Monday, 05 December 2016
Composing the Infinispan Docker image
In the previous post we showed how to manipulate the Infinispan Docker container configuration at both runtime and boot time.
Before diving into multi-host Docker usage, in this post we’ll explore how to create multi-container Docker applications involving Infinispan with the help of Docker Compose.
For this we’ll look at a typical scenario of an Infinispan server backed by an Oracle database as a cache store.
All the code for this sample can be found on github.
In order to have a cache with persistence with Oracle, we need to do some configuration: configure the driver in the server, create the data source associated with the driver, and configure the cache itself with JDBC persistence.
Let’s take a look at each of those steps:
Obtaining and configuring the driver
The driver (ojdbc6.jar) should be downloaded and placed in the 'driver' folder of the sample project.
The module.xml declaration used to make it available on the server is as follows:
Configuring the Data source
The data source is configured in the "datasource" element of the server configuration file as shown below:
and inside the "datasource/drivers" element, we need to declare the driver:
Putting all together
From now on, without using Docker we’d be ready to download and install Oracle following the specific instructions for your OS, then download the Infinispan Server, edit the configuration files, copy over the driver jar, figure out how to launch the database and server, taking care not to have any port conflicts.
If it sounds too much work, it’s because it really is. Wouldn’t it be nice to have all these wired together and launched with a simple command line? Let’s take a look at the Docker way next.
Enter Docker Compose
Docker Compose is a tool part of the Docker stack to facilitate configuration, execution and management of related Docker containers.
By describing the application aspects in a single yaml file, it allows centralized control of the containers, including custom configuration and parameters, and it also allows runtime interactions with each of the exposed services.
Composing Infinispan
Our Docker Compose file to assemble the application is given below:
It contains two services:
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one called oracle that uses the wnameless/oracle-xe-11g Docker image, with an environment variable to allow remote connections.
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another one called *infinispan* that uses version 8.2.5.Final of the Infinispan Server image. It is launched with a custom command pointing to the changed configuration file and it also mounts two volumes in the container: one for the driver and its module.xml and another for the folder holding our server xml configuration.
Launching
To start the application, just execute
To inspect the status of the containers:
To follow the Infinispan server logs, use:
Infinispan usually starts faster than the database, and since the server waits until the database is ready (more on that later), keep an eye in the log output for "Infinispan Server 8.2.5.Final (WildFly Core 2.0.10.Final) started". After that, both Infinispan and Oracle are properly initialized.
When dealing with dependent containers in Docker based environments, it’s highly recommended to make the connection obtention between parties robust enough so that the fact that one dependency is not totally initialized doesn’t cause the whole application to fail when starting.
Although Compose does have a depends_on instruction, it simply starts the containers in the declared order but it has no means to detected when a certain container is fully initialized and ready to serve requests before launching a dependent one.
One may be tempted to simply write some glue script to detect if a certain port is open, but that does not work in practice: the network socket may be opened, but the background service could still be in transient initialization state.
The recommended solution for this it to make whoever depends on a service to retry periodically until the dependency is ready. On the Infinispan + Oracle case, we specifically configured the data source with retries to avoid failing at once if the database is not ready:
When starting the application via Compose you’ll notice that Infinispan print some WARN with connection exceptions until Oracle is available: don’t panic, this is expected!
Conclusion
Docker Compose is a powerful and easy to use tool to launch applications involving multiple containers: in this post it allowed to start Infinispan plus Oracle with custom configurations with a single command. It’s also a handy tool to have during development and testing phase of a project, specially when using/evaluating Infinispan with its many possible integrations.
Be sure to check other examples of using Docker Compose involving Infinispan: the Infinispan+Spark Twitter demo, and the Infinispan+Apache Flink demo.
Tags: compose jdbc docker persistence server modules oracle cache store
Wednesday, 23 January 2013
Infinispan AS 7.x modules
The latest Infinispan 5.2.0.CR2 release includes a set of modules for JBoss AS 7.x. By installing these modules, it is possible to deploy user applications without packaging the Infinispan JARs within the deployments (WARs, EARs, etc), thus minimizing their size. In order not to conflict with the Infinispan modules which are already present within an AS installation, the modules provided by the Infinispan distribution are located within their own slot identified by the major.minor versions (e.g. slot="5.2"). In order to tell the AS deployer that we want to use the Infinispan APIs within our application, we need to add explicit dependencies to the deployment’s MANIFEST:
If you are using Maven to generate your artifacts, mark the Infinispan dependencies as provided and configure your artifact archiver to generate the appropriate MANIFEST.MF file:
Tags: as7 modules deployment
