How to be notified when all futures in Future.compose chain succeeded? - kotlin

Question

My application (typical REST server that calls other REST services internally) has two main classes to perform the bootstrapping procedure.
There is the Application.kt class that is supposed to configure the vertx instance itself and to register certain modules (jackson kotlin integration for example):
class Application(
private val profileSetting: String? = System.getenv("ACTIVE_PROFILES"),
private val logger: Logger = LoggerFactory.getLogger(Application::class.java)!!
) {
fun bootstrap() {
val profiles = activeProfiles()
val meterRegistry = configureMeters()
val vertx = bootstrapVertx(meterRegistry)
vertx.deployVerticle(ApplicationBootstrapVerticle(profiles)) { startup ->
if (startup.succeeded()) {
logger.info("Application startup finished")
} else {
logger.error("Application startup failed", startup.cause())
vertx.close()
}
}
}
}
In addition there is a ApplicationBootstrapVerticle.kt class that is supposed to deploy the different verticles in a defined order. Some of them in sequence, some of them in parallel:
class ApplicationBootstrapVerticle(
private val profiles: List<String>,
private val logger: Logger = LoggerFactory.getLogger(ApplicationBootstrapVerticle::class.java)
) : AbstractVerticle() {
override fun start(startFuture: Future<Void>) {
initializeApplicationConfig().compose {
logger.info("Application configuration initialized")
initializeScheduledJobs()
}.compose {
logger.info("Scheduled jobs initialized")
initializeRestEndpoints()
}.compose {
logger.info("Http server started")
startFuture
}.setHandler { ar ->
if (ar.succeeded()) {
startFuture.complete()
} else {
startFuture.fail(ar.cause())
}
}
}
private fun initializeApplicationConfig(): Future<String> {
return Future.future<String>().also {
vertx.deployVerticle(
ApplicationConfigVerticle(profiles),
it.completer()
)
}
}
private fun initializeScheduledJobs(): CompositeFuture {
val stationsJob = Future.future<String>()
val capabilitiesJob = Future.future<String>()
return CompositeFuture.all(stationsJob, capabilitiesJob).also {
vertx.deployVerticle(
StationQualitiesVerticle(),
stationsJob.completer()
)
vertx.deployVerticle(
VideoCapabilitiesVerticle(),
capabilitiesJob.completer()
)
}
}
private fun initializeRestEndpoints(): Future<String> {
return Future.future<String>().also {
vertx.deployVerticle(
RestEndpointVerticle(dispatcherFactory = RouteDispatcherFactory(vertx)),
it.completer()
)
}
}
}
I am not sure if this is the supposed way to bootstrap an application, if there is any. More important though, I am not sure if I understand the Future.compose mechanics correctly.
The application starts up successfully and I see all desired log messages except the
Application startup finished
message. Also the following code is never called in case of successs:
}.setHandler { ar ->
if (ar.succeeded()) {
startFuture.complete()
} else {
startFuture.fail(ar.cause())
}
}
In case of an failure though, for example when my application configuration files (yaml) cannot be parsed because there is an unknown field in the destination entity, the log message
Application startup failed
appears in the logs and also the code above is invoked.
I am curious what is wrong with my composed futures chain. I thought that the handler would be called after the previous futures succeeded or one of them failed but I think it's only called in case of success.
Update
I suppose that an invocation of startFuture.complete() was missing. By adapting the start method, it finally worked:
override fun start(startFuture: Future<Void>) {
initializeApplicationConfig().compose {
logger.info("Application configuration initialized")
initializeScheduledJobs()
}.compose {
logger.info("Scheduled jobs initialized")
initializeRestEndpoints()
}.compose {
logger.info("Http server started")
startFuture.complete()
startFuture
}.setHandler(
startFuture.completer()
)
}
I am not sure though, if this is the supposed way to handle this future chain.

Answer 1

The solution that worked for me looks like this:
override fun start(startFuture: Future<Void>) {
initializeApplicationConfig().compose {
logger.info("Application configuration initialized")
initializeScheduledJobs()
}.compose {
logger.info("Scheduled jobs initialized")
initializeRestEndpoints()
}.setHandler { ar ->
if(ar.succeeded()) {
logger.info("Http server started")
startFuture.complete()
} else {
startFuture.fail(ar.cause())
}
}
}