bun

Event Horizon with Bun

An EventStore implementation for looplab/eventhorizon powered by BUN, a lightweight Go ORM for PostgreSQL, MySQL, MSSQL, and SQLite.

Notice

I'm fairly new to Go, so do not expect the code to be brilliant or very reliable. Please shoot constructive feedback, PRs and ideas.

Todo

• [high] Implement snapshots
• [low] Make it work with MSSQL (it's my least priority b/c I never use it)

Usage

Both the event store and the repo need first a BUN DB handle, see docs on how to connect to a DB:

• https://bun.uptrace.dev/guide/golang-orm.html#connecting-to-a-database
• https://bun.uptrace.dev/guide/drivers.html

See test_helpers.go and individual test files for more examples.

Event Store

config, err := pgx.ParseConfig("{schema}://{user}:{password}@{hostname}:{port}/{dbname}")
if err != nil {
  panic("could not parse dsn")
}
config.DefaultQueryExecMode = pgx.QueryExecModeSimpleProtocol

sqldb := stdlib.OpenDB(*config)

db = bun.NewDB(sqldb, pgdialect.New())
store, err := ehbun.NewEventStore(*db)

...

Repo

In order to have a working general repository with BUN, a model needs to be defined with two mappers, one to map the eh.Entity to the BUN model and one the other way around, map the BUN model to the eh.Entity.

The two, eh.Entity and the BUN model, can be combined into a single struct. But just don't use reflect.DeepEqual (or similar) in this case.

config, err := pgx.ParseConfig("{schema}://{user}:{password}@{hostname}:{port}/{dbname}")
if err != nil {
  panic("could not parse dsn")
}
config.DefaultQueryExecMode = pgx.QueryExecModeSimpleProtocol

sqldb := stdlib.OpenDB(*config)

db = bun.NewDB(sqldb, pgdialect.New())

// BUN model
dbModel := new(TodoModel)
mapDbEntityToEhEntity := func(m interface{}) eh.Entity {
    model := m.(*model)
    return &mocks.Model{
        ID:        model.ID,
        Version:   model.Version,
        Content:   model.Content,
        CreatedAt: model.CreatedAt.UTC(),
    }
}
mapEhEntityToDbEntity := func(e interface{}) interface{} {
    entity := e.(*mocks.Model)
    return &model{
        ID:        entity.ID,
        Version:   entity.Version,
        Content:   entity.Content,
        CreatedAt: entity.CreatedAt.UTC(),
    }
}

repo, err := ehbun.NewRepo(*db, dbModel, mapDbEntityToEhEntity, mapEhEntityToDbEntity)
...

Tests

Provided is a Docker Compose environment to test the event store against PostgreSQL, MySQL and MSSQL.

An environment variable DSN is required to specify the connection details.

All DSNs, except SQLite, must begin with a scheme!

The reason is to be able to distinguish between PostgreSQL, MySQL and MSSQL. Unfortunately, go-sql-driver/mysql does not support schemes in the DSN, but it will be stripped automatically inside the tests.

The tests are a little bit slow because the tables are always reset (drop+create) in order to run a clean and updated database.

DSN="{schema}://{user}:{password}@{hostname}:{port}/{dbname}" go test

PostgreSQL

DSN="postgres://postgres:postgres@postgres:5432/postgres?search_path=public&sslmode=disable" go test

For more options see https://bun.uptrace.dev/postgres/#pgx and https://github.com/jackc/pgx

MySQL

DSN="mysql://mysql:mysql@tcp(mysql:3306)/mysql" go test

For more options see https://github.com/go-sql-driver/mysql#dsn-data-source-name and https://bun.uptrace.dev/guide/drivers.html#mysql

MSSQL

MSSQL is not supported yet.

SQLite

DSN="file::memory:?cache=shared" go test