Make queue strategy configurable and default to Fifo (#463)

* Change idle timeout default to 10 minutes

* Revert lifo for now while we investigate connection thrashing issues

* Make queue strategy configurable

* test revert idle time out

* Add pgcat start to python test

Author: zainkabani

src/config.rs

@@ -292,6 +292,9 @@ pub struct General {
     #[serde(default = "General::default_server_lifetime")]
     pub server_lifetime: u64,
 
+    #[serde(default = "General::default_server_round_robin")] // False
+    pub server_round_robin: bool,
+
     #[serde(default = "General::default_worker_threads")]
     pub worker_threads: usize,
 
@@ -352,7 +355,7 @@ impl General {
     }
 
     pub fn default_idle_timeout() -> u64 {
-        60000 // 1 minute
+        600000 // 10 minutes
     }
 
     pub fn default_shutdown_timeout() -> u64 {
@@ -390,6 +393,10 @@ impl General {
     pub fn default_prometheus_exporter_port() -> i16 {
         9930
     }
+
+    pub fn default_server_round_robin() -> bool {
+        true
+    }
 }
 
 impl Default for General {
@@ -424,7 +431,8 @@ impl Default for General {
             auth_query: None,
             auth_query_user: None,
             auth_query_password: None,
-            server_lifetime: 1000 * 3600 * 24, // 24 hours,
+            server_lifetime: Self::default_server_lifetime(),
+            server_round_robin: false,
             validate_config: true,
         }
     }
@@ -983,6 +991,7 @@ impl Config {
             "Default max server lifetime: {}ms",
             self.general.server_lifetime
         );
+        info!("Sever round robin: {}", self.general.server_round_robin);
         match self.general.tls_certificate.clone() {
             Some(tls_certificate) => {
                 info!("TLS certificate: {}", tls_certificate);

src/pool.rs

@@ -389,6 +389,11 @@ impl ConnectionPool {
                             .min()
                             .unwrap();
 
+                        let queue_strategy = match config.general.server_round_robin {
+                            true => QueueStrategy::Fifo,
+                            false => QueueStrategy::Lifo,
+                        };
+
                         debug!(
                             "[pool: {}][user: {}] Pool reaper rate: {}ms",
                             pool_name, user.username, reaper_rate
@@ -401,7 +406,7 @@ impl ConnectionPool {
                             .idle_timeout(Some(std::time::Duration::from_millis(idle_timeout)))
                             .max_lifetime(Some(std::time::Duration::from_millis(server_lifetime)))
                             .reaper_rate(std::time::Duration::from_millis(reaper_rate))
-                            .queue_strategy(QueueStrategy::Lifo)
+                            .queue_strategy(queue_strategy)
                             .test_on_check_out(false);
 
                         let pool = if config.general.validate_config {

tests/python/tests.py

@@ -63,6 +63,7 @@ def cleanup_conn(conn: psycopg2.extensions.connection, cur: psycopg2.extensions.
 
 
 def test_normal_db_access():
+    pgcat_start()
     conn, cur = connect_db(autocommit=False)
     cur.execute("SELECT 1")
     res = cur.fetchall()