Use deadpool fork with tracing (#5276)

* Use deadpool fork with tracing

* Implement minimum Redis connections

* fix typos maybe

* address pr comments

apps/labrinth/src/database/redis/mod.rs

@@ -3,6 +3,7 @@ use ariadne::ids::base62_impl::{parse_base62, to_base62};
 use chrono::{TimeZone, Utc};
 use dashmap::DashMap;
 use deadpool_redis::{Config, Runtime};
+use futures::TryStreamExt;
 use futures::future::Either;
 use futures::stream::{FuturesUnordered, StreamExt};
 use prometheus::{IntGauge, Registry};
@@ -14,7 +15,7 @@ use std::fmt::{Debug, Display};
 use std::future::Future;
 use std::hash::Hash;
 use std::time::Duration;
-use tracing::{Instrument, info_span};
+use tracing::{Instrument, info, info_span};
 use util::{cmd, redis_pipe};
 
 pub mod util;
@@ -25,7 +26,7 @@ const ACTUAL_EXPIRY: i64 = 60 * 30; // 30 minutes
 #[derive(Clone)]
 pub struct RedisPool {
     pub url: String,
-    pub pool: util::InstrumentedPool,
+    pub pool: deadpool_redis::Pool,
     cache_list: DashMap<String, util::CacheSubscriber>,
     meta_namespace: String,
 }
@@ -69,11 +70,35 @@ impl RedisPool {
 
         let pool = RedisPool {
             url,
-            pool: util::InstrumentedPool::new(pool),
+            pool,
             cache_list: DashMap::with_capacity(2048),
             meta_namespace: meta_namespace.unwrap_or("".to_string()),
         };
 
+        let redis_min_connections = dotenvy::var("REDIS_MIN_CONNECTIONS")
+            .ok()
+            .and_then(|x| x.parse::<usize>().ok())
+            .unwrap_or(0);
+        let spawn_min_connections = (0..redis_min_connections)
+            .map(|_| {
+                let pool = pool.clone();
+                tokio::spawn(async move { pool.pool.get().await })
+            })
+            .collect::<FuturesUnordered<_>>();
+        tokio::spawn({
+            let pool = pool.clone();
+            async move {
+                // collect the connections into a buffer while we're spawning them,
+                // to make sure that we're not `get`ing any connections we previously took
+                let _connections =
+                    spawn_min_connections.try_collect::<Vec<_>>().await;
+                info!(
+                    pool_status = ?pool.pool.status(),
+                    "Finished getting {redis_min_connections} initial Redis connections"
+                );
+            }
+        });
+
         let interval = Duration::from_secs(30);
         let max_age = Duration::from_secs(5 * 60); // 5 minutes
         let pool_ref = pool.clone();