前言

我們經(jīng)常需要根據(jù)用戶對自己數(shù)據(jù)的一些操作來做一些事情.

比如如果用戶刪除了自己的賬號,我們就給他發(fā)短信罵他,去發(fā)短信求他回來.

類似于這種功能,當(dāng)然可以在業(yè)務(wù)邏輯層實(shí)現(xiàn),在收到用戶的刪除請求之后執(zhí)行這一操作,但是數(shù)據(jù)庫的binlog為我們提供了另外一種操作方法.

要監(jiān)聽binlog,需要兩步,第一步當(dāng)然是你的mysql需要開啟這一個功能,第二個是要寫程序來對日志進(jìn)行讀取.

mysql開啟binlog.

首先mysql的binlog日常是不打開的,因此我們需要:

找到mysql的配置文件my.cnf,這個因操作系統(tǒng)不一樣,位置也不一定一樣,可以自己找一下,

在其中加入以下內(nèi)容:

[mysqld]
server_id = 1
log-bin = mysql-bin
binlog-format = ROW

之后重啟mysql.

/ ubuntu
service mysql restart
// mac
mysql.server restart

監(jiān)測是否開啟成功

進(jìn)入mysql命令行,執(zhí)行:

show variables like '%log_bin%' ;

如果結(jié)果如下圖,則說明成功了:

查看正在寫入的binlog狀態(tài):

代碼讀取binlog

引入依賴

我們使用開源的一些實(shí)現(xiàn),這里因?yàn)橐恍┢婀值脑?我選用了mysql-binlog-connector-java這個包,(官方github倉庫)[github.com/shyiko/mysq…]具體依賴如下:

<!-- https://mvnrepository.com/artifact/com.github.shyiko/mysql-binlog-connector-java -->
 <dependency>
 <groupId>com.github.shyiko</groupId>
 <artifactId>mysql-binlog-connector-java</artifactId>
 <version>0.17.0</version>
 </dependency>

當(dāng)然,對binlog的處理有很多開源實(shí)現(xiàn),阿里的cancl就是一個,也可以使用它.

寫個demo

根據(jù)官方倉庫中readme里面,來簡單的寫個demo.

 public static void main(String[] args) {
 BinaryLogClient client = new BinaryLogClient("hostname", 3306, "username", "passwd");
 EventDeserializer eventDeserializer = new EventDeserializer();
 eventDeserializer.setCompatibilityMode(
 EventDeserializer.CompatibilityMode.DATE_AND_TIME_AS_LONG,
 EventDeserializer.CompatibilityMode.CHAR_AND_BINARY_AS_BYTE_ARRAY
 );
 client.setEventDeserializer(eventDeserializer);
 client.registerEventListener(new BinaryLogClient.EventListener() {

 @Override
 public void onEvent(Event event) {
 // TODO
 dosomething();
 logger.info(event.toString());
 }
 });
 client.connect();
 }

這個完全是根據(jù)官方教程里面寫的,在onEvent里面可以寫自己的業(yè)務(wù)邏輯,由于我只是測試,所以我在里面將每一個event都打印了出來.

之后我手動登錄到mysql,分別進(jìn)行了增加,修改,刪除操作,監(jiān)聽到的log如下:

