// GetResponse looks up a response matching the specified cmdID and
// returns true if found. The response is deserialized into the
// supplied reply parameter. If no response is found, returns
// false. If a command is pending already for the cmdID, then this
// method will block until the the command is completed or the
// response cache is cleared.
func (rc *ResponseCache) GetResponse(e engine.Engine, cmdID proto.ClientCmdID, reply proto.Response) (bool, error) {
// Do nothing if command ID is empty.
if cmdID.IsEmpty() {
return false, nil
}
// Pull response from the cache and read into reply if available.
rwResp := proto.ReadWriteCmdResponse{}
key := keys.ResponseCacheKey(rc.raftID, &cmdID)
ok, err := engine.MVCCGetProto(e, key, proto.ZeroTimestamp, true, nil, &rwResp)
if ok && err == nil {
gogoproto.Merge(reply, rwResp.GetValue().(gogoproto.Message))
}
return ok, err
}
// GetResponse looks up a response matching the specified cmdID and
// returns true if found. The response is deserialized into the
// supplied reply parameter. If no response is found, returns
// false. If a command is pending already for the cmdID, then this
// method will block until the the command is completed or the
// response cache is cleared.
func (rc *ResponseCache) GetResponse(cmdID proto.ClientCmdID, reply proto.Response) (bool, error) {
// Do nothing if command ID is empty.
if cmdID.IsEmpty() {
return false, nil
}
// If the response is in the cache or we experienced an error, return.
rwResp := proto.ReadWriteCmdResponse{}
key := keys.ResponseCacheKey(rc.raftID, &cmdID)
ok, err := engine.MVCCGetProto(rc.engine, key, proto.ZeroTimestamp, true, nil, &rwResp)
if ok && err == nil {
gogoproto.Merge(reply, rwResp.GetValue().(gogoproto.Message))
}
return ok, err
}
// 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 rwResp proto.ReadWriteCmdResponse
key := keys.ResponseCacheKey(rc.raftID, &cmdID)
ok, err := engine.MVCCGetProto(e, key, proto.ZeroTimestamp, true, nil, &rwResp)
if err != nil {
return proto.ResponseWithError{}, err
}
if ok {
resp := rwResp.GetValue().(proto.Response)
header := resp.Header()
defer func() { header.Error = nil }()
return proto.ResponseWithError{resp, header.GoError()}, nil
}
return proto.ResponseWithError{}, nil
}
// GetResponse looks up a response matching the specified cmdID and
// returns true if found. The response is deserialized into the
// supplied reply parameter. If no response is found, returns
// false. If a command is pending already for the cmdID, then this
// method will block until the the command is completed or the
// response cache is cleared.
func (rc *ResponseCache) GetResponse(cmdID proto.ClientCmdID, reply proto.Response) (bool, error) {
// Do nothing if command ID is empty.
if cmdID.IsEmpty() {
return false, nil
}
// If the command is inflight, wait for it to complete.
rc.Lock()
for {
if cond, ok := rc.inflight[makeCmdIDKey(cmdID)]; ok {
log.Infof("waiting on cmdID: %s", &cmdID)
cond.Wait()
} else {
break
}
}
// Adding inflight here is preemptive; we don't want to hold lock
// while fetching from the on-disk cache. The vast, vast majority of
// calls to GetResponse will be cache misses, so this saves us
// from acquiring the lock twice: once here and once below in the
// event we experience a cache miss.
rc.addInflightLocked(cmdID)
rc.Unlock()
// If the response is in the cache or we experienced an error, return.
rwResp := proto.ReadWriteCmdResponse{}
key := engine.ResponseCacheKey(rc.raftID, &cmdID)
if ok, err := engine.MVCCGetProto(rc.engine, key, proto.ZeroTimestamp, nil, &rwResp); ok || err != nil {
rc.Lock() // Take lock after fetching response from cache.
defer rc.Unlock()
rc.removeInflightLocked(cmdID)
if err == nil && rwResp.GetValue() != nil {
gogoproto.Merge(reply.(gogoproto.Message), rwResp.GetValue().(gogoproto.Message))
}
return ok, err
}
// There's no command result cached for this ID; but inflight was added above.
return false, 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.raftID, &cmdID)
var rwResp proto.ReadWriteCmdResponse
if !rwResp.SetValue(replyWithErr.Reply) {
panic(fmt.Sprintf("response %T not supported by response cache", replyWithErr.Reply))
}
return engine.MVCCPutProto(e, nil, key, proto.ZeroTimestamp, nil, &rwResp)
}
return nil
}
