深入解析中间件之-Canal
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2022-04-28 09:39:52
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canal: 阿里巴巴mysql数据库binlog的增量订阅&消费组件
MySQL binlog
MySQL主从复制
mysql服务端修改配置并重启
$ vi /etc/my.cnf
[mysqld]
log-bin=mysql-bin
binlog-format=ROW
server_id=1
$ mysql -uroot
CREATE USER canal IDENTIFIED BY 'canal';
GRANT ALL PRIVILEGES ON *.* TO 'canal'@'%' ;
FLUSH PRIVILEGES;
$ sudo service mysqld start
问题：创建canal用户的目的是什么？直接使用现有的用户名可以吗，比如root。
答案：有些用户没有REPLICATION SLAVE, REPLICATION CLIENT的权限，用这些用户连接canal时，无法获取到binlog。
这里的canal用户授权了全部权限，所以客户端可以从canal中获取binlog。
明确两个概念：canal server连接mysql，客户端连接canal server。
- canal指的是canal server，它会读取mysql的binlog，解析后存储起来
- 客户端指的是消费canal server的binlog
本机连接服务端，验证binlog的格式是ROW
$ mysql -h192.168.6.52 -ucanal -pcanal
mysql> show variables like '%binlog_format%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| binlog_format | ROW |
+---------------+-------+
mysql主从复制的原理：
- master将改变记录到二进制日志(binary log)中；
- slave将master的binary log events拷贝到它的中继日志(relay log)；
- slave重做中继日志中的事件，将改变反映它自己的数据。
binlog
在启动canal之前，先来了解下什么是mysql的binlog:
mysql> show binlog events;
| Log_name | Pos | Event_type | Server_id | End_log_pos | Info |
+------------------+-------+-------------+-----------+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| mysql-bin.000001 | 4 | Format_desc | 1 | 106 | Server ver: 5.1.73-log, Binlog ver: 4 |
| mysql-bin.000001 | 106 | Query | 1 | 1864 | use `mysql`; CREATE TABLE IF NOT EXISTS db ( Host char(60) binary DEFAULT '' NOT NULL, Db char(64) binary DEFAULT '' NOT NULL, User char(16) binary DEFAULT '' NOT NULL, Select_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Insert_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Update_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Delete_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Create_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Drop_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Grant_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, References_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Index_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Alter_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Create_tmp_table_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Lock_tables_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Create_view_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Show_view_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Create_routine_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Alter_routine_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Execute_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Event_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Trigger_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, PRIMARY KEY Host (Host,Db,User), KEY User (User) ) engine=MyISAM CHARACTER SET utf8 COLLATE utf8_bin comment='Database privileges' |
| mysql-bin.000001 | 1864 | Query | 1 | 3518 | use `mysql`; CREATE TABLE IF NOT EXISTS host ( Host char(60) binary DEFAULT '' NOT NULL, Db char(64) binary DEFAULT '' NOT NULL, Select_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Insert_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Update_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Delete_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Create_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Drop_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Grant_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, References_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Index_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Alter_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Create_tmp_table_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Lock_tables_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Create_view_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Show_view_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Create_routine_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Alter_routine_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Execute_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, Trigger_priv enum('N','Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL, PRIMARY KEY Host (Host,Db) ) engine=MyISAM CHARACTER SET utf8 COLLATE utf8_bin comment='Host privileges; Merged with database privileges' |
mysql数据文件下会生成mysql-bin.xxx的binlog文件，以及索引文件
[aaa@qq.com canal]$ ll /var/lib/mysql/
总用量 26228
drwx------ 2 mysql mysql 4096 10月 11 14:05 canal_test
-rw-rw---- 1 mysql mysql 10485760 9月 30 22:12 ibdata1
-rw-rw---- 1 mysql mysql 5242880 10月 11 09:57 ib_logfile0
-rw-rw---- 1 mysql mysql 5242880 10月 11 09:57 ib_logfile1
drwx------ 2 mysql mysql 4096 8月 2 11:01 mysql
-rw-rw---- 1 mysql mysql 18451 8月 2 11:01 mysql-bin.000001
-rw-rw---- 1 mysql mysql 929226 8月 2 11:01 mysql-bin.000002
-rw-rw---- 1 mysql mysql 4890698 9月 30 22:12 mysql-bin.000003
-rw-rw---- 1 mysql mysql 897 10月 11 14:06 mysql-bin.000004
-rw-rw---- 1 mysql mysql 76 10月 11 09:57 mysql-bin.index
srwxrwxrwx 1 mysql mysql 0 10月 11 09:57 mysql.sock
针对mysql的操作都会有二进制的事件记录到binlog文件中。下面的一些操作包括创建用户，授权，创建数据库，创建表，插入一条记录。
[aaa@qq.com canal]$ sudo strings /var/lib/mysql/mysql-bin.000004
5.1.73-log
CREATE USER canal IDENTIFIED BY 'canal'
root localhost
GRANT ALL PRIVILEGES ON *.* TO 'canal'@'%'
FLUSH PRIVILEGES
canal_test
create database canal_test ===》创建数据库
canal_test
create table test ( uid int (4) primary key not null auto_increment, name varchar(10) not null) ==》创建表
canal_test
BEGIN ==》插入记录，这里有事务。但是没有把具体的语句打印出来
canal_test
test
canal_test
COMMIT
Canal QuickStart
canal & config
部署canal server到6.52，并启动。查看canal的日志：
[aaa@qq.com canal]$ cat logs/canal/canal.log
2017-10-11 11:31:52.076 [main] INFO com.alibaba.otter.canal.deployer.CanalLauncher - ## start the canal server.
2017-10-11 11:31:52.151 [main] INFO com.alibaba.otter.canal.deployer.CanalController - ## start the canal server[192.168.6.52:11111]
2017-10-11 11:31:52.644 [main] INFO com.alibaba.otter.canal.deployer.CanalLauncher - ## the canal server is running now ......
查看instance的日志：
[aaa@qq.com canal]$ cat logs/example/example.log
2017-10-11 11:31:52.435 [main] INFO c.a.o.c.i.spring.support.PropertyPlaceholderConfigurer - Loading properties file from class path resource [canal.properties]
2017-10-11 11:31:52.444 [main] INFO c.a.o.c.i.spring.support.PropertyPlaceholderConfigurer - Loading properties file from class path resource [example/instance.properties]
2017-10-11 11:31:52.587 [main] INFO c.a.otter.canal.instance.spring.CanalInstanceWithSpring - start CannalInstance for 1-example
2017-10-11 11:31:52.599 [main] INFO c.a.otter.canal.instance.core.AbstractCanalInstance - start successful....
