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Slider service install not required for slider apps to run?

Contributor

I am running HDP 2.3 and was capturing screenshots for a lesson under development for Slider. I created a Slider view, created the yarn home directory in HDFS, copied an HBase slider package to the appropriate location, and restarted Ambari server. It was then I realized the I had forgotten to install the Slider service on my cluster. Thinking it would be a great error message to capture, I went back to the Slider View, created the app per the wizard, and deployed - thinking it would error out and tell me that the service was not installed. To my surprise, the application ran without a problem, and the Slider View allowed me to perform the Flex and other actions with no issues.

Because this is for a training class, I need to understand why this worked. Is there something special about the HBase slider package we make available that allows it to run on a cluster where the service is not installed, or does the HDP or Ambari support slider applications without the need to explicitly install the service? If that's true, what is it that installing Slider on HDP actually accomplishes?

I will post screenshots in a comment below.

Thanks in advance.

1 ACCEPTED SOLUTION

Accepted Solutions

Rising Star

Slider is really just a client library. The Slider View installs its own copy of the Slider jars in a directory like this one:

/var/lib/ambari-server/resources/views/work/SLIDER{2.0.0}/WEB-INF/lib/

When you install the Slider service separately, Slider is installed in the standard service directory /usr/hdp/current/slider-client/, and then you can use the slider shell script to perform Slider operations.

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Contributor
Successfully running application, Slider View:

534-33-appdetails.png

List of installed services, no Slider:

535-40-nosliderwhat.png

Rising Star

Slider is really just a client library. The Slider View installs its own copy of the Slider jars in a directory like this one:

/var/lib/ambari-server/resources/views/work/SLIDER{2.0.0}/WEB-INF/lib/

When you install the Slider service separately, Slider is installed in the standard service directory /usr/hdp/current/slider-client/, and then you can use the slider shell script to perform Slider operations.

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Contributor

Ah, gotcha. So installing the Slider View is functionally equivalent to installing Slider on the cluster, assuming you are launching applications from the View. But to make slider available via CLI, you must install it at the cluster level. Makes sense!

Actually, you don't need to install slider on your cluster at all: you just need it on your local system -it will install itself via HDFS and YARN. This lets you use different versions of slider for different applications, and upgrade without needing any cluster admin.

Contributor

Steve - that's a good point. The question, then, is why make it available as a cluster-level service at all? What is the benefit of providing Slider as an installable option, or providing a Slider view in HDP?

Primarily so that Ambari can use it to deploy and manage things via slider; it doesn't need to be installed on other machines in the cluster.