Pholcus is a distributed, high-concurrency, and powerful web crawler software written in Go. It's designed for high-throughput web scraping, capable of executing multiple web scraping tasks concurrently.
When setting up a Pholcus scraping task, you can prioritize certain web pages by controlling the order in which URLs are added to the queue or by manipulating the logic that determines which pages to visit first. Pholcus itself does not have a built-in priority queue system, but you can implement your own prioritization logic in your scraper.
Here's a basic example of how you might implement prioritization in your Pholcus scraper:
package main
import (
"github.com/henrylee2cn/pholcus/exec"
_ "github.com/henrylee2cn/pholcus_lib" // This is required for Pholcus to load the libraries.
"github.com/henrylee2cn/pholcus/common/goquery" // imported for parsing HTML
)
func main() {
exec.DefaultRun("web")
}
// Here you would define your spider logic.
func init() {
// Replace "YourSpiderName" with the name of your spider
// and implement the scraping logic inside the crawler function.
spider := &Spider{
Name: "YourSpiderName",
// Other fields such as Description, Pausetime, etc.
}
spider.OnStart(func(ctx *Context) {
// Implement your logic to add URLs to the queue here.
// For prioritization, you might want to add more important URLs first.
// High-priority URLs
ctx.AddQueue(&request.Request{Url: "http://high.priority.com", Priority: 0})
// Lower-priority URLs
ctx.AddQueue(&request.Request{Url: "http://low.priority.com", Priority: 1})
// ... add more URLs as needed.
})
spider.OnHTML("selector", func(ctx *Context) {
// Parsing logic goes here
})
// Register the spider
exec.Register(spider)
}
In the code above, the Priority field is a custom field that you might use to sort URLs before adding them to the queue. Pholcus does not use this field natively, so you would have to sort your URL list based on priority before enqueueing them.
When you enqueue URLs, make sure that you add the higher priority URLs to the queue first. This simple approach assumes that Pholcus processes the queue in a first-come, first-served manner, which is typical for queue systems if not otherwise configured.
Please note that the code sample is a conceptual demonstration. You need to adapt the logic to your specific use case and the architecture of your crawler.
Also, if you want a more sophisticated priority system that takes into account dynamic factors during the crawl (for instance, updating priorities based on data extracted from pages), you would need to implement a more complex system, potentially involving a custom data structure or external service to manage the priority queue. This could be done outside of the Pholcus framework and requires a more in-depth approach to how URLs are fed into the crawler.
