func newFromConfig(ld blobserver.Loader, config jsonconfig.Obj) (storage blobserver.Storage, err error) {
sto := &replicaStorage{
replicaPrefixes: config.RequiredList("backends"),
readPrefixes: config.OptionalList("readBackends"),
}
nReplicas := len(sto.replicaPrefixes)
sto.minWritesForSuccess = config.OptionalInt("minWritesForSuccess", nReplicas)
if err := config.Validate(); err != nil {
return nil, err
}
if nReplicas == 0 {
return nil, errors.New("replica: need at least one replica")
}
if sto.minWritesForSuccess == 0 {
sto.minWritesForSuccess = nReplicas
}
// readPrefixes defaults to the write prefixes.
if len(sto.readPrefixes) == 0 {
sto.readPrefixes = sto.replicaPrefixes
}
for _, prefix := range sto.replicaPrefixes {
s, err := ld.GetStorage(prefix)
if err != nil {
// If it's not a storage interface, it might be an http Handler
// that also supports being a target (e.g. a sync handler).
h, _ := ld.GetHandler(prefix)
var ok bool
if s, ok = h.(blobserver.Storage); !ok {
return nil, err
}
}
sto.replicas = append(sto.replicas, s)
}
for _, prefix := range sto.readPrefixes {
s, err := ld.GetStorage(prefix)
if err != nil {
return nil, err
}
sto.readReplicas = append(sto.readReplicas, s)
}
return sto, nil
}
func newFromConfig(ld blobserver.Loader, config jsonconfig.Obj) (storage blobserver.Storage, err error) {
sto := &shardStorage{
shardPrefixes: config.RequiredList("backends"),
}
if err := config.Validate(); err != nil {
return nil, err
}
if len(sto.shardPrefixes) == 0 {
return nil, errors.New("shard: need at least one shard")
}
sto.shards = make([]blobserver.Storage, len(sto.shardPrefixes))
for i, prefix := range sto.shardPrefixes {
shardSto, err := ld.GetStorage(prefix)
if err != nil {
return nil, err
}
sto.shards[i] = shardSto
}
return sto, nil
}