org.springframework.transaction.CannotCreateTransactionException: Could not open JDBC Connection for transaction; nested exception is java.sql.SQLTransientConnectionException: Connection is not available, request timed out after 60059ms.
at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:305) ~[spring-jdbc-5.0.5.RELEASE.jar!/:5.0.5.RELEASE]
at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:378) ~[spring-tx-5.0.5.RELEASE.jar!/:5.0.5.RELEASE]
at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:474) ~[spring-tx-5.0.5.RELEASE.jar!/:5.0.5.RELEASE]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:289) ~[spring-tx-5.0.5.RELEASE.jar!/:5.0.5.RELEASE]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98) ~[spring-tx-5.0.5.RELEASE.jar!/:5.0.5.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.5.RELEASE.jar!/:5.0.5.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-5.0.5.RELEASE.jar!/:5.0.5.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.5.RELEASE.jar!/:5.0.5.RELEASE]
1.系統在低峯的時候訪問快，高峯的時候訪問慢，有時候還會報錯。從打印出SQL的執行時間上看，同樣的SQL有時候10ms，有時候6s，差異非常大。
2.通過分析數據庫慢日誌，發現執行都很快，且數據庫並沒有出現性能瓶頸。
3.判斷是tomcat數據庫連接池太小，檢查果然，最大隻有10。
4.覆盤，SQL執行時快時慢是因爲獲取不到連接在等待，嚴重的時候會等待超時。