Fix Issue #3014 (#3059)

* TenantConfigRequest now supports tenant_id as hex string input instead
of bytes array

* Config file is truncated in each creation/update

libs/pageserver_api/src/models.rs

@@ -117,6 +117,7 @@ impl TenantCreateRequest {
 #[serde_as]
 #[derive(Serialize, Deserialize)]
 pub struct TenantConfigRequest {
+    #[serde_as(as = "DisplayFromStr")]
     pub tenant_id: TenantId,
     #[serde(default)]
     #[serde_as(as = "Option<DisplayFromStr>")]

pageserver/src/tenant.rs

@@ -1690,7 +1690,7 @@ impl Tenant {
         let _enter = info_span!("saving tenantconf").entered();
         info!("persisting tenantconf to {}", target_config_path.display());
 
-        // TODO this will prepend comments endlessly
+        // TODO this will prepend comments endlessly ?
         let mut conf_content = r#"# This file contains a specific per-tenant's config.
 #  It is read in case of pageserver restart.
 
@@ -1703,7 +1703,10 @@ impl Tenant {
 
         let mut target_config_file = VirtualFile::open_with_options(
             target_config_path,
-            OpenOptions::new().write(true).create_new(first_save),
+            OpenOptions::new()
+                .truncate(true) // This needed for overwriting with small config files
+                .write(true)
+                .create_new(first_save),
         )?;
 
         target_config_file

test_runner/regress/test_tenant_conf.py

@@ -133,3 +133,28 @@ tenant_config={checkpoint_distance = 10000, compaction_target_size = 1048576}"""
                     "pitr_interval": 2592000,
                 }.items()
             )
+
+    # update the config with very short config and make sure no trailing chars are left from previous config
+    env.neon_cli.config_tenant(
+        tenant_id=tenant,
+        conf={
+            "pitr_interval": "1 min",
+        },
+    )
+
+    # restart the pageserver and ensure that the config is still correct
+    env.pageserver.stop()
+    env.pageserver.start()
+
+    with closing(env.pageserver.connect()) as psconn:
+        with psconn.cursor(cursor_factory=psycopg2.extras.RealDictCursor) as pscur:
+            pscur.execute(f"show {tenant}")
+            res = pscur.fetchone()
+            log.info(f"after restart res: {res}")
+            assert all(
+                i in res.items()
+                for i in {
+                    "compaction_period": 20,
+                    "pitr_interval": 60,
+                }.items()
+            )