Note
|
This repository contains the guide documentation source. To view the guide in published form, view it on the Open Liberty website. |
Learn how to containerize and run your microservices with Open Liberty using Docker.
You can easily deploy your microservices in different environments in a lightweight and portable manner by using containers. From development to production and across your DevOps environments, you can deploy your microservices consistently and efficiently with containers. You can run a container from a container image. Each container image is a package of what you need to run your microservice or application, from the code to its dependencies and configuration.
You’ll learn how to build container images and run containers using Docker for your microservices.
You’ll construct Dockerfile
files, create Docker images by using the docker build
command, and run the image as Docker containers
by using docker run
command.
The two microservices that you’ll be working with are called system
and inventory
. The system
microservice returns the JVM system properties
of the running container. The inventory
microservice adds the properties from the system
microservice to the inventory. This guide demonstrates how both microservices can run and communicate
with each other in different Docker containers.
Before you begin, Docker needs to be installed. For installation instructions, refer to the official Docker documentation. You will build and run the microservices in Docker containers.
Make sure to start your Docker daemon before you proceed.
Navigate to the start
directory to begin.
You can find the starting Java project in the start
directory. It is a multi-module Maven project that is made up of the system
and inventory
microservices. Each microservice lives in its own corresponding directory, system
and inventory
.
To try out the microservices by using Maven, run the following Maven goal to build the system
microservice and run it inside Open Liberty:
mvn -pl system liberty:run
Open another command-line session and run the following Maven goal to build the inventory
microservice and run it inside Open Liberty:
mvn -pl inventory liberty:run
To access the inventory
service, which displays the current contents of the inventory, see http://localhost:9081/inventory/systems.
The system
service shows the system properties of the running JVM and can be found at http://localhost:9080/system/properties.
The system properties of your localhost can be added to the inventory
at http://localhost:9081/inventory/systems/localhost.
After you are finished checking out the microservices, stop the Open Liberty servers by pressing CTRL+C
in the command-line sessions where you ran the servers. Alternatively, you can run the liberty:stop
goal in another command-line session:
mvn -pl system liberty:stop
mvn -pl inventory liberty:stop
Run the Maven package
goal to build the application .war
files from the start
directory so that the .war
files reside in the system/target
and inventory/target
directories.
mvn package
To learn more about RESTful web services and how to build them, see
Creating a RESTful web service for details about how to build the system
service.
The inventory
service is built in a similar way.
A Docker image is a binary file. It is made up of multiple layers and is used to run code in a Docker container. Images are built from instructions in Dockerfiles to create a containerized version of the application.
A Dockerfile
is a collection of instructions for building a Docker image that can then be run as a container.
As each instruction is run in a Dockerfile
, a new Docker layer is created. These layers, which are known as intermediate images, are created when a change is made to your Docker image.
Every Dockerfile
begins with a parent or base image over which various commands are run. For example, you can start your image from scratch and run commands that download and install a Java runtime, or you can start from an image that already contains a Java installation.
Learn more about Docker on the official Docker page.
You will be creating two Docker images to run the inventory
service and system
service. The first step is to create Dockerfiles for both services.
Create theDockerfile
for the inventory service.inventory/Dockerfile
inventory/Dockerfile
link:finish/inventory/Dockerfile[role=include]
The FROM
instruction initializes a new build stage, which indicates the parent image of the built image. If you don’t need a parent image, then you can use FROM scratch
, which makes your image a base image.
In this case, you’re using the recommended production image,
openliberty/open-liberty:kernel-java8-openj9-ubi
, as your parent image. If you
don’t want any additional runtime features for your kernel
image, define the
FROM
instruction as FROM open-liberty:kernel
. To use the default image that
comes with the Open Liberty runtime, define the FROM
instruction as FROM
open-liberty
. You can find all the official images and
ubi images on the open-liberty Docker Hub.
It is also recommended to label your Docker images with the LABEL
command, as the label information can help you manage your images. For more information, see Best practices for writing Dockerfiles.
The COPY
instructions are structured as COPY
[--chown=<user>:<group>]
<source>
<destination>
.
They copy local files into the specified destination within your Docker image.
In this case, the inventory
server configuration files that are located at src/main/liberty/config
are copied to the /config/
destination directory.
The inventory
application WAR file inventory.war
, which was created from running mvn package
, is copied to the /config/apps
destination directory.
