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QBean Eager Start

· 2 min read
Alejandro Revilla
Alejandro Revilla
jPOS project founder

QBeans have a very simple lifecycle:

  • init
  • start
  • stop
  • destroy

When Q2 starts, it reads all the QBeans available in the deploy directory and calls init on all of them, then start, using alphabetical order. That's the reason we have an order convention: 00* for the loggers, 10* for the channels, 20* for the MUXes, 30* for the TransactionManagers, etc.

This startup lifecycle has served us well for a very long time, but when we start getting creative with the Environment and the Environment Providers, things start to get awkward.

With the environment providers, we can dereference configuration properties from YAML files, Java properties, or operating system variables. These variables can have a prefix that indicates we need to call a provider loaded via a ServiceLoader. For example, an HSM environment provider allows you to use properties like this: hsm::xxxxxx, where xxxxxx is a cryptogram encrypted under the HSM's LMKs.

To decrypt xxxxxx, we need to call the HSM driver, typically configured using a QBean.

Imagine this deploy directory:

20_hsm_driver.xml
25_cryptoservice.xml

The cryptoservice wants to pick some configuration properties (such as its PGP private key passphrase) using the HSM, but it needs the HSM driver to be already started.

Up until now, Q2 would have called:

  • hsm_driver: init method
  • cryptoservice: init method

But the cryptoservice, at init time, needs to block until the hsm_driver is fully operational, which requires its start callback to be called.

The solution is simple: we now have an eager-start attribute:

<qbean name="xxx" class="org.jpos.xxx.QBeanXXX" eager-start="true">
  ...
  ...
</qbean>

When Q2 sees a QBean with the eager-start attribute set to true, it starts it right away.