Getting Diesel to connect from a Docker container to a Postgres instance via docker-compose

[alexanderbanks]

Setup

I'm trying to run a Diesel/Iron app that connects to a Postgres instance. For development I'm trying to use Docker/Docker-Compose. This might not be a bug with Diesel (it probably isn't), but I was curious if the Diesel maintainers might have some insight into setting this up properly?

Versions

In terms of versions, I'm using the official Rust Docker image, version rust:1.19.0, postgres:9.6.

What are you trying to accomplish?

The dockerfile looks like this:

FROM rust:1.19.0
WORKDIR app
ADD . /app
EXPOSE 3000
RUN cargo build
ENTRYPOINT ["target/debug/app-api"]

With a docker-compose file:

version: '3'
services:
  db:
    image: "postgres:9.6"
    ports:
      - "5432:5432"
    volumes:
      - ./db/db.sql:/docker-entrypoint-initdb.d/01_db.sql
      - ./db/data.sql:/docker-entrypoint-initdb.d/02_data.sql
    environment:
      POSTGRES_DB: my_db
      POSTGRES_PASSWORD: docker
      POSTGRES_USER: docker
  web:
    build: .
    ports:
     - "3000:3000"
    links:
      - "db:db"
    env_file:
      - .env

The env file:

DATABASE_URL=postgresql://docker:docker@db:5432/my_db

What is the expected output?

Diesel connects to the postgres image just like it would a postgres image not on a local network

What is the actual output?

 --> src/schema.rs:1:1
  |
1 | infer_schema!("dotenv:DATABASE_URL");
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: message: Could not load table names from database `postgresql://docker:docker@db:5432/my_db`: StringError("Failed to establish a database connection at postgresql://docker:docker@db:5432/my_db. Error: BadConnection(\"could not translate host name \\\"db\\\" to address: Name or service not known\\n\")")
  = note: this error originates in a macro outside of the current crate

It appears that Diesel isn't resolving db into its actual IP? But that might make sense? Because the image hasn't been created,so there isn't a configuration setup yet to convert db to an IP?

Are you seeing any additional errors?

Nope, that's the only one. I had it working prior to using diesel/infer_schema.

Steps to reproduce

It fails while building the web image, so using the above config will never successfully build an image.

Again, I doubt this is an error with Diesel, I'm mostly just looking for help? I figured submitting an issue might be the best way define the problem?

[sgrif]

I don't know enough about docker to help with your issue, but you can use diesel print-schema instead of infer_schema! to avoid needing a database at compile time.

[ghotiphud]

Docker compose doesn't wait for the DB container to start up. Try https://github.com/vishnubob/wait-for-it

[ghotiphud]

Example use in this repo https://github.com/ghotiphud/rust-web-starter

[alexanderbanks]

@ghotiphud thanks for the response. I actually took the seemingly simpler approach of running diesel print-schema on each DB change and then modifying the schema.rs file with its output.

We can close this, I apologize for not responding to @sgrif . All is well.