How a Web Crawler Works: Insights into a Modern Web Crawler

In the last few years, internet has become too big and too complex to traverse easily. With the need to be present on the search engine bots listing, each page is in a race to get noticed by optimizing its content and curating data to align with the crawling bots’ algorithms. Similarly,  there are multiple parties who wish to access this data and extract it for their benefit. Hence, to bridge this need gap, web crawlers came into existence.

It is a widely known fact that creating and maintaining a single web crawler across all pages present on the internet is no easy task. It is essential for the crawlers to evolve at the same pace as internet is involving in the current scenario. In order to support this evolution, each crawler should get their basic layout right, so new features and code snippets can be extended upon the same crawler. Following is the basic functionality layout how the crawlers should work.

Extract Data from websites

  1. Seed List: Before a crawler sets out on its journey of traversing a list of sites, it is essential to develop a basic seed list of URLs that would in turn consist of Other URLs on their destination pages, from where we can catapult the web crawlers onto their desired path. This takes care of what URLs and pages a crawler would end up extracting since it would go through all the pages that are connected to the Seed URLs and in turn other URLs that would all be transitively connected and interlinked with this initial set of URLs. The crawler would then follow its inbuilt traversing algorithm via which it shall crawl the connected sets of pages and their nodes horizontally or vertically. Nowadays, most of the websites have a sitemap.xml file with a list of all URLs present on the website, to help the search engine bots discover all pages on visit. You can check out one such sitemap example at: Sitemap.
  1. Fetching the Actual Content: Before starting on its journey, each web crawler has some sort of DB to check against , which maintains a list of all seed URLs. Then it needs to check if various urls from a page need to be crawled, it is often based on update frequency of the site(Sidenote – this is why if you update your site more often, so search engines crawl it more often) . Once the URLs to be crawled have been shortlisted, All the URLs that need to be crawled are pushed into the queue that follows a LIFO/FIFO pattern depending upon the crawler’s algorithm and the URLs are removed as and when they get crawled. In most such setup from technical point of view, queue comes as a handy tool to simplify the architecture of the whole system. After that crawler goes and gets the page and saves it on local machine. Actual fetching of the pages in layman’s terms is similar to going on a webpage and then doing a ‘Right click save’. Bots achieve the similar functionalities in various ways. If the site is more interactive have lot of AJAX interactions, then bots have to be more advanced/custom to get the data.After fetching the data, which is then stored separately for extraction and structuring.
    1. Discovery of new urls and sites: There are over 1 Trillion web pages present on the internet, with more web pages coming up each day. Hence it is not feasible to store all these URLs in the queue manually or even mechanically for that matter. Thus each time a crawler is developed, it is essential to add the Discover function in the web crawler code. This way, you can train a crawler to discover URLs by itself that need to be crawled by hopping from one seed URL to the connecting URL and so forth. Now a days, the way webpages are linked and interlinked, bots go from one page to another. However , if there are standalone pages(silos), which neither link to other pages nor are linked from other pages, they are difficult to discover. So webmasters take extra care to put them in sitemap.xml or add the link for them somewhere on the site so that search engines can reach them easily.
  1. Intelligent crawling: Another important task to perform while Discovery of URLs is to check whether these URLs have been crawled previously in the same crawl or not.
      • Deduplication: While discovering more URLs from each page that is crawled, it is highly possible that the crawler might encounter URLs of web pages it has already crawled earlier, since the internet is nothing but a set of interlinked web pages. In order to avoid recrawling these pages and prevent the crawler from going into a loop, it is essential to perform a deduplication check before crawling a page. If that page has already been crawled, you can push that page to the seed list to make further discovery of pages easier. If not, well then go ahead and crawl the page happily.
  • Frequency Adaptation: Crawlers today have developed a niche set of complex queries that can help prevent the excess load on crawler to crawl the pages multiple times a day and also the pages that get crawled multiple times a day, thereby affecting their load time. Hence, while crawling a page, we run another check to see the last time stamp when that page was updated, per crawl. In case a page is updated more frequently, then it makes sense to crawl that page regularly to identify and report the changes accordingly. If a page is updated less frequently, then it is rude to burden the page’s server with repeated crawl requests and hence it is only polite to ease the burden on the crawlers to crawl the page unnecessarily.
    1. Parsing: Once the pages have been fetched, next task is to get information from it. Search engines use various algorithm and heuristics to find information from the text present on the webpage. So that when we search for particular terms, search engines show up relevant pages based on the information they extracted from these pages. Nowadays there is more focus on semantic markup and semantic results, wherein, search engines try to infer various fields present on the webpage. Various markups suggested by schema.org is another good step which helps site owners, as well as search engines. But core of it is that those micro tags help in parsing and inferring information from the text.
    1. Data Storage: When you are writing a crawler, given the sheer volume, storage of data becomes a big enough problem. Considering the amount of data that is crawled and required on a daily basis, traditional SQL databases are not equipped to handle that sort of volume on routine basis, moreover this data doesn’t have much relational attributes. This is where the Hadoop and other nosql systems come into the picture. It can store and query large amounts of  data  easily and finish the processing it within minutes. Some people also use systems such as Cepth and S3 and other similar services that could be used to store and share data across multiple platforms. At times people have also used flat files with reasonable success.