2017-10-11 11:31:52.679 [destination = example , address = /127.0.0.1:3306 , EventParser] WARN c.a.otter.canal.parse.inbound.mysql.MysqlEventParser - prepare to find start position just show master status
canal server的conf下有几个配置文件
➜ canal.deployer-1.0.24 tree conf
conf
├── canal.properties
├── example
│ └── instance.properties
├── logback.xml
└── spring
├── default-instance.xml
├── file-instance.xml
├── group-instance.xml
├── local-instance.xml
└── memory-instance.xml
先来看canal.properties的common属性前四个配置项：
canal.id= 1
canal.ip=
canal.port= 11111
canal.zkServers=
canal.id是canal的编号，在集群环境下，不同canal的id不同，注意它和mysql的server_id不同。
ip这里不指定，默认为本机，比如上面是192.168.6.52，端口号是11111。zk用于canal cluster。
再看下canal.properties下destinations相关的配置：
#################################################
######### destinations #############
#################################################
canal.destinations = example
canal.conf.dir = ../conf
canal.auto.scan = true
canal.auto.scan.interval = 5
canal.instance.global.mode = spring
canal.instance.global.lazy = false
canal.instance.global.spring.xml = classpath:spring/file-instance.xml
这里的canal.destinations = example可以设置多个，比如example1,example2，
则需要创建对应的两个文件夹，并且每个文件夹下都有一个instance.properties文件。
全局的canal实例管理用spring，这里的file-instance.xml最终会实例化所有的destinations instances:
<bean class="com.alibaba.otter.canal.instance.spring.support.PropertyPlaceholderConfigurer" lazy-init="false">
<property name="ignoreResourceNotFound" value="true" />
<property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE"/><!-- 允许system覆盖 -->
<property name="locationNames">
<list>
<value>classpath:canal.properties</value>
<value>classpath:${canal.instance.destination:}/instance.properties</value>
</list>
</property>
</bean>
<bean id="instance" class="com.alibaba.otter.canal.instance.spring.CanalInstanceWithSpring">
<property name="destination" value="${canal.instance.destination}" />
<property name="eventParser"><ref local="eventParser" /></property>
<property name="eventSink"><ref local="eventSink" /></property>
<property name="eventStore"><ref local="eventStore" /></property>
<property name="metaManager"><ref local="metaManager" /></property>
<property name="alarmHandler"><ref local="alarmHandler" /></property>
</bean>
比如canal.instance.destination等于example，就会加载example/instance.properties配置文件
example下instance.properties配置文件不需要修改。一个canal server可以运行多个canal instance。
#################################################
## mysql serverId，这里的slaveId不能和myql集群中已有的server_id一样
canal.instance.mysql.slaveId = 1234
# position info 这里连接的是mysql master的地址。
canal.instance.master.address = 127.0.0.1:3306
canal.instance.master.journal.name =
canal.instance.master.position =
canal.instance.master.timestamp =
#canal.instance.standby.address =
#canal.instance.standby.journal.name =
#canal.instance.standby.position =
#canal.instance.standby.timestamp =
# username/password
canal.instance.dbUsername = canal
canal.instance.dbPassword = canal
canal.instance.defaultDatabaseName =
canal.instance.connectionCharset = UTF-8
canal.instance.filter.regex = .*\\..*
canal.instance.filter.black.regex =
#################################################
simple client
在mysql上创建数据库，创建表，插入一条记录，再修改记录。
create database canal_test;
use canal_test;
create table test ( uid int (4) primary key not null auto_increment, name varchar(10) not null);
insert into test (name) values('10');
修改客户端测试例子的连接信息。其中example对应了canal实例的名称。
String destination = "example";
CanalConnector connector = CanalConnectors.newSingleConnector(
new InetSocketAddress("192.168.6.52", 11111), destination, "canal", "canal");
注意：如果连接有错误，客户端测试例子会立即结束，打印## stop the canal client。正常的话，终端不会退出，会一直运行。
SimpleCanalClientTest控制台的结果如下：
****************************************************
* Batch Id: [1] ,count : [2] , memsize : [263] , Time : 2017-10-11 14:06:06
* Start : [mysql-bin.000004:396:1507701897000(2017-10-11 14:04:57)]
* End : [mysql-bin.000004:491:1507701904000(2017-10-11 14:05:04)]
****************************************************
----------------> binlog[mysql-bin.000004:396] , name[canal_test,] , eventType : QUERY , executeTime : 1507701897000 , delay : 69710ms
sql ----> create database canal_test
----------------> binlog[mysql-bin.000004:491] , name[canal_test,test] , eventType : CREATE , executeTime : 1507701904000 , delay : 62723ms
sql ----> create table test ( uid int (4) primary key not null auto_increment, name varchar(10) not null)
插入一条记录：（其中uid和name的update都等于true）
****************************************************
* Batch Id: [2] ,count : [3] , memsize : [186] , Time : 2017-10-11 14:06:32
* Start : [mysql-bin.000004:659:1507701989000(2017-10-11 14:06:29)]
* End : [mysql-bin.000004:822:1507701989000(2017-10-11 14:06:29)]
****************************************************
================> binlog[mysql-bin.000004:659] , executeTime : 1507701989000 , delay : 3142ms
BEGIN ----> Thread id: 11
----------------> binlog[mysql-bin.000004:785] , name[canal_test,test] , eventType : INSERT , executeTime : 1507701989000 , delay : 3154ms
uid : 1 type=int(4) update=true
name : 10 type=varchar(10) update=true
----------------
END ----> transaction id: 0
================> binlog[mysql-bin.000004:822] , executeTime : 1507701989000 , delay : 3179ms
修改记录：（其中name的update等于true）
****************************************************
* Batch Id: [3] ,count : [3] , memsize : [202] , Time : 2017-10-11 14:49:11
* Start : [mysql-bin.000004:897:1507704547000(2017-10-11 14:49:07)]
* End : [mysql-bin.000004:1076:1507704547000(2017-10-11 14:49:07)]
****************************************************
================> binlog[mysql-bin.000004:897] , executeTime : 1507704547000 , delay : 4048ms
BEGIN ----> Thread id: 13
----------------> binlog[mysql-bin.000004:1023] , name[canal_test,test] , eventType : UPDATE , executeTime : 1507704547000 , delay : 4059ms
uid : 1 type=int(4)
name : zqhxuyuan type=varchar(10) update=true
----------------
END ----> transaction id: 0
================> binlog[mysql-bin.000004:1076] , executeTime : 1507704547000 , delay : 4096ms
canal安装包下的example instance下除了example.log外，还有一个meta.log
[aaa@qq.com canal]$ cat logs/example/meta.log
