Move feed fetching to crawl_feed job, DomainRequestLimiter

`DomainRequestLimiter` is a distributed version of `DomainLocks` based
on redis.

Cargo.lock

@@ -605,12 +605,9 @@ dependencies = [
 
 [[package]]
 name = "cookie-factory"
-version = "0.3.3"
+version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9885fa71e26b8ab7855e2ec7cae6e9b380edff76cd052e07c683a0319d51b3a2"
+checksum = "396de984970346b0d9e93d1415082923c679e5ae5c3ee3dcbd104f5610af126b"
-dependencies = [
- "futures",
-]
 
 [[package]]
 name = "core-foundation"
@@ -658,6 +655,7 @@ dependencies = [
  "clap",
  "dotenvy",
  "feed-rs",
+ "fred 9.1.2",
  "futures",
  "headers",
  "http 1.1.0",
@@ -668,6 +666,7 @@ dependencies = [
  "once_cell",
  "opml",
  "password-auth",
+ "rand",
  "readability",
  "reqwest 0.12.4",
  "serde",
@@ -1014,7 +1013,33 @@ dependencies = [
  "log",
  "parking_lot",
  "rand",
- "redis-protocol",
+ "redis-protocol 4.1.0",
+ "semver",
+ "socket2",
+ "tokio",
+ "tokio-stream",
+ "tokio-util",
+ "url",
+ "urlencoding",
+]
+
+[[package]]
+name = "fred"
+version = "9.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "152397076bd317aa06bca9666e954ad15cde1a8f17b6ea4b007cf0bfc074d1d0"
+dependencies = [
+ "arc-swap",
+ "async-trait",
+ "bytes",
+ "bytes-utils",
+ "crossbeam-queue",
+ "float-cmp",
+ "futures",
+ "log",
+ "parking_lot",
+ "rand",
+ "redis-protocol 5.0.1",
  "semver",
  "socket2",
  "tokio",
@@ -2533,6 +2558,20 @@ dependencies = [
  "nom",
 ]
 
+[[package]]
+name = "redis-protocol"
+version = "5.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "65deb7c9501fbb2b6f812a30d59c0253779480853545153a51d8e9e444ddc99f"
+dependencies = [
+ "bytes",
+ "bytes-utils",
+ "cookie-factory",
+ "crc16",
+ "log",
+ "nom",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.4.1"
@@ -3684,7 +3723,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0460effd120251714fae61067fa3e8b2a3c8202501cdcae375d4bd14194c85cf"
 dependencies = [
  "async-trait",
- "fred",
+ "fred 8.0.6",
  "rmp-serde",
  "thiserror",
  "time",

Cargo.toml

@@ -31,6 +31,7 @@ chrono = { version = "0.4", features = ["serde"] }
 clap = { version = "4.4", features = ["derive", "env"] }
 dotenvy = "0.15"
 feed-rs = "1.3"
+fred = "9"
 futures = "0.3"
 headers = "0.4"
 http = "1.0.0"
@@ -44,6 +45,7 @@ notify = "6"
 once_cell = "1.18"
 opml = "1.1"
 password-auth = "1.0"
+rand = { version = "0.8", features = ["small_rng"] }
 readability = "0.3"
 reqwest = { version = "0.12", features = ["json"] }
 serde = { version = "1", features = ["derive"] }

src/bin/crawler.rs

@@ -66,7 +66,9 @@ pub async fn crawl_fn(job: Crawl, state: Data<Arc<State>>) -> Result<(), CrawlEr
             // self.spawn_crawler_loop(feed, respond_to.clone());
             // TODO: implement uniqueness on jobs per feed for ~1 minute
             apalis
-                .push(AsyncJob::CrawlFeed(CrawlFeedJob { feed }))
+                .push(AsyncJob::CrawlFeed(CrawlFeedJob {
+                    feed_id: feed.feed_id,
+                }))
                 .await
                 .map_err(|err| CrawlError::QueueJobError(err.to_string()))?;
         }

src/bin/worker.rs

@@ -5,11 +5,16 @@ use apalis::prelude::*;
 use apalis_redis::RedisStorage;
 use clap::Parser;
 use dotenvy::dotenv;
+use fred::prelude::*;
+use reqwest::Client;
+use sqlx::postgres::PgPoolOptions;
 use tower::retry::RetryLayer;
 
 use lib::config::Config;
+use lib::domain_request_limiter::DomainRequestLimiter;
 use lib::jobs::{handle_async_job, AsyncJob};
 use lib::log::init_worker_tracing;
+use lib::USER_AGENT;
 
