Hibernate 应用程序中的连接泄漏

Question

I am working in java enterprise application. The application has hibernate framework for backend. Due to recent changes in application some code consumes all JDBC connection pools from weblogic server.

The application connection was property handled in code, for each thread we are create each session using threadlocal class. So there was no issues with creating connection. The application was live more than 5 years.

We are suspecting the recent code changes causes this major issue. Finally we decided to use profiler tool for investigate this issue.

Before that I am going to review the recent code changes, so what are the key points i need to keep in mind in hibernate while reviewing?

This is very critical/serious situation. So suggest me some tips to solve this..

Thanks

Answer 1

Query your database:

select * from pg_stat_activity;

And check which queries are long lasting with idle in transaction status. Try to locate them in your code and research why transaction is not completed.

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Add to persistence.xml :

  <property name="hibernate.c3p0.unreturnedConnectionTimeout" value="60"/>
  <property name="hibernate.c3p0.debugUnreturnedConnectionStackTraces" value="true"/>

unreturnedConnectionTimeout value should be greater than 0 because default is 0 - unlimited. These properties are more testing/debugging purposes and ideally shouldn't be used in a production environment.

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Few things to check in a code/configuration:

• Commit transactions explicitly or use @Transactional . Please note that @Transactional works only for public methods.

• If you're using Hibernate 5.1.0.Final, then persistence.xml should contain:

<property name="hibernate.connection.provider_class" value="org.hibernate.c3p0.internal.C3P0ConnectionProvider" />

Instead of:

<property name="connection.provider_class" value="org.hibernate.connection.C3P0ConnectionProvider" />

• If you're using

<property name="hibernate.enable_lazy_load_no_trans" value="true" />

it may cause connection leaks when lazy loading. Related discussions:

• org.hibernate.LazyInitializationException - could not initialize proxy - no Session
• Solve Hibernate Lazy-Init issue with hibernate.enable_lazy_load_no_trans

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Check related articles:

• The best way to detect database connection leaks
• How we fixed all database connection leaks

Answer 2

Typically this is due to sessions that were not closed. Simple way that I personally use is to create a table (map) of running sessions. On create add an entry in a table, and on session close remove (or mark) entry on map. This way you can identify which sessions were not closed.

Good logger (slf4/log4j) may also be useful, especially NDC ( http://wiki.apache.org/logging-log4j/NDCvsMDC ).

Answer 3

I had to investigate issues with hibernate myself in the past and I found this page from the official documentation gives a lot of good advices already:

http://docs.jboss.org/hibernate/orm/3.3/reference/en/html/performance.html

Answer 4

请检查 session.createQuery() 中使用的所有实体名称，如果使用，可能是查询中使用的类名称不匹配。