The above points formulate a jist of what all goes in the making of a modern web crawler. Our crawler does this and much more. Considering all the above mentioned aspects and including them in the web crawlers, has vastly improved our service and has allowed us to get an edge above all other web crawling services functioning in the market. However, this is just a glimpse of how we can help your company get the data log to analyse and build your strategic decisions upon. We believe in continuous improvisations and reiterations to build a crawler that would surpass all.

Looking to extract data from the web? Find out if our DaaS solution is a right fit for your requirements here.

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Software Engineer – Full time

We’re a team of high-tech Engineers working on fresh big data problems. An integral part of our offerings is web-scale crawl and extraction using cloud computing and machine learning techniques. We’re on a quest for innovative ways to solve the business problems of data acquisition and normalization on the web. Our vision is to make PromptCloud a one-stop brand for data and our growth is geared towards that.
Where we are at PromptCloud- We are a bootstrapped company in the mid-growth phase and are planning to quickly expand (not much in terms of personnel) but heavily with respect to the solutions we can provide to big data problems in the market. We started off with international clients and we have pretty much covered the globe at that.

What PromptCloud expects for this role:

– Sound knowledge of Algorithms and OOP concepts
– Proficiency with Linux/Unix (required)
– Knowledge of any one of the scripting languages – Ruby/Perl/Python
– Graduated from a tier-1 college (IITs, NITs, IIITs, BITs) or you’re dead smart to blow us away with your tech skills
– 1 to 3 years of industry experience in a tech role
– Prior experience with a startup or Big Data technologies is a plus
– Prior exposure to web technologies, Rails, Django is a plus
– Energy and passion for working in a growing company
– Sense of ownership and attention to detailsDevOps experience
– An entrepreneurial and experimental mindset

What you will receive:

– Truckloads of learning
– Friendly environment and a culture for growth
– Collaboratively solving exciting challenges with smart minds around
– Busy days and busier nights that you won’t regret
– All things good or great at any bootstrapped company

Ruby on Rails Developer – Full time

We’re a team of high-tech Engineers working on fresh big data problems. An integral part of our offerings is web-scale crawl and extraction using cloud computing and machine learning techniques. We’re on a quest for innovative ways to solve the business problems of data acquisition and normalization on the web. Our vision is to make PromptCloud a one-stop brand for data and our growth is geared towards that.
Where we are at PromptCloud- We are a bootstrapped company in the mid-growth phase and are planning to quickly expand (not much in terms of personnel) but heavily with respect to the solutions we can provide to big data problems in the market. We started off with international clients and we have pretty much covered the globe at that.

We’re looking for a Ruby on Rails developer to take over various responsibilities in design and development of rails application. The role involves client side as well as server side expertise.

What PromptCloud expects for this role:

– At least 1-2 year experience working with Ruby on Rails (or Django) and MVC
– Experience working with HTML5, CSS3, JS, jQuery, AJAX, and other web technologies
– Experience working with Linux
– UI/UX Design and front end development experience
– Ability to write well-abstracted, reusable code for various UI components
– Should be willing to work independently and take end-to-end ownership with minimal guidance
– Excellent time-management, multi-tasking, communication and interpersonal skills.
– Must have great design and good documentation skills

Applicants having the following skills will be given preference:

– Knowledge of open source tools such as Firebug, Chrome developer tools
– Experience working with Twitter Bootstrap & Node.JS
– Work independently and end-to-end with minimal guidance
– Ability to write well-abstracted, reusable code
– Excellent time-management, multi-tasking, communication and interpersonal skills
– Must have great design and good documentation skills

What you will receive:

– Truckloads of learning
– Friendly environment and a culture for growth
– Collaboratively solving exciting challenges with smart minds around
– Busy days and busier nights that you won’t regret
– All things good or great at any bootstrapped company

DevOps Engineer – Full time

We’re a team of high-tech Engineers working on fresh big data problems. An integral part of our offerings is web-scale crawl and extraction using cloud computing and machine learning techniques. We’re on a quest for innovative ways to solve the business problems of data acquisition and normalization on the web. Our vision is to make PromptCloud a one-stop brand for data and our growth is geared towards that.
Where we are at PromptCloud- We are a bootstrapped company in the mid-growth phase and are planning to quickly expand (not much in terms of personnel) but heavily with respect to the solutions we can provide to big data problems in the market. We started off with international clients and we have pretty much covered the globe at that.

