fix(pageserver): LSN lease edge cases around restarts/migrations (#9055)

Part of #7497, closes #8817.

## Problem

See #8817. 

## Summary of changes

**compute_ctl**

- Renew lsn lease as soon as `/configure` updates pageserver_connstr,
use `state_changed` Condvar for synchronization.

**pageserver**

As mentioned in
https://github.com/neondatabase/neon/issues/8817#issuecomment-2315768076,
we still want some permanent error reported if a lease cannot be
granted. By considering attachment mode and the added
`lsn_lease_deadline` when processing lease requests, we can also bound
the case of bad requests to a very short period after migration/restart.

- Refactor https://github.com/neondatabase/neon/pull/9024 and move
`lsn_lease_deadline` to `AttachedTenantConf` so timeline can easily
access it.
- Have separate HTTP `init_lsn_lease` and  libpq `renew_lsn_lease` API.
  - Always do LSN verification for the initial HTTP lease request.
- LSN verification for the renewal is **still done** when tenants are
not in `AttachedSingle` and we have pass the `lsn_lease_deadline`, which
give plenty of time for compute to renew the lease.
 
**neon_local**

- add and call `timeline_init_lsn_lease` mgmt_api at static endpoint
start. The initial lsn lease http request is sent when we run `cargo
neon endpoint start <static endpoint>`.


## Testing

- Extend `test_readonly_node_gc` to do pageserver restarts and
migration.

## Future Work

- The control plane should make the initial lease request through HTTP
when creating a static endpoint. This is currently only done in
`neon_local`.

Signed-off-by: Yuchen Liang <yuchen@neon.tech>

compute_tools/src/compute.rs

@@ -10,6 +10,7 @@ use std::sync::atomic::AtomicU32;
 use std::sync::atomic::Ordering;
 use std::sync::{Condvar, Mutex, RwLock};
 use std::thread;
+use std::time::Duration;
 use std::time::Instant;
 
 use anyhow::{Context, Result};
@@ -1398,6 +1399,36 @@ LIMIT 100",
         }
         Ok(remote_ext_metrics)
     }
+
+    /// Waits until current thread receives a state changed notification and
+    /// the pageserver connection strings has changed.
+    ///
+    /// The operation will time out after a specified duration.
+    pub fn wait_timeout_while_pageserver_connstr_unchanged(&self, duration: Duration) {
+        let state = self.state.lock().unwrap();
+        let old_pageserver_connstr = state
+            .pspec
+            .as_ref()
+            .expect("spec must be set")
+            .pageserver_connstr
+            .clone();
+        let mut unchanged = true;
+        let _ = self
+            .state_changed
+            .wait_timeout_while(state, duration, |s| {
+                let pageserver_connstr = &s
+                    .pspec
+                    .as_ref()
+                    .expect("spec must be set")
+                    .pageserver_connstr;
+                unchanged = pageserver_connstr == &old_pageserver_connstr;
+                unchanged
+            })
+            .unwrap();
+        if !unchanged {
+            info!("Pageserver config changed");
+        }
+    }
 }
 
 pub fn forward_termination_signal() {

compute_tools/src/lsn_lease.rs

@@ -57,10 +57,10 @@ fn lsn_lease_bg_task(
             .max(valid_duration / 2);
 
         info!(
-            "Succeeded, sleeping for {} seconds",
+            "Request succeeded, sleeping for {} seconds",
             sleep_duration.as_secs()
         );
-        thread::sleep(sleep_duration);
+        compute.wait_timeout_while_pageserver_connstr_unchanged(sleep_duration);
     }
 }
 
@@ -89,10 +89,7 @@ fn acquire_lsn_lease_with_retry(
                 .map(|connstr| {
                     let mut config = postgres::Config::from_str(connstr).expect("Invalid connstr");
                     if let Some(storage_auth_token) = &spec.storage_auth_token {
-                        info!("Got storage auth token from spec file");
                         config.password(storage_auth_token.clone());
-                    } else {
-                        info!("Storage auth token not set");
                     }
                     config
                 })
@@ -108,9 +105,11 @@ fn acquire_lsn_lease_with_retry(
                 bail!("Permanent error: lease could not be obtained, LSN is behind the GC cutoff");
             }
             Err(e) => {
-                warn!("Failed to acquire lsn lease: {e} (attempt {attempts}");
+                warn!("Failed to acquire lsn lease: {e} (attempt {attempts})");
 
-                thread::sleep(Duration::from_millis(retry_period_ms as u64));
+                compute.wait_timeout_while_pageserver_connstr_unchanged(Duration::from_millis(
+                    retry_period_ms as u64,
+                ));
                 retry_period_ms *= 1.5;
                 retry_period_ms = retry_period_ms.min(MAX_RETRY_PERIOD_MS);
             }