fix: Fix database connections in house keeper (matter-labs#610)

## What ❔

Use correct connections for databases in house keeper.

## Why ❔

Databases are divided in 2 on mainnet and testnet

## Checklist

- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [x] Tests for the changes have been added / updated.
- [ ] Documentation comments have been added / updated.
- [x] Code has been formatted via `zk fmt` and `zk lint`.
- [x] Spellcheck has been run via `cargo spellcheck
--cfg=./spellcheck/era.cfg --code 1`.

core/lib/zksync_core/src/house_keeper/fri_prover_queue_monitor.rs

@@ -7,18 +7,21 @@ use zksync_prover_utils::periodic_job::PeriodicJob;
 pub struct FriProverStatsReporter {
     reporting_interval_ms: u64,
     prover_connection_pool: ConnectionPool,
+    db_connection_pool: ConnectionPool,
     config: FriProverGroupConfig,
 }
 
 impl FriProverStatsReporter {
     pub fn new(
         reporting_interval_ms: u64,
         prover_connection_pool: ConnectionPool,
+        db_connection_pool: ConnectionPool,
         config: FriProverGroupConfig,
     ) -> Self {
         Self {
             reporting_interval_ms,
             prover_connection_pool,
+            db_connection_pool,
             config,
         }
     }
@@ -85,7 +88,9 @@ impl PeriodicJob for FriProverStatsReporter {
 
         // FIXME: refactor metrics here
 
-        if let Some(l1_batch_number) = conn
+        let mut db_conn = self.db_connection_pool.access_storage().await.unwrap();
+
+        if let Some(l1_batch_number) = db_conn
             .proof_generation_dal()
             .get_oldest_unprocessed_batch()
             .await
@@ -96,7 +101,7 @@ impl PeriodicJob for FriProverStatsReporter {
             )
         }
 
-        if let Some(l1_batch_number) = conn
+        if let Some(l1_batch_number) = db_conn
             .proof_generation_dal()
             .get_oldest_not_generated_batch()
             .await

core/lib/zksync_core/src/lib.rs

@@ -1088,13 +1088,16 @@ async fn add_house_keeper_to_task_futures(
         .clone()
         .context("house_keeper_config")?;
     let postgres_config = configs.postgres_config.clone().context("postgres_config")?;
-    let connection_pool = ConnectionPool::singleton(postgres_config.replica_url()?)
-        .build()
-        .await
-        .context("failed to build a connection pool")?;
+    let connection_pool = ConnectionPool::builder(
+        postgres_config.replica_url()?,
+        postgres_config.max_connections()?,
+    )
+    .build()
+    .await
+    .context("failed to build a connection pool")?;
     let l1_batch_metrics_reporter = L1BatchMetricsReporter::new(
         house_keeper_config.l1_batch_metrics_reporting_interval_ms,
-        connection_pool,
+        connection_pool.clone(),
     );
 
     let prover_connection_pool = ConnectionPool::builder(
@@ -1192,6 +1195,7 @@ async fn add_house_keeper_to_task_futures(
     let fri_prover_stats_reporter = FriProverStatsReporter::new(
         house_keeper_config.fri_prover_stats_reporting_interval_ms,
         prover_connection_pool.clone(),
+        connection_pool.clone(),
         fri_prover_group_config,
     );
     task_futures.push(tokio::spawn(fri_prover_stats_reporter.run()));