00:23:13.331 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=0, eventType=ROTATE, serverId=1, headerLength=19, dataLength=28, nextPosition=0, flags=32}, data=RotateEventData{binlogFilename='mysql-bin.000001', binlogPosition=886}}
00:23:13.334 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468403000, eventType=FORMAT_DESCRIPTION, serverId=1, headerLength=19, dataLength=100, nextPosition=0, flags=0}, data=FormatDescriptionEventData{binlogVersion=4, serverVersion='5.7.23-0ubuntu0.16.04.1-log', headerLength=19, dataLength=95}}
00:23:23.715 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468603000, eventType=ANONYMOUS_GTID, serverId=1, headerLength=19, dataLength=46, nextPosition=951, flags=0}, data=null}
00:23:23.716 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468603000, eventType=QUERY, serverId=1, headerLength=19, dataLength=51, nextPosition=1021, flags=8}, data=QueryEventData{threadId=4, executionTime=0, errorCode=0, database='pf', sql='BEGIN'}}
00:23:23.721 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468603000, eventType=TABLE_MAP, serverId=1, headerLength=19, dataLength=32, nextPosition=1072, flags=0}, data=TableMapEventData{tableId=108, database='pf', table='student', columnTypes=15, 3, columnMetadata=135, 0, columnNullability={}}}
00:23:23.724 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468603000, eventType=EXT_WRITE_ROWS, serverId=1, headerLength=19, dataLength=23, nextPosition=1114, flags=0}, data=WriteRowsEventData{tableId=108, includedColumns={0, 1}, rows=[
    [[B@546a03af, 2]
]}}
00:23:23.725 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468603000, eventType=XID, serverId=1, headerLength=19, dataLength=12, nextPosition=1145, flags=0}, data=XidEventData{xid=28}}
00:23:55.872 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468635000, eventType=ANONYMOUS_GTID, serverId=1, headerLength=19, dataLength=46, nextPosition=1210, flags=0}, data=null}
00:23:55.872 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468635000, eventType=QUERY, serverId=1, headerLength=19, dataLength=51, nextPosition=1280, flags=8}, data=QueryEventData{threadId=4, executionTime=0, errorCode=0, database='pf', sql='BEGIN'}}
00:23:55.873 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468635000, eventType=TABLE_MAP, serverId=1, headerLength=19, dataLength=32, nextPosition=1331, flags=0}, data=TableMapEventData{tableId=108, database='pf', table='student', columnTypes=15, 3, columnMetadata=135, 0, columnNullability={}}}
00:23:55.875 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468635000, eventType=EXT_UPDATE_ROWS, serverId=1, headerLength=19, dataLength=31, nextPosition=1381, flags=0}, data=UpdateRowsEventData{tableId=108, includedColumnsBeforeUpdate={0, 1}, includedColumns={0, 1}, rows=[
    {before=[[B@6833ce2c, 1], after=[[B@725bef66, 3]}
]}}
00:23:55.875 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468635000, eventType=XID, serverId=1, headerLength=19, dataLength=12, nextPosition=1412, flags=0}, data=XidEventData{xid=41}}
00:24:22.333 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468662000, eventType=ANONYMOUS_GTID, serverId=1, headerLength=19, dataLength=46, nextPosition=1477, flags=0}, data=null}
00:24:22.334 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468662000, eventType=QUERY, serverId=1, headerLength=19, dataLength=51, nextPosition=1547, flags=8}, data=QueryEventData{threadId=4, executionTime=0, errorCode=0, database='pf', sql='BEGIN'}}
00:24:22.334 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468662000, eventType=TABLE_MAP, serverId=1, headerLength=19, dataLength=32, nextPosition=1598, flags=0}, data=TableMapEventData{tableId=108, database='pf', table='student', columnTypes=15, 3, columnMetadata=135, 0, columnNullability={}}}
00:24:22.335 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468662000, eventType=EXT_DELETE_ROWS, serverId=1, headerLength=19, dataLength=23, nextPosition=1640, flags=0}, data=DeleteRowsEventData{tableId=108, includedColumns={0, 1}, rows=[
    [[B@1888ff2c, 3]
]}}
00:24:22.335 [main] INFO util.MysqlBinLog - Event{header=EventHeaderV4{timestamp=1556468662000, eventType=XID, serverId=1, headerLength=19, dataLength=12, nextPosition=1671, flags=0}, data=XidEventData{xid=42}}

根據(jù)自己的業(yè)務(wù),封裝一個更好使,更定制的工具類

開始的時候打算貼代碼的,,,但是代碼越寫越多,索性傳在github上了,這里只貼部分的實(shí)現(xiàn).代碼傳送門

實(shí)現(xiàn)思路

1. 支持對單個表的監(jiān)聽,因?yàn)槲覀儾幌胝娴膶λ袛?shù)據(jù)庫中的所有數(shù)據(jù)表進(jìn)行監(jiān)聽.
2. 可以多線程消費(fèi).
3. 把監(jiān)聽到的內(nèi)容轉(zhuǎn)換成我們喜聞樂見的形式(文中的數(shù)據(jù)結(jié)構(gòu)不一定很好,我沒想到更加合適的了).

所以實(shí)現(xiàn)思路大致如下:

1. 封裝個客戶端,對外只提供獲取方法,屏蔽掉初始化的細(xì)節(jié)代碼.
2. 提供注冊監(jiān)聽器(偽)的方法,可以注冊對某個表的監(jiān)聽(重新定義一個監(jiān)聽接口,所有注冊的監(jiān)聽器實(shí)現(xiàn)這個就好).
3. 真正的監(jiān)聽器只有客戶端,他將此數(shù)據(jù)庫實(shí)例上的所有操作,全部監(jiān)聽到并轉(zhuǎn)換成我們想要的格式LogItem放進(jìn)阻塞隊(duì)列里面.
4. 啟動多個線程,消費(fèi)阻塞隊(duì)列,對某一個LogItem調(diào)用對應(yīng)的數(shù)據(jù)表的監(jiān)聽器,做一些業(yè)務(wù)邏輯.

