Open Source For You — December 2017

90 | DECEMBER 2017 | OPEN SOURCE FOR YOU | http://www.OpenSourceForU.com

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5. Services

• Service broker: Cloud Foundry has external components
  like a database, SaaS applications and platform features
  (e.g., the platform can offer services for analytics or
  machine learning), which are classified as services. These
  services can be bound to an application and be consumed
  by it. The service broker is responsible for provisioning an
  instance of the service and binding it to the application.

6. Messaging

• The platform’s component VMs communicate with each
  other and share messages over HTTP and HTTPS. This
  component is responsible for sharing messages, and also
  storing long-lived data (like the IP address of a container in
  a Consul server) and short-lived data (like application status
  and heartbeat messages) on Diego’s bulletin board system.

7. Metrics and logging

• Metrics collector: This collects statistics from the
  components, which are used for book-keeping and health
  management by the framework as well as by the operators
  managing the infrastructure.


• Loggregator: Applications built on top of the Cloud
  Foundry stack need to write their logs on the system output
  streams. These streams are received by the Loggregator,
  which can be used to redirect them to file systems,
  databases or to external log management services.
  Cloud Foundry is a highly scalable, easy-to-manage, open
  source platform that can be used to develop applications of all
  types and sizes. To get further information about the ecosystem,
  you can visit https://www.cloudfoundry.org.

to download, and how to configure the apps to communicate

with bound services. Services are often externally managed

components that may or may not be hosted on the Cloud

Foundry stack (examples include databases, caches, etc). They

are available in the marketplace, and can be consumed by the

application by binding to them.

Cloud Foundry architecture

Cloud Foundry components can be broadly classified

under the following categories.

1. Routing

• Router: This is the entry point into the Cloud Foundry (CF)
  instance. CF provides REST services for administration
  purposes too. So, the call is initially received by the router
  and redirected to the cloud controller, if it’s an administration
  call, or to an application running on the stack.

2. Authentication

• User account and authentication (UAA) server: The role of
  the UAA server is to log in users and issue OAuth tokens
  for those logged in, which can be used by the applications.
  It can also provide SSO services, and has endpoints for
  registering OAuth clients and user management functions.

3. Application life cycle

• Cloud connector: The cloud connector is responsible for
  the deployment of applications. When you push an app to
  CF, it reaches the cloud connector, which coordinates with
  other components and deploys the application on individual
  cells in your space.


• Application availability components (nsync, BBS
  and Cell Reps): These components are responsible
  for the health management of the applications. They
  constantly monitor an application’s state and reconcile
  them with their expected states, starting and stopping
  processes as required.

4. App storage and execution

• BLOB storage: This is binary storage, which stores your
  application binaries and the buildpacks that are used to run
  the applications.


• Application execution framework (Diego): Application
  instances, application tasks and staging tasks all run as
  Garden containers on the Diego cell VMs. The Diego cell rep
  component manages the life cycle of those containers and the
  processes running in them. It reports their status to the Diego
  BBS, and emits their logs and metrics to Loggregator.

Figure 1: Cloud landscapes

Figure 2: Cloud Foundry architecture

By: Shiva Saxena

The author is a FOSS enthusiast. He currently works as a

consultant, and is involved in developing enterprise application

and Software-as-a-Service (SaaS) products. He has hands-on

development experience with Android, Apache Camel, C#, .NET,

Hadoop, HTML5, Java, OData, PHP, React, etc, and loves to

explore new and bleeding-edge technologies. He can be reached

at [email protected].

Metrics Collector Loggregator

Service Broker

Application Execution

Framework

Cloud Controller Application availability services

UAA Server

Router Routing

Authentication

App Lifecycle

App Storage

and Execution

Metrics and

Logging

Messaging

Services

BLOS Store

Components for internal communication between VMs