大众点评链路监控cat源码的几个片段分析(初始化 messageId的传递)

青旅半醒 2022-02-03 01:09 545阅读 0赞

关注的几个点：

a tcp连接netty的使用 ***TODO***

b 服务间调用messageId rootId parentId的传递如何实现  第4点有提到

c mybatis如何作为一个transation类似的消息也加入 messageTree的 因为之前记录都是的都是url 使用拦截器 参考第5点

几个片段

1 D:\\work\\git\\taimei\\cat\\cat-client\\src\\main\\java\\com\\dianping\\cat\\Cat.java

初始化cat

// this should be called during application initialization time

public static void initialize(File configFile) \{

try \{

if (!s\_init) \{

synchronized (s\_instance) \{

if (!s\_init) \{

PlexusContainer container = ContainerLoader.getDefaultContainer();

ModuleContext ctx = new DefaultModuleContext(container);

Module module = ctx.lookup(Module.class, CatClientModule.ID);

if (!module.isInitialized()) \{

ModuleInitializer initializer = ctx.lookup(ModuleInitializer.class);

ctx.setAttribute("cat-client-config-file", configFile);

initializer.execute(ctx, module);

log("INFO", "Cat is lazy initialized!");

s\_init = true;

\} catch (Exception e) \{

errorHandler(e);

加载client.xml地方

![WEBRESOURCE0a360e493076bc8b05f3a53751387e92][]

2 MessageTree 的一个主要实现

public class DefaultMessageTree implements MessageTree \{

private ByteBuf m\_buf;

private String m\_domain;

private String m\_hostName;

private String m\_ipAddress;

private Message m\_message;

private String m\_messageId;

private String m\_parentMessageId;

private String m\_rootMessageId;

private String m\_sessionToken;

private String m\_threadGroupName;

private String m\_threadId;

private String m\_threadName;

private MessageId m\_formatMessageId;

private boolean m\_discard = true;

private boolean m\_processLoss = false;

private boolean m\_hitSample = false;

private List<Event> events = new ArrayList<Event>(); // by flyer messageTree主要存储的信息 主要就是这些message

private List<Transaction> transactions = new ArrayList<Transaction>();

private List<Heartbeat> heartbeats = new ArrayList<Heartbeat>();

private List<Metric> metrics = new ArrayList<Metric>();

3 有很多context类

![WEBRESOURCEd0ffdfb625fcc627b6b6d15f6e86efa5][]

主要看这个上下文

@Named(type = MessageManager.class)

public class DefaultMessageManager extends ContainerHolder implements MessageManager, Initializable, LogEnabled \{

还有这个

![WEBRESOURCE374041a5a1cff9c95be06262f6d128d7][]

4 catFilter写入rootId parentId messageId 信息到header传递给下一个请求.

代码路径

package com.dianping.cat.servlet;

public class CatFilter implements Filter \{

ID_SETUP {
    			private String m_servers;
    
    			private String getCatServer() {
    				if (m_servers == null) {
    					DefaultMessageManager manager = (DefaultMessageManager) Cat.getManager();
    					List<Server> servers = manager.getConfigManager().getServers();
    
    					m_servers = Joiners.by(',').join(servers, new IBuilder<Server>() {
    						@Override
    						public String asString(Server server) {
    							String ip = server.getIp();
    							Integer httpPort = server.getHttpPort();
    
    							if ("127.0.0.1".equals(ip)) {
    								ip = NetworkInterfaceManager.INSTANCE.getLocalHostAddress();
    							}
    
    							return ip + ":" + httpPort;
    						}
    					});
    				}
    
    				return m_servers;
    			}
    
    			@Override
    			public void handle(Context ctx) throws IOException, ServletException {
    				boolean isTraceMode = Cat.getManager().isTraceMode();
    
