This is the replication service for ElectricSQL.

It's an Elixir application that integrates with Postgres over logical replication and Satellite (ElectricSQL's client-side replication component that works with SQLite) via a web socket interface.

Docker and Elixir 1.14 compiled with Erlang 24.

See the Makefile for usage. Setup using:

make deps compile

Run the dependencies using:

make start_dev_env

Run the tests:

make tests

And then develop using:

make shell

This runs active-active replication with Postgres over logical replication and exposes a protocol buffers API over web sockets on localhost:5133.

For example to write some data into one of the Postgres instances:

docker exec -it -e PGPASSWORD=password electric_db_a_1 psql -h 127.0.0.1 -U electric -d electric

There's a second instance, electric-db_b_1, if you want to see data being replicated between them.

Note that you can tear down all the containers with:

make stop_dev_env

The Electric application is configured using environment variables. Everything that doesn't have a default is required to run.

Authentication

By default, in dev mode, electric uses insecure authentication. This just accepts a user id as the authentication token and authorizes the connection as that user.

Token based authentication requires a signed JWT token with a user_id claim, and a valid issuer.

To turn on token-based authentication in dev mode and when running in production, set the following environment variables:

• SATELLITE_AUTH_SIGNING_KEY - Some random string used as the HMAC signing key. Must be at least 32 bytes long.

• SATELLITE_AUTH_SIGNING_ISS - The JWT issuer (the iss field in the JWT).

You can generate a valid token using these configuration values by running mix electric.gen.token, e.g:

$ export SATELLITE_AUTH_SIGNING_KEY=00000000000000000000000000000000
$ export SATELLITE_AUTH_SIGNING_ISS=my.electric.server
$ mix electric.gen.token my_user my_other_user

The generated token(s) must be passed in the token field of the SatAuthReq protocol message.

For them to work, you must run the electric server configured with the same SATELLITE_AUTH_SIGNING_KEY and SATELLITE_AUTH_SIGNING_ISS set.

When running locally, you can apply migrations directly using make apply_migration. First make sure you've built your migrations in your application folder, then set the MIGRATIONS_DIR environment variable to the path to the migrations folder:

export MIGRATIONS_DIR='../path/to/migrations'

Now (re)run the electric service (with the env var set):

make shell

You can now apply named migrations using:

make apply_migration name=$MIGRATION_NAME

Where MIGRATION_NAME is the name of a migration folder created using electric migrations new, for example:

make apply_migration name=1666288253_create_items

Note that if, when running on OSX, you get errors like:

could not connect to the publisher: connection to server at \"host.docker.internal\" (192.168.65.2), port 5433 failed

You may need to adjust your docker networking or run Electric within docker. To run within Docker, you can build the docker image locally:

make docker-build

And then run with the right env vars, e.g.:

docker run -it -p "5433:5433" -p "5133:5133" \
    -e "VAXINE_HOST=host.docker.internal"
    -e "ELECTRIC_HOST=host.docker.internal"
    -e "CONNECTORS=pg1=postgresql:https://electric:[email protected]:54321/electric;pg2=postgresql:https://electric:[email protected]:54322/electric" \
    docker.io/library/electric:local-build