Explicitly set port in postgresql.conf

Hadron doesn't bind Postgres to the default Postgres port of 5432 it
seems, and requires using a different port. Neon binds to the default
port. Writing out the default port makes no difference, so do it always
regardless of Lakebase mode.

Signed-off-by: Tristan Partin <tristan.partin@databricks.com>

compute_tools/src/compute.rs

@@ -1459,12 +1459,18 @@ impl ComputeNode {
         let tls_config = self.tls_config(&pspec.spec);
         let databricks_settings = spec.databricks_settings.as_ref();
 
+        let postgres_port = self
+            .params
+            .connstr
+            .port()
+            .expect("port must be present in connstr");
         // Remove/create an empty pgdata directory and put configuration there.
         self.create_pgdata()?;
         config::write_postgres_conf(
             pgdata_path,
             &self.params,
             &pspec.spec,
+            postgres_port,
             self.params.internal_http_port,
             tls_config,
             databricks_settings,
@@ -1960,10 +1966,16 @@ impl ComputeNode {
 
         // Write new config
         let pgdata_path = Path::new(&self.params.pgdata);
+        let postgres_port = self
+            .params
+            .connstr
+            .port()
+            .expect("port must be present in connstr");
         config::write_postgres_conf(
             pgdata_path,
             &self.params,
             &spec,
+            postgres_port,
             self.params.internal_http_port,
             tls_config,
             spec.databricks_settings.as_ref(),

compute_tools/src/config.rs

@@ -47,6 +47,7 @@ pub fn write_postgres_conf(
     pgdata_path: &Path,
     params: &ComputeNodeParams,
     spec: &ComputeSpec,
+    postgres_port: u16,
     extension_server_port: u16,
     tls_config: &Option<TlsConfig>,
     databricks_settings: Option<&DatabricksSettings>,
@@ -283,6 +284,10 @@ pub fn write_postgres_conf(
         writeln!(file, "neon.disable_logical_replication_subscribers=false")?;
     }
 
+    // Explicitly set the port based on the connstr, overriding any previous port setting.
+    // Note: It is important that we don't specify a different port again after this.
+    writeln!(file, "port = {postgres_port}")?;
+
     // We need Postgres to send logs to rsyslog so that we can forward them
     // further to customers' log aggregation systems.
     if spec.logs_export_host.is_some() {