RxJava VS config

Is this similar RxJava, the reactive extensions library for https://github.com/ReactiveX/RxJava ? I have made that work in Clojure in production.

Since you mentioned java, there is RxJava and RxAndroid. Google general recommendation now is to use kotlin coroutines if you're considering writing your app with that.

It's very quick though. In terms of the correctness of the syntax, I've never seen an issue while translating a single file or a single function. When I took the entire RxJava code base 5 years ago, right clicked on the source folder and converted to Kotlin, I found lots of problems. File by file I've never seen any issues though, but I also haven't done it much.

You all beat me to MapStruct and Testcontainers. Honorable mention to RxJava, which I use in Desktop apps.

RxJava with RxRelay (and rx-combinetuple-kt)

RxJava2

More information about rxJava, check it out here: (HERE)[https://github.com/ReactiveX/RxJava]

Concurrency: Kotlin coroutines for general use, Rx or Flow for reactive programming (you can technically use Rx for regular concurrency as well, but not really what it's meant for)

If you're just looking at making a service call on a regular interval and notifying the user when there's an actual change in data, you can also look into RxJava https://github.com/ReactiveX/RxJava. From here you can "subscribe" to your service call, and then every time you make your service call you can have it look for changes compared to the previous emission .distinctUntilChanged() and then only notify it's subscribers when it notices an actual change. From there you can trigger a local notification and push to a LiveData (assuming MVVM) or otherwise update the UI to match as well.

``` io.reactivex.rxjava3.exceptions.OnErrorNotImplementedException: The exception was not handled due to missing onError handler in the subscribe() method call. Further reading: https://github.com/ReactiveX/RxJava/wiki/Error-Handling | java.lang.IllegalStateException: Migration didn't properly handle: feed_group(org.schabi.newpipe.database.feed.model.FeedGroupEntity). Expected: TableInfo{name='feed_group', columns={name=Column{name='name', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue='null'}, uid=Column{name='uid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, icon_id=Column{name='icon_id', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, sort_order=Column{name='sort_order', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}}, foreignKeys=[], indices=[Index{name='index_feed_group_sort_order', unique=false, columns=[sort_order]}]} Found: TableInfo{name='feed_group', columns={uid=Column{name='uid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, name=Column{name='name', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue='null'}, icon_id=Column{name='icon_id', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, sort_order=Column{name='sort_order', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='0'}}, foreignKeys=[], indices=[]} at io.reactivex.rxjava3.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:717) at io.reactivex.rxjava3.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:714) at io.reactivex.rxjava3.internal.subscribers.LambdaSubscriber.onError(LambdaSubscriber.java:79) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$BaseObserveOnSubscriber.checkTerminated(FlowableObserveOn.java:209) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$ObserveOnSubscriber.runAsync(FlowableObserveOn.java:394) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$BaseObserveOnSubscriber.run(FlowableObserveOn.java:176) at io.reactivex.rxjava3.android.schedulers.HandlerScheduler$ScheduledRunnable.run(HandlerScheduler.java:123) at android.os.Handler.handleCallback(Handler.java:938) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:223) at android.app.ActivityThread.main(ActivityThread.java:7665) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:594) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) Caused by: java.lang.IllegalStateException: Migration didn't properly handle: feed_group(org.schabi.newpipe.database.feed.model.FeedGroupEntity). Expected: TableInfo{name='feed_group', columns={name=Column{name='name', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue='null'}, uid=Column{name='uid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, icon_id=Column{name='icon_id', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, sort_order=Column{name='sort_order', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}}, foreignKeys=[], indices=[Index{name='index_feed_group_sort_order', unique=false, columns=[sort_order]}]} Found: TableInfo{name='feed_group', columns={uid=Column{name='uid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, name=Column{name='name', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue='null'}, icon_id=Column{name='icon_id', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, sort_order=Column{name='sort_order', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='0'}}, foreignKeys=[], indices=[]} at