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WIP - Reject duplicate submissions #876

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@noliveleger noliveleger commented May 8, 2023

Description

TBC

Additional info

would supersede #859

@noliveleger noliveleger requested a review from jnm May 8, 2023 19:46
@noliveleger noliveleger force-pushed the duplicate-submissions branch 3 times, most recently from 9b39237 to 53c6320 Compare May 9, 2023 18:45
@@ -52,7 +52,7 @@ jobs:
- name: Install Python dependencies
run: pip-sync dependencies/pip/dev_requirements.txt
- name: Run pytest
run: pytest -vv -rf
run: pytest -vv -rf --disable-warnings
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🤔

@@ -32,6 +32,7 @@ test:
POSTGRES_PASSWORD: kobo
POSTGRES_DB: kobocat_test
SERVICE_ACCOUNT_BACKEND_URL: redis://redis_cache:6379/4
GIT_LAB: "True"
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maybe something more descriptive like SKIP_TESTS_WITH_CONCURRENCY

@@ -40,7 +41,7 @@ test:
script:
- apt-get update && apt-get install -y ghostscript gdal-bin libproj-dev gettext openjdk-11-jre
- pip install -r dependencies/pip/dev_requirements.txt
- pytest -vv -rf
- pytest -vv -rf --disable-warnings
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🤔

Comment on lines +90 to +94
fakeredis.FakeStrictRedis(),
):
with patch(
'onadata.apps.django_digest_backends.cache.RedisCacheNonceStorage._get_cache',
fakeredis.FakeStrictRedis,
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why is one instantiated and the other isn't?

results[result] += 1

assert results[status.HTTP_201_CREATED] == 1
assert results[status.HTTP_409_CONFLICT] == DUPLICATE_SUBMISSIONS_COUNT - 1
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does the OpenRosa spec allow returning a 409? and do Enketo and Collect handle a 409 properly? i can't find the code, but i remember wanting to return a 40x that wasn't 400 but being forced to use 400 only because without it Collect wouldn't display the error message i was sending. could've been Enketo, though, or i might be misremembering entirely

Comment on lines +171 to +176
# The start-time requirement protected submissions with identical responses
# from being rejected as duplicates *before* KoBoCAT had the concept of
# submission UUIDs. Nowadays, OpenRosa requires clients to send a UUID (in
# `<instanceID>`) within every submission; if the incoming XML has a UUID
# and still exactly matches an existing submission, it's certainly a
# duplicate (https://docs.opendatakit.org/openrosa-metadata/#fields).
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We should reject outright any submission without a UUID

Comment on lines +189 to +194
if existing_instance:
existing_instance.check_active(force=False)
# ensure we have saved the extra attachments
new_attachments = save_attachments(existing_instance, media_files)
if not new_attachments:
raise DuplicateInstanceError()
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@jnm jnm Jun 14, 2023

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Wouldn't ConflictingXMLHashInstanceError be raised already and block us from getting here? Nevermind; I misunderstood, and that exception only has to do with concurrent processing of submissions with identical XML

Comment on lines +229 to +238
if is_postgresql:
cur = connection.cursor()
cur.execute('SELECT pg_try_advisory_lock(%s::bigint);', (int_lock,))
acquired = cur.fetchone()[0]
else:
prefix = os.getenv('KOBOCAT_REDIS_LOCK_PREFIX', 'kc-lock')
key_ = f'{prefix}:{int_lock}'
redis_lock = settings.REDIS_LOCK_CLIENT.lock(key_, timeout=60)
acquired = redis_lock.acquire(blocking=False)
yield acquired
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I don't think support for something other than PostgreSQL is needed. We already depend on Postgres for many things.

Moot point, then, but just to say it: I think all os.getenv() for configuration (and default values) should be in the settings files

Comment on lines -544 to +581
except DuplicateInstance:
response = OpenRosaResponse(t("Duplicate submission"))
except ConflictingXMLHashInstanceError:
response = OpenRosaResponse(t('Conflict with already existing instance'))
response.status_code = 409
response['Location'] = request.build_absolute_uri(request.path)
error = response
except DuplicateInstanceError:
response = OpenRosaResponse(t('Duplicate instance'))
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@jnm jnm Jun 14, 2023

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A conflicting XML hash with no additional attachments is the same thing as a duplicate instance. If the XML is the same but there are additional attachments, no exception should be raised; this is normal operation. I don't think a new exception class is needed. I also don't think that DuplicateInstanceError can be reached anymore, but that's addressed by a different comment [was based on a misunderstanding]

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@jnm jnm Jul 6, 2023

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The thing that confused me about this is that the verbiage is wrong. It's not a really a conflict with an existing instance, it's unwanted concurrent processing of two (or more) instances with identical XML.

I think ideally we should wait (a short amount of time) to try to acquire the lock before returning an error. I don't know what happens in Enketo now, but it's easy to imagine that a client would asynchronously send the following requests concurrently:

  1. Submission XML (hash abc123) + dog.jpg
  2. Submission XML (hash abc123) + cat.jpg
  3. Submission XML (hash abc123) + gecko.jpg

Ideally, all three requests would succeed. Let's assume request 1 arrives first and is still processing while requests 2 and 3 are received by the server: what I understand this PR would do is reject requests 2 and 3 immediately with an error code. I think we should wait (again, briefly) for request 1 to finish1 before returning an immediate rejection.

If the waiting takes too long, then we do have to reject in order to avoid sapping the worker pool with useless spinning. The message we return should be effectively "try again later", not something about a conflict with an existing instance. The HTTP code has to be dependent on the OpenRosa specification and compatible with Enketo and ODK Collect. Hopefully, those requirements are one and the same, but we'll have to test.

Footnotes

  1. Addendum: Whoops, we don't really need to spin until request 1 finishes, we just need to wait until the row has been created in logger_instance. Imagine one POST has 50 files: locking while all 50 are written to storage is not what we want. We should still avoid storing the same attachment multiple times for a submission, so within a single submission, we should have some kind of attachment uniqueness constraint (if we don't already).

@@ -1,6 +1,7 @@
# coding: utf-8
import os

from fakeredis import FakeConnection, FakeStrictRedis, FakeServer
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Ah, was the support for locking without PostgreSQL exclusively for unit testing?

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Unit testing, at least on GitLab, is already using PostgreSQL, so I don't think we need to support any non-Postgres locking mechanisms for this

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2 participants