Responsibilities:

– Ensure 100% availability and reliability of our service,
– Help the company make optimized infrastructural choices.
– Create and implement tools that manage infrastructure.
– Work independently and end-to-end with minimal guidance.

Skills:
On the system side
– Experience with Puppet/Chef/Ansible, Amazon Web Services (AWS), Git, Graphite and related tools for large-scale systems management
– Experience working with linux system monitoring and analysis
– Good understanding of distributed computing environments
– Open to working non-standard hours in critical situations
– Replication of databases (both relational or NoSQL) across geographical regions using various consistency models
– Experience with package management systems such as APT or RPM
On the development side
– Basic coding/scripting ability in Ruby, Python or any other scripting language
– Write clean, elegant and reusable OO code. This is not a sysadmin job.
– Ability to write well-abstracted, reusable code and good documentation skills
– Some understanding of REST and other web technologies is a plus.
– The ideal candidate for this position should have good attention to details, along with excellent time-management, multi-tasking, communication and interpersonal skills.

What you will receive:

– Truckloads of learning
– Friendly environment and a culture for growth
– Collaboratively solving exciting challenges with smart minds around
– Busy days and busier nights that you won’t regret
– All things good or great at any bootstrapped company

Marketing Manager – Full time

PromptCloud is looking for a growth hacker to take over responsibilities in developing and executing strategic marketing programs to meet growth objectives, develop market awareness and communicate client results. The analyst works with the Digital and Inbound Marketing Manager and other business segment executives, product management and sales leadership in supporting sales tools to attract, win and retain clients. Essentially, this profile touches all aspects of marketing and business development, thus evolving into being a successful growth-in-charge for the organization.
He/she partners with all functions within marketing as well as key external departments to drive successful, cross-functional marketing and sales initiatives and contributes towards the successful development and maintenance of key performance indicators that lead PromptCloud to 5x growth in the next 3 years.

Desired Skills and Experience:
– Tech (CS) along with an MBA degree from a top B-school
– Minimum 2 years of experience in a marketing/business analyst role
– Good experience in top and bottom level funnels
– Strong business acumen, highly developed analytical skills and recognized for innovative and creative approaches to problem solving
– Inherent empathy for the customer
– Highly professional written and verbal communication skills, along with interpersonal skills
– Hands-on experience with blogging, copywriting, content marketing & PR
– Experience in social media marketing (planning and execution) is a plus
– Experience working with a B2B/enterprise startup is a big plus
– Excellent time-management, multi-tasking and interpersonal skill

Responsibilities include:
– Understanding PromptCloud’s technology well as you progress, and using it to ideate on marketing strategies across geographies
– Performing timely market researches driven towards opening newer marketing and revenue channels that would directly affect technology roadmap (essentially growth hacking) and tracking various growth and marketing initiatives using key metrics customized to PromptCloud’s environment.
– Growing a community of big data enthusiasts on social media sites like LinkedIn and Twitter, and the technology ecosystem, and prospecting within the group
– Coordinating with vendors on collated improvements to company website via A/B testing, etc. and maintaining the same
– Collaborating with the SEO team on launching and monitoring PPC campaigns
– Creating content for various online and offline channels, and further coordinating with vendors towards this goal
– Publicizing content generated on various online and offline channels, as deemed appropriate with regular research
– Taking end-to-end ownership of tasks with moderate to minimal guidance.

What you will receive:

– Truckloads of learning
– Friendly environment and a culture for growth
– Collaboratively solving exciting challenges with smart minds around
– Busy days and busier nights that you won’t regret
– All things good or great at any bootstrapped company

(This position is currently inactive, you can still apply if you’re interested.)

