sails-util-cold
v0.0.10
Published
Create a cold copy of models, for data consistency. Quite like event sourcing.
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sails-util-cold
You have to install it in the project where you want your models to be coldified.
How to use it
As this module tries to be compatible with all ways of injecting models in sails, including mvcsloader, you have to tell it to coldify models :
var cold = require('sails-util-cold')(sails);
cold.cold(__dirname + '/api/models');
Your models must have a cold
property set to true if you want them to be coldified.
What does it do
Coldify content
Cold creates cold copies of your contents, in order to keep track of every modification applied to it. This is an alternative to Event sourcing like described my Martin Fowler.
This way, you have 2 main versions of every piece of content : the "hot" one, and the "cold" ones, that you don't need to worry about.
The "hot" model is still named after your model (ie. MyModel) and the cold copy is named "Cold" (ie. MyModelCold).
Link cold contents to cold contents
Furthermore, Cold also doubles every relational attributes of your models. The relation, of type collection
(many-to-many or one-to-many) or model
(one-to-one), is kept as the original, pointing to the hot model from the cold one.
But Cold will create the same relational attribute "coldified", pointing to the cold instance of the pointed model if it exists.
Example : If model "Pet" has a relation to "Human" via "Owner" attribute, "PetCold" will have "Owner" attribute linking to "Human" model and "OwnerCold" attribute linking to "HumanCold" model.
Benefits
Every time you update a content (an instance of a model, let's say the dog "Pluto", instance of "Pet" model), Cold creates a cold copy of Pluto, so you have 2 instances of "PetCold" : the original one and the new one.
Time 0 :
Pet
ID | Name | Toy --- | --- | --- 1 | Pluto | Ball
PetCold
ID | Name | Toy | coldReference --- | --- | --- | --- 1 | Pluto | Ball | 1
Time 1 : We change Pluto's toy, he prefers now shoe
Pet
ID | Name | Toy --- | --- | --- 1 | Pluto | Shoe
PetCold
ID | Name | Toy | coldReference --- | --- | --- | --- 1 | Pluto | Ball | 1 2 | Pluto | Shoe | 1
Use it with caution !
Even if Cold tried to be the lightest possible, it is a huge amount of data that will be added to your database. Use it only if you absolutely need it on production environments, and don't set "cold" property on models that don't need it.
Todo
- Add a
cold
property on attributes, to specify if they have to be copied in cold copy of the model - Add sails-specific cold methods like
findCold
and so on