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layout: page title: "Introducing a new re-usable component with CloudSim Express" permalink: /examples/introducing-new-reusable-component

Introducing a new re-usable component with CloudSim Express

Please refer to README.md for a detailed description about re-usable components.

In this example, we are going to introduce a new re-usable component and use it in the system model script.

We will create a new component to represent a zone monitor. It is a part of the zone, alongside wih the datacenter, broker, and workload generator.

Unlike in other examples that we worked with extensions, this task involves extending CloudSim Express. Therefore, it is recommended to avoid this approach as much as possible to avoid excess development overhead, if there is an alternative approach to define the scenario using existing components.

Defining schematics and writing handlers

  1. CloudSim Express needs to know the schematics of the new component. To add that information, open simulation-elements.yaml file.
  2. Add the following object. 
        ZoneMonitor:
       type: object
       properties:
          name:
             type: string
  3. Add our ZoneMonitor as an attribute of the Zone. 
        Zone:
        ~ Everything else
        monitor:
          $ref: '#/components/schemas/ZoneMonitor'
  4. Build the core component by executing mvn clean install inside the module folder. This will generate PoJo for the new component.
  5. In our design, the ZoneMonitor will do nothing but print its name, for the simplicity. Even to do that, we need to integrate it into the system model building process. Here are the steps of system model building with default component and their handlers.
    • When a Zone component is set as the simulation system model, then at first, its handler's handle method is called. With vanilla CloudSim Express, the handle method of DefaultZoneHandler.java is called. Within that, the subsequent handlers are called to build the CloudSim system model in a top-down approach. Feel free to traverse through the code of the DefaultZoneHandler.java.
  6. Therefore, firstly we need to create a custom handler for our new component to convert YAML object into Java logic. Afterward, to integrate the custom handler, we need to override the default zone handler and call our custom handler in it's handle method. For both, we create a custom handler and an extended zone handler as extensions, in a new java project.
    1. Create a simple Maven project.
      1. Go to a new folder.
      2. Execute mvn archetype:generate -DarchetypeGroupId=org.apache.maven.archetypes -DarchetypeArtifactId=maven-archetype-simple -DarchetypeVersion=1.4
        • Pre-requisite: Maven
      3. Enter followings when prompted.
        1. groupId = org.cloudbus.cloudsim.express.examples
        2. artifactId = custom-reusable-component
        3. version = 1.0-SNAPSHOT
        4. package = org.cloudbus.cloudsim.express.examples
        5. Press Enter to confirm.
      4. Configure dependencies.
        1. Go to the custom-reusable-component project folder.
        2. Open pom.xml
        3. Within the <dependencies> tag, copy the following to declare CloudSim Express as a dependency
          • Pre-requisite: You must build cloudsim-express project at least once.
          • Copy and paste the following. 
            <dependency>
    <artifactId>cloudsim-express-extensions</artifactId>
    <groupId>org.cloudbus.cloudsim.cloudsim-express</groupId>
    <version>0.1-SNAPSHOT</version>
</dependency>
        4. Create the custom component handler class in the /src/main/java/org/cloudbus/cloudsim/express/examples/ folder by creating a new file CustomZoneMonitorHandler.java. Also create the extended zone handler by creating a new file CustomZoneHandler.java
          • Delete the generated App.java file.
        5. Implement the logic accordingly.
        6. Build the project by executing mvn clean install from the project root directory (i.e., where the pom.xml file resides).

Deploying the new re-usable component

  1. Build the CloudSim Express project by executing mvn clean install at its root.
  2. Extract the <cloudsim-express-root>/release-artifacts/cloudsim-express.zip, and copy the updated simulator.jar file to the CloudSim Express tool that we used for previous examples, and replace the existing simulator.jar with that.
    • Alternatively, you can get the whole new release, extract, and use. But then again we need to update the system model script in that case. Therefore, we only update the simulator component to make it much easier.
  3. Copy the custom-reusable-component jar file from <custom-workload-generator>/target/custom-reusable-component-1.0-SNAPSHOT.jar, to cloudsim-express-tool-location/extensions.
  4. Modify the system-model.yaml to use the custom workload generator.
    • From: 
      ...
Zone: &Zone
name: "default zone"
datacenter: *Datacenter
broker:
 variant:
    className: "org.cloudbus.cloudsim.DatacenterBroker"
 name: "RegionalBroker"
workloadGenerator:
 variant:
   className: "org.crunchycookie.research.distributed.computing.cloudsim.workload.impl.DummyWorkloadGenerator"   
...
    • To: 
      ...
Zone: &Zone
name: "default zone"
datacenter: *Datacenter
broker:
 variant:
    className: "org.cloudbus.cloudsim.DatacenterBroker"
 name: "RegionalBroker"
workloadGenerator:
 variant:
   className: "org.crunchycookie.research.distributed.computing.cloudsim.workload.impl.DummyWorkloadGenerator"   
monitor:
 name: "This is the newly introduced re-usable component"
...
  5. Register new element handlers with high priority. Open configs.properties file, and add both custom handlers before the default zone handler. From:
# priority list is used to determine which handler to select.
element.handler.priority.1=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultDatacenterCharacteristicsHandler
element.handler.priority.2=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultDatacenterHandler
element.handler.priority.3=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultGlobalDatacenterNetworkHandler
element.handler.priority.4=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultHostHandler
element.handler.priority.5=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultProcessingElementHandler
element.handler.priority.6=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultZoneHandler

To:

# priority list is used to determine which handler to select.
element.handler.priority.1=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultDatacenterCharacteristicsHandler
element.handler.priority.2=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultDatacenterHandler
element.handler.priority.3=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultGlobalDatacenterNetworkHandler
element.handler.priority.4=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultHostHandler
element.handler.priority.5=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultProcessingElementHandler
element.handler.priority.6=org.cloudbus.cloudsim.express.examples.CustomZoneHandler
element.handler.priority.7=org.cloudbus.cloudsim.express.examples.CustomZoneMonitorHandler
element.handler.priority.8=org.cloudbus.cloudsim.express.handler.impl.cloudsim.DefaultZoneHandler
  1. Executes the simulation via sh ./cloudsim-express.sh
  2. Check the CloudSim Express logs and observe the printed message by the custom component handler. 
    ...
This is the newly introduced re-usable component
[main] INFO  org.cloudbus.cloudsim.express.manager.impl.CloudSimSimulationManager - Starting CloudSim simulation
...

The newly introduced component ZoneMonitor, can now be used to defined different system models.

Materials

The related materials are included in the resources folder.