1. The number of letters that we send to DVLA will be not be correct (see 20ead82463/app/celery/letters_pdf_tasks.py (L136))
This may raise an alert with DVLA when they find we have sent them fewer letter than we have reported.
2. When we get the PDF from S3 we will get a file not found 20ead82463/app/celery/letters_pdf_tasks.py (L244)
The error will not prevent the collate task from completing but we will see an alert email for the exception and raise questions.
Although this situation is very unlikely because we have a 15 minute window between the last letter deadline date and the time we kick off the collate task we should still mitigate these issues. I updated the queries to only return letters with billable_units > 0, all valid letters should have at least 1 billable unit.
It is possible that the personalisation for a templated letter can make the letter exceed 10 pages or 5 sheets. We are not validating the letters posted via the API for this validation error. It is only possible to validate the letter once we create the PDF in notifications-template-preview. This means that the letter can only get a validation-failed status after the client has received a 201 from the POST to /v2/notifications.
NOTE: we only validate the preview row of a CSV for this validation error, this change will mean that it is possible for a letter to be marked as validation-failed after a successful file upload.
A new task to update the notification to `validation-failed` has been added to the API. If we find that the letter is too long once we have created the PDF we call the `update-validation-failed-for-templated-letter` task rather than `update-billable-units-for-letter` task.
New work flow for a letter in brief:
API - receives POST /v2/notifications
:: save to db
:: put CREATE_LETTERS_PDF task on queue for template preview to consume
TEMPLATE-PREVIEW - consumes task CREATE_LETTERS_PDF
:: create PDF
:: count pages of PDF
:: IF page count exceeds 10 pages
put in the letters-invalid-pdf S3 bucket with metadata (similar to the precompiled letters)
put `update-validation-failed-for-templated-letter` task on the queue for the API to consume
ELSE
put PDF in the `letters-pdf` bucket
put `update-billable-units-for-letter` task on the queue
API - consumes `update-billable-units-for-letter` OR `update-validation-failed-for-templated-letter` task
:: IF `update-billable-units-for-letter` task:
update billable units for notification as usual
:: ELSE `update-validation-failed-for-templated-letter`:
update notification_status = `validation-failed`
ADMIN - view notification page for letter
:: show validation letter for templated letter
There will be 3 PRs in order to make this change, one for the API, template-preview and the admin app.
Deployment plan
Deploy Admin first
Deploy API
Deploy template-preview
Related PRs:
alphagov/notifications-template-preview#619alphagov/notifications-admin#4107https://www.pivotaltracker.com/story/show/169209742
Previously we were catching one type of exception if something went
wrong adding a notification to the queue for high volume services.
In reality there are two types of exception so this adds a second
handler to cover both.
For context, this is code we changed experimentally as part of the
upgrade to Celery 5 [1]. At the time we didn't check how the new
exception compared to the old one. It turns out they behaved the
same and we were always vulnerable to the scenario now covered by
the second exception, where the behaviour has changed in Celery 5 -
testing with a large task invocation gives...
Before (Celery 3, large-ish task):
'process_job.apply_async(["a" * 200000])'...
boto.exception.SQSError: SQSError: 400 Bad Request
<?xml version="1.0"?><ErrorResponse xmlns="http://queue.amazonaws.com/doc/2012-11-05/"><Error><Type>Sender</Type><Code>InvalidParameterValue</Code><Message>One or more parameters are invalid. Reason: Message must be shorter than 262144 bytes.</Message><Detail/></Error><RequestId>96162552-cd96-5a14-b3a5-7f503300a662</RequestId></ErrorResponse>
Before (Celery 3, very large task):
<hangs forever>
After (Celery 5, large-ish task):
botocore.exceptions.ClientError: An error occurred (InvalidParameterValue) when calling the SendMessage operation: One or more parameters are invalid. Reason: Message must be shorter than 262144 bytes.
After (Celery 5, very large task):
botocore.parsers.ResponseParserError: Unable to parse response (syntax error: line 1, column 0), invalid XML received. Further retries may succeed:
b'HTTP content length exceeded 1662976 bytes.'
