feature/atomic-many-updates flaw - Functional test to demonstrate Doctrine ODM queries load inconsistent data from the database while a concurrent request is writing to the same record

[blockjon]

This PR's branch has linage to feature/atomic-many-updates. I created it to demonstrate that the atomic feature that you are shooting for seems not to solve for a key data inconsistency problem I am grappling with.

The ODM does not save database records with embedded documents in an atomic fashion.

Even with ODM versioning, a concurrent PHP request which loads a Mongo record while another PHP request is writing the same record will load an incomplete and inconsistent version of the Mongo record into a Doctrine ODM model. This has been a repeated cause of data loss and corruption.

Repro steps:

Run this unit test:

phpunit --filter testDataConsistencyUsingEmbeddedDocuments ./tests/Doctrine/ODM/MongoDB/Tests/Functional/VersionTest.php 

Result:

PHPUnit 4.1.6 by Sebastian Bergmann.

Configuration read from /srv/repos/instant-server/extrashared/mongodb-odm/phpunit.xml

F

Time: 315 ms, Memory: 3.25Mb

There was 1 failure:

1) Doctrine\ODM\MongoDB\Tests\Functional\VersionTest::testDataConsistencyUsingEmbeddedDocuments
Version #2 of the versioned user object should have a phone number embedded document. However, 0 phone number embedded documents were found
Failed asserting that 0 matches expected 1.

/srv/repos/instant-server/extrashared/mongodb-odm/tests/Doctrine/ODM/MongoDB/Tests/Functional/VersionTest.php:84

FAILURES!
Tests: 1, Assertions: 3, Failures: 1.

[malarzm]

Closing since we introduced another PR for the feature and feature/atomic-many-updates is not relevant