[DPE-4114] Test: Scale to zero units

src/charm.py

@@ -92,6 +92,7 @@
 
 PRIMARY_NOT_REACHABLE_MESSAGE = "waiting for primary to be reachable from this unit"
 EXTENSIONS_DEPENDENCY_MESSAGE = "Unsatisfied plugin dependencies. Please check the logs"
+DIFFERENT_VERSIONS_PSQL_BLOCKING_MESSAGE = "Please select the correct version of postgresql to use. No need to use different versions of postgresql."
 
 Scopes = Literal[APP_SCOPE, UNIT_SCOPE]
 
@@ -478,6 +479,11 @@ def _on_peer_relation_changed(self, event: HookEvent):
         try:
             # Update the members of the cluster in the Patroni configuration on this unit.
             self.update_config()
+            if self._patroni.cluster_system_id_mismatch(unit_name=self.unit.name):
+                self.unit.status = BlockedStatus(
+                    "Failed to start postgresql. The storage belongs to a third-party cluster"
+                )
+                return
         except RetryError:
             self.unit.status = BlockedStatus("failed to update cluster members on member")
             return
@@ -514,6 +520,8 @@ def _on_peer_relation_changed(self, event: HookEvent):
 
         self._update_new_unit_status()
 
+        self._validate_database_version()
+
     # Split off into separate function, because of complexity _on_peer_relation_changed
     def _start_stop_pgbackrest_service(self, event: HookEvent) -> None:
         # Start or stop the pgBackRest TLS server service when TLS certificate change.
@@ -1572,6 +1580,18 @@ def client_relations(self) -> List[Relation]:
                 relations.append(relation)
         return relations
 
+    def _validate_database_version(self):
+        """Checking that only one version of Postgres is used."""
+        peer_db_version = self.app_peer_data.get("database-version")
+
+        if self.unit.is_leader() and peer_db_version is None:
+            self.app_peer_data.update({"database-version": self._patroni.get_postgresql_version()})
+            return
+
+        if peer_db_version != self._patroni.get_postgresql_version():
+            self.unit.status = BlockedStatus(DIFFERENT_VERSIONS_PSQL_BLOCKING_MESSAGE)
+        return
+
 
 if __name__ == "__main__":
     main(PostgresqlOperatorCharm)

src/cluster.py

@@ -4,6 +4,7 @@
 
 """Helper class used to manage cluster lifecycle."""
 
+import glob
 import logging
 import os
 import pwd
@@ -647,3 +648,39 @@ def update_synchronous_node_count(self, units: int = None) -> None:
                 # Check whether the update was unsuccessful.
                 if r.status_code != 200:
                     raise UpdateSyncNodeCountError(f"received {r.status_code}")
+
+    def cluster_system_id_mismatch(self, unit_name: str) -> bool:
+        """Check if the Patroni service is down.
+
+        If there is the error storage belongs to third-party cluster in its logs.
+
+        Returns:
+            "True" if an error occurred due to the fact that the storage belongs to someone else's cluster.
+        """
+        last_log_file = self._last_patroni_log_file()
+        unit_name = unit_name.replace("/", "-")
+        if (
+            f" CRITICAL: system ID mismatch, node {unit_name} belongs to a different cluster:"
+            in last_log_file
+        ):
+            return True
+        return False
+
+    def _last_patroni_log_file(self) -> str:
+        """Get last log file content of Patroni service.
+
+        If there is no available log files, empty line will be returned.
+
+        Returns:
+            Content of last log file of Patroni service.
+        """
+        log_files = glob.glob(f"{PATRONI_LOGS_PATH}/*.log")
+        if len(log_files) == 0:
+            return ""
+        latest_file = max(log_files, key=os.path.getmtime)
+        try:
+            with open(latest_file) as last_log_file:
+                return last_log_file.read()
+        except OSError as e:
+            logger.exception("Failed to read last patroni log file", exc_info=e)
+            return ""

tests/integration/ha_tests/helpers.py

@@ -807,7 +807,7 @@ def storage_id(ops_test, unit_name):
             return line.split()[1]
 
 
-async def add_unit_with_storage(ops_test, app, storage):
+async def add_unit_with_storage(ops_test, app, storage, is_blocked: bool = False):
     """Adds unit with storage.
 
