Anymail: retry sending failed emails

Before this commit, emails that couldn’t be sent were simply discarded,
because the code didn’t check the status from anymail.

Anymail exposes a status for each recipient of an email, raising many
questions on the expected behavior should one fail to be delivered out
of multiple recipients.

As a first step, simply trust Mailjet API Status field.

https://anymail.dev/en/stable/sending/django_email/#refused-recipients
https://anymail.dev/en/stable/sending/anymail_additions/#anymail.message.AnymailStatus

itou/utils/tasks.py

@@ -1,6 +1,7 @@
 import logging
 from functools import partial
 
+import sentry_sdk
 from django.conf import settings
 from django.core.mail import get_connection
 from django.core.mail.backends.base import BaseEmailBackend
@@ -111,8 +112,8 @@ def _async_send_messages(serializable_email_messages):
     return len(messages)
 
 
-@task(retries=_NB_RETRIES, retry_delay=settings.SEND_EMAIL_DELAY_BETWEEN_RETRIES_IN_SECONDS)
-def _async_send_message(serialized_email):
+@task(retries=_NB_RETRIES, retry_delay=settings.SEND_EMAIL_DELAY_BETWEEN_RETRIES_IN_SECONDS, context=True)
+def _async_send_message(serialized_email, task=None):
     """
     An `EmailMessage` instance holds references to some non-serializable
     ressources, such as a connection to the email backend (if not `None`).
@@ -123,6 +124,16 @@ def _async_send_message(serialized_email):
     with get_connection(backend=settings.ASYNC_EMAIL_BACKEND) as connection:
         email = _deserializeEmailMessage(serialized_email)
         connection.send_messages([email])
+    # Mailjet has a global flag for an email to indicate success.
+    # Anymail iterates over recipients and assign each a status, following its
+    # documented API. Mailjet indicating success is good enough.
+    # https://dev.mailjet.com/email/guides/send-api-v31/
+    esp_response = email.anymail_status.esp_response.json()
+    [result] = esp_response["Messages"]
+    if result["Status"] != "success":
+        if task and task.retries:
+            raise Exception("Huey, please retry this task.")
+        sentry_sdk.capture_message(f"Could not send email: {result}", "error")
     return 1
 
 

requirements/dev.txt

@@ -1300,6 +1300,11 @@ requests==2.32.0 \
     # via
     #   -r requirements/test.txt
     #   django-anymail
+    #   requests-mock
+requests-mock==1.12.1 \
+    --hash=sha256:b1e37054004cdd5e56c84454cc7df12b25f90f382159087f4b6915aaeef39563 \
+    --hash=sha256:e9e12e333b525156e82a3c852f22016b9158220d2f47454de9cae8a77d371401
+    # via -r requirements/test.txt
 respx==0.21.1 \
     --hash=sha256:05f45de23f0c785862a2c92a3e173916e8ca88e4caad715dd5f68584d6053c20 \
     --hash=sha256:0bd7fe21bfaa52106caa1223ce61224cf30786985f17c63c5d71eff0307ee8af

requirements/test.in

@@ -21,5 +21,7 @@ pytest-randomly  # https://github.com/pytest-dev/pytest-randomly
 pytest-subtests  # https://github.com/pytest-dev/pytest-subtests
 pytest-xdist  # https://pypi.org/project/pytest-xdist/
 unittest-parametrize  # https://github.com/adamchainz/unittest-parametrize
+# Mock Anymail requests.
+requests-mock  # https://github.com/jamielennox/requests-mock
 respx  # https://lundberg.github.io/respx/
 syrupy  # https://github.com/tophat/syrupy

requirements/test.txt

@@ -1177,6 +1177,11 @@ requests==2.32.0 \
     # via
     #   -r requirements/base.txt
     #   django-anymail
+    #   requests-mock
+requests-mock==1.12.1 \
+    --hash=sha256:b1e37054004cdd5e56c84454cc7df12b25f90f382159087f4b6915aaeef39563 \
+    --hash=sha256:e9e12e333b525156e82a3c852f22016b9158220d2f47454de9cae8a77d371401
+    # via -r requirements/test.in
 respx==0.21.1 \
     --hash=sha256:05f45de23f0c785862a2c92a3e173916e8ca88e4caad715dd5f68584d6053c20 \
     --hash=sha256:0bd7fe21bfaa52106caa1223ce61224cf30786985f17c63c5d71eff0307ee8af

tests/utils/test_emails.py

@@ -1,7 +1,8 @@
+import pytest
 from django.core.mail.message import EmailMessage
 from factory import Faker
 
