定义消息处理接口
// Processor provides the methods necessary to classify and process any message which
// arrives through the Broadcast interface.
type Processor interface {
// ClassifyMsg inspects the message header to determine which type of processing is necessary
ClassifyMsg(chdr *cb.ChannelHeader) Classification
// ProcessNormalMsg will check the validity of a message based on the current configuration. It returns the current
// configuration sequence number and nil on success, or an error if the message is not valid
ProcessNormalMsg(env *cb.Envelope) (configSeq uint64, err error)
// ProcessConfigUpdateMsg will attempt to apply the config update to the current configuration, and if successful
// return the resulting config message and the configSeq the config was computed from. If the config update message
// is invalid, an error is returned.
ProcessConfigUpdateMsg(env *cb.Envelope) (config *cb.Envelope, configSeq uint64, err error)
// ProcessConfigMsg takes message of type `ORDERER_TX` or `CONFIG`, unpack the ConfigUpdate envelope embedded
// in it, and call `ProcessConfigUpdateMsg` to produce new Config message of the same type as original message.
// This method is used to re-validate and reproduce config message, if it's deemed not to be valid anymore.
ProcessConfigMsg(env *cb.Envelope) (*cb.Envelope, uint64, error)
}