Add portable analogs of some common channel call errors

gossip/gossip.go

@@ -9,12 +9,19 @@ package gossip
 import (
 	"crypto/x509"
 
+	"github.com/pkg/errors"
 	"github.com/rkcloudchain/rksync/channel"
 	"github.com/rkcloudchain/rksync/common"
 	"github.com/rkcloudchain/rksync/filter"
 	"github.com/rkcloudchain/rksync/protos"
 )
 
+// Portable analogs of some common channel call errors
+var (
+	ErrChannelExist    = errors.New("channel already exists")
+	ErrChannelNotExist = errors.New("channel does not exist")
+)
+
 type channelRoutingFilterFactory func(channel.Channel) filter.RoutingFilter
 
 // Gossip is the interface of the gossip component

gossip/service.go

@@ -247,7 +247,7 @@ func (g *gossipService) CreateChain(chainMac common.ChainMac, chainID string, fi
 	}
 
 	if c := g.chanState.getChannelByMAC(chainMac); c != nil {
-		return nil, errors.Errorf("Channel (%s) already exists", chainID)
+		return nil, ErrChannelExist
 	}
 
 	gc := g.chanState.joinChannel(chainMac, chainID, true)
@@ -261,7 +261,7 @@ func (g *gossipService) CloseChain(chainMac common.ChainMac, notify bool) error
 
 	gc := g.chanState.getChannelByMAC(chainMac)
 	if gc == nil {
-		return errors.Errorf("Failed to find channel with mac: %s", chainMac)
+		return ErrChannelNotExist
 	}
 	chainState := gc.Self()
 	msg, err := chainState.Envelope.ToRKSyncMessage()