Add more information to timeline-related APIs (#1673)

Resolves #1488.

- implemented `GET tenant/:tenant_id/timeline/:timeline_id/wal_receiver` endpoint
- returned `thread_id` in `thread_mgr::spawn` 
- added `latest_gc_cutoff_lsn` field to `LocalTimelineInfo` struct

test_runner/batch_others/test_pageserver_api.py

@@ -1,6 +1,12 @@
 from uuid import uuid4, UUID
 import pytest
-from fixtures.zenith_fixtures import ZenithEnv, ZenithEnvBuilder, ZenithPageserverHttpClient
+from fixtures.zenith_fixtures import (
+    DEFAULT_BRANCH_NAME,
+    ZenithEnv,
+    ZenithEnvBuilder,
+    ZenithPageserverHttpClient,
+    ZenithPageserverApiException,
+)
 
 
 # test that we cannot override node id
@@ -48,6 +54,39 @@ def check_client(client: ZenithPageserverHttpClient, initial_tenant: UUID):
         assert local_timeline_details['timeline_state'] == 'Loaded'
 
 
+def test_pageserver_http_get_wal_receiver_not_found(zenith_simple_env: ZenithEnv):
+    env = zenith_simple_env
+    client = env.pageserver.http_client()
+
+    tenant_id, timeline_id = env.zenith_cli.create_tenant()
+
+    # no PG compute node is running, so no WAL receiver is running
+    with pytest.raises(ZenithPageserverApiException) as e:
+        _ = client.wal_receiver_get(tenant_id, timeline_id)
+        assert "Not Found" in str(e.value)
+
+
+def test_pageserver_http_get_wal_receiver_success(zenith_simple_env: ZenithEnv):
+    env = zenith_simple_env
+    client = env.pageserver.http_client()
+
+    tenant_id, timeline_id = env.zenith_cli.create_tenant()
+    pg = env.postgres.create_start(DEFAULT_BRANCH_NAME, tenant_id=tenant_id)
+
+    res = client.wal_receiver_get(tenant_id, timeline_id)
+    assert list(res.keys()) == [
+        "thread_id",
+        "wal_producer_connstr",
+        "last_received_msg_lsn",
+        "last_received_msg_ts",
+    ]
+
+    # make a DB modification then expect getting a new WAL receiver's data
+    pg.safe_psql("CREATE TABLE t(key int primary key, value text)")
+    res2 = client.wal_receiver_get(tenant_id, timeline_id)
+    assert res2["last_received_msg_lsn"] > res["last_received_msg_lsn"]
+
+
 def test_pageserver_http_api_client(zenith_simple_env: ZenithEnv):
     env = zenith_simple_env
     client = env.pageserver.http_client()

test_runner/fixtures/zenith_fixtures.py

@@ -786,6 +786,15 @@ class ZenithPageserverHttpClient(requests.Session):
         assert isinstance(res_json, dict)
         return res_json
 
+    def wal_receiver_get(self, tenant_id: uuid.UUID, timeline_id: uuid.UUID) -> Dict[Any, Any]:
+        res = self.get(
+            f"http://localhost:{self.port}/v1/tenant/{tenant_id.hex}/timeline/{timeline_id.hex}/wal_receiver"
+        )
+        self.verbose_error(res)
+        res_json = res.json()
+        assert isinstance(res_json, dict)
+        return res_json
+
     def get_metrics(self) -> str:
         res = self.get(f"http://localhost:{self.port}/metrics")
         self.verbose_error(res)