The COPY
instructions use the 1001
user ID and 0
group because the openliberty/open-liberty:kernel-java8-openj9-ubi
image runs by default with the USER 1001
(non-root) user for security purposes. Otherwise, the files and directories that are copied over are owned by the root user.
Place the RUN configure.sh
command at the end to get a pre-warmed Docker image. It improves the startup time of running your Docker container.
The Dockerfile
for the system
service follows the same instructions as the inventory
service, except that some labels
are updated, and the system.war
archive is copied into /config/apps
.
Create theDockerfile
for the system service.system/Dockerfile
system/Dockerfile
link:finish/system/Dockerfile[role=include]
Now that your microservices are packaged and you have written your Dockerfiles, you will build your Docker images by using the docker build
command.
Run the following commands to build container images for your application:
docker build -t system:1.0-SNAPSHOT system/.
docker build -t inventory:1.0-SNAPSHOT inventory/.
The -t
flag in the docker build
command allows the Docker image to be labeled (tagged) in the name[:tag]
format.
The tag for an image describes the specific image version. If the optional [:tag]
tag is not specified, the latest
tag is created by default.
To verify that the images are built, run the docker images
command to list all local Docker images:
docker images
Or, run the docker images
command with --filter
option to list your images:
docker images -f "label=org.opencontainers.image.authors=Your Name"
Your two images, inventory
and system
, should appear in the list of all Docker images:
REPOSITORY TAG IMAGE ID CREATED SIZE inventory 1.0-SNAPSHOT 08fef024e986 4 minutes ago 471MB system 1.0-SNAPSHOT 1dff6d0b4f31 5 minutes ago 470MB
Now that you have your two images built, you will run your microservices in Docker containers:
docker run -d --name system -p 9080:9080 system:1.0-SNAPSHOT
docker run -d --name inventory -p 9081:9081 inventory:1.0-SNAPSHOT
The flags are described in the table below:
Flag | Description |
---|---|
-d |
Runs the container in the background. |
--name |
Specifies a name for the container. |
-p |
Maps the host ports to the container ports. For example: |
Next, run the docker ps
command to verify that your containers are started:
docker ps
Make sure that your containers are running and show Up
as their status:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 2b584282e0f5 inventory:1.0-SNAPSHOT "/opt/ol/helpers/run…" 2 seconds ago Up 1 second 9080/tcp, 9443/tcp, 0.0.0.0:9081->9081/tcp inventory 99a98313705f system:1.0-SNAPSHOT "/opt/ol/helpers/run…" 3 seconds ago Up 2 seconds 0.0.0.0:9080->9080/tcp, 9443/tcp system
If a problem occurs and your containers exit prematurely, the containers don’t appear in the container
list that the docker ps
command displays. Instead, your containers appear with an Exited
status when they run the docker ps -a
command. Run the docker logs system
and docker logs inventory
commands to view the
container logs for any potential problems. Run the docker stats system
and docker stats inventory
commands to display a live stream of usage statistics for your containers. You can also double-check that your Dockerfiles are correct. When you
find the cause of the issues, remove the faulty containers with the docker rm system
and docker rm inventory
commands. Rebuild
your images, and start the containers again.
To access the application, point your browser to the http://localhost:9081/inventory/systems URL. An empty list is expected because no system properties are stored in the inventory yet.
Next, retrieve the system
container’s IP address by using the system
container’s name that is defined when it ran the Docker containers.
Run the following command to retrieve the system
IP address:
docker inspect -f "{{.NetworkSettings.IPAddress }}" system
You find the system
container’s IP address:
172.17.0.2
In this case, the IP address for the system
service is 172.17.0.2
. Take note of this IP address to add the system properties to the inventory
service.
Point your browser to http://localhost:9081/inventory/systems/[system-ip-address]
by replacing [system-ip-address]
with the IP address you obtained earlier.
You see a result in JSON format with the system properties of your local JVM. When you visit this URL, these system
properties are automatically stored in the inventory. Go back to http://localhost:9081/inventory/systems and
you see a new entry for [system-ip-address]
.
inventory/server.xml
link:finish/inventory/src/main/liberty/config/server.xml[role=include]
As mentioned at the beginning of this guide, one of the advantages of using containers is that they are portable and can be moved and deployed efficiently across all of your DevOps environments. Configuration often changes across different environments, and by externalizing your server configuration, you can simplify the development process.