2017-10-11 14:06:03.728 - clientId:1001 cursor:[mysql-bin.000004,396,1507701897000] address[/127.0.0.1:3306]
2017-10-11 14:06:04.589 - clientId:1001 cursor:[mysql-bin.000004,491,1507701904000] address[localhost/127.0.0.1:3306]
2017-10-11 14:06:29.589 - clientId:1001 cursor:[mysql-bin.000004,822,1507701989000] address[localhost/127.0.0.1:3306]
2017-10-11 14:49:08.589 - clientId:1001 cursor:[mysql-bin.000004,1076,1507704547000] address[localhost/127.0.0.1:3306]
Cannal Internal Overview
canal client & server
canal client与canal server之间是C/S模式的通信，客户端采用NIO，服务端采用Netty。
canal server启动后，如果没有canal client，那么canal server不会去mysql拉取binlog。
try {
connector.connect();
connector.subscribe();
while (running) {
Message message = connector.getWithoutAck(batchSize); // 获取指定数量的数据
long batchId = message.getId();
int size = message.getEntries().size();
printSummary(message, batchId, size);
printEntry(message.getEntries());
connector.ack(batchId); // 提交确认
connector.rollback(batchId); // 处理失败, 回滚数据
}
} finally {
connector.disconnect();
}
canal client与canal server之间属于增量订阅/消费，流程图如下：（其中C端是canal client，S端是canal server）
canal client调用connect()方法时，类型为PacketType.HANDSHAKE，接着写入CLIENTAUTHENTICATION。然后调用subscribe()方法，类型为SUBSCRIPTION。
对应服务端采用netty处理RPC请求（CanalServerWithNetty）:
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
public ChannelPipeline getPipeline() throws Exception {
ChannelPipeline pipelines = Channels.pipeline();
pipelines.addLast(FixedHeaderFrameDecoder.class.getName(), new FixedHeaderFrameDecoder());
// 处理客户端的HANDSHAKE请求
pipelines.addLast(HandshakeInitializationHandler.class.getName(),
new HandshakeInitializationHandler(childGroups));
// 处理客户端的CLIENTAUTHENTICATION请求
pipelines.addLast(ClientAuthenticationHandler.class.getName(),
new ClientAuthenticationHandler(embeddedServer));
// 处理客户端的会话请求，包括SUBSCRIPTION，GET等
SessionHandler sessionHandler = new SessionHandler(embeddedServer);
pipelines.addLast(SessionHandler.class.getName(), sessionHandler);
return pipelines;
}
});
ClientAuthenticationHandler处理鉴权后，会移除HandshakeInitializationHandler和ClientAuthenticationHandler
以client发送GET，server从mysql得到binlog后，返回MESSAGES给client为例，说明client和server的rpc交互过程：
SimpleCanalConnector发送GET请求，并读取响应结果的流程：
public Message getWithoutAck(int batchSize, Long timeout, TimeUnit unit) throws CanalClientException {
waitClientRunning();
int size = (batchSize <= 0) ? 1000 : batchSize;
long time = (timeout == null || timeout < 0) ? -1 : timeout; // -1代表不做timeout控制
if (unit == null) unit = TimeUnit.MILLISECONDS;
// client发送GET请求
writeWithHeader(Packet.newBuilder()
.setType(PacketType.GET)
.setBody(Get.newBuilder()
.setAutoAck(false)
.setDestination(clientIdentity.getDestination())
.setClientId(String.valueOf(clientIdentity.getClientId()))
.setFetchSize(size)
.setTimeout(time)
.setUnit(unit.ordinal())
.build()
.toByteString())
.build()
.toByteArray());
// client获取GET结果
return receiveMessages();
}
private Message receiveMessages() throws IOException {
// 读取server发送的数据包
Packet p = Packet.parseFrom(readNextPacket());
switch (p.getType()) {
case MESSAGES: {
Messages messages = Messages.parseFrom(p.getBody());
Message result = new Message(messages.getBatchId());
for (ByteString byteString : messages.getMessagesList()) {
result.addEntry(Entry.parseFrom(byteString));
}
return result;
}
}
}
服务端SessionHandler处理客户端发送的GET请求流程：
case GET:
// 读取客户端发送的数据包，封装为Get对象
Get get = CanalPacket.Get.parseFrom(packet.getBody());
// destination表示canal instance
if (StringUtils.isNotEmpty(get.getDestination()) && StringUtils.isNotEmpty(get.getClientId())) {
clientIdentity = new ClientIdentity(get.getDestination(), Short.valueOf(get.getClientId()));
Message message = null;
if (get.getTimeout() == -1) {// 是否是初始值
message = embeddedServer.getWithoutAck(clientIdentity, get.getFetchSize());
} else {
TimeUnit unit = convertTimeUnit(get.getUnit());
message = embeddedServer.getWithoutAck(clientIdentity, get.getFetchSize(), get.getTimeout(), unit);
}
// 设置返回给客户端的数据包类型为MESSAGES
Packet.Builder packetBuilder = CanalPacket.Packet.newBuilder();
packetBuilder.setType(PacketType.MESSAGES);
// 构造Message
Messages.Builder messageBuilder = CanalPacket.Messages.newBuilder();
messageBuilder.setBatchId(message.getId());
if (message.getId() != -1 && !CollectionUtils.isEmpty(message.getEntries())) {
for (Entry entry : message.getEntries()) {
messageBuilder.addMessages(entry.toByteString());
}
}
packetBuilder.setBody(messageBuilder.build().toByteString());
// 输出数据，返回给客户端
NettyUtils.write(ctx.getChannel(), packetBuilder.build().toByteArray(), null);
}
get/ack/rollback协议介绍：
- Message getWithoutAck(int batchSize)，允许指定batchSize，一次可以获取多条，每次返回的对象为Message，包含的内容为：
– batch id 唯一标识
– entries 具体的数据对象，对应的数据对象格式：EntryProtocol.proto - void rollback(long batchId)，顾命思议，回滚上次的get请求，重新获取数据。基于get获取的batchId进行提交，避免误操作
- void ack(long batchId)，顾命思议，确认已经消费成功，通知server删除数据。基于get获取的batchId进行提交，避免误操作
EntryProtocol.protod对应的canal消息结构如下：
Entry
Header
logfileName [binlog文件名]
logfileOffset [binlog position]
executeTime [binlog里记录变更发生的时间戳,精确到秒]
schemaName
tableName
eventType [insert/update/delete类型]
entryType [事务头BEGIN/事务尾END/数据ROWDATA]
storeValue [byte数据,可展开，对应的类型为RowChange]
RowChange
isDdl [是否是ddl变更操作，比如create table/drop table]
sql [具体的ddl sql]
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 [Column类型的数组，变更前的数据字段]
afterColumns [Column类型的数组，变更后的数据字段]
Column
index
sqlType [jdbc type]
name [column name]
isKey [是否为主键]
updated [是否发生过变更]
isNull [值是否为null]
value [具体的内容，注意为string文本]
SessionHandler中服务端处理客户端的其他类型请求，都会调用CanalServerWithEmbedded的相关方法：
case SUBSCRIPTION:
Sub sub = Sub.parseFrom(packet.getBody());
embeddedServer.subscribe(clientIdentity);
case GET:
Get get = CanalPacket.Get.parseFrom(packet.getBody());
message = embeddedServer.getWithoutAck(clientIdentity, get.getFetchSize());
case CLIENTACK:
ClientAck ack = CanalPacket.ClientAck.parseFrom(packet.getBody());
embeddedServer.ack(clientIdentity, ack.getBatchId());
case CLIENTROLLBACK:
ClientRollback rollback = CanalPacket.ClientRollback.parseFrom(packet.getBody());
embeddedServer.rollback(clientIdentity);// 回滚所有批次
CanalServerWithEmbedded
CanalServer包含多个Instance，它的成员变量canalInstances记录了instance名称与实例的映射关系。
