2017年1月19日星期四

Web Scraping|Use Proxy Server for Web Scraping

       
             

Web Scraper or spider becomes more and more popular in data science. This auto-technique can help us retrieve loads of customized data from Web or database. However, the major issue is that requesting too many pages in too short a period of time by a single IP address can be easily traced by the website, thus being blocked by the target website. To limit the chances of getting blocked, we should try to avoid scraping a website with a single IP Address. And normally, we use proxy servers which include discrete proxy IP address whenever the requests are routed over the crawling server.
Concerned about proxy server, the reliability of the proxy should always come first to our mind. Actually, there are around 1000 places to buy proxies and some unreliable proxies would go too fast, which might cause themselves to get blocked. There are also other approaches that can be more related to out-sourcing the IP rotation(think proxy as a service), but these services usually come at a higher cost. Since there is a cost of purchasing the proxy and a cost of re-implementing the proxy each time you purchase a new one. Much often the time, reliability does come at a cost and you will often find that "free" will be very unreliable, "cheap" will be somewhat unreliable and "more expensive" will usually come at a premium. Therefore, the Cloud-based data extraction concept is proposed recently.
The Cloud-based Web Scraping is a true Cloud-based service, it can run from any OS and any browser. We don’t have to host anything ourselves, and everything is done in the cloud. Plus, all the website page views, data formation, transformation can be handled on someone else’s server. Web proxy requirements can be managed by ourselves. On the cloud side, these machines are independent, they can be accessed and run without installing from any PC with Internet access around the world. This service will manage our data with incredible back-end hardware, more specific, we can utilize its anonymous proxy feature that could rotate tons of IP’s addresses to prevent getting blocked by the target website. Actually, we can take a more succinct and efficient approach by using certain Data Scraper Tool with Cloud-based service, like OctoparseImport.io these tools can schedule and run your task any time on the cloud side with tons of PCs running at the same time. Plus, these scraper tools can also provide us a fast way to manually configure these proxy servers as you need.
Some popular scraper tools in the market include Octoparse, Import.io, Webhose.io, Screen Scraper.
Octoparse is a powerful and free data scraper tool which can scrape almost all the websites. Its cloud-based data extraction can provide rich rotating IP addresss proxy servers for web scraping which has limited the chances of getting blocked and saved much time for manual configuration. They have provided precise instructions and clear guidelines to follow the scraping steps. Basically, for this tool, you needn't have any coding skills. Anyway, if you want to deepen and strengthen your crawling and scraping, it has offered a public API if you are in need. Besides, their back-up support is efficient and available.
Import.io  is also an easy-to-use desktop data scraper. It has succinct and effective user interface and simple navigation. For this tool, it also requires less coding skills. Import.io possesses many powerful featrues as well, like Cloud-based service which can help us better take care of our scheduled task and level up our mining ablility for their rotating IP address. However, Improt.io has hard time navigating through combinations of javascript/POST.
Webhose.io is a browser-based data scraping tool which uses various data crawling techniques to crawl amounts of data from multiple channelsWhile it may behave not so good as the previous introduced tools about their cloud service, which means the scraping process dealing with IP rotation or proxy configuration might be somewhat complex. They have provided both free and paid service plan as you need.
Screen Scraper is pretty neat and can wrestle with certain difficult tasks including precise localization, navigation and data extractions, however it does require you have basic programming/tokenization skills if you want to have it perform at its utmost. It implies that you should configure the settings and set the parameters manually most of the time, the pros that you can customize your distinct mining process, while the cons is that it is abit time-consuming and complex. Plus, it is a bit expensive.



Author: The Octoparse Team



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