Merge pull request #1128 from filecoin-project/feat/chain-export-2

Implement chain import and exporting

api/api_full.go

@@ -38,6 +38,7 @@ type FullNode interface {
 	ChainGetNode(ctx context.Context, p string) (interface{}, error)
 	ChainGetMessage(context.Context, cid.Cid) (*types.Message, error)
 	ChainGetPath(ctx context.Context, from types.TipSetKey, to types.TipSetKey) ([]*store.HeadChange, error)
+	ChainExport(context.Context, *types.TipSet) (<-chan []byte, error)
 
 	// syncer
 	SyncState(context.Context) (*SyncState, error)

api/apistruct/struct.go

@@ -56,6 +56,7 @@ type FullNodeStruct struct {
 		ChainGetNode           func(ctx context.Context, p string) (interface{}, error)                             `perm:"read"`
 		ChainGetMessage        func(context.Context, cid.Cid) (*types.Message, error)                               `perm:"read"`
 		ChainGetPath           func(context.Context, types.TipSetKey, types.TipSetKey) ([]*store.HeadChange, error) `perm:"read"`
+		ChainExport            func(context.Context, *types.TipSet) (<-chan []byte, error)                          `perm:"read"`
 
 		SyncState          func(context.Context) (*api.SyncState, error)                `perm:"read"`
 		SyncSubmitBlock    func(ctx context.Context, blk *types.BlockMsg) error         `perm:"write"`
@@ -361,6 +362,10 @@ func (c *FullNodeStruct) ChainGetPath(ctx context.Context, from types.TipSetKey,
 	return c.Internal.ChainGetPath(ctx, from, to)
 }
 
+func (c *FullNodeStruct) ChainExport(ctx context.Context, ts *types.TipSet) (<-chan []byte, error) {
+	return c.Internal.ChainExport(ctx, ts)
+}
+
 func (c *FullNodeStruct) SyncState(ctx context.Context) (*api.SyncState, error) {
 	return c.Internal.SyncState(ctx)
 }

chain/stmgr/stmgr.go

@@ -607,3 +607,32 @@ func (sm *StateManager) MarketBalance(ctx context.Context, addr address.Address,
 
 	return b[0], nil
 }
+
+func (sm *StateManager) ValidateChain(ctx context.Context, ts *types.TipSet) error {
+	tschain := []*types.TipSet{ts}
+	for ts.Height() != 0 {
+		next, err := sm.cs.LoadTipSet(ts.Parents())
+		if err != nil {
+			return err
+		}
+
+		tschain = append(tschain, next)
+		ts = next
+	}
+
+	lastState := tschain[len(tschain)-1].ParentState()
+	for i := len(tschain) - 1; i >= 0; i-- {
+		cur := tschain[i]
+		log.Infof("computing state (height: %d, ts=%s)", cur.Height(), cur.Cids())
+		if cur.ParentState() != lastState {
+			return xerrors.Errorf("tipset chain had state mismatch at height %d", cur.Height())
+		}
+		st, _, err := sm.TipSetState(ctx, cur)
+		if err != nil {
+			return err
+		}
+		lastState = st
+	}
+
+	return nil
+}

chain/store/store.go

@@ -1,10 +1,12 @@
 package store
 
 import (
+	"bytes"
 	"context"
 	"crypto/sha256"
 	"encoding/binary"
 	"encoding/json"
+	"io"
 	"sync"
 
