|
Note
|
This repository contains the guide documentation source. To view the guide in published form, view it on the Open Liberty website. |
Explore how to report and check the health of a microservice with MicroProfile Health.
You will learn how to use MicroProfile Health to report the health status of microservices and take appropriate actions based on this report.
MicroProfile Health allows services to report their health, and it publishes the overall health status to a defined
endpoint. A service reports UP if it is available and reports DOWN if it is unavailable. MicroProfile Health reports
an individual service status at the endpoint and indicates the overall status as UP if all the services are UP. A service
orchestrator can then use the health statuses to make decisions.
A service checks its own health by performing necessary self-checks and then reports its overall status by implementing the API provided by MicroProfile Health. A self-check can be a check on anything that the service needs, such as a dependency, a successful connection to an endpoint, a system property, a database connection, or the availability of required resources.
You will add self-checks to the system and inventory services, which have been provided for you, and implement what is
necessary to report health status by using MicroProfile Health.
The finish directory in the root directory of this guide contains two services that are configured
to use MicroProfile Health. Feel free to give them a try before you proceed.
To try out the services, navigate to the finish directory and then run the Maven install and
liberty:start-server goals to build the services and run them in Open Liberty:
cd finish mvn install liberty:start-server
The system and inventory services can be found at the following URLs:
Visit the http://localhost:9080/health URL to see the health report of the two services as well as the overall
health status of the application. One check shows the state of the system service, and the other shows the state of
the inventory service. As you might expect, both services are in the UP state, and the overall health status of
the application is UP.
When you are done checking out the services, stop the Open Liberty server by running the following command:
mvn liberty:stop-server
Navigate to the start directory to begin.
A health report will be generated automatically for all services that enable MicroProfile Health. The
mpHealth feature has already been enabled for you in the src/main/liberty/config/server.xml
file.
All services must provide an implementation of the HealthCheck interface, which will be used to
verify their health.
server.xml
link:finish/src/main/liberty/config/server.xml[role=include]Create theSystemHealthclass.src/main/java/io/openliberty/guides/system/SystemHealth.java
SystemHealth.java
link:finish/src/main/java/io/openliberty/guides/system/SystemHealth.java[role=include]The @Health annotation indicates that this particular bean implements the
HealthCheck interface. By pairing this annotation with the ApplicationScoped
context from the Contexts and Dependency Injections API, the bean is discovered
automatically when the http://localhost:9080/health endpoint receives a request.
The call() method is used to return the health status of a particular service.
In this case, you are simply checking if the server name is defaultServer and
returning UP if it is, and DOWN otherwise. The
HealthCheckResponse.named() method is used to indicate what service the health
check is done for. Overall, this is a very simple implementation of the call()
method. In a real development environment, you would want to orchestrate much more meaningful
health checks.
Create theInventoryHealthclass.src/main/java/io/openliberty/guides/inventory/InventoryHealth.java
InventoryHealth.java
link:finish/src/main/java/io/openliberty/guides/inventory/InventoryHealth.java[role=include]This time, you are checking whether or not the service is in maintenance or if it’s down.
For simplicity, the custom io_openliberty_guides_inventory_inMaintenance
MicroProfile Config property defined in the resources/CustomConfigSource.json
file is used to indicate whether the service is in maintenance or not. This file has already
been created for you. To check if the service is down, simply make a HTTP GET request to
the system service and check the status returned by the response. You make a GET request
to the system service rather than the inventory service because the inventory service
depends on the system service. In other words, the inventory service wouldn’t work if
the system service is down. If the status is not 200, then the service is not running.
Based on these two factors, the isHealthy() method returns whether
or not the inventory service is healthy.
If you are curious about the injected inventoryConfig object or if
you want more information on MicroProfile Config, see
Configuring microservices.
CustomConfigSource.json
link:finish/resources/CustomConfigSource.json[role=include]While the server is running, navigate to the http://localhost:9080/health URL to find the the health report on the two services.
Put the inventory service in maintenance by setting the io_openliberty_guides_inventory_inMaintenance
property to true in the resources/CustomConfigSource.json file. Because
this configuration file is picked up dynamically, simply refresh the http://localhost:9080/health
URL you will see that the state of the inventory service has changed to DOWN. The
overall state of the application has also changed to DOWN as a result. Point to the
http://localhost:9080/inventory/systems URL to verify that the inventory service is
indeed in maintenance. Set the io_openliberty_guides_inventory_inMaintenance
property back to false once you are done.
CustomConfigSource.json
link:finish/resources/CustomConfigSource.json[role=include]You will implement two test methods, testIfServicesAreUp() and testIfInventoryServiceIsDown(), to
validate the health of the system and inventory services.
Create theHealthTestclass.src/test/java/it/io/openliberty/guides/health/HealthTest.java
HealthTest.java
link:finish/src/test/java/it/io/openliberty/guides/health/HealthTest.java[role=include]Let’s break down the test cases:
-
The
testIfServicesAreUp()test case compares the generated health report with the actual status of the services. -
The
testIfInventoryServiceIsDown()test case puts theinventoryservice in maintenance by setting theio_openliberty_guides_inventory_inMaintenanceproperty totrueand then compares the generated health report with the actual status of the service.
A few more tests have been included to verify the basic functionalitiy of the system and inventory
services. They can be found under the src/test/java/it/io/openliberty/guides/inventory/InventoryEndpointTest.java
and src/test/java/it/io/openliberty/guides/system/SystemEndpointTest.java files.
If a test failure occurs, then you might have introduced a bug into the code. These tests
will run automatically as a part of the Maven build process when you run the mvn install
command. You can also run these tests separately from the build by using the mvn verify
command, but first make sure that the server is stopped.
CustomConfigSource.json
link:finish/resources/CustomConfigSource.json[role=include]InventoryEndpointTest.java
link:finish/src/test/java/it/io/openliberty/guides/inventory/InventoryEndpointTest.java[role=include]SystemEndpointTest.java
link:finish/src/test/java/it/io/openliberty/guides/system/SystemEndpointTest.java[role=include]-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running it.io.openliberty.guides.health.HealthTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 3.504 sec - in it.io.openliberty.guides.health.HealthTest
Running it.io.openliberty.guides.inventory.InventoryEndpointTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.326 sec - in it.io.openliberty.guides.inventory.InventoryEndpointTest
Running it.io.openliberty.guides.system.SystemEndpointTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.011 sec - in it.io.openliberty.guides.system.SystemEndpointTest
Results :
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0To see whether the tests detect a failure, manually change the configuration of
io_openliberty_guides_inventory_inMaintenance from false to true
in the resources/CustomConfigSource.json file. Re-run the Maven build. You will see a
test failure occur because the initial status of the inventory service is DOWN.
You just learned how to add health checks to report the states of microservices by using MicroProfile Health in Open Liberty. Then, you wrote tests to validate the generated health report.
Feel free to try one of the related MicroProfile guides. They demonstrate additional technologies that you can learn and expand on top of what you built here.