-from itou.utils.tasks import AsyncEmailBackend
+from itou.utils.tasks import AsyncEmailBackend, _async_send_message
 
 
 class TestAsyncEmailBackend:
@@ -28,3 +29,91 @@ def test_send_messages_splits_recipients(self, django_capture_on_commit_callback
             assert email.from_email == "[email protected]"
             assert email.subject == "subject"
             assert email.body == "body"
+
+
+@pytest.fixture
+def anymail_mailjet_settings(settings):
+    settings.ASYNC_EMAIL_BACKEND = "anymail.backends.mailjet.EmailBackend"
+    settings.ANYMAIL = {
+        "MAILJET_API_URL": settings.ANYMAIL["MAILJET_API_URL"],
+        "MAILJET_API_KEY": "MAILJET_API_SECRET",
+        "MAILJET_SECRET_KEY": "MAILJET_SECRET_KEY",
+    }
+    return settings
+
+
+class TestAsyncSendMessage:
+    EXC_TEXT = "Exception: Huey, please retry this task."
+
+    def test_send_ok(self, anymail_mailjet_settings, caplog, requests_mock):
+        requests_mock.post(
+            f"{anymail_mailjet_settings.ANYMAIL['MAILJET_API_URL']}send",
+            # https://dev.mailjet.com/email/guides/send-api-v31/#send-in-bulk
+            json={
+                "Messages": [
+                    {
+                        "Status": "success",
+                        "To": [
+                            {
+                                "Email": "[email protected]",
+                                "MessageUUID": "124",
+                                "MessageID": 20547681647433001,
+                                "MessageHref": "https://api.mailjet.com/v3/message/20547681647433001",
+                            },
+                        ],
+                    },
+                ],
+            },
+        )
+        _async_send_message({"to": ["[email protected]"], "cc": [], "bcc": [], "subject": "Hi", "body": "Hello"})
+        assert self.EXC_TEXT not in caplog.text
+
+    def test_raises_on_error(self, anymail_mailjet_settings, caplog, requests_mock):
+        """An exception is raised, to make Huey retry the task."""
+        requests_mock.post(
+            f"{anymail_mailjet_settings.ANYMAIL['MAILJET_API_URL']}send",
+            # https://dev.mailjet.com/email/guides/send-api-v31/#send-in-bulk
+            json={
+                "Messages": [
+                    {
+                        "Errors": [
+                            {
+                                "ErrorIdentifier": "88b5ca9f-5f1f-42e7-a45e-9ecbad0c285e",
+                                "ErrorCode": "send-0003",
+                                "StatusCode": 400,
+                                "ErrorMessage": 'At least "HTMLPart", "TextPart" or "TemplateID" must be provided.',
+                                "ErrorRelatedTo": ["HTMLPart", "TextPart"],
+                            },
+                        ],
+                        "Status": "error",
+                    },
+                ],
+            },
+        )
+        _async_send_message({"to": ["[email protected]"], "cc": [], "bcc": [], "subject": "Hi", "body": "Hello"})
+        assert self.EXC_TEXT in caplog.text
+
+    def test_logs_to_sentry_after_using_all_retries(self, anymail_mailjet_settings, caplog, requests_mock, mocker):
+        error_payload = {
+            "Errors": [
+                {
+                    "ErrorIdentifier": "88b5ca9f-5f1f-42e7-a45e-9ecbad0c285e",
+                    "ErrorCode": "send-0003",
+                    "StatusCode": 400,
+                    "ErrorMessage": 'At least "HTMLPart", "TextPart" or "TemplateID" must be provided.',
+                    "ErrorRelatedTo": ["HTMLPart", "TextPart"],
+                },
+            ],
+            "Status": "error",
+        }
+        requests_mock.post(
+            f"{anymail_mailjet_settings.ANYMAIL['MAILJET_API_URL']}send",
+            # https://dev.mailjet.com/email/guides/send-api-v31/#send-in-bulk
+            json={"Messages": [error_payload]},
+        )
+        sentry_mock = mocker.patch("itou.utils.tasks.sentry_sdk.capture_message")
+        _async_send_message(
+            {"to": ["[email protected]"], "cc": [], "bcc": [], "subject": "Hi", "body": "Hello"}, retries=0
+        )
+        sentry_mock.assert_called_once_with(f"Could not send email: {error_payload}", "error")
+        assert self.EXC_TEXT not in caplog.text