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MongoEngine + Relational + Privileges = Goodness!
Marcel van den Elston 29 November 2012
Transcript of MongoEngine + Relational + Privileges = Goodness!
Progressive Planning use case doesn't fit
RESTful API through Django-Tastypie
Wonderful. but. very. inefficient. Why abandon Django? not at all scalable without hard-coded SQL magic and lowest-level adding to Django and modding of Tastypie
no object level privileges
no offline working/syncing
no `private clusters` for corporates through partitioning
forced to optimize the wrong stuff in the wrong domain
started to `feel wrong` (aka `got smelly`) everything is JSON (BSON)!
deployment is a breeze
web-scalable and flexible out of the box (Replica Sets)
very active development + growing community
`feels` much better and more human(e) Why adopt MongoDB? computers can do more than digitize paper-era-thinking
`real` projects are about creative, excited, communicative, opinionated, multi-skilled human beings trying to achieve stuff together.
`real` projects are volatile, highly interdependent, multi-constrained, interactive, networked, constantly changing, uncertain, stressful
Progressive Planning supports REAL PROJECTS, i.e. YOU. Why Progressive Planning? (not about `resources` with statistical deviations that need to be measured and controlled) NoSQL = NoSchema = No Deal
small, transparent, active, mature, well-documented, readable, responsive authors
Django is not all bad: it seemed easier to port our existing code to something with similar syntax Why MongoEngine? turned out to be true after we created TastyMongo, mongoengine-relational and mongoengine-privileges for our inherently highly related data we have 2-way relations (1:n, n:m)
we need denormalization
we need caching
we need triggers when stuff changes
we don't want headaches Why `mongoengine-relational`? TastyMongo MongoEngine Progressive Planning + Relational + Privileges + TastyMongo = Goodness! Marcel van den Elst no joins! hard-coded brittleness, inconsistency, boiler-plate As it turned out we hardly used any of Django's features and most legacy stuff (non-AJAX tailored) actually got in the way Django-Tastypie is lovely until you need performance manages changes to relations (1:1, 1:n, m:n)
automatically updates the other side (atomic saves/deletes).
memoizes document fields to monitor differences
creates hooks for custom code when relational fields change
correctly handles and compares mixed types and states(!) of mongoengine relations
only 1 tiny extension to mongoengine's declarative syntax: just using the `related_name` argument sets everything up. mongoengine-relational features transparently caches documents in a thread-safe, self-attaching DocumentCache on the request object
setup couldn't be easier: DocumentCache( request ) suffices
interact with the cache through `add`, `get`, `remove`, or let the overridden internals take care of it: accessing a related field with <document>.<fieldname> uses the cache bonus: DocumentCache ObjectId strings, un-dereferenced ObjectIds, dereferenced objects, cached objects and DBRefs we need document-level and field-level permissions
we couldn't find an existing mixin that correctly and transparently handled object level privileges across relations Why `mongoengine-privileges`? on_change(...)
on_change_foo() mongoengine-privileges leverages mongoengine-relational
mixin with straightforward API mongoengine-privileges features may_foo(...) we had a RESTful API (TastyPie) that worked like a charm with our backbone-relational framework
we LOVED that functionality and separation of concerns!
but Tastypie is Django-Tastypie and we ditched Django
so we took all the good parts and created `TastyMongo`! Why `TastyMongo`? (except for its gross inefficiency) RESTful API for mongoengine (HTTP conform)
very similar to the great Django-Tastypie, but more consistent and simpler API
declarative syntax (like Django's or mongoengine's)
Django-style cross-relational filtering (`books__author__name`) that constructs the required separate NoSQL queries
error handling (without forcing HTML down AJAX throat...)
small functions that can easily be overridden where required
managed relations between resources (mapping to Documents)
Document field introspection and mapping to Resource fields
custom URI schemas
(de)serialization (JSON, XML, CSV, whatever you write) TastyMongo features because we had no install base and legacy to support again: no joins in NoSQL! Pyramid 'cause `they done things right`!
better Request/Response objects (Webob) compared to Django
nice traversal API
we actually use 90% of Pyramid, and used only about 20% of Django Why `Pyramid`?