    				HttpServletRequest req = ctx.getRequest();
    				HttpServletResponse res = ctx.getResponse();
    				MessageProducer producer = Cat.getProducer();
    				int mode = ctx.getMode();
    
    				switch (mode) {
    				case 0:
    					ctx.setId(producer.createMessageId());
    					break;
    				case 1:
    					ctx.setRootId(req.getHeader("X-CAT-ROOT-ID"));
    					ctx.setParentId(req.getHeader("X-CAT-PARENT-ID"));
    					ctx.setId(req.getHeader("X-CAT-ID"));
    					break;
    				case 2:
    					ctx.setRootId(producer.createMessageId());
    					ctx.setParentId(ctx.getRootId());
    					ctx.setId(producer.createMessageId());
    					break;
    				default:
    					throw new RuntimeException(String.format("Internal Error: unsupported mode(%s)!", mode));
    				}
    
    				if (isTraceMode) {
    					MessageTree tree = Cat.getManager().getThreadLocalMessageTree();
    
    					tree.setMessageId(ctx.getId());
    					tree.setParentMessageId(ctx.getParentId());
    					tree.setRootMessageId(ctx.getRootId());
    
    					res.setHeader("X-CAT-SERVER", getCatServer());
    
    					switch (mode) {
    					case 0:
    						res.setHeader("X-CAT-ROOT-ID", ctx.getId());
    						break;
    					case 1:
    						res.setHeader("X-CAT-ROOT-ID", ctx.getRootId());
    						res.setHeader("X-CAT-PARENT-ID", ctx.getParentId());
    						res.setHeader("X-CAT-ID", ctx.getId());
    						break;
    					case 2:
    						res.setHeader("X-CAT-ROOT-ID", ctx.getRootId());
    						res.setHeader("X-CAT-PARENT-ID", ctx.getParentId());
    						res.setHeader("X-CAT-ID", ctx.getId());
    						break;
    					}
    				}
    
    				ctx.handle();
    			}
    		},

**5 mybatis信息采集的问题**

官方整理了一个mybatis的拦截器

[https://github.com/dianping/cat/blob/master/integration/mybatis/CatMybatisPlugin.java][https_github.com_dianping_cat_blob_master_integration_mybatis_CatMybatisPlugin.java]

主要代码如下

<table> 
 <tbody> 
  <tr> 
   <td>@Override</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>public Object intercept(Invocation invocation) throws Throwable { </td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>MappedStatement mappedStatement = this.getStatement(invocation);</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>String methodName = this.getMethodName(mappedStatement);</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td><strong>Transaction t = Cat.newTransaction("SQL", methodName);</strong></td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>String sql = this.getSql(invocation,mappedStatement);</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>SqlCommandType sqlCommandType = mappedStatement.getSqlCommandType();</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td><strong>Cat.logEvent("SQL.Method", sqlCommandType.name().toLowerCase(), Message.SUCCESS, sql);</strong></td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>String url = this.getSQLDatabaseUrlByStatement(mappedStatement);</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>Cat.logEvent("SQL.Database", url);</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>return doFinish(invocation,t);</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>}</td> 
  </tr> 
 </tbody> 
</table>

可看到是主动写入一个**Transaction （就是一个message)**** **到当前的messageTree里面 然后就采集到了，可以跟一下里面代码

下面是关闭的过程

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0FsYmVydEZseQ_size_16_color_FFFFFF_t_70][]

[WEBRESOURCE0a360e493076bc8b05f3a53751387e92]: http://note.youdao.com/yws/res/3464/WEBRESOURCE0a360e493076bc8b05f3a53751387e92
[WEBRESOURCEd0ffdfb625fcc627b6b6d15f6e86efa5]: http://note.youdao.com/yws/res/3459/WEBRESOURCEd0ffdfb625fcc627b6b6d15f6e86efa5
[WEBRESOURCE374041a5a1cff9c95be06262f6d128d7]: http://note.youdao.com/yws/res/3466/WEBRESOURCE374041a5a1cff9c95be06262f6d128d7
[https_github.com_dianping_cat_blob_master_integration_mybatis_CatMybatisPlugin.java]: https://github.com/dianping/cat/blob/master/integration/mybatis/CatMybatisPlugin.java
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0FsYmVydEZseQ_size_16_color_FFFFFF_t_70]: /images/20220203/8faa460aa9b240eeac4a14850eaa43bd.png