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-serverThe 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-serverNavigate to the start directory to begin.
A health report will be generated automatically for all services that enable MicroProfile Health. This
feature has already been enabled for you in the src/main/liberty/config/server.xml file:
<feature>mpHealth-1.0</feature>All services must provide an implementation of the HealthCheck interface, which will be used to
verify their health.
Implement the HealthCheck interface in the src/main/java/io/openliberty/guides/system/SystemHealth.java file:
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.
Implement the HealthCheck interface in the src/main/java/io/openliberty/guides/inventory/InventoryHealth.java file:
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,
a 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.
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.
You will implement two test methods, testIfServicesAreUp() and testIfInventoryServiceIsDown(), to
validate the health of the system and inventory services.
Begin by creating a test class in the src/test/java/it/io/openliberty/guides/health/HealthTest.java file:
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 cases 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.
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T E S T S
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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. 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.