 	"github.com/filecoin-project/go-address"
@@ -19,11 +21,16 @@ import (
 
 	lru "github.com/hashicorp/golang-lru"
 	block "github.com/ipfs/go-block-format"
+	"github.com/ipfs/go-blockservice"
+	car "github.com/ipfs/go-car"
 	"github.com/ipfs/go-cid"
 	dstore "github.com/ipfs/go-datastore"
 	hamt "github.com/ipfs/go-hamt-ipld"
+	blockstore "github.com/ipfs/go-ipfs-blockstore"
 	bstore "github.com/ipfs/go-ipfs-blockstore"
+	format "github.com/ipfs/go-ipld-format"
 	logging "github.com/ipfs/go-log/v2"
+	dag "github.com/ipfs/go-merkledag"
 	cbg "github.com/whyrusleeping/cbor-gen"
 	pubsub "github.com/whyrusleeping/pubsub"
 	"golang.org/x/xerrors"
@@ -917,6 +924,84 @@ func (cs *ChainStore) GetTipsetByHeight(ctx context.Context, h uint64, ts *types
 	}
 }
 
+func recurseLinks(bs blockstore.Blockstore, root cid.Cid, in []cid.Cid) ([]cid.Cid, error) {
+	data, err := bs.Get(root)
+	if err != nil {
+		return nil, err
+	}
+
+	top, err := cbg.ScanForLinks(bytes.NewReader(data.RawData()))
+	if err != nil {
+		return nil, err
+	}
+
+	in = append(in, top...)
+	for _, c := range top {
+		var err error
+		in, err = recurseLinks(bs, c, in)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return in, nil
+}
+
+func (cs *ChainStore) Export(ctx context.Context, ts *types.TipSet, w io.Writer) error {
+	if ts == nil {
+		ts = cs.GetHeaviestTipSet()
+	}
+	bsrv := blockservice.New(cs.bs, nil)
+	dserv := dag.NewDAGService(bsrv)
+	return car.WriteCarWithWalker(ctx, dserv, ts.Cids(), w, func(nd format.Node) ([]*format.Link, error) {
+		var b types.BlockHeader
+		if err := b.UnmarshalCBOR(bytes.NewBuffer(nd.RawData())); err != nil {
+			return nil, err
+		}
+
+		var out []*format.Link
+		for _, p := range b.Parents {
+			out = append(out, &format.Link{Cid: p})
+		}
+
+		cids, err := recurseLinks(cs.bs, b.Messages, nil)
+		if err != nil {
+			return nil, err
+		}
+
+		for _, c := range cids {
+			out = append(out, &format.Link{Cid: c})
+		}
+
+		if b.Height == 0 {
+			cids, err := recurseLinks(cs.bs, b.ParentStateRoot, nil)
+			if err != nil {
+				return nil, err
+			}
+
+			for _, c := range cids {
+				out = append(out, &format.Link{Cid: c})
+			}
+		}
+
+		return out, nil
+	})
+}
+
+func (cs *ChainStore) Import(r io.Reader) (*types.TipSet, error) {
+	header, err := car.LoadCar(cs.Blockstore(), r)
+	if err != nil {
+		return nil, xerrors.Errorf("loadcar failed: %w", err)
+	}
+
+	root, err := cs.LoadTipSet(types.NewTipSetKey(header.Roots...))
+	if err != nil {
+		return nil, xerrors.Errorf("failed to load root tipset from chainfile: %w", err)
+	}
+
+	return root, nil
+}
+
 type chainRand struct {
 	cs   *ChainStore
 	blks []cid.Cid

cli/chain.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"os"
 	"strings"
 	"time"
 
@@ -26,6 +27,7 @@ var chainCmd = &cli.Command{
 		chainSetHeadCmd,
 		chainListCmd,
 		chainGetCmd,
+		chainExportCmd,
 	},
 }
 
