euen / sumo_db

Erlang Persistency Framework

sumo_db

About

This is a work in progress. There's also an article about sumo_db. This articles might be a little outdated by now, but can still provide some basic information on how to get started.

sumo_db aims to ease db access for erlang applications. It offers a very simple persistance layer capable of interacting with different db's, while offering a consistent api to your code.

Contact Us

For questions or general comments regarding the use of this library, please use our public hipchat room.

If you find any bugs or have a problem while using this library, please open an issue in this repo (or a pull request :)).

And you can check all of our open-source projects at inaka.github.io

Overview

• sumo_db gives you a standard way to define your db schema, regardless of the db implementation (mongo, mysql, redis, elasticsearch, etc.).

• Your entities encapsulate behavior in code (i.e. functions in a module) and state in a sumo:doc() implementation.

• sumo is the main module. It translates to and from sumo internal records into your own state.

• Each repo is managed by a worker pool of processes, each one using a module that implements sumo_repo and calls the actual db driver (e.g: sumo_repo_mysql).

• Some native domain events are supported, that are dispatched through a gen_event:notify/2 automatically when an entity is created, updated, deleted. Also when a schema is created and when all entities of a given type are deleted. Events are described in this article.

• Full conditional logic support when using find_by/2 and delete_by/2 function. You can find more information about the syntax of this conditional logic operators here.

• Support for sorting (asc or desc) based on multiple fields unsing find_by/5 and find_all/4 functions. For example this [{age, desc}, {name, asc}]] will sort descendently by age and ascendently by name.

Backends, Stores and Repositories modules

These three concepts have a specific meaning in the context of sumo_db.

• Backend: holds the connection to a single instance of a database, which can be MySql, MongoDB, ElasticSearch or any other that's implemented.

• Store: implements the specific operations that modify the contents of the backend and retrieves the information it holds.

• Repository: the application that uses sumo_db should implement one repository for each entity that's defined in it. The repository is the module that bridges the model and the store.

Implementing an Adapter

TO implement an adapter, you must implement two behaviors: sumo_backend and sumo_store.

Events

Sumo dispatches events when things happen. An Event has this structure:

{EventId, Model, Event, Args}

• EventId is a reference() which identifies the event
• Model is the model where the event happend, for example, if we are creating a new entitiy in the model people the value of Model would be people.
• Event is the type of the event.
• Args extra data sent.

Supported types of events:

• pre_persisted just before persisting some entity. This event has the entity we want to persist as Args. It is dispatched on this function:
  • sumo:persist/2
• persisted just after persisting some entity. This event has the persisted entity as Args. This Event has the same EventId as its pre_persisted event. It is dispatched on this function:
  • sumo:persist/2
• pre_delete_all just before deleting all entities for a model. This event has no Args. It is dispatched on this function:
  • sumo:delete_all/1
• deleted_all just after deleting all entities for a model. This event has no Args. This Event has the same EventId as its pre_delete_all event. It is dispatched on this function:
  • sumo:delete_all/1
• pre_deleted just before deleting an entity. This event has the entity id as Args. It is dispatched on this function:
  • sumo:delete/2
• deleted just after deleting an entity. This event has the entity id as Args. This Event has the same EventId as its pre_deleted event. It is dispatched on this function:
  • sumo:delete/2
• pre_deleted_total just before deleting by some delete conditions. This event has the sumo conditions as Args. It is dispatched on this function:
  • sumo:delete_by/2
• deleted_total just after deleting by some delete conditions. This event has a list with the number of entities deleted and the delete conditions as Args. This Event has the same EventId as its pre_deleted_total event. It is dispatched on this function:
  • sumo:delete_by/2
• pre_schema_created just before creating a sumo schema. This event has no Args. It is dispatched on this function:
  • sumo:create_schema/2
• schema_created just after creating a sumo schema. This event has no Args. This Event has the same EventId as its pre_schema_created event. It is dispatched on this function:
  • sumo:create_schema/2

Sumo requires users to add their own gen_event's in order to handle those events. In order to add them Users have to configure sumo properly. In the config file we can add them like this under sumo_db configuration:

{events, [
     {'_', sumo_test_people_events_manager},
     {people, sumo_test_people_events_manager}
   ]}

Sumo allows us to add a gen_event to one type of model (i.e. people) or for all ('_').

Example

See: examples/blog for a full example. To run it, while being in the top level directory:

make all blog

Running Dialyzer

$ rebar3 dialyzer

Running Tests

$ rebar3 ct

Change Log

All notable changes to this project will be documented in the CHANGELOG.md.

Contributors

We want to thank all of our contributors for their hard work :muscle:.