Support for statement interceptors

[gauravrmazra]

I am curious to know if this API can provide interceptor support. I want to execute some piece of code before and after every jdbc query. The support I am thinking of is the one provided by MySQL (StatementInterceptor).

Can I expect something similar to it in future?

[komu]

Hi! Sorry for the delayed answer.

Currently there's no support for interceptors at the statement level.

If you implement your own TransactionManager, Dalesbred will call either withCurrentTransaction or withTransaction whenever it is going to execute a statement. So you could do whatever you wish to do and then delegate the calls to the real TransactionManager. However, Dalesbred will not pass you the Statement it's about to execute, so this might not be enough for your needs.

I'll consider adding this in a future version, but I'd like to know more about your specific use case. Perhaps there's an even better way to support what you need to do?

[gauravrmazra]

The idea behind this is to measure the execution time of SQL basically for tracing purposes.
There are some built-in support available in MySQL JDBC driver and with Apache JDBC connection pool but the wiring/using it is not elegant. We are using Dalesbred in one of our project and I was looking for this kind of support. Now, I wrapped Database class to provide this sort of support but looking forward for some interceptor kind of feature.

[komu]

OK, then you might be happy to find out that Dalesbred already logs all queries. You just have to bump up the log level of org.dalesbred.Database-category. Dalesbred logs using java.util.logging to avoid extra third-party dependencies, but it's possible to redirect those using jul-to-slf4j or similar adapter to logging framework of your choice.

[gauravrmazra]

Tracing db call means to instrument dalesbred for Spring Cloud Sleuth (distributed tracing system) or any Distributed tracing system like htrace, pinpoint, xtrace.

[komu]

Right, I suspected something like this. This is not prettiest solution, but you should be able to write your own java.util.logging.Handler to get callbacks whenever Dalesbred logs the queries. You could then parse the time and SQL from the message and forward them to your tracing framework.

Of course a real callback would be nicer in the future, but this would be something you can do today.

As a related note, it would be nice to have a JDBC-driver that would adapt other JDBC-drivers and add features like tracing or simulated extra latency etc. Then you could use that with any persistence framework to diagnose and test your system. But I don't believe such a thing exists. :(

[gauravrmazra]

java.util.logging.Handler will not solve the purpose.

Yes, Driver/DataSource level support is something which is more elegant as well as complex to maintain and test.

Appreciate for your help.