@@ -385,3 +387,50 @@ func printTipSet(format string, ts *types.TipSet) {
 
 	fmt.Println(format)
 }
+
+var chainExportCmd = &cli.Command{
+	Name:  "export",
+	Usage: "export chain to a car file",
+	Flags: []cli.Flag{
+		&cli.StringFlag{
+			Name: "tipset",
+		},
+	},
+	Action: func(cctx *cli.Context) error {
+		api, closer, err := GetFullNodeAPI(cctx)
+		if err != nil {
+			return err
+		}
+		defer closer()
+		ctx := ReqContext(cctx)
+
+		if !cctx.Args().Present() {
+			return fmt.Errorf("must specify filename to export chain to")
+		}
+
+		fi, err := os.Create(cctx.Args().First())
+		if err != nil {
+			return err
+		}
+		defer fi.Close()
+
+		ts, err := loadTipSet(ctx, cctx, api)
+		if err != nil {
+			return err
+		}
+
+		stream, err := api.ChainExport(ctx, ts)
+		if err != nil {
+			return err
+		}
+
+		for b := range stream {
+			_, err := fi.Write(b)
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	},
+}

cmd/lotus/daemon.go

@@ -5,14 +5,20 @@ package main
 import (
 	"context"
 	"io/ioutil"
+	"os"
 
 	paramfetch "github.com/filecoin-project/go-paramfetch"
+	"github.com/filecoin-project/go-sectorbuilder"
+	blockstore "github.com/ipfs/go-ipfs-blockstore"
 	"github.com/multiformats/go-multiaddr"
 	"golang.org/x/xerrors"
 	"gopkg.in/urfave/cli.v2"
 
 	"github.com/filecoin-project/lotus/api"
 	"github.com/filecoin-project/lotus/build"
+	"github.com/filecoin-project/lotus/chain/stmgr"
+	"github.com/filecoin-project/lotus/chain/store"
+	"github.com/filecoin-project/lotus/chain/vm"
 	"github.com/filecoin-project/lotus/node"
 	"github.com/filecoin-project/lotus/node/modules"
 	"github.com/filecoin-project/lotus/node/modules/testing"
@@ -56,6 +62,14 @@ var DaemonCmd = &cli.Command{
 			Name:  "bootstrap",
 			Value: true,
 		},
+		&cli.StringFlag{
+			Name:  "import-chain",
+			Usage: "on first run, load chain from given file",
+		},
+		&cli.BoolFlag{
+			Name:  "halt-after-import",
+			Usage: "halt the process after importing chain from file",
+		},
 	},
 	Action: func(cctx *cli.Context) error {
 		ctx := context.Background()
@@ -81,6 +95,16 @@ var DaemonCmd = &cli.Command{
 			}
 		}
 
+		chainfile := cctx.String("import-chain")
+		if chainfile != "" {
+			if err := ImportChain(r, chainfile); err != nil {
+				return err
+			}
+			if cctx.Bool("halt-after-import") {
+				return nil
+			}
+		}
+
 		genesis := node.Options()
 		if len(genBytes) > 0 {
 			genesis = node.Override(new(modules.Genesis), modules.LoadGenesis(genBytes))
@@ -129,3 +153,50 @@ var DaemonCmd = &cli.Command{
 		return serveRPC(api, stop, endpoint)
 	},
 }
+
+func ImportChain(r repo.Repo, fname string) error {
+	fi, err := os.Open(fname)
+	if err != nil {
+		return err
+	}
+
+	lr, err := r.Lock(repo.FullNode)
+	if err != nil {
+		return err
+	}
+	defer lr.Close()
+
+	ds, err := lr.Datastore("/blocks")
+	if err != nil {
+		return err
+	}
+
+	mds, err := lr.Datastore("/metadata")
+	if err != nil {
+		return err
+	}
+
+	bs := blockstore.NewBlockstore(ds)
+
+	cst := store.NewChainStore(bs, mds, vm.Syscalls(sectorbuilder.ProofVerifier))
+
+	log.Info("importing chain from file...")
+	ts, err := cst.Import(fi)
+	if err != nil {
+		return xerrors.Errorf("importing chain failed: %w", err)
+	}
+
+	stm := stmgr.NewStateManager(cst)
+
+	log.Infof("validating imported chain...")
+	if err := stm.ValidateChain(context.TODO(), ts); err != nil {
+		return xerrors.Errorf("chain validation failed: %w", err)
+	}
+
+	log.Info("accepting %s as new head", ts.Cids())
+	if err := cst.SetHead(ts); err != nil {
+		return err
+	}
+
+	return nil
+}