androidx.room.RoomOpenHelper.onUpgrade(RoomOpenHelper.java:103) at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onUpgrade(FrameworkSQLiteOpenHelper.java:177) at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:416) at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:316) at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:145) at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:106) at androidx.room.RoomDatabase.inTransaction(RoomDatabase.java:622) at androidx.room.RoomDatabase.assertNotSuspendingTransaction(RoomDatabase.java:399) at androidx.room.RoomDatabase.query(RoomDatabase.java:442) at androidx.room.util.DBUtil.query(DBUtil.java:83) at org.schabi.newpipe.database.feed.dao.FeedDAO_Impl$7.call(FeedDAO_Impl.java:285) at org.schabi.newpipe.database.feed.dao.FeedDAO_Impl$7.call(FeedDAO_Impl.java:282) at io.reactivex.rxjava3.internal.operators.maybe.MaybeFromCallable.subscribeActual(MaybeFromCallable.java:47) at io.reactivex.rxjava3.core.Maybe.subscribe(Maybe.java:5330) at io.reactivex.rxjava3.internal.operators.flowable.FlowableFlatMapMaybe$FlatMapMaybeSubscriber.onNext(FlowableFlatMapMaybe.java:131) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$ObserveOnSubscriber.runAsync(FlowableObserveOn.java:402) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$BaseObserveOnSubscriber.run(FlowableObserveOn.java:176) at io.reactivex.rxjava3.internal.schedulers.ExecutorScheduler$ExecutorWorker$BooleanRunnable.run(ExecutorScheduler.java:322) at io.reactivex.rxjava3.internal.schedulers.ExecutorScheduler$ExecutorWorker.runEager(ExecutorScheduler.java:287) at io.reactivex.rxjava3.internal.schedulers.ExecutorScheduler$ExecutorWorker.run(ExecutorScheduler.java:248) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) at java.lang.Thread.run(Thread.java:923)

I don‘t understand why HOCON (https://github.com/lightbend/config/blob/main/HOCON.md) isn‘t used more often (at least for configuration use cases). It‘s a superset of JSON, has comments, multiline strings, optional quotes, replacement syntax. We use it at many places, and it‘s as nice at it can get.

HOCON is a great human-readable alternative to JSON. It's a superset of JSON with lots of cool features that make it both more readable and easier to use.

Here's a rundown of HOCON's main features: https://github.com/lightbend/config#features-of-hocon

"Typesafe Config" is the library generally used to read configuration files in HOCON format, which this library introduced. It's commonly used in essentially OOP/imperative Scala contexts, including Akka and its ecosystem.

Interesting!

For my own servers I use an internal tool that integrates apps with systemd. You point it at the output of your build system and a config file, and it produces a deb that contains systemd unit files and which registers/starts the server on install/reboot/upgrade, as a regular debian package would. Then it uploads it to the server via sftp and installs it using apt, so dependencies are resolved. As part of the build process it can download and bundle language runtimes (I use it with a JVM), it scans native binaries to find packages that the app should depend on, and you can define your config including package metadata like dependencies and systemd units using the HOCON language [1].

Upshot is you can go from a Gradle or Maven build to a running server with a few lines of config. Oh and it can build debs from any OS, so you can push from macOS and Windows too. If your server needs to depend on e.g. Postgres, you just add that dependency in your config and it'll be up and running after the push.

It also has features to turn on DynamicUser and other sandboxing features. I think I'll experiment with socket activation next, and then bundled BorgBackup.

Net/net it's pretty nice. I haven't tried with containers because many language ecosystems don't seem to really need them for many use cases. If your build tool knows how to download your language runtime and bundle it sans container by just setting up paths correctly, then going without means you can rely on your Linux distribution to keep things up to date with security patches in the background, it means networking works as you'd expect (no accidentally opened firewall ports!) and so on. SystemD knows how to configure resource isolation/cgroups and kernel sandboxing, so if you need those you can just write that into your build config and it's done. Or not, as you wish.

With a deployment tool to automate builds/pushes, systemd to supervise processes and a big beefy dedicated machine to let you scale up, I wonder how much value the container part is really still providing if you don't need the full functionality of Kubernetes.

[1] https://github.com/lightbend/config/blob/main/HOCON.md

Other similar standards: TOML, HOCON

I've also used HOCON pretty extensively for config, and it is better than both YAML and JSON for config with moderate to high complexity.