Ron and Ella Wiki Page

Extremely Serious

Category: Container

Basic Docker Container Management

November 21, 2022 / / 0 Comments

Run Command

Run a command in a new container

Display the help information using the following command:

docker container run --help

Example of creating a container for the swaggerapi/swagger-editor image with the name swagger-editor.

docker container run -it -p 80:8080 --name swagger-editor swaggerapi/swagger-editor

Since the -it options were used, you can stop the container using CTRL+C.

Access the swagger-editor using the following address:

http://localhost

This command can only be used for creating a container based on an image. Once the container was created you can start it using the start command. If you are not sure about the name of the container find it using the list command.

It is better to have a name for the container so that you know what to start (or stop or delete).

List Command

List containers.

Display the help information using the following command:

docker container ls --help

Example of displaying all the containers.

docker container ls --all

Start Command

Start one or more stopped containers

Display the help information using the following command:

docker container start --help

Example of starting the container created from the run command section.

docker container start swagger-editor

Stop Command

Stop one or more running containers

Display the help information using the following command:

docker container stop --help

Example of stopping the container created from the run command section.

docker container stop swagger-editor

Delete Command

Remove one or more containers

Display the help information using the following command:

docker container rm --help

Example of deleting the container created from the run command section.

docker container rm swagger-editor

Container Aware JVM Parameters for Heap Memory

September 30, 2022 / / 0 Comments

JVM Parameters

Modify the java heap memory based on container memory using one of the following JVM parameters:

Parameter Description
-XX:InitialRAMPercentage The initial size of the heap based on the total container memory.
-XX:MinRAMPercentage The maximum heap size based on the size of the JVM running on small heap. The small is heap is of approximately 125MB.
-XX:MaxRAMPercentage The maximum heap size based on the size of the JVM running on greater than small heap.

Displaying the Current Value

Use the following command the display the current value of the container aware JVM Parameters using the following:

docker container run -it --rm openjdk:17.0.2-slim java -XX:+PrintFlagsFinal -version | grep -E ".*RAMPercentage"

Expect to see something like the following:

   double InitialRAMPercentage                     = 1.562500
                   {product} {default}
   double MaxRAMPercentage                         = 25.000000
                   {product} {default}
   double MinRAMPercentage                         = 50.000000
                   {product} {default}

Checking the Current Memory and CPU using JShell

  1. Open a jshell in the container using the following:

    docker container run -it --rm openjdk:17.0.2-slim jshell

  2. Paste the following command in jshell:

    var rt = Runtime.getRuntime();
System.out.printf("Heap size: %dMB%nMaximum size of heap: %dMB%nAvailable processors: %d%n", 
 rt.totalMemory()/1024/1024, rt.maxMemory()/1024/1024, rt.availableProcessors());

  3. Press enter.

    Expect to see something similar to the following:

    rt ==> java.lang.Runtime@1d81eb93
Heap size: 252MB
Maximum size of heap: 3966MB
Available processors: 16
$2 ==> java.io.PrintStream@34c45dca

  4. Type the following in jshell and press enter.

    /exit

Allocating a Memory and CPU to a Container

  1. Execute the following command to allocate 100mb of memory and 1 CPU to the container:

    docker container run -it --rm -m 100m --cpus=1 openjdk:17.0.2-slim jshell

  2. Paste the following command in jshell:

    var rt = Runtime.getRuntime();
System.out.printf("Heap size: %dMB%nMaximum size of heap: %dMB%nAvailable processors: %d%n", 
 rt.totalMemory()/1024/1024, rt.maxMemory()/1024/1024, rt.availableProcessors());

  3. Press enter.

    Expect to see something similar to the following:

    rt ==> java.lang.Runtime@6659c656
Heap size: 7MB
Maximum size of heap: 48MB
Available processors: 1
$2 ==> java.io.PrintStream@2d8e6db6

    Notice the following:

    Value
    Heap size 7MB
    Maximum size of heap 48MB
    Available processors 1

  4. Type the following in jshell and press enter.

    /exit

Modifying the Allocated Maximum Size of Heap Memory

  1. Execute the following command to allocate 100mb of memory and 1 CPU to the container:

    docker container run -it --rm -m 100m --cpus=1 openjdk:17.0.2-slim jshell -R-XX:MinRAMPercentage=80

  2. Paste the following command in jshell:

    var rt = Runtime.getRuntime();
System.out.printf("Heap size: %dMB%nMaximum size of heap: %dMB%nAvailable processors: %d%n", 
 rt.totalMemory()/1024/1024, rt.maxMemory()/1024/1024, rt.availableProcessors());

  3. Press enter.

    Expect to see something similar to the following:

    rt ==> java.lang.Runtime@6659c656
Heap size: 7MB
Maximum size of heap: 77MB
Available processors: 1
$2 ==> java.io.PrintStream@2d8e6db6

    Notice the Maximum size of heap become 77MB. This is because of the JVM argument -XX:MinRAMPercentage=80 passed in jshell as:

    -R-XX:MinRAMPercentage=80

    We use the --XX:MinRAMPercentage=80 because the memory allocated is a small heap.

  4. Type the following in jshell and press enter.

    /exit

© 2024 Ron and Ella Wiki Page

Theme by Anders Noren — Up ↑