Datomic Docker Compose

The Datomic team recently changed the license of the database to Apache 2.0

This let's devolopers use the pro version of Datomic without a license fee and without registration.

This repo provides a docker compose file that set ups a Datomic system with the pro version, so you can use it for development or testing out the database.

I started it as a way of learning how to use Datomic, and then I keep wonderinng "what should I add next to make it more like a production system?". And here we are.

I'm sharing it in case it's useful for someone else who's looking to learn Datomic or want's to try self hosting it. If you have any suggestions or improvements, please let me know.

The system uses a SQL storage service, backed by a Postgres database, and a memcached service for caching.

The datomic architecture is described here

A great video explaining the architecture is Deconstructing the Database

Besides the storage and cache services the compose file sets up a datomic transactor, a peer server, and a console

Requirements

Docker
Clojure (for running the apps)

Running it

To start it:

docker compose up -d

When the setup is finish you should see five containers running with the following names:

;; docker ps --filter="name=datomic-compose" --format "table {{ .Image }}\t{{ .Names }}"
IMAGE                     NAMES
datomic:1.0.6735-java17   datomic-compose-console-1
datomic:1.0.6735-java17   datomic-compose-peer-server-1
datomic:1.0.6735-java17   datomic-compose-transactor-1
memcached:1.6-bullseye    datomic-compose-memcached-1
postgres:15-bullseye      datomic-compose-postgres-1

Stopping it

To stop it:

docker compose down

If you want to remove the volumes:

docker compose down -v

What does the compose file do?

Set up a Postgres database on port 5432 with:
- User and password: datomic/datomic
- A datomic database with a datomic_kvs table
Set up a memcached server on port 11211
Set up a transactor configured to connect to the postgres server and memcached service. You accomplish this setting the sql-url, sql-userand sql-password keys in the files/sql-transactor.properties file:

sql-url=jdbc:postgresql://postgres:5432/datomic
sql-user=datomic
sql-password=datomic

memcached=memcached:11211

(The names postgres and memcached are the names of the services in the docker compose file)

Execute a init script that creates a database in datomic named datomic (this is different from the postgres one)
Run a peer server on port 8998 that connects to the postgres database and memcached service and serves the datomic datomic database

/opt/datomic/bin/run -m datomic.peer-server -h 0.0.0.0 -p 8998 -Ddatomic.memcachedServers=memcached:11211 -a accesskey,secret -d 'datomic,datomic:sql://datomic?jdbc:postgresql://postgres:5432/datomic?user=datomic&password=datomic'

(The command is in the files/peer-server.sh file for convenience) (Note the we set an access key and secret, this is required to connect to the peer server from the client)

Run a console on port 8080 that connects to the peer server

/opt/datomic/bin/run -m datomic.console -p 8080 dev datomic:dev://localhost:8998/

Monitoring

In the monitoring branch of this repo there is a compose file that sets up a Prometheus server and a Grafana server, it's not finished yet, but you can create your own dashboards.

Sample apps

There are two folders with minimal clojure projects, peer and client.

In the peer folder there is a minimal deps.edn project to connect to the running transactor. This is a Peer App Process: Application code that uses the datomic peer library embdedded in the same process.

In the client folder there is another minimal deps.edn project to connect to the running peer server. It only uses the datomic client library.

Running the peer app

To run the peer app:

cd app/peer
clojure -M:repl

This will start a repl with the peer app running. You can connnect to that repl from your editor and evaluate the code in the app/peer/src/datomic_compose/peer.clj file.

Running the client app

To run the client app:

cd app/client
clojure -M:repl

Again, this will start a repl with the client app running. You can connnect to that repl from your editor and evaluate the code in the app/client/src/datomic_compose/client.clj file.

If you executed the code of peer app before, you should see the same data in the client app.

Changing the transactor configuration

If you want to change the transactor configuration, you can do it in the files/sql-transactor.properties file.

The docker-compose.yml is configured has the configs properties to use that file in the transactor service, like this:

    transactor:
    ...
    configs:
        - transactor.properties
    ...

configs:
    transactor.properties:
        file: ./files/sql-transactor.properties

See the docker documentation on top level configs and service configs for more information.

galuque/datomic-compose