[DPE-2777] Basic sharding int test (#279)

## Issue
No integration tests for sainity check

## Solution
Add a sainty check test. i.e. deploy cluster, write data to mongos, read
data from shards

.github/workflows/ci.yaml

@@ -81,6 +81,7 @@ jobs:
           - tls-integration
           - backup-integration
           - metric-integration
+          - sharding-integration
     name: ${{ matrix.tox-environments }}
     needs:
       - lint

tests/integration/sharding_tests/helpers.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+# Copyright 2023 Canonical Ltd.
+# See LICENSE file for licensing details.
+from urllib.parse import quote_plus
+
+from pymongo import MongoClient
+from pytest_operator.plugin import OpsTest
+
+from ..helpers import get_password
+
+MONGOS_PORT = 27018
+MONGOD_PORT = 27017
+
+
+async def generate_mongodb_client(ops_test: OpsTest, app_name: str, mongos: bool):
+    """Returns a MongoDB client for mongos/mongod."""
+    hosts = [unit.public_address for unit in ops_test.model.applications[app_name].units]
+    password = await get_password(ops_test, app_name)
+    port = MONGOS_PORT if mongos else MONGOD_PORT
+    hosts = [f"{host}:{port}" for host in hosts]
+    hosts = ",".join(hosts)
+    auth_source = ""
+    database = "admin"
+
+    return MongoClient(
+        f"mongodb://operator:"
+        f"{quote_plus(password)}@"
+        f"{hosts}/{quote_plus(database)}?"
+        f"{auth_source}"
+    )
+
+
+def write_data_to_mongodb(client, db_name, coll_name, content) -> None:
+    """Writes data to the provided collection and database."""
+    db = client[db_name]
+    horses_collection = db[coll_name]
+    horses_collection.insert_one(content)
+
+
+def verify_data_mongodb(client, db_name, coll_name, key, value) -> bool:
+    """Checks a key/value pair for a provided collection and database."""
+    db = client[db_name]
+    test_collection = db[coll_name]
+    query = test_collection.find({}, {key: 1})
+    return query[0][key] == value

