Ktor with Gradle run configuration "Could not resolve substitution to a value" from environment variables

Question

I have set up a server in Ktor with a Postgres database in Docker, but figured it would be useful to be able to develop the server locally without rebuilding the docker container each time.

In application.conf I have

// ...

db {
    jdbcUrl = ${DATABASE_URL}
    dbDriver = "org.postgresql.Driver"
    dbDriver = ${?DATABASE_DRIVER}
    dbUser = ${DATABASE_USER}
    dbPassword = ${DATABASE_PASSWORD}
}

and in my DatabaseFactory I have

object DatabaseFactory {

    private val appConfig = HoconApplicationConfig(ConfigFactory.load())
    private val dbUrl = appConfig.property("db.jdbcUrl").getString()
    private val dbDriver = appConfig.property("db.dbDriver").getString()
    private val dbUser = appConfig.property("db.dbUser").getString()
    private val dbPassword = appConfig.property("db.dbPassword").getString()

    fun init() {
        Database.connect(hikari())

        transaction {
            val flyway = Flyway.configure().dataSource(dbUrl, dbUser, dbPassword).load()
            flyway.migrate()
        }
    }

    private fun hikari(): HikariDataSource {
        val config = HikariConfig()
        config.driverClassName = dbDriver
        config.jdbcUrl = dbUrl
        config.username = dbUser
        config.password = dbPassword
        config.maximumPoolSize = 3
        config.isAutoCommit = false
        config.transactionIsolation = "TRANSACTION_REPEATABLE_READ"
        config.validate()
        return HikariDataSource(config)
    }

    suspend fun <T> dbQuery(block: () -> T): T =
        withContext(Dispatchers.IO) {
            transaction { block() }
        }

}

I have edited the Gradle run configuration with the following environment config:

DATABASE_URL=jdbc:h2:mem:default;DATABASE_DRIVER=org.h2.Driver;DATABASE_USER=test;DATABASE_PASSWORD=password

When I run the task I get this error: Could not resolve substitution to a value: ${DATABASE_URL}, but if I set a breakpoint on the first line (private val appConfig) and evaluate System.getenv("DATABASE_URL") it is resolved to the correct value.

My questions are:

Why does this not work?
What is the best (or: a good) setup for developing the server without packing it in a container? Preferably without running the database in another container.

It works in debug mode - not sure why that makes a difference. However the app crashes as soon as I try to interact with the H2 database - possibly H2/Postgres differences? — Jørgen, Mar 07 '20 at 16:56

score 1 · Answer 1 · edited May 28 '20 at 13:09

1

You need to specify:

appConfig.property("ktor.db.jdbcUrl").getString()

edited May 28 '20 at 13:09

Chris Catignani

5,040
16
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answered May 28 '20 at 12:19

Leonardo Freitas

11
1

We need to specify `ktor` first. This is missing on the official doc as well https://ktor.io/docs/jwt.html#validate-payload – Chetan Gaikwad Oct 08 '21 at 15:53

score 0 · Answer 2 · answered Mar 07 '20 at 22:45

I found that setting environment variables for the task in gradle.config.kts works:

tasks {
    "run"(JavaExec::class) {
        environment("DATABASE_URL", "jdbc:postgresql://localhost:5432/test")
        environment("DATABASE_USER", "test")
        environment("DATABASE_PASSWORD", "password")
    }
}

(source: Setting environment variables in build.gradle.kts)

As for why my initial approach only works in debug mode I have no idea. As for question #2 I have a suspicion that H2 and Postgres could have some syntactic differences that will cause trouble. Running the database container in the background works fine for now.

score 0 · Answer 3 · answered Oct 08 '21 at 15:55

As answered by @leonardo-freitas we need to specify ktor. first before accessing application.conf properties.

environment.config.property("ktor.db.jdbcUrl").getString()

This is missing on the official doc as well https://ktor.io/docs/jwt.html#validate-payload

Hawklike · Answer 4 · 2022-03-25T14:31:19.757

0

I experienced the same problem. I had to manually restart the IntelliJ (NOT via File). Simply closed the IDE, and then turned it on again. Also, check that your environment variable is permanent.

edited Mar 25 '22 at 14:31

answered Feb 17 '22 at 19:26

Hawklike

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Ktor with Gradle run configuration "Could not resolve substitution to a value" from environment variables

4 Answers4