fix(lib/grandpa): use defaultGrandpaInterval if not set, fixes error on startup (#1982)

Author: noot

lib/grandpa/errors.go

@@ -101,9 +101,6 @@ var (
 	// ErrAuthorityNotInSet is returned when a precommit within a justification is signed by a key not in the authority set
 	ErrAuthorityNotInSet = errors.New("authority is not in set")
 
-	// ErrZeroInterval is returned when the grandpa sub-round interval is set to 0
-	ErrZeroInterval = errors.New("cannot have zero second interval")
-
 	errVoteExists              = errors.New("already have vote")
 	errVoteToSignatureMismatch = errors.New("votes and authority count mismatch")
 	errInvalidVoteBlock        = errors.New("block in vote is not descendant of previously finalised block")

lib/grandpa/grandpa.go

@@ -38,6 +38,7 @@ import (
 
 const (
 	finalityGrandpaRoundMetrics = "gossamer/finality/grandpa/round"
+	defaultGrandpaInterval      = time.Second
 )
 
 var (
@@ -147,7 +148,7 @@ func NewService(cfg *Config) (*Service, error) {
 	}
 
 	if cfg.Interval == 0 {
-		return nil, ErrZeroInterval
+		cfg.Interval = defaultGrandpaInterval
 	}
 
 	ctx, cancel := context.WithCancel(context.Background())