Docker Images Test

Images are the basic building blocks of the Docker, and are organized in a layered manner. The images are utilized as read-only templates for building multiple Docker containers using layered Docker filesystems. The containers so created will share common files and enhance disk usage and downloads on the containers. Once the containers are created, multiple applications can be installed on them. The applications can also be updated to a new version by simply building a new layer on the existing images rather than replacing the whole image or entirely rebuilding the containers. The containers can be mapped to a single image or to multiple images. If a single image is alone over-utilized in creating the containers or if any image remains unmapped to the containers, then such unmapped images will remain under-utilized but still will occupy unnecessary disk space. If too many such unmapped images exists, then the creation of new images may be impacted and applications cannot be bundled to the existing images/containers resulting in a decreased reusability of disk space, increased disk usage and reduction in the building speed of the containers. This is why, administrators need to frequently check for the images and the disk space occupied by those images. The Docker Images test does this check.

This test reports the total number of images that are available on the Docker host/server. In addition, this test helps administrators to compare the numerical statistics of the images that are mapped to the containers and those that are not mapped to any container. Likewise, administrators can also be able to figure out the disk space utilization of images that are mapped to the containers and the disk space utilization of the images that are not mapped to the containers. Using this test, administrators can figure out the images that are sparsely utilized, the images that are consuming too much of disk space etc and take remedial actions to restrict the disk space utilization of the images.

Target of the test : A Docker server

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results for the target Docker server that is being monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The IP address of the host for which this test is to be configured.

Port

The port number at which the specified HOST listens. The default is 2375.

UseSUDO

By default, this flag is set to Yes. You are advised not to change the default setting of this flag.

DD Frequency

Refers to the frequency with which detailed diagnosis measures are to be generated for this test. The default is 1:1. This indicates that, by default, detailed measures will be generated every time this test runs, and also every time the test detects a problem. You can modify this frequency, if you so desire. Also, if you intend to disable the detailed diagnosis capability for this test, you can do so by specifying none against DD frequency.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enabled/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Total Images

Indicates the total number of images available in the Docker server.

Number

 

Images mapped to containers

Indicates the number of images that are mapped to the Docker containers.

Number

Ideally, the value of this measure should be high. A low value of this measure indicates that more number of images are left idle and more disk space is occupied by unused images. This may cause potential space crunch in the disk.

The detailed diagnosis of this measure if enabled, lists the images and the containers to which the images are mapped.

Images not mapped to any container

Indicates the number of images that are not mapped to any Docker container.

Number

Ideally, the value of this measure should be low. The detailed diagnosis of this measure if enabled, lists the images that are not mapped to any Docker containers.

Disk space used by images mapped to containers

Indicates the amount of disk space utilized by the images that are mapped to the Docker containers.

MB

The detailed diagnosis of this measure if enabled, lists the images and the containers.

Disk space used by images not mapped to any container

Indicates the amount of disk space utilized by the images that were not mapped to the Docker containers.

MB

A high value of this measure indicates space crunch in the disk. The detailed diagnosis of this measure if enabled, lists the images, which were not mapped with containers.

The detailed diagnosis of the Images mapped to containers measure lists the Image, Image ID, the containers mapped to the image, the time at which the container was created and size of the image. Using this measure administrators can figure out the image that is widely used to create a container.

Figure 1 : The detailed diagnosis of the Images mapped to containers measure