1.Mycat 使用版本1.6.4，JDK使用1.7.0_79,启动时wrapper.log日志报错：Unable to locate the class io.mycat.MycatStartup
STATUS | wrapper | 2021/02/09 15:34:54 | --> Wrapper Started as Daemon
STATUS | wrapper | 2021/02/09 15:34:54 | Launching a JVM...
INFO | jvm 1 | 2021/02/09 15:34:54 | Wrapper (Version 3.2.3) http://wrapper.tanukisoftware.org
INFO | jvm 1 | 2021/02/09 15:34:54 | Copyright 1999-2006 Tanuki Software, Inc. All Rights Reserved.
INFO | jvm 1 | 2021/02/09 15:34:54 |
INFO | jvm 1 | 2021/02/09 15:34:54 | WrapperSimpleApp: Unable to locate the class io.mycat.MycatStartup: java.lang.UnsupportedClassVersionError:
io/mycat/MycatStartup : Unsupported major.minor version 52.0
INFO | jvm 1 | 2021/02/09 15:34:54 |
INFO | jvm 1 | 2021/02/09 15:34:54 | WrapperSimpleApp Usage:
INFO | jvm 1 | 2021/02/09 15:34:54 | java org.tanukisoftware.wrapper.WrapperSimpleApp {app_class} [app_arguments]
INFO | jvm 1 | 2021/02/09 15:34:54 |
INFO | jvm 1 | 2021/02/09 15:34:54 | Where:
INFO | jvm 1 | 2021/02/09 15:34:54 | app_class: The fully qualified class name of the application to run.
INFO | jvm 1 | 2021/02/09 15:34:54 | app_arguments: The arguments that would normally be passed to the
INFO | jvm 1 | 2021/02/09 15:34:54 | application.
STATUS | wrapper | 2021/02/09 15:34:57 | <-- Wrapper Stopped
解决措施：下载使用jdk1.8.0_281，再启动就正常了。
2.启动时wrapper.log报错：Unable to start JVM: No such file or directory (2)
是因为：/mycat/conf/wrapper.conf文件里配置wrapper.java.command路径有问题
# Java Application
#wrapper.java.command=/usr/java/jdk1.8.0_281/bin/java
wrapper.java.command=%JAVA_HOME%/bin/java
可以使用绝对路径，也可以用%%取环境变量，不能用$JAVA_HOME取环境变量，我开始配成
wrapper.java.command=$JAVA_HOME/bin/java就报错。
3.启动wrapper.log报错Encountered an error running main: java.lang.ExceptionInInitializerError
WrapperSimpleApp: Encountered an error running main: java.lang.ExceptionInInitializerError
INFO | jvm 1 | 2021/02/09 18:01:22 | java.lang.ExceptionInInitializerError
INFO | jvm 1 | 2021/02/09 18:01:22 | at io.mycat.MycatStartup.main(MycatStartup.java:53)
INFO | jvm 1 | 2021/02/09 18:01:22 | at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
INFO | jvm 1 | 2021/02/09 18:01:22 | at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
INFO | jvm 1 | 2021/02/09 18:01:22 | at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
INFO | jvm 1 | 2021/02/09 18:01:22 | at java.lang.reflect.Method.invoke(Method.java:498)
INFO | jvm 1 | 2021/02/09 18:01:22 | at org.tanukisoftware.wrapper.WrapperSimpleApp.run(WrapperSimpleApp.java:240)
INFO | jvm 1 | 2021/02/09 18:01:22 | at java.lang.Thread.run(Thread.java:748)
INFO | jvm 1 | 2021/02/09 18:01:22 | Caused by: io.mycat.config.util.ConfigException: org.xml.sax.SAXParseException; lineNumber: 11; columnNumbe
r: 68; Attribute "parentKey" is required and must be specified for element type "childTable".
INFO | jvm 1 | 2021/02/09 18:01:22 | at io.mycat.config.loader.xml.XMLSchemaLoader.load(XMLSchemaLoader.java:121)
INFO | jvm 1 | 2021/02/09 18:01:22 | at io.mycat.config.loader.xml.XMLSchemaLoader.<init>(XMLSchemaLoader.java:78)
INFO | jvm 1 | 2021/02/09 18:01:22 | at io.mycat.config.loader.xml.XMLSchemaLoader.<init>(XMLSchemaLoader.java:82)
INFO | jvm 1 | 2021/02/09 18:01:22 | at io.mycat.config.ConfigInitializer.<init>(ConfigInitializer.java:76)
INFO | jvm 1 | 2021/02/09 18:01:22 | at io.mycat.config.MycatConfig.<init>(MycatConfig.java:72)
INFO | jvm 1 | 2021/02/09 18:01:22 | at io.mycat.MycatServer.<init>(MycatServer.java:178)
INFO | jvm 1 | 2021/02/09 18:01:22 | at io.mycat.MycatServer.<clinit>(MycatServer.java:121)
INFO | jvm 1 | 2021/02/09 18:01:22 | ... 7 more
INFO | jvm 1 | 2021/02/09 18:01:22 | Caused by: org.xml.sax.SAXParseException; lineNumber: 11; columnNumber: 68; Attribute "parentKey" is requir
ed and must be specified for element type "childTable".
这个原因就是schema.xml配置文件书写的问题，我的这个问题是parentKey拼写错误，这个文件很重要，编辑时一定要注意。
4.mycat能正常启动，wrapper.log显示启动成功，但是mycat.log里一直报错：
2021-02-10 10:30:03.414 WARN [$_NIOREACTOR-0-RW] (io.mycat.backend.mysql.nio.MySQLConnectionAuthenticator.handle(MySQLConnectionAuthenticator.java:91)) - can't connect to mysql server ,errmsg:Client does not support authentication protocol requested by server; consider upgrading MySQL client MySQLConnection@1591334450 [id=2, lastTime=1612924203222, user=root, schema=db01, old shema=db01, borrowed=false, fromSlaveDB=false, threadId=301, charset=utf8, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=192.0.2.105, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=false]
而前端连接时报错：
[root@ms1 conf]# mysql -utest -ptest123 -h192.0.2.105 -P8066 -DTESTDB
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 1045 (HY000): Access denied for user 'test', because password is error
解决措施：
- ALTER USER 'root'@'%' IDENTIFIED WITH mysql_native_password BY '123456aA#'；
按这种方式处理后，再启动mycat，mycat.log不再不错，但是前端命令行登录时依旧报错：说password is error
- 更换mysql的客户端为5.6.51版本，再登录一切正常。
总结：mycat版本更新缓慢，跟mysql8存在一些不兼容的问题。