func newFromConfig(ld blobserver.Loader, config jsonconfig.Obj) (storage blobserver.Storage, err os.Error) {
sto := &replicaStorage{
SimpleBlobHubPartitionMap: &blobserver.SimpleBlobHubPartitionMap{},
}
sto.replicaPrefixes = config.RequiredList("backends")
nReplicas := len(sto.replicaPrefixes)
sto.minWritesForSuccess = config.OptionalInt("minWritesForSuccess", nReplicas)
if err := config.Validate(); err != nil {
return nil, err
}
if nReplicas == 0 {
return nil, os.NewError("replica: need at least one replica")
}
if sto.minWritesForSuccess == 0 {
sto.minWritesForSuccess = nReplicas
}
sto.replicas = make([]blobserver.Storage, nReplicas)
for i, prefix := range sto.replicaPrefixes {
replicaSto, err := ld.GetStorage(prefix)
if err != nil {
return nil, err
}
sto.replicas[i] = replicaSto
}
return sto, nil
}