Remove primary_is_running (#8162)

This was a half-finished mechanism to allow a replica to enter hot
standby mode sooner, without waiting for a running-xacts record. It had
issues, and we are working on a better mechanism to replace it.

The control plane might still set the flag in the spec file, but
compute_ctl will simply ignore it.

compute_tools/src/config.rs

@@ -83,12 +83,6 @@ pub fn write_postgres_conf(
         ComputeMode::Replica => {
             // hot_standby is 'on' by default, but let's be explicit
             writeln!(file, "hot_standby=on")?;
-
-            // Inform the replica about the primary state
-            // Default is 'false'
-            if let Some(primary_is_running) = spec.primary_is_running {
-                writeln!(file, "neon.primary_is_running={}", primary_is_running)?;
-            }
         }
     }
 

control_plane/src/endpoint.rs

@@ -592,7 +592,6 @@ impl Endpoint {
             remote_extensions,
             pgbouncer_settings: None,
             shard_stripe_size: Some(shard_stripe_size),
-            primary_is_running: None,
         };
         let spec_path = self.endpoint_path().join("spec.json");
         std::fs::write(spec_path, serde_json::to_string_pretty(&spec)?)?;

libs/compute_api/src/spec.rs

@@ -96,12 +96,6 @@ pub struct ComputeSpec {
     // Stripe size for pageserver sharding, in pages
     #[serde(default)]
     pub shard_stripe_size: Option<usize>,
-
-    // When we are starting a new replica in hot standby mode,
-    // we need to know if the primary is running.
-    // This is used to determine if replica should wait for
-    // RUNNING_XACTS from primary or not.
-    pub primary_is_running: Option<bool>,
 }
 
 /// Feature flag to signal `compute_ctl` to enable certain experimental functionality.

pgxn/neon/neon.c

@@ -41,7 +41,6 @@ PG_MODULE_MAGIC;
 void		_PG_init(void);
 
 static int	logical_replication_max_snap_files = 300;
-bool primary_is_running = false;
 
 static void
 InitLogicalReplicationMonitor(void)
@@ -289,15 +288,6 @@ _PG_init(void)
 
 	pg_init_extension_server();
 
-	DefineCustomBoolVariable(
-		"neon.primary_is_running",
-		"true if the primary was running at replica startup. false otherwise",
-		NULL,
-		&primary_is_running,
-		false,
-		PGC_POSTMASTER,
-		0,
-		NULL, NULL, NULL);
 	/*
 	 * Important: This must happen after other parts of the extension are
 	 * loaded, otherwise any settings to GUCs that were set before the

test_runner/fixtures/neon_fixtures.py

@@ -3539,7 +3539,6 @@ class Endpoint(PgProtocol, LogUtils):
         # and make tests more stable.
         config_lines = ["max_replication_write_lag=15MB"] + config_lines
 
-        config_lines = ["neon.primary_is_running=on"] + config_lines
         self.config(config_lines)
 
         return self