Elixir: Ecto/Tds error when connecting to SQL Server database - sql-server

Question

I've written an elixir application that connects to two different databases, and I have it working nicely in my remote database dev environment -- connecting with the same exact setup to a different database that is across my vpn. When I run it against a different remote SQL Server database, I get a strange error:
** (DBConnection.ConnectionError) bad return value: {:error, %Tds.Protocol{env: %{trans: <<0>>}, itcp: nil, opts: [password:
:REDACTED, idle_timeout: 5000, name: EventBridge.C3poRepo.Pool,
otp_app: :event_bridge, repo: EventBridge.C3poRepo, timeout: 15000,
pool_timeout: 5000, adapter: Tds.Ecto, username: :ALSO_REDACTED,
database: :REDACTED, hostname: :REDACTED, pool:
DBConnection.Poolboy], pak_data: "", pak_header: "", query:
%Tds.Query{handle: 1, statement: nil}, result: %Tds.Result{columns:
[], command: nil, num_rows: 0, rows: []}, sock: {:gen_tcp,
#Port<0.6472>}, state: :ready, tail: "", transaction: nil, usock: nil}}
The credentials I've got in my configuration for this database are correct--I verified them manually with DBeaver. I believe I'm capable of debugging this but I've run into a bit of that error message that I don't understand. Specifically:
{:error, %Tds.Protocol{env: %{trans: <<0>>}
For the sake of completeness, here the deps section in mix.exs:
defp deps do
[
{:tds_ecto, "~> 2.0.3"},
{:postgrex, ">= 0.0.0"},
{:gen_stage, "~> 0.12"},
{:timex, "~> 3.1"},
{:timex_ecto, "~> 3.0"},
{:poison, "~> 3.1"},
{:ecto, "~> 2.1"}
]
end
What I'm asking is for some insight into what that part of the error message means, or perhaps even some more general feedback on the entire error output.
Here are the two instances of configuration for the Repo in question. First the one that works:
config :event_bridge, EventBridge.FirstRepo,
adapter: Tds.Ecto,
database: "first_repo_development",
username: "testuser",
password: "password_redacted",
hostname: "server_one"
And here is the configuration for the one that doesn't work:
config :event_bridge, EventBridge.FirstRepo,
adapter: Tds.Ecto,
database: "first_repo_staging",
username: "staging_username",
password: "password_redacted",
hostname: "server_twelve"
Both work in DBeaver.

Answer 1

Add
pool_size:
in the db config and try again