     Note: this function exists as a temporary solution until this issue is resolved:
@@ -820,7 +820,14 @@ async def add_unit_with_storage(ops_test, app, storage):
     return_code, _, _ = await ops_test.juju(*add_unit_cmd)
     assert return_code == 0, "Failed to add unit with storage"
     async with ops_test.fast_forward():
-        await ops_test.model.wait_for_idle(apps=[app], status="active", timeout=2000)
+        if is_blocked:
+            application = ops_test.model.applications[app]
+            await ops_test.model.block_until(
+                lambda: "blocked" in {unit.workload_status for unit in application.units},
+                timeout=1500,
+            )
+        else:
+            await ops_test.model.wait_for_idle(apps=[app], status="active", timeout=1500)
     assert (
         len(ops_test.model.applications[app].units) == expected_units
     ), "New unit not added to model"
@@ -862,3 +869,50 @@ async def reused_full_cluster_recovery_storage(ops_test: OpsTest, unit_name) ->
         "/var/snap/charmed-postgresql/common/var/log/patroni/patroni.log*",
     )
     return True
+
+
+async def get_db_connection(ops_test, dbname, is_primary=True, replica_unit_name=""):
+    unit_name = await get_primary(ops_test, APP_NAME)
+    password = await get_password(ops_test, APP_NAME)
+    address = get_unit_address(ops_test, unit_name)
+    if not is_primary and unit_name != "":
+        unit_name = replica_unit_name
+        address = ops_test.model.applications[APP_NAME].units[unit_name].public_address
+    connection_string = (
+        f"dbname='{dbname}' user='operator'"
+        f" host='{address}' password='{password}' connect_timeout=10"
+    )
+    return connection_string, unit_name
+
+
+async def validate_test_data(connection_string):
+    with psycopg2.connect(connection_string) as connection:
+        connection.autocommit = True
+        with connection.cursor() as cursor:
+            cursor.execute("SELECT data FROM test;")
+            data = cursor.fetchone()
+            assert data[0] == "some data"
+    connection.close()
+
+
+async def create_test_data(connection_string):
+    with psycopg2.connect(connection_string) as connection:
+        connection.autocommit = True
+        with connection.cursor() as cursor:
+            # Check that it's possible to write and read data from the database that
+            # was created for the application.
+            cursor.execute("DROP TABLE IF EXISTS test;")
+            cursor.execute("CREATE TABLE test(data TEXT);")
+            cursor.execute("INSERT INTO test(data) VALUES('some data');")
+            cursor.execute("SELECT data FROM test;")
+            data = cursor.fetchone()
+            assert data[0] == "some data"
+    connection.close()
+
+
+async def get_last_added_unit(ops_test, app, prev_units):
+    curr_units = [unit.name for unit in ops_test.model.applications[app].units]
+    new_unit = list(set(curr_units) - set(prev_units))[0]
+    for unit in ops_test.model.applications[app].units:
+        if new_unit == unit.name:
+            return unit

tests/integration/ha_tests/test_restore_cluster.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 # Copyright 2023 Canonical Ltd.
 # See LICENSE file for licensing details.
+import asyncio
 import logging
 
