SpringData Gemfire inserting fake date on Dev env

Question

I am developing some app using Gemfire and it would be great to be able to provide some fake data while in Dev environment.

So instead of doing it in the code like I do today, I was thinking about using spring application-context.xml do pre-load some dummy data in the region I am currently working on. Something close to what DBUnit does but for DEV not Test scope. Later I could just switch envs on Spring and that data would not be loaded.

Is it possible to add data using SpringData Gemfire to a local data grid?

Thanks!

Answer 1

There is no direct support in Spring Data GemFire to load data into a GemFire cluster. However, there are several options afforded to a SDG/GemFire developer to load data.

1. The most common approach is to define a GemFire CacheLoader attached to the Region. However, this approach is "lazy" and only loads data from a (potentially) external data source on a cache miss. Of course, you could program the logic in the CacheLoader to "prefetch" a number of entries in a somewhat "predictive" manner based on data access patterns. See GemFire's User Guide for more details.

Still, we can do better than this since it is more likely that you want to "preload" a particular data set for development purposes.

2. Another, more effective technique, is to use a Spring BeanPostProcessor registered in your Spring ApplicationContext that post processes your "Region" bean after initialization. For instance...

Where the RegionPutAllBeanPostProcessor is implemented as...

package example;

public class RegionPutAllBeanPostProcessor implements BeanPostProcessor {

  private Map regionData;

  private String targetRegionBeanName;

  protected Map getRegionData() {
    return (regionData != null ? regionData : Collections.emptyMap());
  }

  public void setRegionData(final Map regionData) {
    this.regionData = regionData;
  }

  protected String getTargetRegionBeanName() {
    Assert.state(StringUtils.hasText(targetRegionBeanName), "The target Region bean name was not properly specified!");
    return targetBeanName;
  }

  public void setTargetRegionBeanName(final String targetRegionBeanName) {
    Assert.hasText(targetRegionBeanName, "The target Region bean name must be specified!");
    this.targetRegionBeanName = targetRegionBeanName;
  }

  @Override
  public Object postProcessBeforeInitialization(final Object bean, final String beanName) throws BeansException {
    return bean;
  }

  @Override
  @SuppressWarnings("unchecked")
  public Object postProcessAfterInitialization(final Object bean, final String beanName) throws BeansException {
    if (beanName.equals(getTargetRegionBeanName()) && bean instanceof Region) {
      ((Region) bean).putAll(getRegionData());
    }

    return bean;
  }
}

It is not too difficult to imagine that you could inject a DataSource of some type to pre-populate the Region. The RegionPutAllBeanPostProcessor was designed to accept a specific Region (based on the Region beans ID) to populate. So you could defined multiple instances each taking a different Region and different DataSource (perhaps) to populate the Region(s) of choice. This BeanPostProcess just take a Map as the data source, but of course, it could be any Spring managed bean.

Finally, it is a simple matter to ensure that this, or multiple instances of the RegionPutAllBeanPostProcessor is only used in your DEV environment by taking advantage of Spring bean profiles...

<beans>
  ...

  <beans profile="DEV">
    <bean class="example.RegionPutAllBeanPostProcessor">
      ...
    </bean>
    ...
  </beans>
</beans>

Usually, loading pre-defined data sets is very application-specific in terms of the "source" of the pre-defined data. As my example illustrates, the source could be as simple as another Map. However, it would be a JDBC DataSource, or perhaps a Properties file or well, anything for that matter. It is usually up to the developers preference.

Though, one thing that might be useful to add to Spring Data GemFire would be to load data from a GemFire Cache Region Snapshot. I.e. data that may have been dumped from a QA or UAT environment, or perhaps even scrubbed from PROD for testing purposes. See GemFire Snapshot Service for more details.

Also see the JIRA ticket (SGF-408) I just filed to add this support.

Hopefully this gives you enough information and/or ideas to get going. Later, I will add first-class support into SDG's XML namespace for preloading data sets.

Regards, John