Short Lived Microservice using spring-cloud-starter-task

Tasks in spring boot are generally used for short lived microservices. This example microservice sends http GET request and log the response using Spring Cloud Task.

Use case

• run microservice as task (short live microservice) and stop automatically once the HTTP request finished.
• send HTTP GET inside commandLineRunner
• configure Http base url in application.yml
• deploy service on Cloud Foundry

Deploy service on Cloud Foundry

1. compile app and create jar

    mvn clean install
   

2. Push an app using --health-check-type none and no-route parameters

   cf push -f manifest-dev.yml --health-check-type none --no-route --no-start

   Notice: In general, CF tasks has no routes as they are meant to perform background tasks.

3. Run this app as cf task

   cf run-task task-service ".java-buildpack/open_jdk_jre/bin/java org.springframework.boot.loader.JarLauncher" --name "task-service"

   syntax: cf.exe run-task APP_NAME COMMAND [-k DISK] [-m MEMORY] [--name TASK_NAME]

Trigger task automatically

1. CF tasks can be scheduled using jobs. There is a service broker available in PCF marketplace.https://network.pivotal.io/products/p -scheduler-for-pcf

cf create-job task-service task-service-job ".java-buildpack/open_jdk_jre/bin/java org.springframework.boot.loader.JarLauncher"

2 run job

cf run-job task-service

create schedule for the job. This enables job to be execute after defined time interval. The scheduler accepts MIN HOUR DAY-OF-MONTH MONTH DAY-OF-WEEK format. For instance, the following will execute task-service-job on 5th of every month at 10:00am

cf schedule-job task-service-job "0 10 5 * ? *"

#Troubleshooting

• Pivotal Scheduler CLI plugin is required to interact with cf jobs https://network.pivotal.io/products/p-scheduler-for-pcf

• The example spring boot app does not have "spring-boot-starter-web" dependency in pom.xml. Including the mentioned dependency will keep the app always in "Running" state. The goal is to create short-lived microservice as described in use case section.

<dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-web</artifactId>
 </dependency>  

References

Spring Cloud Task: https://spring.io/projects/spring-cloud-task

cf tasks: https://docs.cloudfoundry.org/devguide/using-tasks.html

cf jobs: https://docs.pivotal.io/scheduler/1-2/using-jobs.html