Suport multiple DB connections by naming respective health-provider and composing them

Issue #96 asked to support for showing health of multiple DB engines/endpoints.

To address this, Pyctuator now supports `ComposeiteHealthProvider` which wraps around
a list of health-providers.

Also, the built-in health-providers now support overrding the default name.

Setting health check for multiple DB engines can be done as follows:
```python
pyctuator.register_health_provider(
    CompositeHealthProvider(
        "db",
        DbHealthProvider(db_engine, "db1"),
        DbHealthProvider(db_engine, "db2"),
    )
)

```

Author: michael.yak

pyctuator/health/composite_health_provider.py

@@ -0,0 +1,48 @@
+from dataclasses import dataclass
+from typing import Mapping
+
+from pyctuator.health.health_provider import HealthProvider, HealthStatus, Status
+
+
+@dataclass
+class CompositeHealthStatus(HealthStatus):
+    status: Status
+    details: Mapping[str, HealthStatus]  # type: ignore[assignment]
+
+
+class CompositeHealthProvider(HealthProvider):
+
+    def __init__(self, name: str, *health_providers: HealthProvider) -> None:
+        super().__init__()
+        self.name = name
+        self.health_providers = health_providers
+
+    def is_supported(self) -> bool:
+        return True
+
+    def get_name(self) -> str:
+        return self.name
+
+    def get_health(self) -> CompositeHealthStatus:
+        health_statuses: Mapping[str, HealthStatus] = {
+            provider.get_name(): provider.get_health()
+            for provider in self.health_providers
+            if provider.is_supported()
+        }
+
+        # Health is UP if no provider is registered
+        if not health_statuses:
+            return CompositeHealthStatus(Status.UP, health_statuses)
+
+        # If there's at least one provider and any of the providers is DOWN, the service is DOWN
+        service_is_down = any(health_status.status == Status.DOWN for health_status in health_statuses.values())
+        if service_is_down:
+            return CompositeHealthStatus(Status.DOWN, health_statuses)
+
+        # If there's at least one provider and none of the providers is DOWN and at least one is UP, the service is UP
+        service_is_up = any(health_status.status == Status.UP for health_status in health_statuses.values())
+        if service_is_up:
+            return CompositeHealthStatus(Status.UP, health_statuses)
+
+        # else, all providers are unknown so the service is UNKNOWN
+        return CompositeHealthStatus(Status.UNKNOWN, health_statuses)

pyctuator/health/db_health_provider.py

@@ -21,21 +21,25 @@ class DbHealthStatus(HealthStatus):
 
 class DbHealthProvider(HealthProvider):
 
-    def __init__(self, engine: Engine) -> None:
+    def __init__(self, engine: Engine, name: str = "db") -> None:
         super().__init__()
         self.engine = engine
+        self.name = name
 
     def is_supported(self) -> bool:
         return importlib.util.find_spec("sqlalchemy") is not None
 
     def get_name(self) -> str:
-        return "db"
+        return self.name
 
     def get_health(self) -> DbHealthStatus:
         try:
             with self.engine.connect() as conn:
                 if self.engine.dialect.do_ping(conn.connection): # type: ignore[arg-type]
-                    return DbHealthStatus(status=Status.UP, details=DbHealthDetails(self.engine.name))
+                    return DbHealthStatus(
+                        status=Status.UP,
+                        details=DbHealthDetails(self.engine.name)
+                    )
 
             return DbHealthStatus(
                 status=Status.UNKNOWN,

pyctuator/health/redis_health_provider.py

@@ -22,15 +22,16 @@ class RedisHealthStatus(HealthStatus):
 
 class RedisHealthProvider(HealthProvider):
 
