feat: cache for posts list

src/cache.rs

@@ -1,10 +1,15 @@
 use crate::models::{Comment, Post, User};
 use crate::rds_conn::RdsConn;
+use rand::Rng;
 use redis::AsyncCommands;
 use rocket::serde::json::serde_json;
 // can use rocket::serde::json::to_string in master version
 
 const INSTANCE_EXPIRE_TIME: usize = 60 * 60;
+
+const MIN_LENGTH: isize = 200;
+const MAX_LENGTH: isize = 900;
+
 macro_rules! post_cache_key {
     ($id: expr) => {
         format!("hole_v2:cache:post:{}", $id)
@@ -150,6 +155,109 @@ impl PostCommentCache {
     }
 }
 
+pub struct PostListCommentCache {
+    key: String,
+    mode: u8,
+    rconn: RdsConn,
+    length: isize,
+}
+
+impl PostListCommentCache {
+    pub async fn init(mode: u8, rconn: &RdsConn) -> Self {
+        let mut cacher = PostListCommentCache {
+            key: format!("hole_v2:cache:post_list:{}", &mode),
+            mode: mode,
+            rconn: rconn.clone(),
+            length: 0,
+        };
+        cacher.set_and_check_length().await;
+        cacher
+    }
+
+    async fn set_and_check_length(&mut self) {
+        let mut l = self.rconn.zcard(&self.key).await.unwrap();
+        if l > MAX_LENGTH {
+            self.rconn
+                .zremrangebyrank::<&String, ()>(&self.key, MIN_LENGTH, -1)
+                .await
+                .unwrap_or_else(|e| {
+                    warn!("cut list cache failed, {}, {}", e, &self.key);
+                });
+            l = MIN_LENGTH;
+        }
+        self.length = l;
+    }
+
+    pub fn need_fill(&self) -> bool {
+        self.length < MIN_LENGTH
+    }
+
+    pub fn i64_len(&self) -> i64 {
+        self.length.try_into().unwrap()
+    }
+
+    pub fn i64_minlen(&self) -> i64 {
+        MIN_LENGTH.try_into().unwrap()
+    }
+
+    fn p2pair(&self, p: &Post) -> (i64, i32) {
+        (
+            match self.mode {
+                0 => (-p.id).into(),
+                1 => -p.last_comment_time.timestamp(),
+                2 => (-p.hot_score).into(),
+                3 => rand::thread_rng().gen_range(0..i64::MAX),
+                _ => panic!("wrong mode"),
+            },
+            p.id,
+        )
+    }
+
+    pub async fn fill(&mut self, ps: &Vec<Post>) {
+        let items: Vec<(i64, i32)> = ps.iter().map(|p| self.p2pair(p)).collect();
+        self.rconn
+            .zadd_multiple(&self.key, &items)
+            .await
+            .unwrap_or_else(|e| {
+                warn!("fill list cache failed, {} {}", e, &self.key);
+            });
+
+        self.set_and_check_length().await;
+    }
+
+    pub async fn put(&mut self, p: &Post) {
+        // 其他都是加到最前面的，但热榜不是。可能导致MIN_LENGTH到MAX_LENGTH之间的数据不可靠
+        // 影响不大，先不管了
+        if p.is_deleted {
+            self.rconn.zrem(&self.key, p.id).await.unwrap_or_else(|e| {
+                warn!(
+                    "remove from list cache failed, {} {} {}",
+                    e, &self.key, p.id
+                );
+            });
+        } else {
+            let (s, m) = self.p2pair(p);
+            self.rconn.zadd(&self.key, m, s).await.unwrap_or_else(|e| {
+                warn!(
+                    "put into list cache failed, {} {} {} {}",
+                    e, &self.key, m, s
+                );
+            });
+        }
+    }
+
+    pub async fn get_pids(&mut self, start: i64, limit: i64) -> Vec<i32> {
+        self.rconn
+            .zrange(
+                &self.key,
+                start.try_into().unwrap(),
+                (start + limit - 1).try_into().unwrap(),
+            )
+            .await
+            .unwrap()
+    }
+}
+
 pub struct UserCache {
     key: String,
     rconn: RdsConn,