phoenix_postgres_pub_sub v0.1.2 PhoenixPostgresPubSub
PhoenixPostgresPubSub
Listen to changes to the tables of your Postgres database. For every INSERT or UPDATE in a specified table, a function will be called with the payload.
Installation
If available in Hex, the package can be installed
by adding phoenix_postgres_pub_sub
to your list of dependencies in mix.exs
:
def deps do
[
{:phoenix_postgres_pub_sub, "~> 0.1.0"}
]
end
Configuration
In your config.exs add the following:
config :phoenix_postgres_pub_sub, :config,
adapter: MainModuleOfYourApp, # this should be the main module of your phoenix application
repo: MainModuleOfYourApp.Repo # and this should be the main repo of your phoenix application
In your Application Module change the configuration in the following way:
defmodule MainModuleOfYourApp do
use Application
# See http://elixir-lang.org/docs/stable/elixir/Application.html
# for more information on OTP Applications
def start(_type, _args) do
import Supervisor.Spec, warn: false
children = [
# Start the endpoint when the application starts
supervisor(MainModuleOfYourApp.Endpoint, []),
# Start the Ecto repository
worker(MainModuleOfYourApp.Repo, []),
worker(
PhoenixPostgresPubSub,
[
[
"skills_changes" # this should be always in the format NAME_OF_TABLE_changes,
"users_changes" # this should be always in the format NAME_OF_TABLE_changes,
"companies_changes" # this should be always in the format NAME_OF_TABLE_changes,
...
]
],
restart: :permanent
),
# Here you could define other workers and supervisors as children
# worker(MainModuleOfYourApp.Worker, [arg1, arg2, arg3]),
]
Generate the migration
At this point you have to generate a migration to add the trigger to Postgres. You can do this by running the following command:
mix phoenix_postgres_pub_sub.gen.channel CHOOSE_A_MIGRATION_NAME --table=users
# check the migration file just generated and make your changes if necessary
And run the migration with mix ecto.migration
--table
is the table upon which your want to listen to changes
Generate your adapter
Create a module called something like MainModuleOfYourApp.PhoenixPostgresPubSub
.
This module should have a function called handle_postgres_notification
that accepts two arguments: notification, state
The notification is the one generated by Postgres and sent to this function, while the state is the state of GenServer of PhoenixPostgresPubSub
Test it out
You you have followed all the steps correctly you should be able to make changes to the table on which your are listening to and you should see that the function MainModuleOfYourApp.PhoenixPostgresPubSub.handle_postgres_notification/2
is called every time this happens.
Link to this section Summary
Functions
Returns a specification to start this module under a supervisor
Listen for changes
When the GenServer starts subscribe to the given channel
Initialize the GenServer
Link to this section Functions
Returns a specification to start this module under a supervisor.
See Supervisor
.
Listen for changes
When the GenServer starts subscribe to the given channel
Initialize the GenServer