 #[tokio::main]
 async fn main() -> Result<()> {
@@ -23,11 +28,27 @@ async fn main() -> Result<()> {
     let apalis_storage: RedisStorage<AsyncJob> =
         RedisStorage::new_with_config(redis_conn, apalis_config);
 
+    let redis_config = RedisConfig::from_url(&config.redis_url)?;
+    let redis_pool = RedisPool::new(redis_config, None, None, None, 5)?;
+    redis_pool.connect();
+    redis_pool.wait_for_connect().await?;
+    let domain_request_limiter = DomainRequestLimiter::new(redis_pool, 10, 5, 100, 0.5);
+
+    let http_client = Client::builder().user_agent(USER_AGENT).build()?;
+    let db = PgPoolOptions::new()
+        .max_connections(config.database_max_connections)
+        .acquire_timeout(std::time::Duration::from_secs(3))
+        .connect(&config.database_url)
+        .await?;
+
     Monitor::<TokioExecutor>::new()
         .register_with_count(2, {
             WorkerBuilder::new("worker")
                 .layer(RetryLayer::new(RetryPolicy::default()))
                 .layer(TraceLayer::new())
+                .data(http_client)
+                .data(db)
+                .data(domain_request_limiter)
                 .backend(apalis_storage)
                 .build_fn(handle_async_job)
         })

