Scalability: The system should inherently be distributed and multithreaded, because it has to fetch hundreds of millions of web documents.
Extensibility: Currently, our design supports HTTP(S) communication protocol and text files storage facilities. For augmented functionality, it should also be extensible for different network communication protocols, able to add multiple modules to process, and store various file formats.
Consistency: Since our system involves multiple crawling workers, having data consistency among all of them is necessary.
In the general context, data consistency means the reliability and accuracy of data across a system or dataset. In the web crawler’s context, it refers to the adherence of all the workers to a specific set of rules in their attempt to generate consistent crawled data.
Performance: The system should be smart enough to limit its crawling to a domain, either by time spent or by the count of the visited URLs of that domain. This process is called self-throttling. The URLs crawled per second and the throughput of the content crawled should be optimal.
Improved user interface—customized scheduling: Besides the default recrawling, which is a functional requirement, the system should also support the functionality to perform non-routine customized crawling on the system administrator’s demands.
The non-functional requirements of the web crawler system