[BRC-1405] Mount databricks pg_hba and pg_ident from configmap (#12733)

## Problem

For certificate auth, we need to configure pg_hba and pg_ident for it to
work.

HCC needs to mount this config map to all pg compute pod.

## Summary of changes

Create `databricks_pg_hba` and `databricks_pg_ident` to configure where
the files are located on the pod. These configs are pass down to
`compute_ctl`. Compute_ctl uses these config to update `pg_hba.conf` and
`pg_ident.conf` file.

We append `include_if_exists {databricks_pg_hba}` to `pg_hba.conf` and
similarly to `pg_ident.conf`. So that it will refer to databricks config
file without much change to existing pg default config file.

---------

Co-authored-by: Jarupat Jisarojito <jarupat.jisarojito@databricks.com>
Co-authored-by: William Huang <william.huang@databricks.com>
Co-authored-by: HaoyuHuang <haoyu.huang.68@gmail.com>

compute_tools/src/compute.rs

@@ -1457,6 +1457,8 @@ impl ComputeNode {
         let pgdata_path = Path::new(&self.params.pgdata);
 
         let tls_config = self.tls_config(&pspec.spec);
+        let databricks_settings = spec.databricks_settings.as_ref();
+        let postgres_port = self.params.connstr.port();
 
         // Remove/create an empty pgdata directory and put configuration there.
         self.create_pgdata()?;
@@ -1464,8 +1466,11 @@ impl ComputeNode {
             pgdata_path,
             &self.params,
             &pspec.spec,
+            postgres_port,
             self.params.internal_http_port,
             tls_config,
+            databricks_settings,
+            self.params.lakebase_mode,
         )?;
 
         // Syncing safekeepers is only safe with primary nodes: if a primary
@@ -1505,8 +1510,20 @@ impl ComputeNode {
             )
         })?;
 
-        // Update pg_hba.conf received with basebackup.
-        update_pg_hba(pgdata_path, None)?;
+        if let Some(settings) = databricks_settings {
+            copy_tls_certificates(
+                &settings.pg_compute_tls_settings.key_file,
+                &settings.pg_compute_tls_settings.cert_file,
+                pgdata_path,
+            )?;
+
+            // Update pg_hba.conf received with basebackup including additional databricks settings.
+            update_pg_hba(pgdata_path, Some(&settings.databricks_pg_hba))?;
+            update_pg_ident(pgdata_path, Some(&settings.databricks_pg_ident))?;
+        } else {
+            // Update pg_hba.conf received with basebackup.
+            update_pg_hba(pgdata_path, None)?;
+        }
 
         if let Some(databricks_settings) = spec.databricks_settings.as_ref() {
             copy_tls_certificates(
@@ -1954,12 +1971,16 @@ impl ComputeNode {
 
         // Write new config
         let pgdata_path = Path::new(&self.params.pgdata);
+        let postgres_port = self.params.connstr.port();
         config::write_postgres_conf(
             pgdata_path,
             &self.params,
             &spec,
+            postgres_port,
             self.params.internal_http_port,
             tls_config,
+            spec.databricks_settings.as_ref(),
+            self.params.lakebase_mode,
         )?;
 
         self.pg_reload_conf()?;

compute_tools/src/config.rs

@@ -7,11 +7,14 @@ use std::io::prelude::*;
 use std::path::Path;
 
 use compute_api::responses::TlsConfig;
-use compute_api::spec::{ComputeAudit, ComputeMode, ComputeSpec, GenericOption};
+use compute_api::spec::{
+    ComputeAudit, ComputeMode, ComputeSpec, DatabricksSettings, GenericOption,
+};
 
 use crate::compute::ComputeNodeParams;
 use crate::pg_helpers::{
-    GenericOptionExt, GenericOptionsSearch, PgOptionsSerialize, escape_conf_value,
+    DatabricksSettingsExt as _, GenericOptionExt, GenericOptionsSearch, PgOptionsSerialize,
+    escape_conf_value,
 };
 use crate::tls::{self, SERVER_CRT, SERVER_KEY};
 
@@ -40,12 +43,16 @@ pub fn line_in_file(path: &Path, line: &str) -> Result<bool> {
 }
 
 /// Create or completely rewrite configuration file specified by `path`
+#[allow(clippy::too_many_arguments)]
 pub fn write_postgres_conf(
     pgdata_path: &Path,
     params: &ComputeNodeParams,
     spec: &ComputeSpec,
+    postgres_port: Option<u16>,
     extension_server_port: u16,
     tls_config: &Option<TlsConfig>,
+    databricks_settings: Option<&DatabricksSettings>,
+    lakebase_mode: bool,
 ) -> Result<()> {
     let path = pgdata_path.join("postgresql.conf");
     // File::create() destroys the file content if it exists.
@@ -285,6 +292,24 @@ pub fn write_postgres_conf(
         writeln!(file, "log_destination='stderr,syslog'")?;
     }
 
+    if lakebase_mode {
+        // 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.
+        let port = postgres_port.expect("port must be present in connstr");
+        writeln!(file, "port = {port}")?;
+
+        // This is databricks specific settings.
+        // This should be at the end of the file but before `compute_ctl_temp_override.conf` below
+        // so that it can override any settings above.
+        // `compute_ctl_temp_override.conf` is intended to override any settings above during specific operations.
+        // To prevent potential breakage in the future, we keep it above `compute_ctl_temp_override.conf`.
+        writeln!(file, "# Databricks settings start")?;
+        if let Some(settings) = databricks_settings {
+            writeln!(file, "{}", settings.as_pg_settings())?;
+        }
+        writeln!(file, "# Databricks settings end")?;
+    }
+
     // This is essential to keep this line at the end of the file,
     // because it is intended to override any settings above.
     writeln!(file, "include_if_exists = 'compute_ctl_temp_override.conf'")?;

compute_tools/src/spec.rs

@@ -142,7 +142,7 @@ pub fn update_pg_hba(pgdata_path: &Path, databricks_pg_hba: Option<&String>) ->
     // Update pg_hba to contains databricks specfic settings before adding neon settings
     // PG uses the first record that matches to perform authentication, so we need to have
     // our rules before the default ones from neon.
-    // See https://www.postgresql.org/docs/16/auth-pg-hba-conf.html
+    // See https://www.postgresql.org/docs/current/auth-pg-hba-conf.html
     if let Some(databricks_pg_hba) = databricks_pg_hba {
         if config::line_in_file(
             &pghba_path,