go.mod

@@ -32,7 +32,7 @@ require (
 	github.com/ipfs/go-bitswap v0.1.8
 	github.com/ipfs/go-block-format v0.0.2
 	github.com/ipfs/go-blockservice v0.1.3-0.20190908200855-f22eea50656c
-	github.com/ipfs/go-car v0.0.3-0.20191203022317-23b0a85fd1b1
+	github.com/ipfs/go-car v0.0.3-0.20200121013634-f188c0e24291
 	github.com/ipfs/go-cid v0.0.4
 	github.com/ipfs/go-datastore v0.3.1
 	github.com/ipfs/go-ds-badger2 v0.0.0-20200108185345-7f650e6b2521

go.sum

@@ -106,27 +106,11 @@ github.com/filecoin-project/go-amt-ipld/v2 v2.0.0/go.mod h1:PAZ5tvSfMfWE327osqFX
 github.com/filecoin-project/go-cbor-util v0.0.0-20191219014500-08c40a1e63a2 h1:av5fw6wmm58FYMgJeoB/lK9XXrgdugYiTqkdxjTy9k8=
 github.com/filecoin-project/go-cbor-util v0.0.0-20191219014500-08c40a1e63a2/go.mod h1:pqTiPHobNkOVM5thSRsHYjyQfq7O5QSCMhvuu9JoDlg=
 github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03 h1:2pMXdBnCiXjfCYx/hLqFxccPoqsSveQFxVLvNxy9bus=
-github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03 h1:2pMXdBnCiXjfCYx/hLqFxccPoqsSveQFxVLvNxy9bus=
-github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03 h1:2pMXdBnCiXjfCYx/hLqFxccPoqsSveQFxVLvNxy9bus=
-github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03 h1:2pMXdBnCiXjfCYx/hLqFxccPoqsSveQFxVLvNxy9bus=
-github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03/go.mod h1:+viYnvGtUTgJRdy6oaeF4MTFKAfatX071MPDPBL11EQ=
-github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03/go.mod h1:+viYnvGtUTgJRdy6oaeF4MTFKAfatX071MPDPBL11EQ=
-github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03/go.mod h1:+viYnvGtUTgJRdy6oaeF4MTFKAfatX071MPDPBL11EQ=
-github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03/go.mod h1:+viYnvGtUTgJRdy6oaeF4MTFKAfatX071MPDPBL11EQ=
 github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03/go.mod h1:+viYnvGtUTgJRdy6oaeF4MTFKAfatX071MPDPBL11EQ=
 github.com/filecoin-project/go-data-transfer v0.0.0-20191219005021-4accf56bd2ce h1:Jdejrx6XVSTRy2PiX08HCU5y68p3wx2hNMJJc/J7kZY=
 github.com/filecoin-project/go-data-transfer v0.0.0-20191219005021-4accf56bd2ce/go.mod h1:b14UWxhxVCAjrQUYvVGrQRRsjAh79wXYejw9RbUcAww=
 github.com/filecoin-project/go-fil-markets v0.0.0-20200114015428-74d100f305f8 h1:g3oodvSz+Ou+ObwcVBB2wyt8SHdWpwzMiNJ19U1zZNA=
 github.com/filecoin-project/go-fil-markets v0.0.0-20200114015428-74d100f305f8/go.mod h1:c8NTjvFVy1Ud02mmGDjOiMeawY2t6ALfrrdvAB01FQc=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878 h1:YicJT9xhPzZ1SBGiJFNUCkfwqK/G9vFyY1ytKBSjNJA=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878 h1:YicJT9xhPzZ1SBGiJFNUCkfwqK/G9vFyY1ytKBSjNJA=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878 h1:YicJT9xhPzZ1SBGiJFNUCkfwqK/G9vFyY1ytKBSjNJA=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878 h1:YicJT9xhPzZ1SBGiJFNUCkfwqK/G9vFyY1ytKBSjNJA=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878 h1:YicJT9xhPzZ1SBGiJFNUCkfwqK/G9vFyY1ytKBSjNJA=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878/go.mod h1:40kI2Gv16mwcRsHptI3OAV4nlOEU7wVDc4RgMylNFjU=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878/go.mod h1:40kI2Gv16mwcRsHptI3OAV4nlOEU7wVDc4RgMylNFjU=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878/go.mod h1:40kI2Gv16mwcRsHptI3OAV4nlOEU7wVDc4RgMylNFjU=