因为是一个Map，所以同一个Server不允许出现相同instance名称，比如不能同时有两个example在一个server上。
public class CanalServerWithEmbedded extends AbstractCanalLifeCycle implements CanalServer, CanalService {
private Map<String, CanalInstance> canalInstances;
private CanalInstanceGenerator canalInstanceGenerator;
}
下图表示一个server有两个instance，每个Client连接一个Instance。
每个Canal实例模拟为一个MySQL的slave，所以每个Instance的slaveId必须不一样。比如图中两个Instance的id分别是1234和1235。
注意这里每个Canal Client都对应一个Instance，每个Client在启动时，都会指定一个Destination，这个Destination就表示Instance的名称。
所以CanalServerWithEmbedded处理各种请求时的参数都有ClientIdentity，从ClientIdentity中获取destination，就可以获取出对应的CanalInstance
下面以CanalServerWithEmbedded的订阅方法为例：
public void subscribe(ClientIdentity clientIdentity) throws CanalServerException {
// ClientIdentity表示Canal Client客户端，从中可以获取出客户端指定连接的Destination
// 由于CanalServerWithEmbedded记录了每个Destination对应的Instance，可以获取客户端对应的Instance
CanalInstance canalInstance = canalInstances.get(clientIdentity.getDestination());
if (!canalInstance.getMetaManager().isStart()) {
canalInstance.getMetaManager().start(); // 启动Instance的元数据管理器
}
canalInstance.getMetaManager().subscribe(clientIdentity); // 执行一下meta订阅
Position position = canalInstance.getMetaManager().getCursor(clientIdentity);
if (position == null) {
position = canalInstance.getEventStore().getFirstPosition();// 获取一下store中的第一条
if (position != null) {
canalInstance.getMetaManager().updateCursor(clientIdentity, position); // 更新一下cursor
}
}
// 通知下订阅关系变化
canalInstance.subscribeChange(clientIdentity);
}
每个CanalInstance中包括了四个组件：EventParser、EventSink、EventStore、MetaManager。
服务端主要的处理方法包括get/ack/rollback，这三个方法都会用到Instance上面的几个内部组件，主要还是EventStore和MetaManager：
在这之前，要先理解EventStore的含义，EventStore是一个RingBuffer，有三个指针：Put、Get、Ack。
- Put: Canal Server从MySQL拉取到数据后，放到内存中，Put增加
- Get: 消费者（Canal Client）从内存中消费数据，Get增加
- Ack: 消费者消费完成，Ack增加。并且会删除Put中已经被Ack的数据
这三个操作与Instance组件的关系如下：
客户端通过canal server获取mysql binlog有几种方式（get方法和getWithoutAck）：
- 如果timeout为null，则采用tryGet方式，即时获取
- 如果timeout不为null
- timeout为0，则采用get阻塞方式，获取数据，不设置超时，直到有足够的batchSize数据才返回
- timeout不为0，则采用get+timeout方式，获取数据，超时还没有batchSize足够的数据，有多少返回多少
private Events<Event> getEvents(CanalEventStore eventStore, Position start, int batchSize, Long timeout,
TimeUnit unit) {
if (timeout == null) {
return eventStore.tryGet(start, batchSize); // 即时获取
} else if (timeout <= 0){
return eventStore.get(start, batchSize); // 阻塞获取
} else {
return eventStore.get(start, batchSize, timeout, unit); // 异步获取
}
}
注意：EventStore的实现采用了类似Disruptor的RingBuffer环形缓冲区。RingBuffer的实现类是MemoryEventStoreWithBuffer
get方法和getWithoutAck方法的区别是：
- get方法会立即调用ack
- getWithoutAck方法不会调用ack
EventStore
以10条数据为例，初始时current=-1，第一个元素起始next=0，end=9，循环[0,9]所有元素。
List元素为(A,B,C,D,E,F,G,H,I,J)
| next | entries[next] | next-current-1 | list element |
|---|---|---|---|
| 0 | entries[0] | 0-(-1)-1=0 | A |
| 1 | entries[1] | 1-(-1)-1=1 | B |
| 2 | entries[2] | 2-(-1)-1=2 | C |
| 3 | entries[3] | 3-(-1)-1=3 | D |
| . | ………. | ………. | . |
| 9 | entries[9] | 9-(-1)-1=9 | J |
第一批10个元素put完成后，putSequence设置为end=9。假设第二批又Put了5个元素:(K,L,M,N,O)
current=9，起始next=9+1=10，end=9+5=14，在Put完成后，putSequence设置为end=14。
| next | entries[next] | next-current-1 | list element |
|---|---|---|---|
| 10 | entries[10] | 10-(9)-1=0 | K |
| 11 | entries[11] | 11-(9)-1=1 | L |
| 12 | entries[12] | 12-(9)-1=2 | M |
| 13 | entries[13] | 13-(9)-1=3 | N |
| 14 | entries[14] | 14-(9)-1=3 | O |
这里假设环形缓冲区的最大大小为15个（源码中是16MB），那么上面两批一共产生了15个元素，刚好填满了环形缓冲区。
如果又有Put事件进来，由于环形缓冲区已经满了，没有可用的slot，则Put操作会被阻塞，直到被消费掉。
下面是Put填充环形缓冲区的代码，检查可用slot（checkFreeSlotAt方法）在几个put方法中。
public class MemoryEventStoreWithBuffer extends AbstractCanalStoreScavenge implements CanalEventStore<Event>, CanalStoreScavenge {
private static final long INIT_SQEUENCE = -1;
private int bufferSize = 16 * 1024;
private int bufferMemUnit = 1024; // memsize的单位，默认为1kb大小
private int indexMask;
private Event[] entries;
// 记录下put/get/ack操作的三个下标
private AtomicLong putSequence = new AtomicLong(INIT_SQEUENCE); // 代表当前put操作最后一次写操作发生的位置
private AtomicLong getSequence = new AtomicLong(INIT_SQEUENCE); // 代表当前get操作读取的最后一条的位置
private AtomicLong ackSequence = new AtomicLong(INIT_SQEUENCE); // 代表当前ack操作的最后一条的位置
// 启动EventStore时，创建指定大小的缓冲区，Event数组的大小是16*1024
// 也就是说算个数的话，数组可以容纳16000个事件。算内存的话，大小为16MB
public void start() throws CanalStoreException {
super.start();
indexMask = bufferSize - 1;
entries = new Event[bufferSize];
}
// EventParser解析后，会放入内存中（Event数组，缓冲区）
private void doPut(List<Event> data) {
long current = putSequence.get(); // 取得当前的位置，初始时为-1，第一个元素为-1+1=0
long end = current + data.size(); // 最末尾的位置，假设Put了10条数据，end=-1+10=9
// 先写数据，再更新对应的cursor,并发度高的情况，putSequence会被get请求可见，拿出了ringbuffer中的老的Entry值
for (long next = current + 1; next <= end; next++) {
entries[getIndex(next)] = data.get((int) (next - current - 1));
}
putSequence.set(end);
}
}
Put是生产数据，Get是消费数据，Get一定不会超过Put。比如Put了10条数据，Get最多只能获取到10条数据。但有时候为了保证Get处理的速度，Put和Get并不会相等。
可以把Put看做是生产者，Get看做是消费者。生产者速度可以很快，消费者则可以慢慢地消费。比如Put了1000条，而Get我们只需要每次处理10条数据。
仍然以前面的示例来说明Get的流程，初始时current=-1，假设Put了两批数据一共15条，maxAbleSequence=14，而Get的BatchSize假设为10。
初始时next=current=-1，end=-1。通过startPosition，会设置next=0。最后end又被赋值为9，即循环缓冲区[0,9]一共10个元素。
private Events<Event> doGet(Position start, int batchSize) throws CanalStoreException {
LogPosition startPosition = (LogPosition) start;
long current = getSequence.get();
long maxAbleSequence = putSequence.get();
long next = current;
long end = current;
// 如果startPosition为null，说明是第一次，默认+1处理
if (startPosition == null || !startPosition.getPostion().isIncluded()) { // 第一次订阅之后，需要包含一下start位置，防止丢失第一条记录
next = next + 1;
}
end = (next + batchSize - 1) < maxAbleSequence ? (next + batchSize - 1) : maxAbleSequence;
// 提取数据并返回
for (; next <= end; next++) {
Event event = entries[getIndex(next)];
if (ddlIsolation && isDdl(event.getEntry().getHeader().getEventType())) {
// 如果是ddl隔离，直接返回
if (entrys.size() == 0) {
entrys.add(event);// 如果没有DML事件，加入当前的DDL事件
end = next; // 更新end为当前
} else {
// 如果之前已经有DML事件，直接返回了，因为不包含当前next这记录，需要回退一个位置
end = next - 1; // next-1一定大于current，不需要判断
}
break;
} else {
entrys.add(event);
}
}
// 处理PositionRange，然后设置getSequence为end
getSequence.compareAndSet(current, end)
}
ack操作的上限是Get，假设Put了15条数据，Get了10条数据，最多也只能Ack10条数据。Ack的目的是清空缓冲区中已经被Get过的数据
