Developing a reliable web scraper can be challenging, especially for beginners. There are loads of ifs and buts that you need to consider. For instance, what happens if the response returns unexpected or false data? What happens if the website goes down? What do you do if your IP is blocked?
Whatever types of problems you could encounter, there are ways around them. But the process begins with not making mistakes in the first place. Here is a look at the most common web scraping errors beginners make and how you can avoid them.
Using Unsecure Proxy Servers
You can use free proxies for web scraping. Beginners can connect to them without needing to have special credentials. There are plenty of different proxies to choose from, so you will always be able to find a type of proxy server for your specific needs.
However, web-scraping beginners often overlook the source of the proxy. Seeing as proxies take your information and re-route it via an alternative IP address, it means they have access to any requests you make. So, while free proxies are fantastic for web scraping, they can be non-secure.
For instance, a malicious proxy could change the HTML of the web page you request and relay false information. There is also the risk that the proxy you use could disconnect without warning, and proxy IP addresses could get blocked by websites. Therefore, it is essential that newbies use reliable and trustworthy proxies for web scraping.
Using the Wrong Framework
Beginners also make the mistake of not using the right framework. Make sure you use a reputable framework like Scrapy. It contains features such as rate-limiting, multi-threading, crawling policies, support for distributed crawling, and secure scraping syntax support like CSS and XPath selectors to make the web scraping process easier and more efficient.
Not Rate Limiting Your Web Crawlers
Do not forget to rate-limit your web crawlers. Frameworks like Scrapy allow you to set concurrent connections so that you can limit them. If you are a web-scraping beginner, do not make the mistake of overlooking how important that is.
Overlooking IP Blocks
The last thing you want is to get blocked during your web scraping. So, do not overlook how you will overcome IP blocks. You should address that early on. To avoid blocks, you can use a rotating proxy service that routes your requests via millions of residential proxies, meaning it is virtually impossible for you to get blocked.
Not Being Aware of the Concurrency Rate
If you wish to increase the concurrency rate than what is presently allowed, you can use something like Scrapyd daemon, which can deal with multiple spiders at once. And if you combine that with a rotating proxy, you will be able to quickly scale concurrent connections.
Not Checking Failure Points
If you do not check failure points, then your web scraping could fail. Build-in monitors where you expect the crawler to break down. By building logging and alerting mechanisms, you can detect a lousy crawl or bad data early on. Actively check failure points such as:
- What happens when the root page does not load?
- What happens when the internet is slow or not working?
- What happens when your IP address is blocked?
- What happens when the web page alters its template?
- What happens when you encounter a CAPTCHA?