 import pytest
@@ -37,24 +38,23 @@ async def test_build_and_deploy(ops_test: OpsTest) -> None:
     charm = await ops_test.build_charm(".")
     async with ops_test.fast_forward():
         # Deploy the first cluster with reusable storage
-        await ops_test.model.deploy(
-            charm,
-            application_name=FIRST_APPLICATION,
-            num_units=3,
-            series=CHARM_SERIES,
-            storage={"pgdata": {"pool": "lxd-btrfs", "size": 2048}},
-            config={"profile": "testing"},
+        await asyncio.gather(
+            ops_test.model.deploy(
+                charm,
+                application_name=FIRST_APPLICATION,
+                num_units=3,
+                series=CHARM_SERIES,
+                storage={"pgdata": {"pool": "lxd-btrfs", "size": 2048}},
+                config={"profile": "testing"},
+            ),
+            ops_test.model.deploy(
+                charm,
+                application_name=SECOND_APPLICATION,
+                num_units=1,
+                series=CHARM_SERIES,
+                config={"profile": "testing"},
+            ),
         )
-
-        # Deploy the second cluster
-        await ops_test.model.deploy(
-            charm,
-            application_name=SECOND_APPLICATION,
-            num_units=1,
-            series=CHARM_SERIES,
-            config={"profile": "testing"},
-        )
-
         await ops_test.model.wait_for_idle(status="active", timeout=1500)
 
         # TODO have a better way to bootstrap clusters with existing storage

tests/integration/ha_tests/test_self_healing.py

@@ -5,6 +5,7 @@
 import logging
 
 import pytest
+from pip._vendor import requests
 from pytest_operator.plugin import OpsTest
 from tenacity import Retrying, stop_after_delay, wait_fixed
 
@@ -15,6 +16,7 @@
     get_password,
     get_unit_address,
     run_command_on_unit,
+    scale_application,
 )
 from .conftest import APPLICATION_NAME
 from .helpers import (
@@ -27,10 +29,13 @@
     change_patroni_setting,
     change_wal_settings,
     check_writes,
+    create_test_data,
     cut_network_from_unit,
     cut_network_from_unit_without_ip_change,
     fetch_cluster_members,
     get_controller_machine,
+    get_db_connection,
+    get_last_added_unit,
     get_patroni_setting,
     get_primary,
     get_unit_ip,
@@ -49,8 +54,10 @@
     storage_id,
     storage_type,
     update_restart_condition,
+    validate_test_data,
     wait_network_restore,
 )
+from .test_restore_cluster import SECOND_APPLICATION
 
 logger = logging.getLogger(__name__)
 
@@ -78,6 +85,14 @@ async def test_build_and_deploy(ops_test: OpsTest) -> None:
                 storage={"pgdata": {"pool": "lxd-btrfs", "size": 2048}},
                 config={"profile": "testing"},
             )
+            await ops_test.model.deploy(
+                charm,
+                num_units=1,
+                application_name=SECOND_APPLICATION,
+                series=CHARM_SERIES,
+                storage={"pgdata": {"pool": "lxd-btrfs", "size": 2048}},
+                config={"profile": "testing"},
+            )
     # Deploy the continuous writes application charm if it wasn't already deployed.
     if not await app_name(ops_test, APPLICATION_NAME):
         wait_for_apps = True
@@ -543,3 +558,119 @@ async def test_network_cut_without_ip_change(
     ), "Connection is not possible after network restore"
 
