Add --id argument to safekeeper setting its unique u64 id.

In preparation for storage node messaging. IDs are supposed to be monotonically
assigned by the console. In tests it is issued by ZenithEnv; at the zenith cli
level and fixtures, string name is completely replaced by integer id. Example
TOML configs are adjusted accordingly.

Sequential ids are chosen over Zid mainly because they are compact and easy to
type/remember.

test_runner/batch_others/test_wal_acceptor.py

@@ -521,12 +521,7 @@ class SafekeeperEnv:
             http=self.port_distributor.get_port(),
         )
 
-        if self.num_safekeepers == 1:
-            name = "single"
-        else:
-            name = f"sk{i}"
-
-        safekeeper_dir = os.path.join(self.repo_dir, name)
+        safekeeper_dir = os.path.join(self.repo_dir, f"sk{i}")
         mkdir_if_needed(safekeeper_dir)
 
         args = [
@@ -537,6 +532,8 @@ class SafekeeperEnv:
             f"127.0.0.1:{port.http}",
             "-D",
             safekeeper_dir,
+            "--id",
+            str(i),
             "--daemonize"
         ]
 
@@ -604,9 +601,8 @@ def test_safekeeper_without_pageserver(test_output_dir: str,
 
 
 def test_replace_safekeeper(zenith_env_builder: ZenithEnvBuilder):
-    def safekeepers_guc(env: ZenithEnv, sk_names: List[str]) -> str:
-        return ','.join(
-            [f'localhost:{sk.port.pg}' for sk in env.safekeepers if sk.name in sk_names])
+    def safekeepers_guc(env: ZenithEnv, sk_names: List[int]) -> str:
+        return ','.join([f'localhost:{sk.port.pg}' for sk in env.safekeepers if sk.id in sk_names])
 
     def execute_payload(pg: Postgres):
         with closing(pg.connect()) as conn:
@@ -628,9 +624,9 @@ def test_replace_safekeeper(zenith_env_builder: ZenithEnvBuilder):
             http_cli = sk.http_client()
             try:
                 status = http_cli.timeline_status(tenant_id, timeline_id)
-                log.info(f"Safekeeper {sk.name} status: {status}")
+                log.info(f"Safekeeper {sk.id} status: {status}")
             except Exception as e:
-                log.info(f"Safekeeper {sk.name} status error: {e}")
+                log.info(f"Safekeeper {sk.id} status error: {e}")
 
     zenith_env_builder.num_safekeepers = 4
     env = zenith_env_builder.init()
@@ -638,7 +634,7 @@ def test_replace_safekeeper(zenith_env_builder: ZenithEnvBuilder):
 
     log.info("Use only first 3 safekeepers")
     env.safekeepers[3].stop()
-    active_safekeepers = ['sk1', 'sk2', 'sk3']
+    active_safekeepers = [1, 2, 3]
     pg = env.postgres.create('test_replace_safekeeper')
     pg.adjust_for_wal_acceptors(safekeepers_guc(env, active_safekeepers))
     pg.start()
@@ -678,7 +674,7 @@ def test_replace_safekeeper(zenith_env_builder: ZenithEnvBuilder):
 
     log.info("Recreate postgres to replace failed sk1 with new sk4")
     pg.stop_and_destroy().create('test_replace_safekeeper')
-    active_safekeepers = ['sk2', 'sk3', 'sk4']
+    active_safekeepers = [2, 3, 4]
     env.safekeepers[3].start()
     pg.adjust_for_wal_acceptors(safekeepers_guc(env, active_safekeepers))
     pg.start()

test_runner/fixtures/zenith_fixtures.py

@@ -556,19 +556,15 @@ class ZenithEnv:
                 pg=self.port_distributor.get_port(),
                 http=self.port_distributor.get_port(),
             )
-
-            if config.num_safekeepers == 1:
-                name = "single"
-            else:
-                name = f"sk{i}"
+            id = i  # assign ids sequentially
             toml += f"""
 [[safekeepers]]
-name = '{name}'
+id = {id}
 pg_port = {port.pg}
 http_port = {port.http}
 sync = false # Disable fsyncs to make the tests go faster
             """
-            safekeeper = Safekeeper(env=self, name=name, port=port)
+            safekeeper = Safekeeper(env=self, id=id, port=port)
             self.safekeepers.append(safekeeper)
 
         log.info(f"Config: {toml}")
@@ -848,17 +844,17 @@ class ZenithCli:
         log.info(f"Stopping pageserver with {cmd}")
         return self.raw_cli(cmd)
 
-    def safekeeper_start(self, name: str) -> 'subprocess.CompletedProcess[str]':
-        return self.raw_cli(['safekeeper', 'start', name])
+    def safekeeper_start(self, id: int) -> 'subprocess.CompletedProcess[str]':
+        return self.raw_cli(['safekeeper', 'start', str(id)])
 
     def safekeeper_stop(self,
-                        name: Optional[str] = None,
+                        id: Optional[int] = None,
                         immediate=False) -> 'subprocess.CompletedProcess[str]':
         args = ['safekeeper', 'stop']
+        if id is not None:
+            args.extend(str(id))
         if immediate:
             args.extend(['-m', 'immediate'])
-        if name is not None:
-            args.append(name)
         return self.raw_cli(args)
 
     def pg_create(
@@ -1397,11 +1393,11 @@ class Safekeeper:
     """ An object representing a running safekeeper daemon. """
     env: ZenithEnv
     port: SafekeeperPort
-    name: str  # identifier for logging
+    id: int
     auth_token: Optional[str] = None
 
     def start(self) -> 'Safekeeper':
-        self.env.zenith_cli.safekeeper_start(self.name)
+        self.env.zenith_cli.safekeeper_start(self.id)
 
         # wait for wal acceptor start by checking its status
         started_at = time.time()
@@ -1420,8 +1416,8 @@ class Safekeeper:
         return self
 
     def stop(self, immediate=False) -> 'Safekeeper':
-        log.info('Stopping safekeeper {}'.format(self.name))
-        self.env.zenith_cli.safekeeper_stop(self.name, immediate)
+        log.info('Stopping safekeeper {}'.format(self.id))
+        self.env.zenith_cli.safekeeper_stop(self.id, immediate)
         return self
 
     def append_logical_message(self,