public void ack(Position position) throws CanalStoreException {
cleanUntil(position);
}
public void cleanUntil(Position position) throws CanalStoreException {
long sequence = ackSequence.get();
long maxSequence = getSequence.get();
boolean hasMatch = false;
long memsize = 0;
for (long next = sequence + 1; next <= maxSequence; next++) {
Event event = entries[getIndex(next)];
memsize += calculateSize(event);
boolean match = CanalEventUtils.checkPosition(event, (LogPosition) position);
if (match) {// 找到对应的position，更新ack seq
hasMatch = true;
if (batchMode.isMemSize()) {
ackMemSize.addAndGet(memsize);
// 尝试清空buffer中的内存，将ack之前的内存全部释放掉
for (long index = sequence + 1; index < next; index++) {
entries[getIndex(index)] = null;// 设置为null
}
}
ackSequence.compareAndSet(sequence, next)
}
}
}
rollback回滚方法的实现则比较简单，将getSequence回退到ack位置。
public void rollback() throws CanalStoreException {
getSequence.set(ackSequence.get());
getMemSize.set(ackMemSize.get());
}
下图展示了RingBuffer的几个操作示例：
EventParser WorkFlow
EventStore负责存储解析后的Binlog事件，而解析动作负责拉取Binlog，它的流程比较复杂。需要和MetaManager进行交互。
比如要记录每次拉取的Position，这样下一次就可以从上一次的最后一个位置继续拉取。所以MetaManager应该是有状态的。
EventParser的流程如下：
- Connection获取上一次解析成功的位置 (如果第一次启动，则获取初始指定的位置或者是当前数据库的binlog位点)
- Connection建立链接，发送BINLOG_DUMP指令
- Mysql开始推送Binaly Log
- 接收到的Binaly Log的通过Binlog parser进行协议解析，补充一些特定信息
- 传递给EventSink模块进行数据存储，是一个阻塞操作，直到存储成功
- 存储成功后，定时记录Binaly Log位置
上面提到的Connection指的是实现了ErosaConnection接口的MysqlConnection。EventParser的实现类是实现了AbstractEventParser的MysqlEventParser。
EventParser解析binlog后通过EventSink写入到EventStore，这条链路可以通过EventStore的put方法串联起来：
其实这里还有一个EventTransactionBuffer缓冲区，即Parser解析后先放到缓冲区中，
当事务发生时或者数据超过阈值，就会执行刷新操作：即消费缓冲区的数据，放到EventStore中。
这个缓冲区有两个偏移量指针：putSequence和flushSequence。
Canal HA
单机模拟两个Canal Server，将单机模式复制出两个文件夹，并修改相关配置
canal_m/conf/canal.properties
canal.id= 2
canal.ip=
canal.port= 11112
canal.zkServers=localhost:2181
canal.instance.global.spring.xml = classpath:spring/default-instance.xml
canal_m/conf/example/instance.properties
canal.instance.mysql.slaveId = 1235
canal_s
canal.id= 3
canal.ip=
canal.port= 11113
canal.zkServers=localhost:2181
canal.instance.global.spring.xml = classpath:spring/default-instance.xml
canal_s/conf/example/instance.properties
canal.instance.mysql.slaveId = 1236
启动canal_m
2017-10-12 14:51:45.202 [main] INFO com.alibaba.otter.canal.deployer.CanalLauncher - ## start the canal server.
2017-10-12 14:51:45.776 [main] INFO com.alibaba.otter.canal.deployer.CanalController - ## start the canal server[192.168.6.52:11112]
2017-10-12 14:51:46.687 [main] INFO com.alibaba.otter.canal.deployer.CanalLauncher - ## the canal server is running now ......
启动canal_s
2017-10-12 14:52:18.999 [main] INFO com.alibaba.otter.canal.deployer.CanalLauncher - ## start the canal server.
2017-10-12 14:52:19.208 [main] INFO com.alibaba.otter.canal.deployer.CanalController - ## start the canal server[192.168.6.52:11113]
2017-10-12 14:52:19.364 [main] INFO com.alibaba.otter.canal.deployer.CanalLauncher - ## the canal server is running now ......
master提供服务，canal_m/logs/example/example.log下有日志，而canal_s/logs没有example文件夹
[aaa@qq.com ~]$ tail -f canal_m/logs/example/example.log
2017-10-12 14:51:46.453 [main] INFO c.a.o.c.i.spring.support.PropertyPlaceholderConfigurer - Loading properties file from class path resource [canal.properties]
2017-10-12 14:51:46.463 [main] INFO c.a.o.c.i.spring.support.PropertyPlaceholderConfigurer - Loading properties file from class path resource [example/instance.properties]
2017-10-12 14:51:46.624 [main] INFO c.a.otter.canal.instance.spring.CanalInstanceWithSpring - start CannalInstance for 1-example
2017-10-12 14:51:46.644 [main] INFO c.a.otter.canal.instance.core.AbstractCanalInstance - start successful....
2017-10-12 14:51:46.658 [destination = example , address = /127.0.0.1:3306 , EventParser] WARN c.a.otter.canal.parse.inbound.mysql.MysqlEventParser - prepare to find start position just show master status
查看Canal HA记录在ZK的信息
[zk: 192.168.6.52:2181(CONNECTED) 7] ls /otter/canal/destinations/example/cluster
[192.168.6.52:11112, 192.168.6.52:11113]
[zk: 192.168.6.52:2181(CONNECTED) 10] get /otter/canal/destinations/example/running
{"active":true,"address":"192.168.6.52:11112","cid":2}
启动example的ClusterCanalClientTest
CanalConnector connector = CanalConnectors.newClusterConnector("192.168.6.52:2181", destination, "canal", "canal");
执行SQL：update test set name = 'zqh' where uid=1;，控制台打印日志如下：
****************************************************
* Batch Id: [1] ,count : [3] , memsize : [203] , Time : 2017-10-12 15:05:20
* Start : [mysql-bin.000004:1151:1507791918000(2017-10-12 15:05:18)]
* End : [mysql-bin.000004:1331:1507791918000(2017-10-12 15:05:18)]
****************************************************
================> binlog[mysql-bin.000004:1151] , executeTime : 1507791918000 , delay : 2080ms
BEGIN ----> Thread id: 763
----------------> binlog[mysql-bin.000004:1277] , name[canal_test,test] , eventType : UPDATE , executeTime : 1507791918000 , delay : 2092ms
uid : 1 type=int(4)
name : zqh type=varchar(10) update=true
----------------
END ----> transaction id: 0
================> binlog[mysql-bin.000004:1331] , executeTime : 1507791918000 , delay : 2130ms
再次查看ZK中记录的客户端信息：
- 一个Instance对应一个Client，这里的Instance名称为example，对应的客户端编号是1001
- 为了验证Instance确实是由指定的Client连接，在Server上查看11112端口
[zk: 192.168.6.52:2181(CONNECTED) 18] get /otter/canal/destinations/example/1001/running
{"active":true,"address":"10.57.241.44:53942","clientId":1001}
[zk: 192.168.6.52:2181(CONNECTED) 19] get /otter/canal/destinations/example/1001/cursor
{"@type":"com.alibaba.otter.canal.protocol.position.LogPosition",
"identity":{"slaveId":-1,"sourceAddress":{"address":"localhost","port":3306}},
"postion":{"included":false,"journalName":"mysql-bin.000004","position":1331,"serverId":1,"timestamp":1507791918000}} ==》serverId表示MySQL的server_id
[aaa@qq.com ~]$ netstat -anpt|grep 11112
tcp 0 0 0.0.0.0:11112 0.0.0.0:* LISTEN 27816/java ==》Canal服务端
tcp 0 19 192.168.6.52:11112 10.57.241.44:53942 ESTABLISHED 27816/java ==》Canal客户端
停止canal_m
[aaa@qq.com canal_m]$ bin/stop.sh
dp0652: stopping canal 27816 ...
