Top Cloud Foundry Interview Questions and Answers -We highlight some common questions you might be asked during a job interview for Cloud Foundry related positions.
Cloud Foundry is an open source, multi cloud application platform as a service (PaaS) governed by the Cloud Foundry Foundation, a 501organization.The software was originally developed by VMware and then transferred to Pivotal Software, a joint venture by EMC, VMware and General Electric .Cloud platforms let anyone deploy network apps or services and make them available to the world in a few minutes. When an app becomes popular, the cloud easily scales it to handle more traffic, replacing with a few keystrokes the build-out and migration efforts that once took months. Cloud platforms represent the next step in the evolution of IT, enabling you to focus exclusively on your applications and data without worrying about underlying infrastructure. Cloud Foundry (CF) has become the industry standard. It is an open source platform that you can deploy to run your apps on your own computing infrastructure, or deploy on an IaaS like AWS, vSphere, or OpenStack. You can also use a PaaS deployed by a commercial CF cloud provider. A broad community contributes to and supports Cloud Foundry. The platform’s openness and extensibility prevent its users from being locked into a single framework, set of app services, or cloud. Cloud Foundry is ideal for anyone interested in removing the cost and complexity of configuring infrastructure for their apps. Developers can deploy their apps to Cloud Foundry using their existing tools and with zero modification to their code.
Originally conceived in 2009, Cloud Foundry was designed and developed by a small team at VMware led by Derek Collison and was originally called Project B29. At the time, a different PaaS project written in Java for Amazon EC2 used the name Cloud Foundry. It was founded by Chris Richardson in 2008 and acquired by SpringSource in 2009, the same year VMWare acquired SpringSource. The current project is unrelated to the project under SpringSource, but the name was adopted when the original Spring Source project ended.

What is Cloud Foundry?
Cloud Foundry is an open source cloud platform as a service (PaaS) on which developers can build, deploy, run and scale applications. VMware originally created Cloud Foundry, and it is now part of Pivotal Software, whose parent company is Dell Technologies. There are a number of public Cloud Foundry offerings available for hosting our site such as IBM BlueMix and Pivotal Web Services (PWS).
How cloud foundry works?
To flexibly serve and scale apps online, Cloud Foundry has subsystems that perform specialized functions. Here’s how some of these main subsystems work. . It simply serves and scale apps online without compiling a very complex code. Cloud Foundry handle more traffic without compromising with the app speed.

What are the different cloud foundry components?
Router: The router maintains a dynamic route table for all applications deployed in a load balanced environment, so you don’t need to worry about updating routing information to reflect changes to a deployed application or the underlying DEAs (which we’ll discuss soon). You can also configure Router for high availability, defining the number of routers you’ll require to support a load balanced Cloud Foundry environment.
Authentication: It Contains an OAuth2 server and login server for user identity management.
Application Lifecycle: It Provides application deployment and management services. It includes the Cloud Controller, a service that pushes or deploys an application to Cloud Foundry; pieces of Cloud Foundry's Diego architecture for the management of containerized applications; and nsync, which monitors the state of an application.
Application Storage and Execution: It Contains a Blobstore repository for large files, as well as Diego Cell, another component of the Diego architecture. Every virtual machine (VM) has a Diego Cell that manages when an application starts and stops, as well as the VM's containers.
Services: It helps link applications to certain services, such as databases Services like MongoDB, Redis etc.
Messaging:  It provides the ability for VMs to communicate through HTTP or HTTPS protocols. It includes the Consul server, which stores long-term control data like component IP addresses, as well as the Bulletin Board System (BBS), which stores data that is updated more frequently, such as application status.
Metrics and Logging: Loggregator; the Loggregator (log aggregator) system streams application logs to developers. Metrics Collector-The metrics collector gathers metrics and statistics from the components. Operators can use this information to monitor a Cloud Foundry deployment.

What are the different layers that define architecture of Cloud Foundry?
Layers of cloud Foundry architecture are:
  • Node Controller
  • Walrus
  • Cloud Controller
  • Storage Controller
  • Cluster Controller
These layers are best in making the cloud environment reliable and developers can perform their tasks simply and quickly. Because of these layers, Cloud Foundry is a best technology.

How the components of cloud Foundry communicate?
By simply posting the messages internally with the help of https protocols and http, components can communicate with each other. It is also possible that they can send NATS messages directly to each other.

What is API in Cloud Foundry?
In Cloud Foundry, There are certain tasks that can simply be performed with the help of API. It is possible to simply construct the apps and then integrating the cloud services with other structure. API also avoids the needs to write lengthy programs and thus save a lot of time. In addition to this, guidance on making the communication possible between different apps can also be assured through API. The API endpoint, or target URL, for your Cloud Foundry instance is the URL of the Cloud Controller. This topic explains how to find your API endpoint from the command line, along with your version of the Cloud Controller API. You can also consult your cloud operator to find out this information.

What is Droplet Execution Engine (DEA)?
A DEA is the core of Cloud Foundry functionality. But before going deeper into DEA itself, it’s worth mentioning some of the tools that help DEA achieve its goal.
Build packs: Build packs are the scripts through which Cloud Foundry identifies the required runtime or framework for the application.
Droplet: Droplet is the Cloud Foundry unit of execution.
Warden: Once the droplet is ready, it will need hosting in a suitable environment. In Cloud Foundry, this is called a Warden container. Wardens isolate ephemeral and resource-controlled environments.

What is CLI?
Command Line Interface (CLI) is an interface to deploy and manage your application in cloud foundry environment. Cloud Foundry’s CLI documentation can be found here.

