Skip to main content

Ehcache: deploy multiple versions of a Grails app (fix javax.management.InstanceAlreadyExistsException)

When a Grails application makes use of the Ehcache cache plugin in its default configuration it can be impossibile to perform deploys of multiple versions of the app, even though the container might support it.
The same plugin (in its default configuration) also breaks deploying multiple different Grails apps on the same container.

The problem is in the way the plugin generates the name for the cache (which will then be used to register the cache jmx bean): the name is by default set grails-cache-ehcache. When another second application or another application version is deployed registration will fail because the name already exists. The exception message is the following (indented for clarity):

org.springframework.beans.factory.BeanCreationException:
Error creating bean with name 'ehCacheManagementService':
Invocation of init method failed;
nested exception is net.sf.ehcache.CacheException:
javax.management.InstanceAlreadyExistsException:
net.sf.ehcache:type=CacheManager,name=grails-cache-ehcache

The (undocumented) solution is easy to implement. Edit the Config.groovy file and add the following configuration bit:

grails.cache.config = {
  provider {
    name "ehcache-<yourappname>-"+(new Date().format("yyyyMMddHHmmss"))
  }
}

If you are using the ehcache.xml file instead it might be more difficult to randomize the cache name, but it could be done during the build.

Tested on Grails 2.1.5 and Tomcat 7.

Comments

Popular posts from this blog

From 0 to ZFS replication in 5m with syncoid

The ZFS filesystem has many features that once you try them you can never go back. One of the lesser known is probably the support for replicating a zfs filesystem by sending the changes over the network with zfs send/receive.
Technically the filesystem changes don't even need to be sent over a network: you could as well dump them on a removable disk, then receive  from the same removable disk.

Mirth: recover space when mirthdb grows out of control

I was recently asked to recover a mirth instance whose embedded database had grown to fill all available space so this is just a note-to-self kind of post.
Btw: the recovery, depending on db size and disk speed, is going to take long.

The problem A 1.8 Mirth Connect instance was started, then forgotten (well neglected, actually). The user also forgot to setup pruning so the messages filled the embedded Derby database until it grew to fill all the available space on the disk. The SO is linux.

The solution First of all: free some disk space so that the database can be started in embedded mode from the cli. You can also copy the whole mirth install to another server if you cannot free space. Depending on db size you will need a corresponding amount of space: in my case a 5GB db required around 2GB to start, process logs and then store the temp files during shrinking.

Then open a shell as the user that mirth runs as (you're not running it as root, are you?) and cd into the mirth home. …

Indexing Apache access logs with ELK (Elasticsearch+Logstash+Kibana)

Who said that grepping Apache logs has to be boring?

The truth is that, as Enteprise applications move to the browser too, Apache access logs are a gold mine, it does not matter what your role is: developer, support or sysadmin. If you are not mining them you are most likely missing out a ton of information and, probably, making the wrong decisions.
ELK (Elasticsearch, Logstash, Kibana) is a terrific, Open Source stack for visually analyzing Apache (or nginx) logs (but also any other timestamped data).