从 MySQL 5.6.5 开始新增了一种基于 GTID 的复制方式。通过 GTID 保证了每个在主库上提交的事务在集群中有一个唯一的ID。这种方式强化了数据库的主备一致性，故障恢复以及容错能力。
在原来基于二进制日志的复制中，从库需要告知主库要从哪个偏移量进行增量同步，如果指定错误会造成数据的遗漏，从而造成数据的不一致。借助GTID，在发生主备切换的情况下，MySQL的其它从库可以自动在新主库上找到正确的复制位置，这大大简化了复杂复制拓扑下集群的维护，也减少了人为设置复制位置发生误操作的风险。另外，基于GTID的复制可以忽略已经执行过的事务，减少了数据发生不一致的风险。
注意事项 timestamp columnmaxwell对时间类型（datetime, timestamp, date）都是当做字符串处理的，这也是为了保证数据一致(比如0000-00-00 00:00:00这样的时间在timestamp里是非法的，但mysql却认，解析成java或者python类型就是null/None)。
如果MySQL表上的字段是 timestamp 类型，是有时区的概念，binlog解析出来的是标准UTC时间，但用户看到的是本地时间。比如 f_create_time timestamp 创建时间是北京时间 2018-01-05 21:01:01，那么mysql实际存储的是 2018-01-05 13:01:01，binlog里面也是这个时间字符串。如果不做消费者不做时区转换，会少8个小时。
与其每个客户端都要考虑这个问题，我觉得更合理的做法是提供时区参数，然后maxwell自动处理时区问题，否则要么客户端先需要知道哪些列是timestamp类型，或者连接上原库缓存上这些类型。
binary columnmaxwell可以处理binary类型的列，如blob、varbinary，它的做法就是对二进制列使用 base64_encode，当做字符串输出到json。消费者拿到这个列数据后，不能直接拼装，需要 base64_decode。
表结构不同步如果是拿比较老的binlog，放到新的mysql server上去用maxwell拉去，有可能表结构已经发生了变化，比如binlog里面字段比 schema_host 里面的字段多一个。目前这种情况没有发现异常，比如阿里RDS默认会为 无主键无唯一索引的表，增加一个__##alibaba_rds_rowid##__，在 show create table 和 schema 里面都看不到这个隐藏主键，但binlog里面会有，同步到从库。
另外我们有通过git去管理结构版本，如果真有这种场景，也可以应对。
大事务binlog当一个事物产生的binlog量非常大的时候，比如迁移日表数据，maxwell为了控制内存使用，会自动将处理不过来的binlog放到文件系统
Using kafka version: 0.11.0.1 21:16:07,109 WARN MaxwellMetrics - Metrics will not be exposed: metricsReportingType not configured. 21:16:07,380 INFO SchemaStoreSchema - Creating maxwell database 21:16:07,540 INFO Maxwell - Maxwell v?? is booting (RabbitmqProducer), starting at Position[BinlogPosition[mysql-bin.006235:24980714], lastHeartbeat=0] 21:16:07,649 INFO AbstractSchemaStore - Maxwell is capturing initial schema 21:16:08,267 INFO BinlogConnectorReplicator - Setting initial binlog pos to: mysql-bin.006235:24980714 21:16:08,324 INFO BinaryLogClient - Connected to rm-xxxxxxxxxxx.mysql.rds.aliyuncs.com:3306 at mysql-bin.006235/24980714 (sid:637 9, cid:9182598) 21:16:08,325 INFO BinlogConnectorLifecycleListener - Binlog connected. 03:15:36,104 INFO ListWithDiskBuffer - Overflowed in-memory buffer, spilling over into /tmp/maxwell7935334910787514257events 03:17:14,880 INFO ListWithDiskBuffer - Overflowed in-memory buffer, spilling over into /tmp/maxwell3143086481692829045events但是遇到另外一个问题，overflow随后就出现异常 EventDataDeserializationException: Failed to deserialize data of EventHeaderV4，当我另起一个maxwell指点之前的binlog postion开始解析，却有没有抛异常。事后的数据也表明并没有数据丢失。
问题产生的原因还不明，Caused by: java.net.SocketException: Connection reset，感觉像读取 binlog 流的时候还没读取到完整的event，异常关闭了连接。这个问题比较顽固，github上面类似问题都没有达到明确的解决。（这也从侧面告诉我们，大表数据迁移，也要批量进行，不要一个insert into .. select 搞定）
03:18:20,586 INFO ListWithDiskBuffer - Overflowed in-memory buffer, spilling over into /tmp/maxwell5229190074667071141events 03:19:31,289 WARN BinlogConnectorLifecycleListener - Communication failure. com.github.shyiko.mysql.binlog.event.deserialization.EventDataDeserializationException: Failed to deserialize data of EventHeaderV4{time stamp=1514920657000, eventType=WRITE_ROWS, serverId=2115082720, headerLength=19, dataLength=8155, nextPosition=520539918, flags=0} at com.github.shyiko.mysql.binlog.event.deserialization.EventDeserializer.deserializeEventData(EventDeserializer.java:216) ~[mys ql-binlog-connector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.event.deserialization.EventDeserializer.nextEvent(EventDeserializer.java:184) ~[mysql-binlog-c onnector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.BinaryLogClient.listenForEventPackets(BinaryLogClient.java:890) [mysql-binlog-connector-java-0 .13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.BinaryLogClient.connect(BinaryLogClient.java:559) [mysql-binlog-connector-java-0.13.0.jar:0.13 .0] at com.github.shyiko.mysql.binlog.BinaryLogClient$7.run(BinaryLogClient.java:793) [mysql-binlog-connector-java-0.13.0.jar:0.13.0 ] at java.lang.Thread.run(Thread.java:745) [?:1.8.0_121] Caused by: java.net.SocketException: Connection reset at java.net.SocketInputStream.read(SocketInputStream.java:210) ~[?:1.8.0_121] at java.net.SocketInputStream.read(SocketInputStream.java:141) ~[?:1.8.0_121] at com.github.shyiko.mysql.binlog.io.BufferedSocketInputStream.read(BufferedSocketInputStream.java:51) ~[mysql-binlog-connector- java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.io.ByteArrayInputStream.readWithinBlockBoundaries(ByteArrayInputStream.java:202) ~[mysql-binlo g-connector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.io.ByteArrayInputStream.read(ByteArrayInputStream.java:184) ~[mysql-binlog-connector-java-0.13 .0.jar:0.13.0] at com.github.shyiko.mysql.binlog.io.ByteArrayInputStream.readInteger(ByteArrayInputStream.java:46) ~[mysql-binlog-connector-jav a-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.event.deserialization.AbstractRowsEventDataDeserializer.deserializeLong(AbstractRowsEventDataD eserializer.java:212) ~[mysql-binlog-connector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.event.deserialization.AbstractRowsEventDataDeserializer.deserializeCell(AbstractRowsEventDataD eserializer.java:150) ~[mysql-binlog-connector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.event.deserialization.AbstractRowsEventDataDeserializer.deserializeRow(AbstractRowsEventDataDeserializer.java:132) ~[mysql-binlog-connector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.event.deserialization.WriteRowsEventDataDeserializer.deserializeRows(WriteRowsEventDataDeserializer.java:64) ~[mysql-binlog-connector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.event.deserialization.WriteRowsEventDataDeserializer.deserialize(WriteRowsEventDataDeserializer.java:56) ~[mysql-binlog-connector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.event.deserialization.WriteRowsEventDataDeserializer.deserialize(WriteRowsEventDataDeserializer.java:32) ~[mysql-binlog-connector-java-0.13.0.jar:0.13.0] at com.github.shyiko.mysql.binlog.event.deserialization.EventDeserializer.deserializeEventData(EventDeserializer.java:210) ~[mysql-binlog-connector-java-0.13.0.jar:0.13.0] ... 5 more 03:19:31,514 INFO BinlogConnectorLifecycleListener - Binlog disconnected. 03:19:31,590 WARN BinlogConnectorReplicator - replicator stopped at position: mysql-bin.006236:520531744 -- restarting 03:19:31,595 INFO BinaryLogClient - Connected to rm-xxxxxx.mysql.rds.aliyuncs.com:3306 at mysql-bin.006236/520531744 (sid:6379, cid:9220521) tableMapCache