src/domain_request_limiter.rs

@@ -0,0 +1,123 @@
+use anyhow::{anyhow, Result};
+use fred::{clients::RedisPool, interfaces::KeysInterface, prelude::*};
+use rand::{rngs::SmallRng, Rng, SeedableRng};
+use std::{sync::Arc, time::Duration};
+use tokio::{sync::Mutex, time::sleep};
+
+/// A Redis-based rate limiter for domain-specific requests with jittered retry delay.
+///
+/// This limiter uses a fixed window algorithm with a 1-second window and applies
+/// jitter to the retry delay to help prevent synchronized retries in distributed systems.
+/// It uses fred's RedisPool for efficient connection management.
+///
+/// Limitations:
+/// 1. Fixed window: The limit resets every second, potentially allowing short traffic bursts
+///    at window boundaries.
+/// 2. No token bucket: Doesn't accumulate unused capacity from quiet periods.
+/// 3. Potential overcounting: In distributed systems, there's a small chance of overcounting
+///    near window ends due to race conditions.
+/// 4. Redis dependency: Rate limiting fails open if Redis is unavailable.
+/// 5. Blocking: The acquire method will block until a request is allowed or max_retries is reached.
+///
+/// Usage example:
+/// ```
+/// use fred::prelude::*;
+///
+/// #[tokio::main]
+/// async fn main() -> Result<()> {
+///     let config = RedisConfig::default();
+///     let pool = RedisPool::new(config, None, None, 5)?;
+///     pool.connect();
+///     pool.wait_for_connect().await?;
+///
+///     let limiter = DomainRequestLimiter::new(pool, 10, 5, 100, 0.5);
+///     let domain = "example.com";
+///
+///     for _ in 0..15 {
+///         match limiter.acquire(domain).await {
+///             Ok(()) => println!("Request allowed"),
+///             Err(_) => println!("Max retries reached, request denied"),
+///         }
+///     }
+///
+///     Ok(())
+/// }
+/// ```
+#[derive(Debug, Clone)]
+pub struct DomainRequestLimiter {
+    redis_pool: RedisPool,
+    requests_per_second: u32,
+    max_retries: u32,
+    base_retry_delay_ms: u64,
+    jitter_factor: f64,
+    // TODO: I think I can get rid of this if I instantiate a DomainRequestLimiter per-worker, but
+    // I'm not sure how to do that in apalis (then I could just use thread_rng)
+    rng: Arc<Mutex<SmallRng>>,
+}
+
+impl DomainRequestLimiter {
+    /// Create a new DomainRequestLimiter.
+    ///
+    /// # Arguments
+    /// * `redis_pool` - A fred RedisPool.
+    /// * `requests_per_second` - Maximum allowed requests per second per domain.
+    /// * `max_retries` - Maximum number of retries before giving up.
+    /// * `base_retry_delay_ms` - Base delay between retries in milliseconds.
+    /// * `jitter_factor` - Factor to determine the maximum jitter (0.0 to 1.0).
+    pub fn new(
+        redis_pool: RedisPool,
+        requests_per_second: u32,
+        max_retries: u32,
+        base_retry_delay_ms: u64,
+        jitter_factor: f64,
+    ) -> Self {
+        Self {
+            redis_pool,
+            requests_per_second,
+            max_retries,
+            base_retry_delay_ms,
+            jitter_factor: jitter_factor.clamp(0.0, 1.0),
+            rng: Arc::new(Mutex::new(SmallRng::from_entropy())),
+        }
+    }
+
+    /// Attempt to acquire permission for a request, retrying if necessary.
+    ///
+    /// This method will attempt to acquire permission up to max_retries times,
+    /// sleeping for a jittered delay between each attempt.
+    ///
+    /// # Arguments
+    /// * `domain` - The domain for which to check the rate limit.
+    ///
+    /// # Returns
+    /// Ok(()) if permission is granted, or an error if max retries are exceeded.
+    pub async fn acquire(&self, domain: &str) -> Result<()> {
+        for attempt in 0..=self.max_retries {
+            if self.try_acquire(domain).await? {
+                return Ok(());
+            }
+            if attempt < self.max_retries {
+                let mut rng = self.rng.lock().await;
+                let jitter =
+                    rng.gen::<f64>() * self.jitter_factor * self.base_retry_delay_ms as f64;
+                let delay = self.base_retry_delay_ms + jitter as u64;
+                sleep(Duration::from_millis(delay)).await;
+            }
+        }
+        Err(anyhow!(
+            "Max retries exceeded for domain: {:?}, request denied",
+            domain
+        ))
+    }
+
+    async fn try_acquire(&self, domain: &str) -> Result<bool, RedisError> {
+        let key = format!("rate_limit:{}", domain);
+
+        let count: u32 = self.redis_pool.incr(&key).await?;
+        if count == 1 {
+            self.redis_pool.expire(&key, 1).await?;
+        }
+
+        Ok(count <= self.requests_per_second)
+    }
+}

src/jobs/crawl_feed.rs

@@ -1,16 +1,188 @@
-use anyhow::Result;
+use std::cmp::Ordering;
-use serde::{Deserialize, Serialize};
-use tracing::{info, instrument};
 
-use crate::models::feed::Feed;
+use anyhow::{anyhow, Result};
+use apalis::prelude::*;
+use chrono::{Duration, Utc};
+use feed_rs::parser;
+use http::{header, HeaderMap, StatusCode};
+use reqwest::Client;
+use serde::{Deserialize, Serialize};
+use sqlx::PgPool;
+use tracing::{info, info_span, instrument, warn};
+use url::Url;
+use uuid::Uuid;
+
+use crate::domain_request_limiter::DomainRequestLimiter;
+use crate::models::entry::{CreateEntry, Entry};
+use crate::models::feed::{Feed, MAX_CRAWL_INTERVAL_MINUTES, MIN_CRAWL_INTERVAL_MINUTES};
 
 #[derive(Debug, Deserialize, Serialize, Clone)]
 pub struct CrawlFeedJob {
-    pub feed: Feed,
+    pub feed_id: Uuid,
 }
 
