spider 1.26.3

# Spider

![crate version](https://img.shields.io/crates/v/spider.svg)

Multithreaded async crawler/indexer using [isolates](https://research.cs.wisc.edu/areas/os/Seminar/schedules/papers/Deconstructing_Process_Isolation_final.pdf) and IPC channels for communication with the ability to run decentralized.

## Dependencies

On Linux

- OpenSSL 1.0.1, 1.0.2, 1.1.0, or 1.1.1

## Example

This is a basic async example crawling a web page, add spider to your `Cargo.toml`:

```toml
[dependencies]
spider = "1.26.3"
```

And then the code:

```rust,no_run
extern crate spider;

use spider::website::Website;
use spider::tokio;

#[tokio::main]
async fn main() {
    let url = "https://choosealicense.com";
    let mut website: Website = Website::new(&url);
    website.crawl().await;

    for link in website.get_links() {
        println!("- {:?}", link.as_ref());
    }
}
```

You can use `Configuration` object to configure your crawler:

```rust
// ..
let mut website: Website = Website::new("https://choosealicense.com");
website.configuration.blacklist_url.push("https://choosealicense.com/licenses/".to_string());
website.configuration.respect_robots_txt = true;
website.configuration.subdomains = true;
website.configuration.tld = false;
website.configuration.delay = 0; // Defaults to 0 ms due to concurrency handling
website.configuration.request_timeout = None; // Defaults to 15000 ms
website.configuration.channel_buffer = 100; // Defaults to 50 - tune this depending on on_link_find_callback
website.configuration.user_agent = "myapp/version".to_string(); // Defaults to spider/x.y.z, where x.y.z is the library version
website.on_link_find_callback = Some(|s| { println!("link target: {}", s); s }); // Callback to run on each link find

website.crawl().await;
```

## Regex Blacklisting

There is an optional "regex" crate that can be enabled:

```toml
[dependencies]
spider = { version = "1.26.3", features = ["regex"] }
```

```rust,no_run
extern crate spider;

use spider::website::Website;
use spider::tokio;

#[tokio::main]
async fn main() {
    let mut website: Website = Website::new("https://choosealicense.com");
    website.configuration.blacklist_url.push("/licenses/".to_string());
    website.crawl().await;

    for link in website.get_links() {
        println!("- {:?}", link.as_ref());
    }
}
```

## Features

We have a couple optional feature flags. Regex blacklisting, jemaloc backend, decentralization, serde, gathering full assets, and randomizing User-Agents.

```toml
[dependencies]
spider = { version = "1.26.3", features = ["regex", "ua_generator"] }
```

1. `ua_generator`: Enables auto generating a random real User-Agent. Enabled by default.
1. `regex`: Enables blacklisting paths with regx
1. `jemalloc`: Enables the jemalloc memory backend.
1. `decentralized`: Enables decentralized processing of IO, requires the [spider_worker] startup before crawls.
1. `control`: Enabled the ability to pause, start, and shutdown crawls on demand.
1. `full_resources`: Enables gathering all content that relates to the domain like css,jss, and etc.
1. `serde`: Enables serde serialization support.

[Jemalloc](https://github.com/jemalloc/jemalloc) performs better for concurrency and allows memory to release easier.

This changes the global allocator of the program so test accordingly to measure impact.

```toml
[dependencies]
spider = { version = "1.26.3", features = ["jemalloc"] }
```

## Blocking

If you need a blocking sync imp use a version prior to `v1.12.0`.

## Pause, Resume, and Shutdown

If you are performing large workloads you may need to control the crawler by enabling the `control` feature flag:

```rust
extern crate spider;

use spider::tokio;
use spider::website::Website;

#[tokio::main]
async fn main() {
    use spider::utils::{pause, resume};
    let url = "https://choosealicense.com/";
    let mut website: Website = Website::new(&url);

    tokio::spawn(async move {
        pause(url).await;
        sleep(Duration::from_millis(5000)).await;
        resume(url).await;
    });

    website.crawl().await;
}
```

### Shutdown crawls

Enable the `control` feature flag:

```rust
extern crate spider;

use spider::tokio;
use spider::website::Website;

#[tokio::main]
async fn main() {
    use spider::utils::{shutdown};
    let url = "https://choosealicense.com/";
    let mut website: Website = Website::new(&url);

    tokio::spawn(async move {
        // really long crawl force shutdown ( 30 is a long time for most websites )
        sleep(Duration::from_secs(30)).await;
        shutdown(url).await;
    });

    website.crawl().await;
}
```

### Scrape/Gather HTML

```rust
extern crate spider;

use spider::tokio;
use spider::website::Website;

#[tokio::main]
async fn main() {
    use std::io::{Write, stdout};

    let url = "https://choosealicense.com/";
    let mut website: Website = Website::new(&url);

    website.scrape().await;

    let mut lock = stdout().lock();

    let separator = "-".repeat(url.len());

    for page in website.get_pages().unwrap() {
        writeln!(
            lock,
            "{}\n{}\n\n{}\n\n{}",
            separator,
            page.get_url(),
            page.get_html(),
            separator
        )
        .unwrap();
    }
}
```

### Decentralization

1. cargo install `spider_worker`.
1. `spider_worker`.
1. `SPIDER_WORKER=http://127.0.0.1:3030 cargo run --example example --features decentralized`

Use `SPIDER_WORKER` env variable to adjust the spider worker onto a load balancer.
The proxy needs to match the transport type for the request to fullfill correctly.
If the `scrape` feature flag is use the `SPIDER_WORKER_SCRAPER` env variable to determine the scraper worker.