Troubleshooting thread deadlocks on the server
Java thread deadlocking can occur in a multi-threaded application when two or more threads
need the same lock and block while waiting for it. These threads can be permanently blocked
(deadlocked), waiting for each other.
For developers using the Smart GWT server, if
deadlocks are encountered we recommend the following troubleshooting steps:
- Search
server code for calls to DataSourceManager and audit whether you are following the
documented pooling rules for obtaining and releasing dataSources
- Look at the
deadlocked thread ID and looked at the server logs for the logs for the last request that
thread serviced.
Our default logging messages include the thread ID so you can easily
correlate the logs with the hung thread. You can also adjust server logging sensitivity
via settings in the log4j configuration file (log4j.isc.config.xml).
Note
that the logged thread IDs are shortened by default. If there isn't enough information
shown to correlate with the deadlocked thread you can also change the logging format
(pattern) in the log4j configuration file.
If you are using some other log package, it
should be easy to turn on logging of thread IDs, and you should do so - this is a basic
logging best practice.
See documentation here for more information on server side logging. - Attach a tool such as
Dynatrace so that you can inspect the hung thread.
- Examine any threaded code you may
have, and made sure it likewise follows the rules of pooling (see also
Standalone DataSource Usage)