DevOps Interview Questions

It is a collaboration or blending of software developers and operations people and it is a new concept that has emerged in the Information Technology field. It focuses on delivering software product faster and lowering the failure rate of releases which was usually the case and hence this concept was started and it seems to be growing rapidly.

New software tools have come up to help organizations in automating testing and creating a more streamlined development and release pipeline. This has reduced the errors and the time taken to get the product ready and to release it. It is cross-functional in its nature.

There are many needs of DevOps and some of the important ones are as follows.

It is needed to increase the deployment frequency of a particular product.

It lowers the failure rate of new releases that was very evident before DevOps came into the picture.

It shortens the lead time between fixes. This makes the process less time consuming.

The recovery time in case of a new release crashing is significantly reduced.

Many Industries in the real world use DevOps and it is increasingly becoming popular among the industries and any one of them can be used as an example.
Many e-commerce websites use DevOps and they have had an overall improvement in their processes. One example is about a company called Etsy which was struggling with its existing methods. After using DevOps it has a fully automated deployment pipeline, and its continuous delivery practices have reportedly resulted in more than 50 deployments a day with reduced disruptions.

SSH can be used to handle revision control which would be to post the code on SourceForge or GitHub so everyone can view it.  Also, SSH can be used to post the checklist from the last revision to make sure that any unsolved issues are resolved.

The key principles behind DevOps are as follows.

The main principle behind DevOps is that it creates the continuous deployment. It was mainly created to reduce the various intermediaries between the processes that were making the process long and inefficient. This concept makes the product development a continuous process.

The other important principle of DevOps is the automation that it has brought into the system. The various manual intermediaries have been automated because of the concept of DevOps. Even automated testing has come into the fore.

The other principal of DevOps is monitoring. It has made it easier to monitor the whole process of product development as it is more streamlined and simple. There are a few steps to monitor and most of the IT operations are automated.

Security is another principal behind DevOps. It makes the whole process more secure and since the process is ever improving it makes it more and more secure.

The key areas in relation to application development are as follows.

1. Building the code
   
2. Covering the code
   
3. Testing the units
   
4. Packaging
   
5. Deployment
   
6. Key areas in infrastructure are as follows.
   
7. Provisioning
   
8. Configuration
   
9. Orchestration
   
10. Deployment 
    

The infrastructure code will be in a simple format called JSON.

The JSON code will be organized into files and they are called templates

These templates can be deployed on AWS. After that, they can be managed as stacks

After this the Cloud Formation service will do the Creating, deleting, updating, etc. and other related operations in the stack.

There are various scripting languages that are used in the process of DevOps. However, Python seems to be the most popular and most used scripting language and it is very important that a DevOps engineer has a clear understanding and working knowledge of this scripting language.

DevOps have many advantages to a developer. It makes their life much easier as the process is streamlined and simplified. Other than this it helps the developers to fix the bug and implement new features quickly and also it allows better and clear communication between team members and so the product that is developed will be exactly as per the requirements. Developers have to do coding which is a tough job and DevOps makes it easier.   

• Jenkins
  
• Nagios
  
• Monit
  
• ELK (Elasticsearch, Logstash, Kibana)
  
• Io
  
• Jenkins
  
• Docker
  
• Ansible
  
• Git
  
• Collectd/Collectl

• The different types of Http requests are as follows.
  
• GET
  
• HEAD
  
• PUT
  
• POST
  
• PATCH
  
• DELETE
  
• TRACE
  
• CONNECT
  
• OPTIONS

Memcached is an important aspect of DevOps and it is a free and open source, high-performance, distributed memory object caching system. The main objective of Memcached is to improve the time taken for responding to data that can otherwise be recovered or constructed from some other source or database. It reduces the need to operate SQL database or another source continuously in order to fetch data for the repeated request.

The benefits of Memcached are as follows.

• It helps to speed up the application processes.
  
• It helps to determine what to store and what not to store.
  
• It reduces the number of retrieval requests to the database.
  
• Cuts down the I/O (Input/Output) access (hard disk).
  
• The disadvantages of Memcached are as follows.
  
• It does not act as an ever-present data store.
  
• It cannot be considered as a database.
  
• It is not specific to any application and hence becomes difficult to use.
  
• It does not have the capability to cache large object.
  

The important features of Memcached are as follows.

CAS token is an important feature of Memcached. It is attached to an object retrieved from the cache. The user can use that token to save the updated object.

• It simplifies the code that is present in the process.
• It reduces the delay time of the script which is waiting for results to come back from the server
• The binary protocol can be used instead of ASCII with the newer client
• Memcached helps the user to use binary option and so the client need not always use serialization with complex data. 

The possibility of sharing a single instance of Memcache between multiple projects is present and is high. Memcache is a memory store space, and it can is possible to run Memcache on one or more servers. The user can also configure the client to speak to a particular set of instances. This allows two different Memcache processes to be run on the same host and yet they are completely independent. This will work if the data has not been partitioned, then it becomes necessary to know from which instance to get the data from or to put into.

The Memcached can be updated in the following ways.

Proactively clearing the cache and not waiting for the notifications. Clearing the cache when an insert or update is made will help in keeping Memcache updated.

By resetting the Cache. It is similar to the first method the only difference being rather than just deleting the keys and waiting for the next request for the data to refresh the cache, resetting the values after the insert or update.

There are instances when the cache expires or the websites are hit by several requests that are made by the clients all at the same time. This effect is called as Dogpile effect. This is quite common in occurrence this effect can be prevented by using a semaphore lock. In this system when value expires, the first process acquires the lock and starts generating new value.

The common mistake with the use of Memcached is to use it as a data store, and not as a cache. This is a big error.

Memcached should never be used as the only source of the information that is needed to run the application. Data should always be available through another source as well.

Memcached cannot perform a query over the data or perform over the contents to extract information. Memcached should be used just as a key or value to store.

Memcached does not offer any form of security either in encryption or authentication.