-#[instrument(skip_all, fields(feed_id = %feed.feed_id))]
+#[instrument(skip_all, fields(feed_id = %feed_id))]
-pub async fn crawl_feed(CrawlFeedJob { feed }: CrawlFeedJob) -> Result<()> {
+pub async fn crawl_feed(
-    info!("Crawling feed: {:?}", feed.feed_id);
+    CrawlFeedJob { feed_id }: CrawlFeedJob,
-    Err(anyhow::anyhow!("Not implemented"))
+    http_client: Data<Client>,
+    db: Data<PgPool>,
+    domain_request_limiter: Data<DomainRequestLimiter>,
+) -> Result<()> {
+    let mut feed = Feed::get(&*db, feed_id).await?;
+    info!("got feed from db");
+    let url = Url::parse(&feed.url)?;
+    let domain = url
+        .domain()
+        .ok_or(anyhow!("invalid url: {:?}", feed.url.clone()))?;
+    let mut headers = HeaderMap::new();
+    if let Some(etag) = &feed.etag_header {
+        if let Ok(etag) = etag.parse() {
+            headers.insert(header::IF_NONE_MATCH, etag);
+        } else {
+            warn!(%etag, "failed to parse saved etag header");
+        }
+    }
+    if let Some(last_modified) = &feed.last_modified_header {
+        if let Ok(last_modified) = last_modified.parse() {
+            headers.insert(header::IF_MODIFIED_SINCE, last_modified);
+        } else {
+            warn!(
+                %last_modified,
+                "failed to parse saved last_modified header",
+            );
+        }
+    }
+
+    info!(url=%url, "starting fetch");
+    domain_request_limiter.acquire(domain).await?;
+    let resp = http_client.get(url.clone()).headers(headers).send().await?;
+    let headers = resp.headers();
+    if let Some(etag) = headers.get(header::ETAG) {
+        if let Ok(etag) = etag.to_str() {
+            feed.etag_header = Some(etag.to_string());
+        } else {
+            warn!(?etag, "failed to convert response etag header to string");
+        }
+    }
+    if let Some(last_modified) = headers.get(header::LAST_MODIFIED) {
+        if let Ok(last_modified) = last_modified.to_str() {
+            feed.last_modified_header = Some(last_modified.to_string());
+        } else {
+            warn!(
+                ?last_modified,
+                "failed to convert response last_modified header to string",
+            );
+        }
+    }
+    info!(url=%url, "fetched feed");
+    if resp.status() == StatusCode::NOT_MODIFIED {
+        info!("feed returned not modified status");
+        feed.last_crawled_at = Some(Utc::now());
+        feed.last_crawl_error = None;
+        feed.save(&*db).await?;
+        info!("updated feed in db");
+        return Ok(());
+    } else if !resp.status().is_success() {
+        warn!("feed returned non-successful status");
+        feed.last_crawled_at = Some(Utc::now());
+        feed.last_crawl_error = resp.status().canonical_reason().map(|s| s.to_string());
+        feed.save(&*db).await?;
+        info!("updated feed in db");
+        return Ok(());
+    }
+
+    let bytes = resp.bytes().await?;
+
+    let parsed_feed = parser::parse(&bytes[..])?;
+    info!("parsed feed");
+    feed.url = url.to_string();
+    feed.feed_type = parsed_feed.feed_type.into();
+    feed.last_crawled_at = Some(Utc::now());
+    feed.last_crawl_error = None;
+    if let Some(title) = parsed_feed.title {
+        feed.title = Some(title.content);
+    }
+    if let Some(description) = parsed_feed.description {
+        feed.description = Some(description.content);
+    }
+    let last_entry_published_at = parsed_feed.entries.iter().filter_map(|e| e.published).max();
+    if let Some(prev_last_entry_published_at) = feed.last_entry_published_at {
+        if let Some(published_at) = last_entry_published_at {
+            let time_since_last_entry = if published_at == prev_last_entry_published_at {
+                // No new entry since last crawl, compare current time to last publish instead
+                Utc::now() - prev_last_entry_published_at
+            } else {
+                // Compare new entry publish time to previous publish time
+                published_at - prev_last_entry_published_at
+            };
+            match time_since_last_entry.cmp(&Duration::minutes(feed.crawl_interval_minutes.into()))
+            {
+                Ordering::Greater => {
+                    feed.crawl_interval_minutes = i32::max(
+                        (feed.crawl_interval_minutes as f32 * 1.2).ceil() as i32,
+                        MAX_CRAWL_INTERVAL_MINUTES,
+                    );
+                    info!(
+                        interval = feed.crawl_interval_minutes,
+                        "increased crawl interval"
+                    );
+                }
+                Ordering::Less => {
+                    feed.crawl_interval_minutes = i32::max(
+                        (feed.crawl_interval_minutes as f32 / 1.2).ceil() as i32,
+                        MIN_CRAWL_INTERVAL_MINUTES,
+                    );
+                    info!(
+                        interval = feed.crawl_interval_minutes,
+                        "decreased crawl interval"
+                    );
+                }
+                Ordering::Equal => {}
+            }
+        }
+    }
+    feed.last_entry_published_at = last_entry_published_at;
+    let feed = feed.save(&*db).await?;
+    info!("updated feed in db");
+
+    let mut payload = Vec::with_capacity(parsed_feed.entries.len());
+    for entry in parsed_feed.entries {
+        let entry_span = info_span!("entry", id = entry.id);
+        let _entry_span_guard = entry_span.enter();
+        if let Some(link) = entry.links.get(0) {
+            // if no scraped or feed date is available, fallback to the current time
+            let published_at = entry.published.unwrap_or_else(Utc::now);
+            let entry = CreateEntry {
+                title: entry.title.map(|t| t.content),
+                url: link.href.clone(),
+                description: entry.summary.map(|s| s.content),
+                feed_id: feed.feed_id,
+                published_at,
+            };
+            payload.push(entry);
+        } else {
+            warn!("skipping feed entry with no links");
+        }
+    }
+    let entries = Entry::bulk_upsert(&*db, payload).await?;
+    let (new, updated) = entries
+        .into_iter()
+        .partition::<Vec<_>, _>(|entry| entry.updated_at.is_none());
+    info!(new = new.len(), updated = updated.len(), "saved entries");
+
+    for entry in new {
+        // TODO: queue the entry crawls
+        //
+        // let entry_crawler = EntryCrawlerHandle::new(
+        //     self.pool.clone(),
+        //     self.client.clone(),
+        //     self.domain_locks.clone(),
+        //     self.content_dir.clone(),
+        // );
+        // let mut entry_receiver = entry_crawler.crawl(entry).await;
+        // while let Ok(EntryCrawlerHandleMessage::Entry(result)) = entry_receiver.recv().await {
+        //     let _ = respond_to.send(FeedCrawlerHandleMessage::Entry(result));
+        // }
+    }
+    Ok(())
 }

