github.com/pingcap/ticdc@v0.0.0-20220526033649-485a10ef2652/pkg/pipeline/node.go (about)

     1  // Copyright 2020 PingCAP, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package pipeline
    15  
    16  // Node represents a handle unit for the message stream in the pipeline
    17  // The following functions in this interface will be called in one goroutine.
    18  // It's NO NEED to consider concurrency issues
    19  type Node interface {
    20  
    21  	// Init initializes the node
    22  	// when the pipeline is started, this function will be called in order
    23  	// you can call `ctx.SendToNextNode(msg)` to send the message to the next node
    24  	// but it will return nil if you try to call the `ctx.Message()`
    25  	Init(ctx NodeContext) error
    26  
    27  	// Receive receives the message from the previous node
    28  	// when the node receives a message, this function will be called
    29  	// you can call `ctx.Message()` to receive the message
    30  	// you can call `ctx.SendToNextNode(msg)` to send the message to the next node
    31  	Receive(ctx NodeContext) error
    32  
    33  	// Destory frees the resources in this node
    34  	// you can call `ctx.SendToNextNode(msg)` to send the message to the next node
    35  	// but it will return nil if you try to call the `ctx.Message()`
    36  	Destroy(ctx NodeContext) error
    37  }