Related to Koin injection combine with Ktorm

Demo project

https://github.com/Lisooo790926/Koin_Ktor_Test

Background:

我們使用Ktorm (Database ORM) + Koin (IOC container) 來實作我們的DAO, 如下

class TestDao : KoinComponent {

    private val dataSource: DataSource by inject()
    private val database = Database.connect(dataSource)
    private val random = Random()

    fun selectCount(): Int {
        return database.from(TestTable).select(count())
            .mapNotNull { r -> r.getInt(1) }.single()
    }

    fun insert() {
        database.insert(TestTable) {
            set(it.name, "TestUser")
            set(it.age, random.nextInt())
        }
    }

    fun insertWithInputDatabase(database: Database) {
        database.insert(TestTable) {
            set(it.name, "TestUser")
            set(it.age, random.nextInt())
        }
    }
}

object TestTable : Table<Nothing>("test") {
    val id = long("id")
    val name = varchar("name")
    val age = int("age")
    val createTime = timestamp("create_time")
}

Question:

測試時發現使用 database.useTransaction時, 如果在內部使用Koin的bean而其內部也是透過inject去建立新的connection, 如下

  // ideally this scenario should use the same transaction
  get("/dao-database/use-transaction-to-insert-data") {
      database.useTransaction {
          testDao.insert() // create new connection
          testDao.insert()
          testDao.insert()
          throw Exception("To rollback whole transaction")
      }
  }

我們原先認為他會使用同一條connection, 但此處因為建立一條新的connection而喪失atomic 只有在我們將當前的connection傳進去後, 才能維持atomic

  get("/same-database/use-transaction-to-insert-data") {
      database.useTransaction {
          testDao.insertWithInputDatabase(database) // keep orignal conneciton
          testDao.insertWithInputDatabase(database)
          testDao.insertWithInputDatabase(database)
          throw Exception("To rollback whole transaction")
      }
  }

請問當Koin + Ktorm要使用useTransaction時有甚麼建議嗎, 或者以上問題可以改善嗎?

感謝

[vincentlauvlwj]

還是Database 內部會自動調用pool的connection, 不需要重複建立?

Yes

[Lisooo790926]

所以理想情況一個Database的singleton, 基本連同datasource一起建立即可

single { buildDatabase(config) }

fun buildDatabase(config: ApplicationConfig): Database {
    val hikariConfig = HikariConfig().apply {
        poolName = config.propertyOrNull("dataSource.poolName")?.getString()
        .... 
    return Database.connect(HikariDataSource(hikariConfig))
}

不需要兩個singleton in Koin