// GetResponse looks up a response matching the specified cmdID. If the
// response is found, it is returned along with its associated error.
// If the response is not found, nil is returned for both the response
// and its error. In all cases, the third return value is the error
// returned from the engine when reading the on-disk cache.
func (rc *ResponseCache) GetResponse(e engine.Engine, cmdID proto.ClientCmdID) (proto.ResponseWithError, error) {
// Do nothing if command ID is empty.
if cmdID.IsEmpty() {
return proto.ResponseWithError{}, nil
}
// Pull response from the cache and read into reply if available.
var rcEntry proto.ResponseCacheEntry
key := keys.ResponseCacheKey(rc.rangeID, &cmdID)
ok, err := engine.MVCCGetProto(e, key, proto.ZeroTimestamp, true, nil, &rcEntry)
if err != nil {
return proto.ResponseWithError{}, err
}
if ok {
resp := rcEntry.GetValue().(proto.Response)
header := resp.Header()
defer func() { header.Error = nil }()
return proto.ResponseWithError{Reply: resp, Err: header.GoError()}, nil
}
return proto.ResponseWithError{}, nil
}
// PutResponse writes a response and an error associated with it to the
// cache for the specified cmdID.
func (rc *ResponseCache) PutResponse(e engine.Engine, cmdID proto.ClientCmdID, replyWithErr proto.ResponseWithError) error {
// Do nothing if command ID is empty.
if cmdID.IsEmpty() {
return nil
}
// Write the response value to the engine.
if rc.shouldCacheResponse(replyWithErr) {
// Write the error into the reply before caching.
header := replyWithErr.Reply.Header()
header.SetGoError(replyWithErr.Err)
// Be sure to clear it when you're done!
defer func() { header.Error = nil }()
key := keys.ResponseCacheKey(rc.rangeID, &cmdID)
var rcEntry proto.ResponseCacheEntry
if !rcEntry.SetValue(replyWithErr.Reply) {
panic(fmt.Sprintf("response %T not supported by response cache", replyWithErr.Reply))
}
return engine.MVCCPutProto(e, nil, key, proto.ZeroTimestamp, nil, &rcEntry)
}
return nil
}