close #24, make program aware of the files already on disk

src/filesystem.rs

@@ -34,10 +34,35 @@ pub fn as_path(url: &Url, content_type: &HeaderValue) -> PathBuf {
     url_path
 }
 
+pub async fn check_file_length(file: &PathBuf) -> Option<u64> {
+    match tokio::fs::OpenOptions::new()
+        .write(false)
+        .read(true)
+        .create(false)
+        .open(file).await
+    {
+        Ok(file) => {
+            match file.metadata().await {
+                Ok(meta) => {
+                    return Some(meta.len())
+                },
+                Err(err) => {
+                    error!("Failed to get metadata. {}", err)
+                },
+            }
+        },
+        Err(err) => {
+            error!("Failed to open file for testing... {}", err);
+        },
+    }
+    None
+
+}
+
 pub async fn init(filename: &PathBuf) -> Option<fs::File> {
     let file = async || tokio::fs::OpenOptions::new()
         .write(true)
-        .append(true)
+        .append(false)
         .create(true)
         .open(&filename).await;
 

src/main.rs

@@ -5,17 +5,27 @@
 extern crate html5ever;
 
 use std::{
-    collections::HashSet, fs::File, io::Read, sync::{Arc, LazyLock}
+    collections::HashSet,
+    fs::File,
+    io::Read,
+    sync::{Arc, LazyLock},
 };
 
-use futures_util::StreamExt;
-use opentelemetry::{global::{self}, metrics::{Counter, Meter, UpDownCounter}};
-use opentelemetry_otlp::{Protocol, WithExportConfig};
 use db::{connect, Website};
+use futures_util::StreamExt;
+use opentelemetry::{
+    global::{self},
+    metrics::{Counter, Meter, UpDownCounter},
+};
+use opentelemetry_otlp::{Protocol, WithExportConfig};
 use opentelemetry_sdk::{metrics::SdkMeterProvider, trace::SdkTracerProvider};
 use serde::Deserialize;
 use surrealdb::{engine::remote::ws::Client, Surreal};
-use tokio::{io::{AsyncWriteExt, BufWriter}, sync::RwLock, task::JoinSet};
+use tokio::{
+    io::{AsyncWriteExt, BufWriter},
+    sync::RwLock,
+    task::JoinSet,
+};
 use tracing::{debug, error, info, instrument, level_filters::LevelFilter, trace, warn};
 use tracing_subscriber::{fmt, layer::SubscriberExt, EnvFilter, Layer, Registry};
 
@@ -26,41 +36,29 @@ mod filesystem;
 mod parser;
 
 static METER: LazyLock<Meter> = LazyLock::new(|| global::meter("Internet_Mapper"));
-static BATCH_SIZE: LazyLock<Counter<u64>> = LazyLock::new(||
+static BATCH_SIZE: LazyLock<Counter<u64>> =
-    METER
+    LazyLock::new(|| METER.u64_counter("crawler_batch_size").build());
-        .u64_counter("crawler_batch_size")
+static BEING_PROCESSED: LazyLock<UpDownCounter<i64>> = LazyLock::new(|| {
-        .build()
-);
-static BEING_PROCESSED: LazyLock<UpDownCounter<i64>> = LazyLock::new(||
     METER
         .i64_up_down_counter("crawler_pages_being_processed")
         .build()
-);
+});
-static BEING_PARSED: LazyLock<UpDownCounter<i64>> = LazyLock::new(||
+static BEING_PARSED: LazyLock<UpDownCounter<i64>> = LazyLock::new(|| {
     METER
         .i64_up_down_counter("crawler_pages_being_parsed")
         .build()
-);
+});
-static BEING_STREAMED: LazyLock<UpDownCounter<i64>> = LazyLock::new(|| 
+static BEING_STREAMED: LazyLock<UpDownCounter<i64>> = LazyLock::new(|| {
     METER
         .i64_up_down_counter("crawler_pages_being_streamed")
         .build()
-);
+});
-static GET_IN_FLIGHT: LazyLock<UpDownCounter<i64>> = LazyLock::new(|| 
+static GET_IN_FLIGHT: LazyLock<UpDownCounter<i64>> =
-    METER
+    LazyLock::new(|| METER.i64_up_down_counter("crawler_gets_in_flight").build());
-        .i64_up_down_counter("crawler_gets_in_flight")
+static TOTAL_BYTES_DOWN: LazyLock<Counter<u64>> =
-        .build()
+    LazyLock::new(|| METER.u64_counter("crawler_total_bytes_down").build());
-);
+static SITES_CRAWLED: LazyLock<Counter<u64>> =
-static TOTAL_BYTES_DOWN: LazyLock<Counter<u64>> = LazyLock::new(|| 
+    LazyLock::new(|| METER.u64_counter("crawler_total_sites_crawled").build());
-    METER
-        .u64_counter("crawler_total_bytes_down")
-        .build()
-);
-static SITES_CRAWLED: LazyLock<Counter<u64>> = LazyLock::new(|| 
-    METER
-        .u64_counter("crawler_total_sites_crawled")
-        .build()
-);
 