Imagine a scenario where you are developing an Open Liberty application on
port 9081
but to deploy it to production, it must be available
on port 9091
. To manage this scenario, you can keep two different versions of the
server.xml
file; one for production and one for development. However, trying to
maintain two different versions of a file might lead to mistakes. A better
solution would be to externalize the configuration of the port number and use the
value of an environment variable that is stored in each environment.
In this example, you will use an environment variable to externally configure the
HTTP port number of the inventory
service.
In the inventory/server.xml
file, the default.http.port
variable is declared and is used in the
httpEndpoint
element to define the service
endpoint. The default value of the default.http.port
variable is 9081
. However, this value is only used if no other value is
specified. To find a value for this variable, Open Liberty looks for the
following environment variables, in order:
-
default.http.port
-
default_http_port
-
DEFAULT_HTTP_PORT
When you previously ran the inventory
container, none of the environment variables mentioned were defined and thus the default value of 9081
was used.
Run the following commands to stop and remove the inventory
container and rerun it with the default.http.port
environment variable set:
docker stop inventory
docker rm inventory
docker run -d --name inventory -e default.http.port=9091 -p 9091:9091 inventory:1.0-SNAPSHOT
The -e
flag can be used to create and set the values of environment variables
in a Docker container. In this case, you are setting the default.http.port
environment
variable to 9091
for the inventory
container.
Now, when the service is starting up, Open Liberty finds the
default.http.port
environment variable and uses it to set the value of the
default.http.port
variable to be used in the HTTP
endpoint.
The inventory
service will now be available on the new port number you
specified. You can see the contents of the inventory at
http://localhost:9091/inventory/systems.
You can add your local system properties at
http://localhost:9091/inventory/systems/[system-ip-address]
by
replacing [system-ip-address]
with the IP address you obtained in the previous
section. The system
service remains unchanged and is available at
http://localhost:9080/system/properties
You can externalize the configuration of more than just the port numbers. To learn more about Open Liberty server configuration, check out the Server Configuration Overview docs.
You can test your microservices manually by hitting the endpoints or with automated tests that check your running Docker containers.
Create theSystemEndpointIT
class.system/src/test/java/it/io/openliberty/guides/system/SystemEndpointIT.java
SystemEndpointIT.java
link:finish/system/src/test/java/it/io/openliberty/guides/system/SystemEndpointIT.java[role=include]
The testGetProperties()
method checks for a 200
response code from the system
service endpoint.
Create theInventoryEndpointIT
class.inventory/src/test/java/it/io/openliberty/guides/inventory/InventoryEndpointIT.java
InventoryEndpointIT.java
link:finish/inventory/src/test/java/it/io/openliberty/guides/inventory/InventoryEndpointIT.java[role=include]
-
The
testEmptyInventory()
method checks that theinventory
service has a total of 0 systems before anything is added to it. -
The
testHostRegistration()
method checks that thesystem
service was added toinventory
properly. -
The
testSystemPropertiesMatch()
checks that thesystem
properties match what was added into theinventory
service. -
The
testUnknownHost()
method checks that an error is raised if an unknown host name is being added into theinventory
service. -
The
systemServiceIp
variable has the same value as what you retrieved in the previous section when manually adding thesystem
service into theinventory
service. This value of the IP address is passed in when you run the tests.
Run the Maven package
goal to compile the test classes. Run the Maven failsafe
goal to test the services that are running in the Docker containers by replacing the [system-ip-address]
with the IP address that you determined previously.
mvn package
mvn failsafe:integration-test -Dsystem.ip=[system-ip-address] -Dinventory.http.port=9091 -Dsystem.http.port=9080
If the tests pass, you see a similar output as the following:
------------------------------------------------------- T E S T S ------------------------------------------------------- Running it.io.openliberty.guides.system.SystemEndpointIT Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.653 s - in it.io.openliberty.guides.system.SystemEndpointIT Results: Tests run: 1, Failures: 0, Errors: 0, Skipped: 0 ------------------------------------------------------- T E S T S ------------------------------------------------------- Running it.io.openliberty.guides.inventory.InventoryEndpointIT Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.935 s - in it.io.openliberty.guides.inventory.InventoryEndpointIT Results: Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
When you are finished with the services, run the following commands to stop and remove your containers:
docker stop inventory system
docker rm inventory system
You have just built Docker images and run two microservices on Open Liberty in containers.