-github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878/go.mod h1:40kI2Gv16mwcRsHptI3OAV4nlOEU7wVDc4RgMylNFjU=
 github.com/filecoin-project/go-paramfetch v0.0.0-20200102181131-b20d579f2878/go.mod h1:40kI2Gv16mwcRsHptI3OAV4nlOEU7wVDc4RgMylNFjU=
 github.com/filecoin-project/go-paramfetch v0.0.1 h1:gV7bs5YaqlgpGFMiLxInGK2L1FyCXUE0rimz4L7ghoE=
 github.com/filecoin-project/go-paramfetch v0.0.1/go.mod h1:fZzmf4tftbwf9S37XRifoJlz7nCjRdIrMGLR07dKLCc=
@@ -134,8 +118,6 @@ github.com/filecoin-project/go-sectorbuilder v0.0.1/go.mod h1:3OZ4E3B2OuwhJjtxR4
 github.com/filecoin-project/go-sectorbuilder v0.0.2-0.20200114015900-4103afa82689 h1:2cT5bhm/5I0RY+HBIPdRRrtjCwLj33Qx6DHRs9TCslY=
 github.com/filecoin-project/go-sectorbuilder v0.0.2-0.20200114015900-4103afa82689/go.mod h1:3OZ4E3B2OuwhJjtxR4r7hPU9bCfB+A+hm4alLEsaeDc=
 github.com/filecoin-project/go-statestore v0.1.0 h1:t56reH59843TwXHkMcwyuayStBIiWBRilQjQ+5IiwdQ=
-github.com/filecoin-project/go-statestore v0.1.0 h1:t56reH59843TwXHkMcwyuayStBIiWBRilQjQ+5IiwdQ=
-github.com/filecoin-project/go-statestore v0.1.0/go.mod h1:LFc9hD+fRxPqiHiaqUEZOinUJB4WARkRfNl10O7kTnI=
 github.com/filecoin-project/go-statestore v0.1.0/go.mod h1:LFc9hD+fRxPqiHiaqUEZOinUJB4WARkRfNl10O7kTnI=
 github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
@@ -227,8 +209,9 @@ github.com/ipfs/go-blockservice v0.0.7/go.mod h1:EOfb9k/Y878ZTRY/CH0x5+ATtaipfbR
 github.com/ipfs/go-blockservice v0.1.0/go.mod h1:hzmMScl1kXHg3M2BjTymbVPjv627N7sYcvYaKbop39M=
 github.com/ipfs/go-blockservice v0.1.3-0.20190908200855-f22eea50656c h1:lN5IQA07VtLiTLAp/Scezp1ljFhXErC6yq4O1cu+yJ0=
 github.com/ipfs/go-blockservice v0.1.3-0.20190908200855-f22eea50656c/go.mod h1:t+411r7psEUhLueM8C7aPA7cxCclv4O3VsUVxt9kz2I=
-github.com/ipfs/go-car v0.0.3-0.20191203022317-23b0a85fd1b1 h1:Nq8xEW+2KZq7IkRlkOh0rTEUI8FgunhMoLj5EMkJzbQ=
 github.com/ipfs/go-car v0.0.3-0.20191203022317-23b0a85fd1b1/go.mod h1:rmd887mJxQRDfndfDEY3Liyx8gQVyfFFRSHdsnDSAlk=
+github.com/ipfs/go-car v0.0.3-0.20200121013634-f188c0e24291 h1:Yy0dcFWw8oDV/WJ4S/rkMQRWnJ3tGr9EbgDDv2JhVQw=
+github.com/ipfs/go-car v0.0.3-0.20200121013634-f188c0e24291/go.mod h1:AG6sBpd2PWMccpAG7XLFBBQ/4rfBEtzUNeO2GSMesYk=
 github.com/ipfs/go-cid v0.0.1/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUPQvM=
 github.com/ipfs/go-cid v0.0.2/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUPQvM=
 github.com/ipfs/go-cid v0.0.3/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUPQvM=
@@ -320,6 +303,7 @@ github.com/ipfs/go-unixfs v0.2.2-0.20190827150610-868af2e9e5cb h1:tmWYgjltxwM7PD
 github.com/ipfs/go-unixfs v0.2.2-0.20190827150610-868af2e9e5cb/go.mod h1:IwAAgul1UQIcNZzKPYZWOCijryFBeCV79cNubPzol+k=
 github.com/ipfs/go-verifcid v0.0.1 h1:m2HI7zIuR5TFyQ1b79Da5N9dnnCP1vcu2QqawmWlK2E=
 github.com/ipfs/go-verifcid v0.0.1/go.mod h1:5Hrva5KBeIog4A+UpqlaIU+DEstipcJYQQZc0g37pY0=
+github.com/ipld/go-ipld-prime v0.0.1/go.mod h1:bDDSvVz7vaK12FNvMeRYnpRFkSUPNQOiCYQezMD/P3w=
 github.com/ipld/go-ipld-prime v0.0.2-0.20191108012745-28a82f04c785 h1:fASnkvtR+SmB2y453RxmDD3Uvd4LonVUgFGk9JoDaZs=
 github.com/ipld/go-ipld-prime v0.0.2-0.20191108012745-28a82f04c785/go.mod h1:bDDSvVz7vaK12FNvMeRYnpRFkSUPNQOiCYQezMD/P3w=
 github.com/ipld/go-ipld-prime-proto v0.0.0-20191113031812-e32bd156a1e5 h1:lSip43rAdyGA+yRQuy6ju0ucZkWpYc1F2CTQtZTVW/4=