Oook! cost:1
Instance会在slave节点即canal_s上启动
[aaa@qq.com ~]$ tail -f canal_s/logs/example/example.log
2017-10-12 15:17:21.452 [New I/O server worker #1-1] ERROR com.alibaba.otter.canal.server.netty.NettyUtils - ErrotCode:400 , Caused by :
something goes wrong with channel:[id: 0x0c182149, /10.57.241.44:54008 => /192.168.6.52:11113], exception=com.alibaba.otter.canal.server.exception.CanalServerException: destination:example should start first
2017-10-12 15:17:21.661 [pool-1-thread-1] INFO c.a.o.c.i.spring.support.PropertyPlaceholderConfigurer - Loading properties file from class path resource [canal.properties]
2017-10-12 15:17:21.663 [pool-1-thread-1] INFO c.a.o.c.i.spring.support.PropertyPlaceholderConfigurer - Loading properties file from class path resource [example/instance.properties]
2017-10-12 15:17:21.767 [pool-1-thread-1] WARN org.springframework.beans.TypeConverterDelegate - PropertyEditor [com.sun.beans.editors.EnumEditor] found through deprecated global PropertyEditorManager fallback - consider using a more isolated form of registration, e.g. on the BeanWrapper/BeanFactory!
2017-10-12 15:17:21.968 [pool-1-thread-1] INFO c.a.otter.canal.instance.spring.CanalInstanceWithSpring - start CannalInstance for 1-example
2017-10-12 15:17:21.998 [pool-1-thread-1] INFO c.a.otter.canal.instance.core.AbstractCanalInstance - start successful....
2017-10-12 15:17:22.071 [destination = example , address = /127.0.0.1:3306 , EventParser] WARN c.a.otter.canal.parse.inbound.mysql.MysqlEventParser - prepare to find start position just last position
{"identity":{"slaveId":-1,"sourceAddress":{"address":"localhost","port":3306}},"postion":{"included":false,"journalName":"mysql-bin.000004","position":1331,"serverId":1,"timestamp":1507791918000}}
停止canal_m后，只剩下canal_s，所以Canal集群只有一个节点了：
[zk: 192.168.6.52:2181(CONNECTED) 14] ls /otter/canal/cluster
[192.168.6.52:11113]
[zk: 192.168.6.52:2181(CONNECTED) 5] get /otter/canal/destinations/example/running
{"active":true,"address":"192.168.6.52:11113","cid":3}
切换过程中，Client的日志
2017-10-12 15:17:22.524 [Thread-2] WARN c.alibaba.otter.canal.client.impl.ClusterCanalConnector - failed to connect to:/192.168.6.52:11113 after retry 0 times
2017-10-12 15:17:22.529 [Thread-2] WARN c.a.otter.canal.client.impl.running.ClientRunningMonitor - canal is not run any in node
2017-10-12 15:17:27.695 [Thread-2] INFO c.alibaba.otter.canal.client.impl.ClusterCanalConnector - restart the connector for next round retry.
****************************************************
* Batch Id: [1] ,count : [1] , memsize : [75] , Time : 2017-10-12 15:17:27
* Start : [mysql-bin.000004:1331:1507791918000(2017-10-12 15:05:18)]
* End : [mysql-bin.000004:1331:1507791918000(2017-10-12 15:05:18)]
****************************************************
----------------
END ----> transaction id: 0
================> binlog[mysql-bin.000004:1331] , executeTime : 1507791918000 , delay : 729763ms
再次执行SQL语句
****************************************************
* Batch Id: [2] ,count : [3] , memsize : [198] , Time : 2017-10-12 15:20:56
* Start : [mysql-bin.000004:1406:1507792855000(2017-10-12 15:20:55)]
* End : [mysql-bin.000004:1581:1507792855000(2017-10-12 15:20:55)]
****************************************************
================> binlog[mysql-bin.000004:1406] , executeTime : 1507792855000 , delay : 1539ms
BEGIN ----> Thread id: 763
----------------> binlog[mysql-bin.000004:1532] , name[canal_test,test] , eventType : UPDATE , executeTime : 1507792855000 , delay : 1539ms
uid : 1 type=int(4)
name : zqhx type=varchar(10) update=true
----------------
END ----> transaction id: 0
================> binlog[mysql-bin.000004:1581] , executeTime : 1507792855000 , delay : 1540ms
停止客户端后，查询ZK中的客户端信息。注意，仍然有cursor信息，但是没有running，因为instance没有对应的client了。
[zk: 192.168.6.52:2181(CONNECTED) 1] ls /otter/canal/destinations/example
[running, cluster, 1001]
[zk: 192.168.6.52:2181(CONNECTED) 0] ls /otter/canal/destinations/example/1001
[cursor]
[zk: 192.168.6.52:2181(CONNECTED) 6] get /otter/canal/destinations/example/1001/cursor
{"@type":"com.alibaba.otter.canal.protocol.position.LogPosition",
"identity":{"slaveId":-1,"sourceAddress":{"address":"localhost","port":3306}},
"postion":{"included":false,"journalName":"mysql-bin.000004","position":1581,"serverId":1,"timestamp":1507792855000}}
cursor信息是instance消费binlog的位置，即使客户端停掉了，也仍然保留在zk中。
注意：1001是ClientIdentity的固定编号，相关源码在SimpleCanalConnector的构造方法里。
下面总结下zk中的相关记录：
/otter/canal/
|- cluster ==> [192.168.6.52:11112, 192.168.6.52:11113]
|- destinations ==> instances
|- example1/ ==> instance name
| |- cluster ==> [192.168.6.52:11112, 192.168.6.52:11113]
| |- running ==> {"active":true,"address":"192.168.6.52:11112","cid":2}
| |- 1001
| |-running ==> {"active":true,"address":"10.57.241.44:53942","clientId":1001}
| |- cursor ==> {localhost:3306,"journalName":"mysql-bin.000004","position":1331,"serverId":1}
|- example2/
| |- cluster ==> [192.168.6.52:11112, 192.168.6.52:11113]
| |- running ==> {"active":true,"address":"192.168.6.52:11112","cid":2}
| |- 1001
| |-running ==> {"active":true,"address":"10.57.241.44:53942","clientId":1001}
| |- cursor ==> {localhost:3306,"journalName":"mysql-bin.000004","position":1331,"serverId":1}
下图是Canal Server HA的流程图：
- canal server要启动某个canal instance时都先向zookeeper进行一次尝试启动判断 (实现：创建EPHEMERAL节点，谁创建成功就允许谁启动)
- 创建zookeeper节点成功后，对应的canal server就启动对应的canal instance，没有创建成功的canal instance就会处于standby状态
- 一旦zookeeper发现canal server A创建的节点消失后，立即通知其他的canal server再次进行步骤1的操作，重新选出一个canal server启动instance.
- canal client每次进行connect时，会首先向zookeeper询问当前是谁启动了canal instance，然后和其建立链接，一旦链接不可用，会重新尝试connect.
