From a4e45b8aaff2841114935595555a738175f10182 Mon Sep 17 00:00:00 2001
From: Stanislav Khlud <stanislav.khlud@saritasa.com>
Date: Wed, 18 Sep 2024 13:32:50 +0700
Subject: [PATCH] Add mail check

---
 README.md                             | 11 +++++++
 health_check/contrib/mail/__init__.py |  0
 health_check/contrib/mail/apps.py     | 12 ++++++++
 health_check/contrib/mail/backends.py | 28 +++++++++++++++++
 tests/test_mail.py                    | 44 +++++++++++++++++++++++++++
 tests/testapp/settings.py             |  1 +
 6 files changed, 96 insertions(+)
 create mode 100644 health_check/contrib/mail/__init__.py
 create mode 100644 health_check/contrib/mail/apps.py
 create mode 100644 health_check/contrib/mail/backends.py
 create mode 100644 tests/test_mail.py

diff --git a/README.md b/README.md
index 833fd270..523e018a 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,7 @@ The following health checks are bundled with this project:
 - Celery ping
 - RabbitMQ
 - Migrations
+- Mail
 
 Writing your own custom health checks is also very quick and easy.
 
@@ -74,6 +75,7 @@ Add the `health_check` applications to your `INSTALLED_APPS`:
         'health_check.contrib.s3boto3_storage',     # requires boto3 and S3BotoStorage backend
         'health_check.contrib.rabbitmq',            # requires RabbitMQ broker
         'health_check.contrib.redis',               # requires Redis broker
+        'health_check.contrib.mail',
     ]
 ```
 
@@ -90,6 +92,15 @@ one of these checks, set its value to `None`.
     }
 ```
 
+(Optional) If using the `mail` app, you can configure timeout
+threshold settings; otherwise below defaults are assumed.
+
+```python
+    HEALTH_CHECK = {
+        'MAIL_TIMEOUT': 15,  # seconds
+    }
+```
+
 To use Health Check Subsets, Specify a subset name and associate it with the relevant health check services to utilize Health Check Subsets.
 ```python
     HEALTH_CHECK = {
diff --git a/health_check/contrib/mail/__init__.py b/health_check/contrib/mail/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/health_check/contrib/mail/apps.py b/health_check/contrib/mail/apps.py
new file mode 100644
index 00000000..292c7125
--- /dev/null
+++ b/health_check/contrib/mail/apps.py
@@ -0,0 +1,12 @@
+from django.apps import AppConfig
+
+from health_check.plugins import plugin_dir
+
+
+class HealthCheckConfig(AppConfig):
+    name = "health_check.contrib.mail"
+
+    def ready(self):
+        from .backends import MailHealthCheck
+
+        plugin_dir.register(MailHealthCheck)
diff --git a/health_check/contrib/mail/backends.py b/health_check/contrib/mail/backends.py
new file mode 100644
index 00000000..3ab2cd0d
--- /dev/null
+++ b/health_check/contrib/mail/backends.py
@@ -0,0 +1,28 @@
+import logging
+
+from django.core.mail import get_connection
+
+from health_check.backends import BaseHealthCheckBackend
+from health_check.conf import HEALTH_CHECK
+from health_check.exceptions import ServiceUnavailable
+
+logger = logging.getLogger(__name__)
+
+
+class MailHealthCheck(BaseHealthCheckBackend):
+    """Check that mail backend is working."""
+
+    def check_status(self) -> None:
+        """Open and close connection email server."""
+        try:
+            connection = get_connection(fail_silently=False)
+            connection.timeout = HEALTH_CHECK.get("MAIL_TIMEOUT", 15)
+            logger.debug("Trying to open connection to mail backend.")
+            connection.open()
+            connection.close()
+            logger.debug("Connection established. Mail backend is healthy.")
+        except Exception as error:
+            self.add_error(
+                error=ServiceUnavailable(error),
+                cause=error,
+            )
diff --git a/tests/test_mail.py b/tests/test_mail.py
new file mode 100644
index 00000000..58c9c8ab
--- /dev/null
+++ b/tests/test_mail.py
@@ -0,0 +1,44 @@
+from unittest import mock
+
+from health_check.contrib.mail.backends import MailHealthCheck
+
+
+class TestMailHealthCheck:
+    """Test mail health check."""
+
+    @mock.patch("health_check.contrib.mail.backends.get_connection")
+    def test_mail_conn_ok(self, mocked_backend):
+        """Test everything is OK."""
+
+        # instantiates the class
+        mail_health_checker = MailHealthCheck()
+
+        # invokes the method check_status()
+        mail_health_checker.check_status()
+        assert len(mail_health_checker.errors) == 0, mail_health_checker.errors
+
+        # mock assertions
+        assert mocked_backend.return_value.timeout == 15
+        mocked_backend.return_value.open.assert_called_once()
+        mocked_backend.return_value.close.assert_called_once()
+
+    @mock.patch("health_check.contrib.mail.backends.get_connection")
+    def test_mail_conn_refused(self, mocked_backend):
+        """Test case then connection refused."""
+
+        mocked_backend.return_value.open.side_effect = ConnectionRefusedError(
+            "Refused connection"
+        )
+        # instantiates the class
+        mail_health_checker = MailHealthCheck()
+
+        # invokes the method check_status()
+        mail_health_checker.check_status()
+        assert len(mail_health_checker.errors) == 1, mail_health_checker.errors
+        assert (
+            mail_health_checker.errors[0].message
+            == mocked_backend.return_value.open.side_effect
+        )
+
+        # mock assertions
+        mocked_backend.return_value.open.assert_called_once()
diff --git a/tests/testapp/settings.py b/tests/testapp/settings.py
index 620e7190..bcdfb6ad 100644
--- a/tests/testapp/settings.py
+++ b/tests/testapp/settings.py
@@ -30,6 +30,7 @@
     "health_check.contrib.migrations",
     "health_check.contrib.celery_ping",
     "health_check.contrib.s3boto_storage",
+    "health_check.contrib.mail",
     "tests",
 )