 static CONFIG: LazyLock<Config> = LazyLock::new(|| {
     let mut file = File::open("./Crawler.toml").expect("Failed to read Crawler.toml");
@@ -130,7 +128,12 @@ async fn main() {
     // let mut main_loop_span= TRACER.start("Main-Loop");
     let mut futures = JoinSet::new();
     for _ in 0..CONFIG.batch_size {
-        futures.spawn(process_single_thread(&CONFIG, db.clone(), reqwest.clone(), crawled.clone()));
+        futures.spawn(process_single_thread(
+            &CONFIG,
+            db.clone(),
+            reqwest.clone(),
+            crawled.clone(),
+        ));
     }
 
     while let Some(_) = futures.join_next().await {
@@ -138,7 +141,12 @@ async fn main() {
         // Would roughly be the acceptable amount at which a thread should exit
         if *(crawled.read().await) < CONFIG.budget - CONFIG.batch_size - 1 {
             warn!("Thread terminated early, restarting");
-            futures.spawn(process_single_thread(&CONFIG, db.clone(), reqwest.clone(), crawled.clone()));
+            futures.spawn(process_single_thread(
+                &CONFIG,
+                db.clone(),
+                reqwest.clone(),
+                crawled.clone(),
+            ));
         }
     }
 
@@ -148,7 +156,12 @@ async fn main() {
     info!("Done");
 }
 
-async fn process_single_thread(config: &Config, db: Surreal<Client>, reqwest: reqwest::Client, crawled: Arc<RwLock<usize>>) {
+async fn process_single_thread(
+    config: &Config,
+    db: Surreal<Client>,
+    reqwest: reqwest::Client,
+    crawled: Arc<RwLock<usize>>,
+) {
     while *(crawled.read().await) < config.budget {
         let uncrawled = get_next(&db.clone(), &config).await;
         match uncrawled {
@@ -158,11 +171,11 @@ async fn process_single_thread(config: &Config, db: Surreal<Client>, reqwest: re
                 // Somehow this write doesn't hang on the while's read?
                 let mut c = crawled.write().await;
                 *c += 1;
-            },
+            }
             None => {
                 warn!("fn::get_next() returned None");
                 return;
-            },
+            }
         }
     }
 }
@@ -171,7 +184,6 @@ async fn process_single_thread(config: &Config, db: Surreal<Client>, reqwest: re
 /// Downloads and crawls and stores a webpage.
 /// It is acceptable to clone `db`, `reqwest`, and `s3` because they all use `Arc`s internally. - Noted by Oliver
 async fn process(mut site: Website, db: Surreal<Client>, reqwest: reqwest::Client) {
-
     // METRICS
     debug!(url = &site.site.as_str(), "Process: {}", &site.site);
     BEING_PROCESSED.add(1, &[]);
@@ -183,6 +195,8 @@ async fn process(mut site: Website, db: Surreal<Client>, reqwest: reqwest::Clien
     // Send the http request (get)
     GET_IN_FLIGHT.add(1, &[]);
     if let Ok(response) = request_builder.send().await {
+        let mut skip_download = false;
+
         GET_IN_FLIGHT.add(-1, &[]);
 
