C++ crawler technology: libcurl collection example

Teach you how to use C++ to play with web crawling

Engaged in data crawling old iron understand, the target site's anti-climbing mechanism is like a dog's skin plaster can not be shaken off. This is the time to offerproxy IPThis artifact, especially if it's like ouripipgoThis kind of professional service provider allows you to switch identities at any time like a vest and juggle the target website.

Libcurl basic operation three companies

Let's start with the simplest libcurl sample code to warm up:

CURL curl = curl_easy_init();
if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
    CURLcode res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
}

Although this code can capture web pages, but it is like running naked on the Internet - the site will be blocked by the IP in a minute, we have to give it a "cloak".

The right way to open a proxy IP

Adding a proxy to libcurl is as easy as refueling a car, the point is to find the right gas station. Use theipipgoof the proxy service, the code is changed this way:

// Example of proxy format from ipipgo
const char proxy = "http://vip123:yourpassword@45.76.89.12:8000";

curl_easy_setopt(curl, CURLOPT_PROXY, proxy);
curl_easy_setopt(curl, CURLOPT_PROXYTYPE, CURLPROXY_HTTP); curl_easy_setopt(curl, CURLOPT_PROXYTYPE, CURLPROXY_HTTP).

Be careful not to step in these potholes:

• Don't write the proxy address directly, it is recommended to read it from the configuration file.
• Set the timeout to at least 15 seconds or more, and give enough buffer time when the network fluctuates.
• Remember to turn on error logging and set CURLOPT_VERBOSE to 1!

ipipgo's top five tricks

Practical Tips and Tricks

If you want to play around with proxy IPs, you need to be able to do this:

1. IP Rotation Strategy:It is recommended to change the IP every 50 requests, with ipipgo's API to get dynamic
2. Exception handling:Automatically switch to a new agent when a 403/429 status code is received
3. Speed optimization:Reuse CURL handles to reduce TCP connection overhead

Guidelines on demining of common problems

Q: What should I do if I am still recognized by the website after proxy setting?
A: eighty percent is used transparent proxy, change ipipgo high stash proxy, remember to check whether the request header carries the real IP

Q: How to manage agent pool for multi-threaded crawlers?
A: It is recommended that each thread use the proxy independently, and use the queuing mechanism to manage ipipgo's IP resources to avoid repeated use

Q: What should I do if the agent response is fast or slow?
A: Set speed measurement policy in ipipgo background, prioritize the nodes with delay <200ms, and eliminate slow IPs regularly.

lit. avoiding the pit summarizes

Using a good proxy IP is like stir-frying vegetables to master the fire, the key is to choose the right ingredients. After the actual test.ipipgocan really hit it out of the park in terms of concurrency performance and stability, especially with theirIntelligent RoutingThe function can automatically match the fastest node. Lastly, don't be greedy and use a free agent, if the data is leaked, if the account is blocked, the professional things are still given to the professional people to do.