【Canal源码分析】数据传输协议
Canal的数据传输有两块,一块是进行binlog订阅时,binlog转换为我们所定义的Message,第二块是client与server进行TCP交互时,传输的TCP协议。
一、EntryProtocal
这块是binlog的一个存储。主要的格式如下:
Entry
Header
version [协议的版本号,default = 1]
logfileName [binlog文件名]
logfileOffset [binlog position]
serverId [服务端serverId]
serverenCode [变更数据的编码]
executeTime [变更数据的执行时间]
sourceType [变更数据的来源,default = MYSQL]
schemaName [变更数据的schemaname]
tableName [变更数据的tablename]
eventLength [每个event的长度]
eventType [insert/update/delete类型,default = UPDATE]
props [预留扩展]
gtid [当前事务的gitd]
entryType [事务头BEGIN/事务尾END/数据ROWDATA/HEARTBEAT/GTIDLOG]
storeValue [byte数据,可展开,对应的类型为RowChange]
RowChange
tableId [tableId,由数据库产生]
eventType [数据变更类型,default = UPDATE]
isDdl [标识是否是ddl语句,比如create table/drop table]
sql [ddl/query的sql语句]
rowDatas [具体insert/update/delete的变更数据,可为多条,1个binlog event事件可对应多条变更,比如批处理]
beforeColumns [字段信息,增量数据(修改前,删除前),Column类型的数组]
afterColumns [字段信息,增量数据(修改后,新增后),Column类型的数组]
props [预留扩展]
props [预留扩展]
ddlSchemaName [ddl/query的schemaName,会存在跨库ddl,需要保留执行ddl的当前schemaName]
Column
index [字段下标]
sqlType [jdbc type]
name [字段名称(忽略大小写),在mysql中是没有的]
isKey [是否为主键]
updated [是否发生过变更]
isNull [值是否为null]
props [预留扩展]
value [字段值,timestamp,Datetime是一个时间格式的文本]
length [对应数据对象原始长度]
mysqlType [字段mysql类型]
二、CanalProtocal
这块主要定义了client和server交互的协议。
Packet
magic_number [default = 17]
version [default = 1]
type [PacketType,类型]
compression [压缩,default = NONE]
body [具体内容]
主要的类型和对应的body,都可以在CanalProtocal.proto里面查看到。
enum PacketType {
HANDSHAKE = 1;
CLIENTAUTHENTICATION = 2;
ACK = 3;
SUBSCRIPTION = 4;
UNSUBSCRIPTION = 5;
GET = 6;
MESSAGES = 7;
CLIENTACK = 8;
// management part
SHUTDOWN = 9;
// integration
DUMP = 10;
HEARTBEAT = 11;
CLIENTROLLBACK = 12;
}
//心跳
message HeartBeat {
optional int64 send_timestamp = 1;
optional int64 start_timestamp = 2;
}
//握手
message Handshake {
optional string communication_encoding = 1 [default = "utf8"];
optional bytes seeds = 2;
repeated Compression supported_compressions = 3;
}
// client authentication
message ClientAuth {
optional string username = 1;
optional bytes password = 2; // hashed password with seeds from Handshake message
optional int32 net_read_timeout = 3 [default = 0]; // in seconds
optional int32 net_write_timeout = 4 [default = 0]; // in seconds
optional string destination = 5;
optional string client_id = 6;
optional string filter = 7;
optional int64 start_timestamp = 8;
}
//服务端响应
message Ack {
optional int32 error_code = 1 [default = 0];
optional string error_message = 2; // if something like compression is not supported, erorr_message will tell about it.
}
//客户端提交
message ClientAck {
optional string destination = 1;
optional string client_id = 2;
optional int64 batch_id = 3;
}
// subscription
message Sub {
optional string destination = 1;
optional string client_id = 2;
optional string filter = 7;
}
// Unsubscription
message Unsub {
optional string destination = 1;
optional string client_id = 2;
optional string filter = 7;
}
// PullRequest
message Get {
optional string destination = 1;
optional string client_id = 2;
optional int32 fetch_size = 3;
optional int64 timeout = 4 [default = -1]; // 默认-1时代表不控制
optional int32 unit = 5 [default = 2];// 数字类型,0:纳秒,1:毫秒,2:微秒,3:秒,4:分钟,5:小时,6:天
optional bool auto_ack = 6 [default = false]; // 是否自动ack
}
//消息
message Messages {
optional int64 batch_id = 1;
repeated bytes messages = 2;
}
// TBD when new packets are required
message Dump{
optional string journal = 1;
optional int64 position = 2;
optional int64 timestamp = 3 [default = 0];
}
// 客户端回滚
message ClientRollback{
optional string destination = 1;
optional string client_id = 2;
optional int64 batch_id = 3;
}