Canal Client HA
Canal Client的方式和canal server方式类似，也是利用zookeeper的抢占EPHEMERAL节点的方式进行控制。
关于Canal Client HA的验证，可以参考：blog.csdn.net/xiaolinzi00…
- 在IDEA中同时启动多个客户端，执行一条SQL语句，其中一个客户端会打印日志，另一个不会打印。
- 停止该客户端。
- 再次执行SQL语句，另外一个客户端会打印日志
Client1的日志：
****************************************************
* Batch Id: [3] ,count : [3] , memsize : [198] , Time : 2017-10-12 17:59:59
* Start : [mysql-bin.000004:1656:1507802398000(2017-10-12 17:59:58)]
* End : [mysql-bin.000004:1831:1507802398000(2017-10-12 17:59:58)]
****************************************************
================> binlog[mysql-bin.000004:1656] , executeTime : 1507802398000 , delay : 1188ms
BEGIN ----> Thread id: 768
----------------> binlog[mysql-bin.000004:1782] , name[canal_test,test] , eventType : UPDATE , executeTime : 1507802398000 , delay : 1199ms
uid : 1 type=int(4)
name : zqh type=varchar(10) update=true
----------------
END ----> transaction id: 0
================> binlog[mysql-bin.000004:1831] , executeTime : 1507802398000 , delay : 1236ms
## stop the canal client## canal client is down.
停止Client1后，Client2的日志：
****************************************************
* Batch Id: [4] ,count : [3] , memsize : [198] , Time : 2017-10-12 18:02:15
* Start : [mysql-bin.000004:1906:1507802534000(2017-10-12 18:02:14)]
* End : [mysql-bin.000004:2081:1507802534000(2017-10-12 18:02:14)]
****************************************************
================> binlog[mysql-bin.000004:1906] , executeTime : 1507802534000 , delay : 1807ms
BEGIN ----> Thread id: 768
----------------> binlog[mysql-bin.000004:2032] , name[canal_test,test] , eventType : UPDATE , executeTime : 1507802534000 , delay : 1819ms
uid : 1 type=int(4)
name : zqhx type=varchar(10) update=true
----------------
END ----> transaction id: 0
================> binlog[mysql-bin.000004:2081] , executeTime : 1507802534000 , delay : 1855ms
观察ZK节点中instance对应的client节点，在Client切换时，会进行变更。
比如下面的客户端从56806端口切换到了56842端口。
把所有客户端都关闭后，1001下没有running。表示instance没有客户端消费binlog了。
[zk: 192.168.6.52:2181(CONNECTED) 29] get /otter/canal/destinations/example/1001/running
{"active":true,"address":"10.57.241.44:56806","clientId":1001}
[zk: 192.168.6.52:2181(CONNECTED) 30] get /otter/canal/destinations/example/1001/running
Node does not exist: /otter/canal/destinations/example/1001/running
[zk: 192.168.6.52:2181(CONNECTED) 31] get /otter/canal/destinations/example/1001/running
{"active":true,"address":"10.57.241.44:56842","clientId":1001}
[zk: 192.168.6.52:2181(CONNECTED) 32] ls /otter/canal/destinations/example/1001
[cursor]
具体实现相关类有：ClientRunningMonitor/ClientRunningListener/ClientRunningData。
client running相关控制，主要为解决client自身的failover机制。
canal client允许同时启动多个canal client，通过running机制，可保证只有一个client在工作，其他client做为冷备.
当运行中的client挂了，running会控制让冷备中的client转为工作模式，
这样就可以确保canal client也不会是单点. 保证整个系统的高可用性.
下图左边是客户端的HA实现，右边是服务端的HA实现
Develop Canal Client
subscribe change
重新看下CanalServerWithEmbedded的订阅方法。我们知道客户端在连接服务端的某个destination之后，会紧接着调用subscribe()方法。
客户端连接服务端时，必须指定destination名称，因为一个服务端可能有多个destination。比如服务端启动了两个Instance，它们的destination名称分别是example1和example2。
假设有两个客户端A和B，A连接example1，B连接example2。 服务端的canalInstances字典为：{example1=>Instance1，example2->Instance2}。
那么ClientA的destination等于example1，对应的服务端实例为Instance1。ClientB的destination等于example2，对应的服务端实例为Instance3。
/**
* 客户端订阅，重复订阅时会更新对应的filter信息
*/
public void subscribe(ClientIdentity clientIdentity) throws CanalServerException {
CanalInstance canalInstance = canalInstances.get(clientIdentity.getDestination());
if (!canalInstance.getMetaManager().isStart()) {
canalInstance.getMetaManager().start();
}
canalInstance.getMetaManager().subscribe(clientIdentity); // 执行一下meta订阅
// 根据Client从MetaManager中获取最近一次的Cursor
Position position = canalInstance.getMetaManager().getCursor(clientIdentity);
if (position == null) { // 如果没有
position = canalInstance.getEventStore().getFirstPosition();// 获取一下store中的第一条
if (position != null) {
canalInstance.getMetaManager().updateCursor(clientIdentity, position); // 更新一下cursor
}
logger.info("subscribe successfully, {} with first position:{} ", clientIdentity, position);
} else { // 有就直接使用
logger.info("subscribe successfully, use last cursor position:{} ", clientIdentity, position);
}
// 通知下订阅关系变化
canalInstance.subscribeChange(clientIdentity);
}
这里面关于订阅方法有两个地方，CanalInstance本身调用了subscribeChange，它关联的MetaManager也调用了subscribe方法。
一个CanalServer可以有多个CanalInstance，每个Instance都会有一个MetaManager。而一个Instance对应一个Client。
那么，这么说来，一个MetaManager也就只会有一个Client了。但是从下面的数据结构来看的话，一个MetaManager貌似可以有多个Destination。
public class MemoryMetaManager extends AbstractCanalLifeCycle implements CanalMetaManager {
protected Map<String, List<ClientIdentity>> destinations;
protected Map<ClientIdentity, MemoryClientIdentityBatch> batches;
protected Map<ClientIdentity, Position> cursors;
public synchronized void subscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException {
List<ClientIdentity> clientIdentitys = destinations.get(clientIdentity.getDestination());
if (clientIdentitys.contains(clientIdentity)) {
clientIdentitys.remove(clientIdentity);
}
clientIdentitys.add(clientIdentity);
}
}
猜测：多个Client可以连接到同一个Instance（虽然只会有一个Instance起作用），所以一个MetaManager可以管理多个Client。
NO！Client的HA与MetaManager记录的Client是不一样的。HA表示同一时间只有一个Client起作用，那么MetaManager不可能同时记录两个Client。
官方ClientAPI文档上：ClientIdentity是canal client和server交互之间的身份标识，目前clientId写死为1001.