     await is_cluster_updated(ops_test, primary_name, use_ip_from_inside=True)
+
+
+@pytest.mark.group(1)
+async def test_deploy_zero_units(ops_test: OpsTest, charm):
+    """Scale the database to zero units and scale up again."""
+    app = await app_name(ops_test)
+    dbname = f"{APPLICATION_NAME.replace('-', '_')}_first_database"
+    connection_string, _ = await get_db_connection(ops_test, dbname=dbname)
+
+    # Start an application that continuously writes data to the database.
+    await start_continuous_writes(ops_test, app)
+
+    logger.info("checking whether writes are increasing")
+    await are_writes_increasing(ops_test)
+
+    # Connect to the database.
+    # Create test data.
+    logger.info("connect to DB and create test table")
+    await create_test_data(connection_string)
+
+    # Test to check the use of different versions postgresql.
+    # Release of a new version of charm with another version of postgresql,
+    # it is necessary to implement a test that will check the use of different versions of postgresql.
+
+    unit_ip_addresses = []
+    primary_storage = ""
+    for unit in ops_test.model.applications[app].units:
+        # Save IP addresses of units
+        unit_ip_addresses.append(await get_unit_ip(ops_test, unit.name))
+
+        # Save detached storage ID
+        if await unit.is_leader_from_status():
+            primary_storage = storage_id(ops_test, unit.name)
+
+    logger.info(f"get storage id app: {SECOND_APPLICATION}")
+    second_storage = ""
+    for unit in ops_test.model.applications[SECOND_APPLICATION].units:
+        if await unit.is_leader_from_status():
+            second_storage = storage_id(ops_test, unit.name)
+            break
+
+    # Scale the database to zero units.
+    logger.info("scaling database to zero units")
+    await scale_application(ops_test, app, 0)
+    await scale_application(ops_test, SECOND_APPLICATION, 0)
+
+    # Checking shutdown units.
+    for unit_ip in unit_ip_addresses:
+        try:
+            resp = requests.get(f"http://{unit_ip}:8008")
+            assert (
+                resp.status_code != 200
+            ), f"status code = {resp.status_code}, message = {resp.text}"
+        except requests.exceptions.ConnectionError:
+            assert True, f"unit host = http://{unit_ip}:8008, all units shutdown"
+        except Exception as e:
+            assert False, f"{e} unit host = http://{unit_ip}:8008, something went wrong"
+
+    # Scale up to one unit.
+    logger.info("scaling database to one unit")
+    await add_unit_with_storage(ops_test, app=app, storage=primary_storage)
+    await ops_test.model.wait_for_idle(
+        apps=[APP_NAME, APPLICATION_NAME], status="active", timeout=1500
+    )
+
+    connection_string, _ = await get_db_connection(ops_test, dbname=dbname)
+    logger.info("checking whether writes are increasing")
+    await are_writes_increasing(ops_test)
+
+    logger.info("check test database data")
+    await validate_test_data(connection_string)
+
+    logger.info("database scaling up to two units using third-party cluster storage")
+    new_unit = await add_unit_with_storage(
+        ops_test, app=app, storage=second_storage, is_blocked=True
+    )
+
+    logger.info(f"remove unit {new_unit.name} with storage from application {SECOND_APPLICATION}")
+    await ops_test.model.destroy_units(new_unit.name)
+
+    await are_writes_increasing(ops_test)
+
+    logger.info("check test database data")
+    await validate_test_data(connection_string)
+
+    # Scale up to two units.
+    logger.info("scaling database to two unit")
+    prev_units = [unit.name for unit in ops_test.model.applications[app].units]
+    await scale_application(ops_test, application_name=app, count=2)
+    unit = await get_last_added_unit(ops_test, app, prev_units)
+
+    logger.info(f"check test database data of unit name {unit.name}")
+    connection_string, _ = await get_db_connection(
+        ops_test, dbname=dbname, is_primary=False, replica_unit_name=unit.name
+    )
+    await validate_test_data(connection_string)
+    assert await reused_replica_storage(
+        ops_test, unit_name=unit.name
+    ), "attached storage not properly re-used by Postgresql."
+
+    # Scale up to three units.
+    logger.info("scaling database to three unit")
+    prev_units = [unit.name for unit in ops_test.model.applications[app].units]
+    await scale_application(ops_test, application_name=app, count=3)
+    unit = await get_last_added_unit(ops_test, app, prev_units)
+
+    logger.info(f"check test database data of unit name {unit.name}")
+    connection_string, _ = await get_db_connection(
+        ops_test, dbname=dbname, is_primary=False, replica_unit_name=unit.name
+    )
+    await validate_test_data(connection_string)
+    assert await reused_replica_storage(
+        ops_test, unit_name=unit.name
+    ), "attached storage not properly re-used by Postgresql."
+
+    await check_writes(ops_test)