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MessageDB

MessageDB is a fully-featured event store and message store implemented in PostgreSQL for Pub/Sub, Event Sourcing, Messaging, and Evented Microservices applications. It was extracted from the Eventide Project to make it easier for users to write clients in the language of their choosing.

Within EquinoxJS, MessageDB is the PostgreSQL option for production systems that want a stream store with clear category semantics. It pairs well with the Equinox service model because the domain stays storage-agnostic while read models, reactions and access strategies can still be tuned explicitly.

If your default instinct is "we already run Postgres", this is the page to look at first. MessageDB gives EquinoxJS a straightforward PostgreSQL deployment story without pretending a generic events table and a stream store are the same thing.

Use MessageDB when you want:

  • PostgreSQL as the operational substrate
  • category-based consumers and checkpoints
  • store-supported inline projections when needed
  • a mature stream-store model rather than a generic event table

The companion docs cover both reactions and inline projections, which together cover the main PostgreSQL read-model shapes teams tend to need.

Installing

MessageDB installer​

MessageDB offers its own installer, it can be used as such

$ export PGHOST=localhost
$ export PGPORT=5432
$ export PGUSER=postgres
$ export MDB_VERSION=1.3.0
$ mkdir -p /tmp/mdb
$ curl -sL -o /tmp/message_db.tar.gz https://github.com/message-db/message-db/archive/refs/tags/v$MDB_VERSION.tar.gz
$ tar -xf /tmp/message_db.tar.gz --directory /tmp/mdb
$ (cd /tmp/mdb/message-db-$MDB_VERSION/database && ./install.sh)

pg-migrations​

While this can work well it's not particularly great to use in IaC scenarios as the installer is not idempotent. To combat this we offer a set of migrations you can use with @databases/pg-migrations.

$ pnpm i @databases/pg-migrations
$ npx pg-migrations \
  --directory ./node_modules/@equinox-js/message-db/migrations \
  --version-table eqx_mdb_migrations_version \
  --migrations-table eqx_mdb_migrations_applied