Simple question How does one schedule a task in Ktor Code se

Question

Simple question How does one schedule a task in Ktor Code seems to indicate it is capable but docs are missing as soon as you have to reverse engineer someone else s library to use it you should question whether you should be using it for anything meaningful says me lol Here is how spring does it ``` Scheduled fixedRate = 60000 ```

rocketraman · Answer

Ktor is a web framework not a general application framework Why would it provide scheduling capabilities

Gunslingor · Answer

Maybe your right probably are yeah you are lol just got used to spring I guess everyone has their own definition of what these things are lol My task is to update a database every hour whose data gets served up over REST the invocation of that scheduled task will be within fun Application api which is ktor So I should just use something like this you think <https kotlinlang org api latest jvm stdlib kotlin concurrent java util timer schedule html>

rocketraman · Answer

Yeah Spring s ` Scheduled` annotation just abstracts over the JDKs executer API See <https docs oracle com javase 6 docs api java util concurrent ScheduledExecutorService html>

rocketraman · Answer

I think for advanced use cases it might use Quartz but you don t really need that unless you want to do cluster aware job execution and task status persistence

Gunslingor · Answer

Thanks man really helps to bounce shit off another brain smiley

Casey Brooks · Answer

Since ktor is all based on coroutines I ve been starting to play around with the idea of spawning a background queue at application startup through a custom Feature Initial tests seem to work pretty well but I have no idea how well it would work with any kind of load

Gunslingor · Answer

I haven t really figured out coroutines yet at all really I mean I know multithreading and multiprocessing like I know how to breath but I don t get the change in terminology or the distinction Here is where it looks like ktor added a scheduling feature but I don t know <https github com ktorio ktor pull 1272 files>

rocketraman · Answer

A simple scheduled task with a coroutine is basically a `while` loop with a call to `delay` that idiom can extend to all sorts of use cases

Gunslingor · Answer

hmm hoping there is a library I can use to take of the while loop part it can get complicated can t it

rocketraman · Answer

That pull request was closed as stale so it was never actually merged into ktor

Gunslingor · Answer

hmm okay makes sense

Casey Brooks · Answer

It shoudn t take much to copy that PR to a separate library with attribution of course

rocketraman · Answer

Architecturally I don t know why you would combine updating your db data with your REST service There is no reason to couple those things together and plenty of reason not to

Gunslingor · Answer

Your right already realized it moment ago and created Applilcation service for the ktor main to consume also got Application api and web to separate that stuff cause some of the content is entirely data driven

Gunslingor · Answer

Here is what I got trying to do pure kotlin limit the java as much as possible Not sure why Application is greyed out it isn t for the web and api functions See anything wrong with this I feel like I should be invoking the Application object or something and not its children also don t really understand the module yet love the connector and embeddedServer thingy but wonder if embeddedServer is okay for enterprise applications just thinking outloud

rocketraman · Answer

Nothing wrong with using `embeddedServer` Personally I wouldn t mix the `Aggregator` with the ktor app at all as I don t see any need to I d probably start a separate coroutine or scheduled thread for that via `ScheduledExecutorService` which is newer and more robust than `Timer` Don t know what your `web` and `api` calls are doing so can t comment there

Gunslingor · Answer

serving up HTML and REST JSON data

rocketraman · Answer

Ok yeah all good there

Gunslingor · Answer

cool I guess the reason I was intending to put everything in ktor s main is mainly because I want to be able to kick off all services for this website at once with a single gradle task

rocketraman · Answer

You can still put it inside the same `main` Its not ktor s main when you use the embedded server its just `main` slightly smiling face

Gunslingor · Answer

ok move the aggregator out of the env and remove the Application association that makes sense Still not really sure about what the module is really doing should web api have their own module or be together in one

Gunslingor · Answer

Read the docs but wasn t clear

rocketraman · Answer

As I understand it the `module` is just ktor s way of combining all your web apps features and routing information Its providing you a nice DSL as `Application` is its receiver

rocketraman · Answer

Your aggregator makes no use of `Application` at all so there is no need to couple them together

Gunslingor · Answer

makes perfect sense man thanks I m always fighting myself between the way I want a thing to work the way I think a thing works and the way a thing actually works lol the toils of an engineer learning

rocketraman · Answer

I think you would create separate modules for web and api if you want them to have different pipelines e g different features headers exception handling etc

Gunslingor · Answer

Yeah not sure the application functions themselves are refered to as modules in the below link <https ktor io servers application html> seems it would make more sense if module was called Application but I guess that word is too long lol

rocketraman · Answer

I m not sure either but the call to `Application module` adds a module to a list of modules Also note the top level docs <https ktor io servers index html> indicate gt Application modules are started one by one when an application is started and every module can configure an instance of the application An application instance is configured by installing features and intercepting pipelines

rocketraman · Answer

Which implies to me if you want different features pipelines you want different modules

Gunslingor · Answer

and every module can configure an instance of the application that is the part that is confusing

Gunslingor · Answer

so modules can configure applications and applications configure modules

Gunslingor · Answer

meh I guess it doesn t matter lol overthinking it now I am

rocketraman · Answer

It is confusing yes I don t think they mean instance of an Application literally

rocketraman · Answer

An instance of the application gt one application

Gunslingor · Answer

Ahhhhh your a smart dude

rocketraman · Answer

I could still be wrong though slightly smiling face My ktor apps all have one module Try it out with a couple of test modules and see

Gunslingor · Answer

Yeah really trying to use everything Kotlin use everything new no old if possible starting some new projects It is a challenge not a lot of secondary content online for this stuff and much of the primary content is old or incomplete I think NET did what kotlin is trying to do quite a while back but NET sucks it just has more sources so was easier to pickup faster I guess

rocketraman · Answer

All depends on your background with a Java background Kotlin for me was way easier to pick up than NET I find NET has the same problem of outdated information x 10 there every doc depends on which of 10 NET versions you are actually running and then there is the whole NET NET Core split migration Plus I find Microsoft s documentation generally sucks its likely to get better now its all on GitHub

Gunslingor · Answer

yeah kotlin docs aren t bad MS does suck

Gunslingor · Answer

What would you say should go in here ```fun Application api ``` currently I have routing and a function for json output in there but should routing be segregated for a large project and if so what would that look like e g Application api routes or many can it be turned into a class with member routes Also if it is separated what else is there obviously there would have to be more than routes