PromptCloud is looking for an ambitious content marketing all-rounder who would be responsible for writing well-researched and informative content for the blog, website and other marketing collateral. The person should be an auto-pilot and self- thinker and have strong convictions along with efficient proofreading and paraphrasing skills. There will be a steep learning. As a company, we like to work with people who are smarter than their years, fast learners, and quick thinkers. Responsibility-shirkers need not apply. This is an amazing place to grow rapidly and make a real impact. If you’re someone who doesn’t tolerate low expectations, then you might be the right person for our team.

Job Responsibilities:
– Responsible for generating new opportunities: key business function is prospecting new accounts and also to manage and execute research activities as required to compile successful campaign target lists.
– Responsible for segmenting and identifying qualified outbound leads via various communication channels through in-depth understanding of their use case.
– He/she will assist in expanding the company’s database of prospects.
– He/she will be responsible for retargeting of outbound leads and launching various client-nurturing campaigns and account management including up-sell and cross sell.
– He/she will be responsible for arranging various outbound campaigns for increasing brand awareness and revenue.
Establish annual, quarterly, monthly, or weekly sales and collection plans and prioritize and schedule own –
activities so these targets are met.
– Responsible for responding to RFPs and other queries from outbound leads.
– Advising customers on forthcoming product developments and discussing special promotions.
– Understand PromptCloud’s technology well enough.

Desired skills and experience:
– Should be an MBA with a tech background.
– 2 – 4 years of experience in a similar role.
– Experience of software sales/ business development.
– Should be a Techno functional who can map Technology to Business Processes.
– Excellent written skills and ability to communicate well with clients from various geographies.
– Should have experience in handling customer queries.
– Excellent listening skills.
– Ability to understand customer’s industry and core business processes, and then identify the problems they are facing.
– Ability to understand and describe how solutions and features can address the business issues that customers are facing.
– Target focused individual contributor.
– This is an independent role with minimal guidance / interference so give us a shout only if you can ideate as well as execute end to end.

What you will receive:

– Truckloads of learning
– Friendly environment and a culture for growth
– Collaboratively solving exciting challenges with smart minds around
– Busy days and busier nights that you won’t regret
– All things good or great at any bootstrapped company

(This position is currently inactive, you can still apply if you’re interested.)

Content Writer & Social Media Marketer – Full time

PromptCloud is looking for an ambitious content marketing all-rounder who would be responsible for writing well-researched and informative content for the blog, website and other marketing collateral. The person should be an auto-pilot and self- thinker and have strong convictions along with efficient proofreading and paraphrasing skills. There will be a steep learning. As a company, we like to work with people who are smarter than their years, fast learners, and quick thinkers. Responsibility-shirkers need not apply. This is an amazing place to grow rapidly and make a real impact. If you’re someone who doesn’t tolerate low expectations, then you might be the right person for our team.

Desired Skills and Experience:
– Excellent written communication skills
– 1-2 years of full-time experience with content writing
– Should have exposure in public writing, blogs
– High attention to detail
– Hands-on experience with blogging, copywriting, content marketing & PR
– A good hang of the nuances of English language and grammar rules
– Experience in social media marketing (planning and execution) is a big plus
– Ability to learn and adapt to the latest online marketing trends
– Experience working with a B2B/enterprise startup is a plus
– Excellent time-management, multi-tasking and interpersonal skills

Responsibilities include:
– Writing engaging content for the blog, website and emails
– Creating newsletters targeted towards a B2B audience
– Generating SEO-friendly content across sources and sharing them on social media channels
– Independently coming up with GREAT content from time to time
– Developing measurable content marketing strategies
– Growing a community of big data enthusiasts on social media sites like LinkedIn and Twitter
– Understanding PromptCloud’s technology well as you progress
– Taking end-to-end ownership of tasks with moderate to minimal guidance
– Should have understanding of promotion of own articles on various platforms
– Should be familiar with keyword research and ROI on content in terms of visitors, likes, comments, leads etc
– Take ownership of on-page SEO and content promotion on various platforms including but not limited to blogs, forums and social media sites
– Have a basic understanding of Google webmaster and Analytics
– Assist in content strategy and keyword strategy to increase traffic for the website
– In-depth knowledge of and enthusiasm for social media along with demonstrated awareness of social media trends/developments
– Ability to work in a fast-moving and team-oriented environment
This is an independent role with minimal guidance / interference so give us a shout only if you can ideate as well as execute end to end.

What you will receive:

– Truckloads of learning
– Friendly environment and a culture for growth
– Collaboratively solving exciting challenges with smart minds around
– Busy days and busier nights that you won’t regret
– All things good or great at any bootstrapped company

(This position is currently inactive, you can still apply if you’re interested.)