-    def __init__(self, redis: Redis) -> None:
+    def __init__(self, redis: Redis, name: str = "redis") -> None:
         super().__init__()
         self.redis = redis
+        self.name = name
 
     def is_supported(self) -> bool:
         return importlib.util.find_spec("redis") is not None
 
     def get_name(self) -> str:
-        return "redis"
+        return self.name
 
     def get_health(self) -> RedisHealthStatus:
         try:

pyctuator/impl/pyctuator_impl.py

@@ -119,7 +119,7 @@ def get_health(self) -> HealthSummary:
         if service_is_down:
             return HealthSummary(Status.DOWN, health_statuses)
 
-        # IF there's at least one provider and none of the providers is DOWN and at least one is UP, the service is UP
+        # If there's at least one provider and none of the providers is DOWN and at least one is UP, the service is UP
         service_is_up = any(health_status.status == Status.UP for health_status in health_statuses.values())
         if service_is_up:
             return HealthSummary(Status.UP, health_statuses)

tests/health/test_composite_health_provider.py

@@ -0,0 +1,75 @@
+from dataclasses import dataclass
+
+from pyctuator.health.composite_health_provider import CompositeHealthProvider, CompositeHealthStatus
+from pyctuator.health.health_provider import HealthProvider, HealthStatus, Status, HealthDetails
+
+
+@dataclass
+class CustomHealthDetails(HealthDetails):
+    details: str
+
+
+class CustomHealthProvider(HealthProvider):
+
+    def __init__(self, name: str, status: HealthStatus) -> None:
+        super().__init__()
+        self.name = name
+        self.status = status
+
+    def is_supported(self) -> bool:
+        return True
+
+    def get_name(self) -> str:
+        return self.name
+
+    def get_health(self) -> HealthStatus:
+        return self.status
+
+
+def test_composite_health_provider_no_providers() -> None:
+    health_provider = CompositeHealthProvider(
+        "comp1",
+    )
+
+    assert health_provider.get_name() == "comp1"
+
+    assert health_provider.get_health() == CompositeHealthStatus(
+        status=Status.UP,
+        details={}
+    )
+
+
+def test_composite_health_provider_all_up() -> None:
+    health_provider = CompositeHealthProvider(
+        "comp2",
+        CustomHealthProvider("hp1", HealthStatus(Status.UP, CustomHealthDetails("d1"))),
+        CustomHealthProvider("hp2", HealthStatus(Status.UP, CustomHealthDetails("d2"))),
+    )
+
+    assert health_provider.get_name() == "comp2"
+
+    assert health_provider.get_health() == CompositeHealthStatus(
+        status=Status.UP,
+        details={
+            "hp1": HealthStatus(Status.UP, CustomHealthDetails("d1")),
+            "hp2": HealthStatus(Status.UP, CustomHealthDetails("d2")),
+        }
+    )
+
+
+def test_composite_health_provider_one_down() -> None:
+    health_provider = CompositeHealthProvider(
+        "comp3",
+        CustomHealthProvider("hp1", HealthStatus(Status.UP, CustomHealthDetails("d1"))),
+        CustomHealthProvider("hp2", HealthStatus(Status.DOWN, CustomHealthDetails("d2"))),
+    )
+
+    assert health_provider.get_name() == "comp3"
+
+    assert health_provider.get_health() == CompositeHealthStatus(
+        status=Status.DOWN,
+        details={
+            "hp1": HealthStatus(Status.UP, CustomHealthDetails("d1")),
+            "hp2": HealthStatus(Status.DOWN, CustomHealthDetails("d2")),
+        }
+    )

tests/health/test_db_health_provider.py

@@ -33,6 +33,8 @@ def test_sqlite_health() -> None:
     engine = create_engine("sqlite:///:memory:", echo=True)
     health_provider = DbHealthProvider(engine)
     assert health_provider.get_health() == DbHealthStatus(status=Status.UP, details=DbHealthDetails("sqlite"))
+    assert health_provider.get_name() == "db"
+    assert DbHealthProvider(engine, "kuki").get_name() == "kuki"
 
 
 @pytest.mark.usefixtures("require_sql_alchemy", "require_pymysql", "require_mysql_server")