src/jobs/mod.rs

@@ -1,6 +1,7 @@
 use apalis::prelude::*;
-use apalis_redis::RedisStorage;
+use reqwest::Client;
 use serde::{Deserialize, Serialize};
+use sqlx::PgPool;
 use thiserror::Error;
 use tracing::{error, info, instrument};
 
@@ -8,6 +9,8 @@ mod crawl_feed;
 
 pub use crawl_feed::CrawlFeedJob;
 
+use crate::domain_request_limiter::DomainRequestLimiter;
+
 #[derive(Debug, Deserialize, Serialize, Clone)]
 pub enum AsyncJob {
     HelloWorld(String),
@@ -27,13 +30,18 @@ pub async fn handle_async_job(
     // TODO: add task_id to tracing instrumentation context
     // it casuses a panic in 0.6.0 currently, see: https://github.com/geofmureithi/apalis/issues/398
     // task_id: Data<TaskId>,
+    http_client: Data<Client>,
+    db: Data<PgPool>,
+    domain_request_limiter: Data<DomainRequestLimiter>,
 ) -> Result<(), AsyncJobError> {
     let result = match job {
         AsyncJob::HelloWorld(name) => {
             info!("Hello, {}!", name);
             Ok(())
         }
-        AsyncJob::CrawlFeed(job) => crawl_feed::crawl_feed(job).await,
+        AsyncJob::CrawlFeed(job) => {
+            crawl_feed::crawl_feed(job, http_client, db, domain_request_limiter).await
+        }
     };
 
     match result {

src/lib.rs

@@ -3,6 +3,7 @@ pub mod api_response;
 pub mod auth;
 pub mod config;
 pub mod domain_locks;
+pub mod domain_request_limiter;
 pub mod error;
 pub mod handlers;
 pub mod headers;