初始化代碼:

 public MysqlBinLogListener(Conf conf) {
 BinaryLogClient client = new BinaryLogClient(conf.host, conf.port, conf.username, conf.passwd);
 EventDeserializer eventDeserializer = new EventDeserializer();
 eventDeserializer.setCompatibilityMode(
 EventDeserializer.CompatibilityMode.DATE_AND_TIME_AS_LONG,
 EventDeserializer.CompatibilityMode.CHAR_AND_BINARY_AS_BYTE_ARRAY
 );
 client.setEventDeserializer(eventDeserializer);
 this.parseClient = client;
 this.queue = new ArrayBlockingQueue<>(1024);
 this.conf = conf;
 listeners = new ConcurrentHashMap<>();
 dbTableCols = new ConcurrentHashMap<>();
 this.consumer = Executors.newFixedThreadPool(consumerThreads);
 }

注冊代碼:

 public void regListener(String db, String table, BinLogListener listener) throws Exception {
 String dbTable = getdbTable(db, table);
 Class.forName("com.mysql.jdbc.Driver");
 // 保存當(dāng)前注冊的表的colum信息
 Connection connection = DriverManager.getConnection("jdbc:mysql://" + conf.host + ":" + conf.port, conf.username, conf.passwd);
 Map<String, Colum> cols = getColMap(connection, db, table);
 dbTableCols.put(dbTable, cols);

 // 保存當(dāng)前注冊的listener
 List<BinLogListener> list = listeners.getOrDefault(dbTable, new ArrayList<>());
 list.add(listener);
 listeners.put(dbTable, list);
 }

在這個步驟中,我們在注冊監(jiān)聽者的同時,獲得了該表的schema信息,并保存到map里面去,方便后續(xù)對數(shù)據(jù)進(jìn)行處理.

監(jiān)聽代碼:

 @Override
 public void onEvent(Event event) {
 EventType eventType = event.getHeader().getEventType();

 if (eventType == EventType.TABLE_MAP) {
 TableMapEventData tableData = event.getData();
 String db = tableData.getDatabase();
 String table = tableData.getTable();
 dbTable = getdbTable(db, table);
 }

 // 只處理添加刪除更新三種操作
 if (isWrite(eventType) || isUpdate(eventType) || isDelete(eventType)) {
 if (isWrite(eventType)) {
 WriteRowsEventData data = event.getData();
 for (Serializable[] row : data.getRows()) {
  if (dbTableCols.containsKey(dbTable)) {
  LogItem e = LogItem.itemFromInsert(row, dbTableCols.get(dbTable));
  e.setDbTable(dbTable);
  queue.add(e);
  }
 }
 }
 }
 }

我偷懶了,,,這里面只實(shí)現(xiàn)了對添加操作的處理,其他操作沒有寫.

消費(fèi)代碼:

 public void parse() throws IOException {
 parseClient.registerEventListener(this);

 for (int i = 0; i < consumerThreads; i++) {
 consumer.submit(() -> {
 while (true) {
  if (queue.size() > 0) {
  try {
  LogItem item = queue.take();
  String dbtable = item.getDbTable();
  listeners.get(dbtable).forEach(l -> {
  l.onEvent(item);
  });

  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  Thread.sleep(1000);
 }
 });
 }
 parseClient.connect();
 }

消費(fèi)時,從隊(duì)列中獲取item,之后獲取對應(yīng)的一個或者多個監(jiān)聽者,分別消費(fèi)這個item.

測試代碼:

 public static void main(String[] args) throws Exception {
 Conf conf = new Conf();
 conf.host = "hostname";
 conf.port = 3306;
 conf.username = conf.passwd = "hhsgsb";

 MysqlBinLogListener mysqlBinLogListener = new MysqlBinLogListener(conf);
 mysqlBinLogListener.parseArgsAndRun(args);
 mysqlBinLogListener.regListener("pf", "student", item -> {
 System.out.println(new String((byte[])item.getAfter().get("name")));
 logger.info("insert into {}, value = {}", item.getDbTable(), item.getAfter());
 });
 mysqlBinLogListener.regListener("pf", "teacher", item -> System.out.println("teacher ===="));

 mysqlBinLogListener.parse();
 }

在這段很少的代碼里,注冊了兩個監(jiān)聽者,分別監(jiān)聽student和teacher表,并分別進(jìn)行打印處理,經(jīng)測試,在teacher表插入數(shù)據(jù)時,可以獨(dú)立的運(yùn)行定義的業(yè)務(wù)邏輯.

注意:這里的工具類并不能直接投入使用,因?yàn)槔锩嬗性S多的異常處理沒有做,且功能僅監(jiān)聽了插入語句,可以用來做實(shí)現(xiàn)的參考.

參考文章

• github.com/shyiko/mysq…
• http://www.dbjr.com.cn/article/166761.htm

總結(jié)

以上就是這篇文章的全部內(nèi)容了，希望本文的內(nèi)容對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價值，謝謝大家對腳本之家的支持。

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