[1]: 29c92a9e54
These tasks need to repeatedly get the same template and service from
the database. We should be able to improve their performance by getting
the template and service from the cache instead, like we do in the REST
endpoint code.
Flake8 Bugbear checks for some extra things that aren’t code style
errors, but are likely to introduce bugs or unexpected behaviour. A
good example is having mutable default function arguments, which get
shared between every call to the function and therefore mutating a value
in one place can unexpectedly cause it to change in another.
This commit enables all the extra warnings provided by Flake8 Bugbear,
except for:
- the line length one (because we already lint for that separately)
- B903 Data class should either be immutable or use `__slots__` because
this seems to false-positive on some of our custom exceptions
- B902 Invalid first argument 'cls' used for instance method because
some SQLAlchemy decorators (eg `declared_attr`) make things that
aren’t formally class methods take a class not an instance as their
first argument
It disables:
- _B306: BaseException.message is removed in Python 3_ because I think
our exceptions have a custom structure that means the `.message`
attribute is still present
Matches the work done in other repos:
- https://github.com/alphagov/notifications-admin/pull/3172/files
This code is already restricted to SMS and email, so this is only to make it obvious if there is a code refactor down the line. Perhaps this is overkill and we back out this commit.
When we initially added a new task to persist the notifications for a high volume service we wanted to implement it as quickly as possible, so ignored SMS.
This will allow a high volume service to send SMS, the SMS will be sent to a queue to then persist and send the SMS, similar to emails.
At this point I haven't added a new application to consume the new save-api-sms-tasks. But we can add a separate application or be happy with how the app scales for both email and sms.
Years ago we started to implement a way to schedule a notification. We hit a problem but we never came up with a good solution and the feature never made it back to the top of the priority list.
This PR removes the code for scheduled_for. There will be another PR to drop the scheduled_notifications table and remove the schedule_notifications service permission
Unfortunately, I don't think we can remove the `scheduled_for` attribute from the notification.serialized method because out clients might fail if something is missing. For now I have left it in but defaulted the value to None.
Same as we’re doing for templates.
This means avoiding a database call, even for services that don’t hit
our API so often.
They’ll still need to go to the database for the API keys, because we’re
not comfortable putting the API key secrets in Redis.
But once a service has got its keys from the database we commit the
transaction, so the connection can be freed up until we need it again to
insert the notification.
Same as we’ve done for templates.
For high volume services this should mean avoiding calls to external
services, either the database or Redis.
TTL is set to 2 seconds, so that’s the maximum time it will take for
revoking an API key or renaming a service to propagate.
Some of the tests created services with the same service ID. This
caused intermittent failures because the cache relies on unique service
IDs (like we have in the real world) to key itself.
By serialising these straight away we can:
- not go back to the database later, potentially closing the connection
sooner
- potentially cache the serialised data, meaning we don’t touch the
database at all
For some reason our V1 get template response wraps the whole template in
a dictionary with one key, `'data'`:
0d99033889/app/template/rest.py (L166)
That means when the admin app caches the response it also caches it in
this format.
The API needs to do the same, otherwise it will be cacheing data with a
schema that the admin app isn’t expecting, and vice-versa.
In the previous PR I removed the `update_notification` method to reduce the need for another update query. However, that meant the notification was marked as delivered without an updated_at timestamp.
It is weird to set the updated_at when we create the notification. So is this a better fix? Or do I put the update back now?
I recommend we push this fix now.
After the commit we issue two calls to the db to get service and get notification. This is because after the commit the ORM wants to ensure that the data model objects are the latest.
So far this is just a proof of concept, but the letter flow needs to be updated and we should be able to get rid of research mode. And it needs some tidy up.
For services that have permission to send international letters we
should not reject letters that are addressed to another country. We
should still reject letters that are badly-addressed.
This is part of moving away from `postcode` and towards `address line 7`
We think it will be easier for people to map their existing data to our
API if we let them fill in any 3 lines, instead of requiring at least
1, 2, and postcode specifically.
We don’t need to reformat the postcode here once template preview takes
care of it when rendering the PDF.
It’s better (and less code) to store what people give us, so we give
them back the same thing.
