Gpars (Groovy Parallel Systems) is the best solution for your concurrency problems with mutable objects. Gpars gives you a number of high-level abstractions for writing concurrent and parallel code in Groovy (map/reduce, fork/join, asynchronous closures, actors, agents, dataflow concurrency and other concepts), which can make your Java and Groovy code concurrent and/or parallel with little effort. Gpars is bundled in Groovy starting from version of 2.1.
I had an issue with deploying my Grails project to Cloud Foundry with using cloudfoundry-grails-plugin. My application was using Tomcat 7 unlike Cloud Foundry, which use Tomcat 6. In other words, to have a Grails application with Tomcat 7 run, I had to deploy the entire Tomcat 7 directory, but before it should be slightly reconfigured.
Suppose you have a system with ElasticSearch server installed and need to upgrade it to a newer version. Below is a step-by-step guide explaining how you can do it, but note that it only works for ElasticSearch pre-1.x versions. It's also assumed that you have already stopped your ElasticSearch cluster before upgrading.
Assume you have a page with pagination that displays some objects table (selected from DB with GORM criteria) in your Grails application. If you want to know total number of possible results (as if there are no pagination parameters), you can do it in this way:
This code snippet shows how to update project configuration settings from a Grails plugin executable script. The script changes the configuration by copying the settings from a default config file, placed in the plugin's folder, to the Config.groovy. This is usually very useful during a plugin installation when you need to provide some default configuration: