are present.
+		for _, deletedBlock := range deletedBlocks {
+			delete(blockHashMap, deletedBlock)
+		}
+		err = db.View(func(tx database.Tx) error {
+			for hash, wantBytes := range blockHashMap {
+				gotBytes, err := tx.FetchBlock(&hash)
+				if err != nil {
+					return err
+				}
+				if !bytes.Equal(gotBytes, wantBytes) {
+					return fmt.Errorf("got bytes %x, want bytes %x",
+						gotBytes, wantBytes)
+				}
+			}
+			return nil
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	ffldb.TstRunWithMaxBlockFileSize(db, uint32(blockFileSize), func() {
+		testfn(t, db)
+	})
+}
+
 // TestInterface performs all interfaces tests for this database driver.
 func TestInterface(t *testing.T) {
 	t.Parallel()

database/ffldb/export_test.go

@@ -11,7 +11,9 @@ The functions are only exported while the tests are being run.
 
 package ffldb
 
-import "github.com/btcsuite/btcd/database"
+import (
+	"github.com/btcsuite/btcd/database"
+)
 
 // TstRunWithMaxBlockFileSize runs the passed function with the maximum allowed
 // file size for the database set to the provided value.  The value will be set

database/interface.go

@@ -389,6 +389,26 @@ type Tx interface {
 	// implementations.
 	FetchBlockRegions(regions []BlockRegion) ([][]byte, error)
 
+	// PruneBlocks deletes the block files until it reaches the target size
+	// (specificed in bytes).
+	//
+	// The interface contract guarantees at least the following errors will
+	// be returned (other implementation-specific errors are possible):
+	//   - ErrTxNotWritable if attempted against a read-only transaction
+	//   - ErrTxClosed if the transaction has already been closed
+	//
+	// NOTE: The data returned by this function is only valid during a
+	// database transaction.  Attempting to access it after a transaction
+	// has ended results in undefined behavior.  This constraint prevents
+	// additional data copies and allows support for memory-mapped database
+	// implementations.
+	PruneBlocks(targetSize uint64) ([]chainhash.Hash, error)
+
+	// BeenPruned returns if the block storage has ever been pruned.
+	//
+	// Implementation specific errors are possible.
+	BeenPruned() (bool, error)
+
 	// ******************************************************************
 	// Methods related to both atomic metadata storage and block storage.
 	// ******************************************************************

rpcserver.go

@@ -1214,7 +1214,7 @@ func handleGetBlockChainInfo(s *rpcServer, cmd interface{}, closeChan <-chan str
 		BestBlockHash: chainSnapshot.Hash.String(),
 		Difficulty:    getDifficultyRatio(chainSnapshot.Bits, params),
 		MedianTime:    chainSnapshot.MedianTime.Unix(),
-		Pruned:        false,
+		Pruned:        cfg.Prune != 0,
 		SoftForks: &btcjson.SoftForks{
 			Bip9SoftForks: make(map[string]*btcjson.Bip9SoftForkDescription),
 		},

server.go

@@ -44,8 +44,8 @@ import (
 const (
 	// defaultServices describes the default services that are supported by
 	// the server.
-	defaultServices = wire.SFNodeNetwork | wire.SFNodeBloom |
-		wire.SFNodeWitness | wire.SFNodeCF
+	defaultServices = wire.SFNodeNetwork | wire.SFNodeNetworkLimited |
+		wire.SFNodeBloom | wire.SFNodeWitness | wire.SFNodeCF
 
 	// defaultRequiredServices describes the default services that are
 	// required to be supported by outbound peers.
@@ -2730,6 +2730,9 @@ func newServer(listenAddrs, agentBlacklist, agentWhitelist []string,
 	if cfg.NoCFilters {
 		services &^= wire.SFNodeCF
 	}
+	if cfg.Prune != 0 {
+		services &^= wire.SFNodeNetwork
+	}
 
 	amgr := addrmgr.New(cfg.DataDir, btcdLookup)
 
@@ -2831,6 +2834,7 @@ func newServer(listenAddrs, agentBlacklist, agentWhitelist []string,
 		SigCache:     s.sigCache,
 		IndexManager: indexManager,
 		HashCache:    s.hashCache,
+		Prune:        cfg.Prune * 1024 * 1024,
 	})
 	if err != nil {
 		return nil, err

wire/protocol.go

@@ -93,18 +93,23 @@ const (
 	// SFNode2X is a flag used to indicate a peer is running the Segwit2X
 	// software.
 	SFNode2X
+
+	// SFNodeNetWorkLimited is a flag used to indicate a peer supports serving
+	// the last 288 blocks.
+	SFNodeNetworkLimited = 1 << 10
 )
 
 // Map of service flags back to their constant names for pretty printing.
 var sfStrings = map[ServiceFlag]string{
-	SFNodeNetwork: "SFNodeNetwork",
-	SFNodeGetUTXO: "SFNodeGetUTXO",
-	SFNodeBloom:   "SFNodeBloom",
-	SFNodeWitness: "SFNodeWitness",
-	SFNodeXthin:   "SFNodeXthin",
-	SFNodeBit5:    "SFNodeBit5",
-	SFNodeCF:      "SFNodeCF",
-	SFNode2X:      "SFNode2X",
+	SFNodeNetwork:        "SFNodeNetwork",
+	SFNodeGetUTXO:        "SFNodeGetUTXO",
+	SFNodeBloom:          "SFNodeBloom",
+	SFNodeWitness:        "SFNodeWitness",
+	SFNodeXthin:          "SFNodeXthin",
+	SFNodeBit5:           "SFNodeBit5",
+	SFNodeCF:             "SFNodeCF",
+	SFNode2X:             "SFNode2X",
+	SFNodeNetworkLimited: "SFNodeNetworkLimited",
 }
 
 // orderedSFStrings is an ordered list of service flags from highest to
@@ -118,6 +123,7 @@ var orderedSFStrings = []ServiceFlag{
 	SFNodeBit5,
 	SFNodeCF,
 	SFNode2X,
+	SFNodeNetworkLimited,
 }
 
 // String returns the ServiceFlag in human-readable form.

wire/protocol_test.go

@@ -21,7 +21,8 @@ func TestServiceFlagStringer(t *testing.T) {
 		{SFNodeBit5, "SFNodeBit5"},
 		{SFNodeCF, "SFNodeCF"},
 		{SFNode2X, "SFNode2X"},
-		{0xffffffff, "SFNodeNetwork|SFNodeGetUTXO|SFNodeBloom|SFNodeWitness|SFNodeXthin|SFNodeBit5|SFNodeCF|SFNode2X|0xffffff00"},
+		{SFNodeNetworkLimited, "SFNodeNetworkLimited"},
+		{0xffffffff, "SFNodeNetwork|SFNodeGetUTXO|SFNodeBloom|SFNodeWitness|SFNodeXthin|SFNodeBit5|SFNodeCF|SFNode2X|SFNodeNetworkLimited|0xfffffb00"},
 	}
 
 	t.Logf("Running %d tests", len(tests))