node/impl/full/chain.go

@@ -3,6 +3,7 @@ package full
 import (
 	"context"
 	"fmt"
+	"io"
 	"strconv"
 	"strings"
 
@@ -18,6 +19,7 @@ import (
 	"github.com/ipfs/go-path"
 	"github.com/ipfs/go-path/resolver"
 	mh "github.com/multiformats/go-multihash"
+	"github.com/prometheus/common/log"
 	"go.uber.org/fx"
 	"golang.org/x/xerrors"
 
@@ -312,3 +314,34 @@ func (a *ChainAPI) ChainGetMessage(ctx context.Context, mc cid.Cid) (*types.Mess
 
 	return cm.VMMessage(), nil
 }
+
+func (a *ChainAPI) ChainExport(ctx context.Context, ts *types.TipSet) (<-chan []byte, error) {
+	r, w := io.Pipe()
+	out := make(chan []byte)
+	go func() {
+		defer w.Close()
+		if err := a.Chain.Export(ctx, ts, w); err != nil {
+			log.Errorf("chain export call failed: %s", err)
+			return
+		}
+	}()
+
+	go func() {
+		defer close(out)
+		for {
+			buf := make([]byte, 4096)
+			n, err := r.Read(buf)
+			if err != nil {
+				log.Errorf("chain export pipe read failed: %s", err)
+				return
+			}
+			select {
+			case out <- buf[:n]:
+			case <-ctx.Done():
+				log.Warnf("export writer failed: %s", ctx.Err())
+			}
+		}
+	}()
+
+	return out, nil
+}