feat(infra): enable configuring min & max cockroach pool conns (#922)

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## Changes

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lib/bolt/config/src/ns.rs

@@ -286,6 +286,8 @@ pub struct Turnstile {
 pub struct Service {
 	pub count: usize,
 	pub resources: ServiceResources,
+	pub crdb_min_connections: Option<u64>,
+	pub crdb_max_connections: Option<u64>,
 }
 
 #[derive(Serialize, Deserialize, Clone, Debug)]

lib/bolt/config/src/service.rs

@@ -36,9 +36,6 @@ pub struct ServiceConfig {
 
 	#[serde(default)]
 	pub resources: ServiceResourcesMap,
-
-	#[serde(default)]
-	pub cockroachdb: CockroachDB,
 }
 
 #[derive(Deserialize, Clone, Debug)]
@@ -240,24 +237,6 @@ impl Default for ServiceResourcesMap {
 	}
 }
 
-#[derive(Deserialize, Clone, Debug)]
-#[serde(rename_all = "kebab-case", deny_unknown_fields)]
-pub struct CockroachDB {
-	// Sets a minimum number of connections to the database. This is important to ensure that
-	// the initial queries are not delayed by a large surge of TCP connections immediately
-	// after startup.
-	//
-	// To figure out a healthy number for this value, see the `rivet_crdb_pool_conn_size`
-	// metric to see how many connections are being used for a given service.
-	pub min_connections: usize,
-}
-
-impl Default for CockroachDB {
-	fn default() -> Self {
-		Self { min_connections: 1 }
-	}
-}
-
 mod defaults {
 	pub fn singleton() -> bool {
 		false

lib/bolt/core/src/context/service.rs

@@ -923,10 +923,12 @@ impl ServiceContextData {
 			);
 		}
 
-		env.insert(
-			"CRDB_MIN_CONNECTIONS".into(),
-			self.config().cockroachdb.min_connections.to_string(),
-		);
+		if let Some(x) = ns_service_config.crdb_min_connections {
+			env.insert("CRDB_MIN_CONNECTIONS".into(), x.to_string());
+		}
+		if let Some(x) = ns_service_config.crdb_max_connections {
+			env.insert("CRDB_MAX_CONNECTIONS".into(), x.to_string());
+		}
 
 		if project_ctx.ns().prometheus.is_some() && self.depends_on_prometheus_api() {
 			env.insert(
@@ -1374,10 +1376,14 @@ impl ServiceContextData {
 				config::ns::ClusterKind::SingleNode { .. } => config::ns::Service {
 					count: 1,
 					resources: self.config().resources.single_node.clone(),
+					crdb_min_connections: None,
+					crdb_max_connections: None,
 				},
 				config::ns::ClusterKind::Distributed { .. } => config::ns::Service {
 					count: 2,
 					resources: self.config().resources.distributed.clone(),
+					crdb_min_connections: None,
+					crdb_max_connections: None,
 				},
 			});