         let headers = response.headers();
@@ -197,30 +211,57 @@ async fn process(mut site: Website, db: Surreal<Client>, reqwest: reqwest::Clien
 
         let ct = match (CT, ct) {
             (None, None) => {
-                warn!("Server did not respond with Content-Type header. Url: {} Headers: ({:?})", site.site.to_string(), headers);
+                warn!(
-                return
+                    "Server did not respond with Content-Type header. Url: {} Headers: ({:?})",
-            },
+                    site.site.to_string(),
+                    headers
+                );
+                return;
+            }
             (None, Some(a)) => a,
             (Some(a), None) => a,
             (Some(a), Some(_)) => a,
         };
 
         // create filepath (handles / -> /index.html)
-        let path = filesystem::as_path(&site.site, ct);
+        let real_path = filesystem::as_path(&site.site, ct);
-        let mut tmp_path= path.clone();
+        let mut tmp_path = real_path.clone();
         if !(tmp_path.add_extension("crawl_temp")) {
             warn!("Failed to add extension to file");
             // fallback ig
             tmp_path = tmp_path.with_extension("crawl_temp");
         }
 
+        // CODE FOR UPDATING DOWNLOADED CONTENT:
+        // Check the Content-Length header (we assume the server is telling the truth) (I don't see
+        // a reason for it to lie in this case).
+        // And see if the file on the disk is the same length.
+        // Yes, technically this isn't perfect, but the other option is storing ETags, which I
+        // don't want to do right now.
+        if let Some(len) = headers.get("Content-Length") {
+            if let Ok(s) = len.to_str() {
+                // length is in bytes
+                if let Ok(len) = s.parse::<u64>() {
+                    if let Some(disk_len) = filesystem::check_file_length(&real_path).await {
+                        if disk_len == len {
+                            skip_download = true;
+                        }
+                    }
+                }
+            }
+        }
+
+
+        if skip_download {
+            trace!("Skipping download...");
+        } else {
             // make sure that the file is good to go
             if let Some(file) = filesystem::init(&tmp_path).await {
                 // Get body from response
                 // stream the response onto the disk
                 let mut stream = response.bytes_stream();
 
-            let should_parse = path.to_string_lossy().ends_with(".html");
+                let should_parse = real_path.to_string_lossy().ends_with(".html");
                 let mut writer = BufWriter::new(file);
                 let mut buf: Vec<u8> = Vec::new();
 
@@ -239,18 +280,18 @@ async fn process(mut site: Website, db: Surreal<Client>, reqwest: reqwest::Clien
                             if should_parse {
                                 data.iter().for_each(|f| buf.push(*f));
                             }
-                    },
+                        }
                         Err(err) => {
                             error!("{err}")
-                    },
+                        }
                     }
                 }
                 let _ = writer.flush().await;
                 // rename the temp file into the real file name
-            if let Err(err) = tokio::fs::rename(&tmp_path, &path).await {
+                if let Err(err) = tokio::fs::rename(&tmp_path, &real_path).await {
                     error!(
                         from = &*tmp_path.to_string_lossy(),
-                    to = &*path.to_string_lossy(),
+                        to = &*real_path.to_string_lossy(),
                         "Error renaming file: {}",
                         err
                     );
@@ -289,6 +330,7 @@ async fn process(mut site: Website, db: Surreal<Client>, reqwest: reqwest::Clien
                 site.status_code = code.as_u16();
                 Website::store_all(vec![site.clone()], &db).await;
             }
+        }
     } else {
         error!(url = site.site.as_str(), "Failed to get: {}", &site.site);
     }
@@ -336,7 +378,7 @@ fn load_logging(config: &Config) {
             .with_file(true)
             .json()
             .with_writer(writer)
-            .with_filter(filter)
+            .with_filter(filter),
     );
 
     tracing::subscriber::set_global_default(registry).expect("Failed to set default subscriber");
@@ -355,5 +397,3 @@ fn load_metrics(config: &Config) -> SdkMeterProvider {
         .build();
     metrics_provider
 }
-
-