google-cloud-spanner google-cloud-spanner-emulator

Cloud Spanner Emulator - docker initialization

I'm trying to setup a docker container that starts cloud spanner and that initializes it.

Using this official docker image provided by google: gcr.io/cloud-spanner-emulator/emulator

I'm looking to automatically initialize spanner on start.

I tried various things with the docker file, to summarize:

FROM gcr.io/cloud-spanner-emulator/emulator

RUN some gcloud command after to initialize local spanner db

But absence of informations on how this image works makes it hard to find if it's even possible to initialize it everytime the container starts.

I repeat myself, I need this to be run automatically when the container mounts. It's going to build pipelines.

Is there a way to do that with this provided docker image? Or should I create my own dockerfile that installs the emulator via gcloud cli?

Solution

Here is a docker file example that allows to start docker emulator and to initialize with some custom gcloud commands

FROM google/cloud-sdk:slim

RUN apt-get install -y google-cloud-sdk google-cloud-sdk-spanner-emulator

COPY ./start_spanner.bash start_spanner.bash
COPY ./schema.ddl schema.ddl

CMD ./start_spanner.bash

Here is a sample content of file start_spanner.bash.

See https://docs.docker.com/config/containers/multi-service_container/ for details about set -m (job controls).
See https://cloud.google.com/spanner/docs/emulator for info about how to use gcloud and emulator together

#!/bin/bash

set -m

gcloud beta emulators spanner start --host-port=0.0.0.0:9010 &

# configure gcloud cli to connect to emulator
gcloud config set auth/disable_credentials true
gcloud config set project someproject
gcloud config set api_endpoint_overrides/spanner http://localhost:9020/

# create spanner instance
gcloud spanner instances create someinstance \
  --config=emulator-config \
  --description="Test Instance" \
  --nodes=1

# create spanner database with the given schema
gcloud spanner databases create somedb \
 --instance=someinstance \
 --ddl-file=schema.ddl

fg %1

And the file schema.ddl is just your spanner ddl to run to create tables in the emulator as per spanner's documentation.