theAntimon
Running Phonix with SQLite for weather-data directly on the Pi (with nerves)
Hi,
I’m new to nerves but already managed to build the Weather Station (and also read the Binary-Clock-Book).
Now I want to modify the Weather-Station to make phoenix actually run directly on the Pi, so that I don’t need another Computer to hold the database. I started with adding hello_phoenix next to my sensor_hub folder. This worked good enough. After flashing the weather station I can see the phoenix default page in my browser. Now I need to add a database. I couldn’t find that much anywhere about that, but finally tried this to run SQLite on the pi. I had dependency problems when trying to add the :sqlite_ecto2 dependency but since the hello_phoenix example already had :ecto_sql and :ecto_sqlite3 in the mix.exs I skipped that step in the article. Then I configured the config.exs as described with
config :ui, Ui.Repo,
adapter: Sqlite.Ecto2,
database: "#{Mix.env}.sqlite3"
config :ui, ecto_repos: [Ui.Repo]
Running iex -S mix on my host now creates a database file at the root-level. But that one is not named ‘host.sqlite3’ as I understand it from the article but just ‘ui_dev.db’. It seems ecto is not asking for the database name I specified. Well this is not that much of a problem since I actually want to run it on the pi, right? But since I need to configure (later in the article) the place for the database on the pi by writing
config :ui, Ui.Repo,
adapter: Sqlite.Ecto2,
database: "/root/#{Mix.env}.sqlite3"
config :ui, ecto_repos: [Ui.Repo]
into a config/rpi2.exs. Well, that also doesn’t create any file into ‘/root/rpi2.sqlite3’ as far as I can see the filesystem on the pi (I checked with File.ls/1 after ssh-ing to the pi). Ok, Seems I have to fix the root of that problem. Does anyone have an idea what I am doing wrong? Has anybody done that before (running phoenix with a database for the weather-data on the target).
I wonder why I couldn’t find any good project modification for the weather-station anywhere. For me it is a obvious thing to do and I’m really wondering why it is not already included in the book. I don’t see that much of a use for a weather-station on a raspberry pi which needs another computer to run the database…
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axelson
I’d recommend trying Ecto SQLite3 instead of SQLite2: GitHub - elixir-sqlite/ecto_sqlite3: An Ecto SQLite3 adapter. · GitHub
The readme of the project should help you get started with it and there’s not really any nerves-specific setup that you’ll need I think.
To create the database I usually create a release module like:
defmodule Dash.Release do
@app :dash
def migrate do
load_app()
for repo <- repos() do
{:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :up, all: true))
end
end
def rollback(repo, version) do
load_app()
{:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :down, to: version))
end
defp repos do
Application.fetch_env!(@app, :ecto_repos)
end
defp load_app do
Application.load(@app)
end
end
Then connect to your Pi via ssh and run Dash.Release.migrate() and that should create the sqlite file on the Pi.
Good luck!
axelson
/data is actually a symlink to /root so database: "/root/#{Mix.env}.sqlite3" will work. Although using /data directly is generally recommended since that may change in the future.
jordan0day
As mentioned in the nerves docs here: Frequently Asked Questions — nerves v1.14.3, you’ll probably want to place your DB somewhere under the /data partition. I believe the root filesystem on nerves is read-only by default.
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