What is Deployment in Cloud Foundry?
A deployment is something that turns a static release into runnable software on VMs. A Deployment Manifest defines the actual values of parameters needed by a deployment. During a deployment process, BOSH substitutes the parameters in the release and makes the software run on the configuration as planned.

What is BOSH?
BOSH is an open source tool for release engineering, deployment, lifecycle management, and monitoring of distributed systems. BOSH is a tool for deploying all the components we’ve discussed above in distributed nodes. BOSH orchestrates the deployment process of a distributed system. Detailed documentation on BOSH can be found here.

Why is Virtualization required in implementing the Cloud Foundry?
Handling the service level policies is the first thing that demands virtualization in Cloud Foundry. In addition to this, handling cloud operating system is also made easy with virtualization. The most important is virtualization is very useful when it comes to keeping the user level and the backend level concepts different from each other. Moreover, its helps in cutting down the errors that declare their presence time to time.

What do you know about hosting static files in Cloud Foundry?
In Cloud Foundary, after creating the account and setting up the command line interface tool, applications can simply deploy. Generally, static files need a Web server such as Nginx or Apache. The platform undoubtedly takes care of configuration after this and applications can be hosted.

How the users and workspaces are organized by Cloud Foundry?
In Cloud Foundary, Cloud controller or manager can simply define orgs as well as workspaces within assign roles such as auditor, developer and admin to every user to organize user access to control resource use and to the cloud. The UAA server simply braces access control and can store the information of user either internally or externally through SAML and LDAP.

What are the major categories of Cloud Computing?
Three major categories of Cloud Computing:
Infrastructure as a Service (IaaS): which provides only a base infrastructure, leaving the end user responsible for platform and environment configuration necessary to deploy applications. Amazon Web Services and Microsoft Azure are prime examples of IaaS.
Software as a Service (SaaS): It like Gmail or Salesforce.com.
Platform as a Service (PaaS):  which helps to reduce the development overhead (environment configuration) by providing a ready-to-use platform. PaaS services can be hosted on top of infrastructure provided by an IaaS.
Is there any essential things that are being paid attention to before proceeding with cloud foundry?
Although Cloud Foundry is a secure platform, there are certain things that one must consider and they are:
  • Loss of Data
  • Compatibility issues
  • Uptime
  • Business continuity
  • Compliance
  • Data integrity
  • Data Storage
What is nsync, BBS, and CellRep?
Nsync: It receives a message from the Cloud Controller when the user scales an app. It writes the number of instances into a DesiredLRP structure in the Diego BBS database.
BBS: uses its convergence process to monitor the DesiredLRP and ActualLRP values. It launches or kills application instances as appropriate to ensure the ActualLRP count matches the DesiredLRP count.
Cell Rep monitors: It containers and provides the ActualLRP value.

Where resources are stored in Cloud Foundry?
A Git system is there in Cloud foundry that is used on github for controlling simply the buldpacks, source code, important documentation as well as other resources. It is also possible that developers use github for custom configurations. Large binary files like droplets are stored in internal or external blobstore which is maintained by the Cloud Foundry. When it comes to sharing or storing the information which is temporary, Consul and MYSQL is being considered by Cloud Foundry.

 Can you explain system integrators in Cloud Foundry?
In Cloud Foundary, System integrators are very useful in providing a game plan of complex process which is used to design a cloud platform. Integrator enables to build correct private and hybrid cloud network as they are equipped with all the information related to creating data center.

What is the difference between scalability and elasticity in Cloud Foundry?
Scalability is an approach in Cloud Foundry with the help of which blooming workload can be handled by growing in magnitude the supply of resource capacity. On the other side, elasticity reflects the notion of assigning and eliminating of resource capacity on a large amount. Both Scalability and Elasticity are required to derive best results. Also, both these can be considered as the characteristics of Cloud Foundry.

What Security aspects are available with the Cloud Foundry?
Cloud Foundry assures several security aspects and common ones are
Access Control: Users are provided permission to control the access of others who enter the cloud environment
Identity Management: authorizing the application services is done by identity management
Authorization and Authentication: To ensure security, cloud Foundry only allows the authenticated and authorized users to access applications, data or any information.

What do you know about cloud load balancing?
Cloud Foundry installation complete this tasks at three different levels
Cloud Foundry controller simply runs the applications and some other operations on the cloud virtual machines simply balancing the demand.
 Bosch simply comes out with virtual machines on the head of a computing infrastructure. After this, it expands and run cloud foundry on the top of cloud. A manifest document is followed to simply configure this deployment process.
 Router simply route the traffic to Virtual machines that runs the apps in such a way that it start working with a client-provided load balancer.

What are the platforms that are used for the large scale Cloud Foundry?
There are two common platforms that are considered when it comes to large scale Cloud Foundry and they are MapReduce and Apache Hadoop. Both of them are compatible and best in doing their task

What is the difference between Cloud Foundry and traditional data centers?
Traditional data centers were always having issues related to software or hardware and thus a lot of money is required. On the other side Cloud Foundry is a good approach. It doesn’t needs a lot of money to be invested for its maintenance as well as management. Also, in terms of scalability, cloud Foundry is an excellent approach as compare to the traditional data centers.

What is PCF?
Pivotal Cloud Foundry is a cloud-native platform for deploying and operating modern applications adopted by many enterprises. PCF has many moving parts, including your own app code, which means identifying the causes of problems is complicated.

What are benefits of Cloud Foundry?
Benefits of Cloud Foundry
  • Application health management
  • Application portability
  • Application auto-scaling
  • Centralized platform administration
  • Centralized logging
  • Dynamic routing
  • Integration with external logging components like Elasticsearch and Logstash
  • Role based access for deployed applications
  • Support for various IaaS providers
  • Provision for vertical and horizontal scaling
  • Infrastructure security
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