Stop changing the value of neon.extension_server_port at runtime (#9972)

On reconfigure, we no longer passed a port for the extension server
which caused us to not write out the neon.extension_server_port line.
Thus, Postgres thought we were setting the port to the default value of
0. PGC_POSTMASTER GUCs cannot be set at runtime, which causes the
following log messages:

> LOG: parameter "neon.extension_server_port" cannot be changed without
restarting the server
> LOG: configuration file
"/var/db/postgres/compute/pgdata/postgresql.conf" contains errors;
unaffected changes were applied

Fixes: https://github.com/neondatabase/neon/issues/9945

Signed-off-by: Tristan Partin <tristan@neon.tech>

compute_tools/src/bin/compute_ctl.rs

@@ -335,6 +335,7 @@ fn wait_spec(
         pgdata: pgdata.to_string(),
         pgbin: pgbin.to_string(),
         pgversion: get_pg_version_string(pgbin),
+        http_port,
         live_config_allowed,
         state: Mutex::new(new_state),
         state_changed: Condvar::new(),
@@ -389,7 +390,6 @@ fn wait_spec(
 
     Ok(WaitSpecResult {
         compute,
-        http_port,
         resize_swap_on_bind,
         set_disk_quota_for_fs: set_disk_quota_for_fs.cloned(),
     })
@@ -397,8 +397,6 @@ fn wait_spec(
 
 struct WaitSpecResult {
     compute: Arc<ComputeNode>,
-    // passed through from ProcessCliResult
-    http_port: u16,
     resize_swap_on_bind: bool,
     set_disk_quota_for_fs: Option<String>,
 }
@@ -408,7 +406,6 @@ fn start_postgres(
     #[allow(unused_variables)] matches: &clap::ArgMatches,
     WaitSpecResult {
         compute,
-        http_port,
         resize_swap_on_bind,
         set_disk_quota_for_fs,
     }: WaitSpecResult,
@@ -481,12 +478,10 @@ fn start_postgres(
         }
     }
 
-    let extension_server_port: u16 = http_port;
-
     // Start Postgres
     let mut pg = None;
     if !prestartup_failed {
-        pg = match compute.start_compute(extension_server_port) {
+        pg = match compute.start_compute() {
             Ok(pg) => Some(pg),
             Err(err) => {
                 error!("could not start the compute node: {:#}", err);

compute_tools/src/compute.rs

@@ -79,6 +79,8 @@ pub struct ComputeNode {
     /// - we push spec and it does configuration
     /// - but then it is restarted without any spec again
     pub live_config_allowed: bool,
+    /// The port that the compute's HTTP server listens on
+    pub http_port: u16,
     /// Volatile part of the `ComputeNode`, which should be used under `Mutex`.
     /// To allow HTTP API server to serving status requests, while configuration
     /// is in progress, lock should be held only for short periods of time to do
@@ -611,11 +613,7 @@ impl ComputeNode {
     /// Do all the preparations like PGDATA directory creation, configuration,
     /// safekeepers sync, basebackup, etc.
     #[instrument(skip_all)]
-    pub fn prepare_pgdata(
-        &self,
-        compute_state: &ComputeState,
-        extension_server_port: u16,
-    ) -> Result<()> {
+    pub fn prepare_pgdata(&self, compute_state: &ComputeState) -> Result<()> {
         let pspec = compute_state.pspec.as_ref().expect("spec must be set");
         let spec = &pspec.spec;
         let pgdata_path = Path::new(&self.pgdata);
@@ -625,7 +623,7 @@ impl ComputeNode {
         config::write_postgres_conf(
             &pgdata_path.join("postgresql.conf"),
             &pspec.spec,
-            Some(extension_server_port),
+            self.http_port,
         )?;
 
         // Syncing safekeepers is only safe with primary nodes: if a primary
@@ -1243,7 +1241,7 @@ impl ComputeNode {
         // Write new config
         let pgdata_path = Path::new(&self.pgdata);
         let postgresql_conf_path = pgdata_path.join("postgresql.conf");
-        config::write_postgres_conf(&postgresql_conf_path, &spec, None)?;
+        config::write_postgres_conf(&postgresql_conf_path, &spec, self.http_port)?;
 
         // TODO(ololobus): We need a concurrency during reconfiguration as well,
         // but DB is already running and used by user. We can easily get out of
@@ -1284,10 +1282,7 @@ impl ComputeNode {
     }
 
     #[instrument(skip_all)]
-    pub fn start_compute(
-        &self,
-        extension_server_port: u16,
-    ) -> Result<(std::process::Child, std::thread::JoinHandle<()>)> {
+    pub fn start_compute(&self) -> Result<(std::process::Child, std::thread::JoinHandle<()>)> {
         let compute_state = self.state.lock().unwrap().clone();
         let pspec = compute_state.pspec.as_ref().expect("spec must be set");
         info!(
@@ -1362,7 +1357,7 @@ impl ComputeNode {
             info!("{:?}", remote_ext_metrics);
         }
 
-        self.prepare_pgdata(&compute_state, extension_server_port)?;
+        self.prepare_pgdata(&compute_state)?;
 
         let start_time = Utc::now();
         let pg_process = self.start_postgres(pspec.storage_auth_token.clone())?;

compute_tools/src/config.rs

@@ -37,7 +37,7 @@ pub fn line_in_file(path: &Path, line: &str) -> Result<bool> {
 pub fn write_postgres_conf(
     path: &Path,
     spec: &ComputeSpec,
-    extension_server_port: Option<u16>,
+    extension_server_port: u16,
 ) -> Result<()> {
     // File::create() destroys the file content if it exists.
     let mut file = File::create(path)?;
@@ -127,9 +127,7 @@ pub fn write_postgres_conf(
         writeln!(file, "# Managed by compute_ctl: end")?;
     }
 
-    if let Some(port) = extension_server_port {
-        writeln!(file, "neon.extension_server_port={}", port)?;
-    }
+    writeln!(file, "neon.extension_server_port={}", extension_server_port)?;
 
     // This is essential to keep this line at the end of the file,
     // because it is intended to override any settings above.