tests/integration/sharding_tests/test_sharding.py

@@ -0,0 +1,120 @@
+#!/usr/bin/env python3
+# Copyright 2023 Canonical Ltd.
+# See LICENSE file for licensing details.
+import pytest
+from pytest_operator.plugin import OpsTest
+
+from .helpers import generate_mongodb_client, verify_data_mongodb, write_data_to_mongodb
+
+SHARD_ONE_APP_NAME = "shard-one"
+SHARD_TWO_APP_NAME = "shard-two"
+CONFIG_SERVER_APP_NAME = "config-server-one"
+SHARD_REL_NAME = "sharding"
+CONFIG_SERVER_REL_NAME = "config-server"
+MONGODB_KEYFILE_PATH = "/var/snap/charmed-mongodb/current/etc/mongod/keyFile"
+TIMEOUT = 15 * 60
+
+
+@pytest.mark.abort_on_fail
+async def test_build_and_deploy(ops_test: OpsTest) -> None:
+    """Build and deploy a sharded cluster."""
+    my_charm = await ops_test.build_charm(".")
+    await ops_test.model.deploy(
+        my_charm,
+        num_units=2,
+        config={"role": "config-server"},
+        application_name=CONFIG_SERVER_APP_NAME,
+    )
+    await ops_test.model.deploy(
+        my_charm, num_units=2, config={"role": "shard"}, application_name=SHARD_ONE_APP_NAME
+    )
+    await ops_test.model.deploy(
+        my_charm, num_units=2, config={"role": "shard"}, application_name=SHARD_TWO_APP_NAME
+    )
+
+    async with ops_test.fast_forward():
+        await ops_test.model.wait_for_idle(
+            apps=[CONFIG_SERVER_APP_NAME, SHARD_ONE_APP_NAME, SHARD_TWO_APP_NAME],
+            idle_period=20,
+            raise_on_blocked=False,
+            timeout=TIMEOUT,
+        )
+
+    # TODO Future PR: assert that CONFIG_SERVER_APP_NAME, SHARD_ONE_APP_NAME, SHARD_TWO_APP_NAME
+    # are blocked waiting for relaitons
+
+
+@pytest.mark.abort_on_fail
+async def test_cluster_active(ops_test: OpsTest) -> None:
+    """Tests the integration of cluster components works without error."""
+    await ops_test.model.integrate(
+        f"{SHARD_ONE_APP_NAME}:{SHARD_REL_NAME}",
+        f"{CONFIG_SERVER_APP_NAME}:{CONFIG_SERVER_REL_NAME}",
+    )
+    await ops_test.model.integrate(
+        f"{SHARD_TWO_APP_NAME}:{SHARD_REL_NAME}",
+        f"{CONFIG_SERVER_APP_NAME}:{CONFIG_SERVER_REL_NAME}",
+    )
+
+    async with ops_test.fast_forward():
+        await ops_test.model.wait_for_idle(
+            apps=[CONFIG_SERVER_APP_NAME, SHARD_ONE_APP_NAME, SHARD_TWO_APP_NAME],
+            idle_period=20,
+            status="active",
+            timeout=TIMEOUT,
+        )
+
+    # TODO Future PR: assert that CONFIG_SERVER_APP_NAME, SHARD_ONE_APP_NAME, SHARD_TWO_APP_NAME
+    # have the correct active statuses.
+
+
+async def test_sharding(ops_test: OpsTest) -> None:
+    """Tests writing data to mongos gets propagated to shards."""
+    # write data to mongos on both shards.
+    mongos_client = await generate_mongodb_client(
+        ops_test, app_name=CONFIG_SERVER_APP_NAME, mongos=True
+    )
+
+    # write data to shard one
+    write_data_to_mongodb(
+        mongos_client,
+        db_name="animals_database_1",
+        coll_name="horses",
+        content={"horse-breed": "unicorn", "real": True},
+    )
+    mongos_client.admin.command("movePrimary", "animals_database_1", to=SHARD_ONE_APP_NAME)
+
+    # write data to shard two
+    write_data_to_mongodb(
+        mongos_client,
+        db_name="animals_database_2",
+        coll_name="horses",
+        content={"horse-breed": "pegasus", "real": True},
+    )
+    mongos_client.admin.command("movePrimary", "animals_database_2", to=SHARD_TWO_APP_NAME)
+
+    # log into shard 1 verify data
+    shard_one_client = await generate_mongodb_client(
+        ops_test, app_name=SHARD_ONE_APP_NAME, mongos=False
+    )
+    has_correct_data = verify_data_mongodb(
+        shard_one_client,
+        db_name="animals_database_1",
+        coll_name="horses",
+        key="horse-breed",
+        value="unicorn",
+    )
+    assert has_correct_data, "data not written to shard-one"
+
+    # log into shard 2 verify data
+    shard_two_client = await generate_mongodb_client(
+        ops_test, app_name=SHARD_TWO_APP_NAME, mongos=False
+    )
+    has_correct_data = verify_data_mongodb(
+        shard_two_client,
+        db_name="animals_database_2",
+        coll_name="horses",
+        key="horse-breed",
+        value="pegasus",
+    )
+    assert has_correct_data, "data not written to shard-two"

tox.ini

@@ -177,6 +177,21 @@ deps =
 commands =
     pytest -v --tb native --log-cli-level=INFO -s --durations=0 {posargs} {[vars]tests_path}/integration/metrics_tests/test_metrics.py
 
+[testenv:sharding-integration]
+description = Run sharding integration tests
+pass_env =
+    {[testenv]pass_env}
+    CI
+    CI_PACKED_CHARMS
+deps =
+    pytest
+    juju==3.2.0.1
+    pytest-mock
+    pytest-operator
+    -r {tox_root}/requirements.txt
+commands =
+    pytest -v --tb native --log-cli-level=INFO -s --durations=0 {posargs} {[vars]tests_path}/integration/sharding_tests/test_sharding.py
+
 
 [testenv:integration]
 description = Run all integration tests