Clojurians Log v2

This is long overdue but I finally wrote that blog post 😄 https://clojurians.slack.com/archives/C8NUSGWG6/p1760426101677749 Any feedback to the setup would be appreciated!

Here’s the deploy.yml - kamal’s configuration

# Name of your application. Used to uniquely configure containers.
service: shipclojure-datom

# Name of the container image to pull from docker
image: stoica94/shipclojure-datom

# Deploy to these servers.
servers:
 - hetzner-shipclojure # alias for the ip


# Inject ENV variables into containers (secrets come from .kamal/secrets).
env:
 clear:
   # Datomic configuration
   DATOMIC_DB_URI: "datomic:"
   MEMCACHED_URL: "shipclojure-datom-memcached:11211"
   
   
accessories
  # PostgreSQL database - Used for datomic storage
  db:
    image: postgres:17.5-bookworm
    host: hetzner-shipclojure
    # Make port available only to localhost not public to the internet
    port: "127.0.0.1:5432:5432"
    env:
      clear:
        POSTGRES_USER: datomic
        POSTGRES_PASSWORD: datomic
        POSTGRES_DB: datomic
    files:
      - resources/storage/init.sql:/docker-entrypoint-initdb.d/setup.sql
    directories:
      - datomic_storage_data:/var/lib/postgresql/data

  # Memcached
  memcached:
    image: memcached:1.6-bookworm
    host: hetzner-shipclojure
    port: "127.0.0.1:11211:11211"  # Only accessible locally
    options:
      health-cmd: "echo 'stats' | nc localhost 11211"
      health-interval: 30s
      health-timeout: 10s
      health-retries: 3

  # Datomic Transactor
  transactor:
    image: stoica94/datomic-pro-clj-1-12-bookworm-slim:1.0.7364 # prebuilt version of the image from resources/images/datomic/Dockerfile
    host: hetzner-shipclojure
    port: "127.0.0.1:4334:4334"  # Only accessible locally for peer connections
    cmd: "/opt/datomic/bin/transactor /opt/datomic/config/transactor.properties"
    files:
      - resources/storage/sql-transactor.properties:/opt/datomic/config/transactor.properties
    directories:
      - datomic_transactor_logs:/opt/datomic/logs

###################################################################

protocol=sql
host=localhost
port=4334


###################################################################

# kamal let's you use <service>-<accessory> to describe the host of that
accessory
sql-url=jdbc:
sql-user=datomic
sql-password=datomic

## The Postgres driver is included with Datomic. For other SQL
## databases, you will need to install the driver on the
## transactor classpath, by copying the file into lib/,
## and place the driver on your peer's classpath.
sql-driver-class=org.postgresql.Driver

## Recommended settings for -Xmx1g usage, e.g. dev laptops.
memory-index-threshold=32m
memory-index-max=256m
object-cache-max=128m

;; uri is mapped to the env variable DATOMIC_DB_URI
(defn create-datomic-db [uri]
  (let [halt? (atom false)]
    (loop []
      (try
        (let [created? (d/create-database uri)]
          (if created?
            (t/log! :info "Datomic database created successfully")
            (t/log! :info "Datomic database already exists")))
        (reset! halt? true)
        (catch Exception e
          (t/log! :warn ["Failed to create datomic database, retrying in 5 seconds. Error: " (.getMessage e)])
          (Thread/sleep 5000)))
      (when-not @halt?
        (recur)))))

(defmethod ig/init-key :db.datomic/connection
  [_ {:keys [db-uri schema-file]}]
  (t/log! {:level :info} "Creating datomic connection")
  (create-datomic-db db-uri)
  (let [conn (d/connect db-uri)]
    (transact-all conn (read-txs schema-file))
    conn))

2025-06-21T09:32:10.095183367Z 2025-06-21T09:32:10.093509363Z WARN LOG hetzner-shipclojure-ef0118fed3aa saas.datomic.core[36,11] Failed to create datomic database, retrying in 5 seconds. Error:  Error communicating with HOST localhost on PORT 4334
2025-06-21T09:32:15.108218045Z 2025-06-21T09:32:15.107553803Z WARN LOG hetzner-shipclojure-ef0118fed3aa saas.datomic.core[36,11] Failed to create datomic database, retrying in 5 seconds. Error:  Error communicating with HOST localhost on PORT 4334

The peer process connects to storage to retrieve the location of the transactor. That part looks to be working. Storage is telling you that the transactor is at localhost, which is what you specified in your transactor.properties. So you're very close! You need to set the right host name at the top of the properties file 😊

Ah you mean I need transaction.properties

host=shipclojure-datom-transactor

Yes

When the transactor starts it writes this host name to storage, which is how the peer finds it.

Awesome! Thank you, Christian!

Fixed and deployment ready 🚀! I’ll make a blog post about using kamal to deploy a datomic clojure web app. This took me 4 days to figure out 😵

What’s cool about kamal is that once you figure out the deployment for one destination, deploying to any other VM is just having ssh access to it and knowing the host/ip

Yes, all apis are listed here https://docs.datomic.com/clojure/index.html