Why does Phoenix (ecto/Postgresx) fail to Connect in dev

Question

I am beginning my Elixir/Phoenix journey and having some trouble with my postgres connection.

When I start up my server I get:

 $ mix phoenix.server
 [error] Postgrex.Protocol (#PID<0.214.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.217.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.218.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.211.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.215.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.219.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.216.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.213.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.212.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [error] Postgrex.Protocol (#PID<0.210.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused
 [info] Running Rumbl.Endpoint with Cowboy using http://localhost:4000
 [error] Postgrex.Protocol (#PID<0.215.0>) failed to connect: ** (Postgrex.Error) tcp connect: connection refused - :econnrefused

Being new to Elixir, Phoenix, and Ecto I am unclear how to debug this problem. Any suggestions as to what my problem is or how I might go about debugging it would be much appreciated.

My app's set up

I have a basic app

mix phoenix.new rumbl
cd rumbl
mix deps.get
mix deps.compile

My config/dev.exs has the following db setup

# Configure your database
config :rumbl, Rumbl.Repo,
  adapter: Ecto.Adapters.Postgres,
  username: "elixir",
  database: "rumbl_dev",
  hostname: "localhost",
  pool_size: 10

When I run mix ecto.create there are no errors and I can see the rumbl_dev when I run \l in psql. It is owned by the elixir user too.

Running mix ecto.migrate throws the same connections errors

My pg_hba.conf file has the following

local   all             all                                     trust
# IPv4 local connections:
host    all             all             127.0.0.1/32            trust
# IPv6 local connections:
host    all             all             ::1/128                 trust

Here is what I see when I log in with psql

$ psql --dbname=rumbl_dev --username=elixir --host=127.0.0.1 --password
Password for user elixir:
psql (9.4.5)
Type "help" for help.

rumbl_dev=>

Answer 1

This happened to me twice, after macOS crashed.

Most recently I used this:

Fix 1

1. Run postgres -D /usr/local/var/postgres

2. Copy the number after PID if you see something like this:

   FATAL:  lock file "postmaster.pid" already exists 
   HINT:   Is another postmaster (PID 379) running in data directory "/usr/local/var/postgres"?
   

3. kill -9 PID with the process # in place of PID.

---

The steps that worked for me previously:

Fix 2

brew update
brew upgrade
brew postgresql-upgrade-database