(目前canal server上的一个instance只能有一个client消费，clientId的设计是为1个instance多client消费模式而预留的，暂时不需要理会)
也就是说：一个Instance还是有可能有多个Client连接上来的。
这里的数据结构为什么这么设计，还需要参考AbstractMetaManagerTest的doSubscribeTest方法来理解。
对于相同的destination，可以订阅不同的client。下面的示例分别订阅了[client1,client2]和[client1,client3]。
public void doSubscribeTest(CanalMetaManager metaManager) {
ClientIdentity client1 = new ClientIdentity(destination, (short) 1);
metaManager.subscribe(client1);
metaManager.subscribe(client1); // 重复调用：删除旧的client1，并继续增加新的client1
ClientIdentity client2 = new ClientIdentity(destination, (short) 2);
metaManager.subscribe(client2);
List<ClientIdentity> clients = metaManager.listAllSubscribeInfo(destination);
Assert.assertEquals(Arrays.asList(client1, client2), clients);
metaManager.unsubscribe(client2);
ClientIdentity client3 = new ClientIdentity(destination, (short) 3);
metaManager.subscribe(client3);
clients = metaManager.listAllSubscribeInfo(destination);
Assert.assertEquals(Arrays.asList(client1, client3), clients);
}
CanalServerWithEmbedded的订阅方法最后还会调用AbstractCanalInstance的subscribeChange方法。
这里会设置表名的filter，以及黑名单。配置项在instance.properties中。
# table regex
canal.instance.filter.regex = .*\\..*
# table black regex
canal.instance.filter.black.regex =
filter表示客户端要通过Canal Server获取MySQL哪些表的binlog，上面配置项表示获取所有表。
public class AbstractCanalInstance extends AbstractCanalLifeCycle implements CanalInstance {
protected Long canalId; // 和manager交互唯一标示
protected String destination; // 队列名字
protected CanalEventStore<Event> eventStore; // 有序队列
protected CanalEventParser eventParser; // 解析对应的数据信息
protected CanalEventSink<List<CanalEntry.Entry>> eventSink; // 链接parse和store的桥接器
protected CanalMetaManager metaManager; // 消费信息管理器
protected CanalAlarmHandler alarmHandler; // alarm报警机制
@Override
public boolean subscribeChange(ClientIdentity identity) {
if (StringUtils.isNotEmpty(identity.getFilter())) {
logger.info("subscribe filter change to " + identity.getFilter());
AviaterRegexFilter aviaterFilter = new AviaterRegexFilter(identity.getFilter());
boolean isGroup = (eventParser instanceof GroupEventParser);
if (isGroup) {
// 处理group的模式
List<CanalEventParser> eventParsers = ((GroupEventParser) eventParser).getEventParsers();
for (CanalEventParser singleEventParser : eventParsers) {// 需要遍历启动
((AbstractEventParser) singleEventParser).setEventFilter(aviaterFilter);
}
} else {
((AbstractEventParser) eventParser).setEventFilter(aviaterFilter);
}
}
// filter的处理规则
// a. parser处理数据过滤处理
// b. sink处理数据的路由&分发,一份parse数据经过sink后可以分发为多份，每份的数据可以根据自己的过滤规则不同而有不同的数据
// 后续内存版的一对多分发，可以考虑
return true;
}
}
对应在EventParser中，存在两个Filter的引用。比如上面eventParser.setEventFilter()方法会设置AbstractEventParser的eventFilter。
public abstract class AbstractEventParser<EVENT> extends AbstractCanalLifeCycle implements CanalEventParser<EVENT> {
protected CanalLogPositionManager logPositionManager = null;
protected CanalEventSink<List<CanalEntry.Entry>> eventSink = null;
protected CanalEventFilter eventFilter = null;
protected CanalEventFilter eventBlackFilter = null;
}
EventParser Implement
AbstractEventParser的start()方法是解析binlog的主要方法。在启动transactionBuffer和BinLogParser后，会启动一个后台的工作线程parseThread一直运行：
注意：下面的几个步骤是嵌套在一个while死循环里，最后会进行sleep。
// 开始执行replication
// 1. 构造Erosa连接
erosaConnection = buildErosaConnection();
// 2. 启动一个心跳线程
startHeartBeat(erosaConnection);
// 3. 执行dump前的准备工作
preDump(erosaConnection);
// 4. 连接MySQL数据库
erosaConnection.connect();
// 5. 获取最后的位置信息
EntryPosition startPosition = findStartPosition(erosaConnection);
logger.info("find start position : {}", startPosition.toString());
// 重新链接，因为在找position过程中可能有状态，需要断开后重建
erosaConnection.reconnect();
// 定义回调函数，当解析成功后，sink()方法会暂存到缓冲区transactionBuffer中。缓冲区的数据会通过心跳线程放入EventSink
final SinkFunction sinkHandler = new SinkFunction<EVENT>() {
private LogPosition lastPosition;
public void sink(EVENT event) {
CanalEntry.Entry entry = parseAndProfilingIfNecessary(event);
if (entry != null) {
transactionBuffer.add(entry);
this.lastPosition = buildLastPosition(entry); // 记录一下对应的positions
}
}
};
// 6. 开始dump数据
if (StringUtils.isEmpty(startPosition.getJournalName()) && startPosition.getTimestamp() != null) {
erosaConnection.dump(startPosition.getTimestamp(), sinkHandler);
} else {
erosaConnection.dump(startPosition.getJournalName(), startPosition.getPosition(), sinkHandler);
}
这里的erosaConnection指的是Canal Server到MySQL的连接。
而前面我们说的客户端（CanalClient）连接CanalConnector指的是CanalClient到CanalServer的连接。
CanalServer到MySQL的连接是要获取binlog的dump数据包。而CanalClient到CanalServer有多种请求（GET/ACK等）。
我们不会具体分析dump的流程，不过看下erosaConnection的MySQL实现MysqlConnection是如何在获取到事件后调用回调函数。
public void dump(String binlogfilename, Long binlogPosition, SinkFunction func) throws IOException {
updateSettings();
sendBinlogDump(binlogfilename, binlogPosition);
// connector指的是CanalServer到MySQL Master服务器的连接，创建一个拉取线程拉取MySQL的binlog
DirectLogFetcher fetcher = new DirectLogFetcher(connector.getReceiveBufferSize());
fetcher.start(connector.getChannel());
LogDecoder decoder = new LogDecoder(LogEvent.UNKNOWN_EVENT, LogEvent.ENUM_END_EVENT);
LogContext context = new LogContext();
while (fetcher.fetch()) { // 由于设置了缓冲区的大小，每次dump都只会拉取一批数据
LogEvent event = null;
event = decoder.decode(fetcher, context);
if (!func.sink(event)) break; // 调用回调方法
}
}
服务端有一个心跳线程，它的目的是消费transactionBuffer，并写入到EventSink中。
protected boolean consumeTheEventAndProfilingIfNecessary(List<CanalEntry.Entry> entrys) {
boolean result = eventSink.sink(entrys,
(runningInfo == null) ? null : runningInfo.getAddress(), destination);
return result;
}
EventSink最终会将数据写入到EventStore中，即Put到RingBuffer中。
eunomia
[zk: 192.168.6.55:2181(CONNECTED) 3] ls /otter/canal/destinations
[octopus_demeter, example_bak, namelist_test, xiaopang2, namelist2, xiaopang3, namelist1, example, xiaopang]
[zk: 192.168.6.55:2181(CONNECTED) 4] ls /otter/canal/destinations/xiaopang
[eunomia, cluster, 1001, running]
[zk: 192.168.6.55:2181(CONNECTED) 5] ls /otter/canal/destinations/xiaopang/eunomia
[_c_2a900d4e-75fb-4445-b30c-04e1bdb2e5d9-lock-0001381746, runnning, _c_ea33db37-9193-4c75-9e61-85e59e123109-lock-0001381738]
// Eunomia Server？还是Canal Client？
[zk: 192.168.6.55:2181(CONNECTED) 7] get /otter/canal/destinations/xiaopang/eunomia/runnning
10.57.17.100
[zk: 192.168.6.55:2181(CONNECTED) 18] get /otter/canal/destinations/xiaopang/1001/running
{"active":true,"address":"10.57.17.100:60661","clientId":1001}