chain export should work now

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)
 }

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,
 	},
 }
 
@@ -386,7 +388,7 @@ func printTipSet(format string, ts *types.TipSet) {
 	fmt.Println(format)
 }
 
-func chainExportCmd = &cli.Command{
+var chainExportCmd = &cli.Command{
 	Name:  "export",
 	Usage: "export chain to a car file",
 	Action: func(cctx *cli.Context) error {
@@ -397,5 +399,33 @@ func chainExportCmd = &cli.Command{
 		defer closer()
 		ctx := ReqContext(cctx)
 
+		if !cctx.Args().Present() {
+			return fmt.Errorf("must specify filename to export chain to")
+		}
+
+		ts, err := parseTipSet(api, ctx, cctx.Args().Slice())
+		if err != nil {
+			return err
+		}
+
+		fi, err := os.Create(cctx.Args().First())
+		if err != nil {
+			return err
+		}
+		defer fi.Close()
+
+		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
 	},
 }

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 close(out)
+		if err := a.Chain.Export(ctx, ts, w); err != nil {
+			log.Errorf("chain export call failed: %s", err)
+			return
+		}
+	}()
+
+	go func() {
+		defer r.Close()
+		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.Done())
+			}
+		}
+	}()
+
+	return out, nil
+}