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Vibe Coding, Kotlin, Finance, and Data Visualization

Recently, I came across a paper discussing an experiment and tried to reproduce it. Here’s a brief summary: - Portfolio A: In a bull market, grows by 20%; in a bear market, drops by 20%. - Portfolio B: In a bull market, grows by 25%; in a bear market, drops by 35%. - Bull market probability: 75%. According to the paper, both portfolios should have a one-year expected return of 10%.

Treat life like a marathon, not like a sprint

Like most of us, I am daily flooded with thoughts about life, my objective position in it, whether I am missing anything, or whether I need to do better. Am I providing enough for my family? Is my career on track? Am I being healthy enough? Am I just passing through life instead of aiming to strive? Those thoughts have been slowly mitigated, but they never got away. Over time, I have been slowly accepting this reality, and I came to realise that all the marathon training and long-distance running have helped me come to terms with these facts.

Uploading SARIF Reports to GitHub

Recently I wanted to add Lint reports to a repository on GitHub. The goal is to report potential Lint violations when new code is committed, to make sure that all the committed code is lint-warning-free and pretty. My first idea was to look for a GitHub action that could run ./gradlew lint and report it as a PR comment. After asking about ideas in the Android Study Group, Carter Jernigan and Justin Brooks suggested me to upload directly the SARIF files into GitHub.

KotlinConf 2024 announcements

The first day of the KotlinConf 2024 is over, and there has been a significant amount. After 5 years the conference happened again at The Bella Center in Copenhagen, a fantastic venue close to the historical center of the Danish capital. The last two weeks have been intense, with the Google I/O announcing another set of relevant features for Android and Kotlin developers. Most notably, Google is now supporting KMP for Android development.

HTTP chunk requests with Android and ktor

In this very short article, I will explain briefly what is a chunk or streamed HTTP request, what are the benefits of using it, and how it works in Android. Android apps use HTTP requests to download data from a backend. This information is stored and processed on the app to make it functional. HTTP requests are executed using different frameworks on Android. The most common ones are Retrofit or OkHttp.

My Investing Summary of 2022

Another solar rotation passed, and the world experienced a plethora of unexpected events. In the aftermath of the Corona epidemic that altered the course of the last couple of years, we had the unfortunate invasion of Ukraine by Russian forces, the tightening of Corona measures in China (and toward the end of the year, their withdrawal and gradual reopening of the economy), an ongoing economic recession, the rate hike by the FED and the general uncertainty of the most immediate future.

KMP, iOS Developers and Production

Kotlin Multiplatform (or KMP, KMM Mobile, etc) has been widely used for a number of years in applications that are currently in production. JetBrains compiled a website listing some of the companies that are currently using KMP. Since the advent of the mobile platforms we enjoy today, there has always been a certain market interest to push multiplatform technologies, such as Cordova, Xamarin, and others. With more or less success, those technologies aimed to provide a unified framework to develop multiple codebases, mostly focusing on the aspect of pricing (create code once, deploy multiple times).

A recapitulation of investing in pandemic times

It has been around 14 months since the pandemic started. We have all been affected by it to a greater or lesser degree, and the investing world has not been an exception (although surprisingly, the stock market is one of the winners of the pandemic). In this post I will share how the pandemic changed my investment thesis, the things I learned, and the mistakes I did. 14 months into the crisis of our generation (and with a few months to recover whatever the new normal will be), we now know that things will never be the way they used to be.

A short story of randomness (I)

I have always been fascinated by the above comic strip. A discussion on randomness and determinism becomes as much a philosophical issue as it is a practical one. They are used in a variety of applications: from the obvious cryptography, gaming or gambling to the less evident politics or arts. How can we be sure that a number is random? Will observing the process mine our efforts on generating the random number, similar to the observation of a cat inside a box with a decaying radioactive atom?

From Java to Kotlin and back (III): Calling Java from Kotlin

This article is part of a series. You can find the remaining article of the series here: From Java to Kotlin and back (I) — Calling Kotlin from Java From Java to Kotlin and back (II): Calling Kotlin from Java In this last chapter of the series, we will evaluate consideration when calling Java code from Kotlin. One could argue that even in this situation happens often, keeping considerations in mind for some code that might legacy is not that practical.

HTTP chunk requests with Android and ktor

Planted May 23, 2023

In this very short article, I will explain briefly what is a chunk or streamed HTTP request, what are the benefits of using it, and how it works in Android.

Android apps use HTTP requests to download data from a backend. This information is stored and processed on the app to make it functional.

HTTP requests are executed using different frameworks on Android. The most common ones are Retrofit or OkHttp.

Simplifying the underlying network operations, and after identifying the IP address of the computer hosting the requested URL, an HTTP request looks like follows:

View Gist on Medium

The HTTP request contains (among others) the following fields:

  • The HTTP method used: GET, POST, PUT, PATCH or DELETE. There are actually 8 different HTTP methods, being the remaining ones CONNECT, OPTIONS and TRACE.
  • Authorization headers (things like an API Key, or the Auth key we will need to identify ourselves as lefit clients).
  • Metadata headers for encoding, language, charsets, content type, etc.

The full specification of the HTTP 1.1 protocol can be found in the RFC 2616, whereas the HTTP 1.0 specification can be found in the RFC 1945.

In a world where multiple SDKs provide us with an abstraction layer and simplify those operations, RFCs might not be needed to check often. Android developers, for instance, can benefit from the usage of multiple frameworks (Retrofit, OkHttp, Ktor, etc…) that provide already all of the required implementations. This was not always like that: in previous times, it was necessary to check RFCs with certain frequency, since feature-complete SDKs where not always available on each stack.

Executing standard HTTP requests works at a high level as follows:

When the backend has processed the request, it returns it at once to the client. This works for most cases, but there are cases where we want to optimize further.

Imagine an endpoint that contains a complex logic that eventually takes more time until the full data is ready. Or maybe the endpoint relies on further subqueries to prepare the entire data, which will take some time until it is ready. In this case, it might be worth considering a Chunk (or streamed) request.

HTTP Streaming is a data transfer technique that allows a backend to continuously send chunks of data to a client over a single HTTP connection that remains open indefinitely (or until the data has been processed). A request like this can be of advantage to allow a client to dispose immediately of certain data, while the backend processes the rest.

This might remind the reader of using Sockets. HTTP and Sockets work similarly, although there are a few differences between them.

  • Websockets are event-driven, whereas HTTP is not. Generally, the best choice for real-time communication is sockets, since they have a lesser overhead to initialize and maintain a connection.
  • Sockets are a full-duplex asynchronous messaging mechanism. Both client and server can exchange messages independently.

There are also a few more differences in how they operate at the network level. This falls out of the scope of this article, but if you are interested you can read the Wikipedia article that explains the OSI model.

However, there might be cases where it is more convenient to use an HTTP Streamed request. From infrastructure to reusing certain models already being handled by the HTTP client, the casuistic can be wide.

Ktor supports this relatively out-of-the-box. The following snippet is able to execute a streamed request from a given API:

View Gist on Medium

To verify that this is working, you can execute a cURL against the streaming API, using a command similar to the one below:

View Gist on Medium

When you execute this, there is an interesting twist in the story. You will be able to see the response from the backend as you normally see it, but this time each chunk will be separated by a number, specifying the size of the next chunk:

As promised, this is not the longest article I’ve written, but I hope it provides some context on Streamed requests, and how they work — and eventually, you can get some inspiration to apply when for your project, in case you need them.

I write my thoughts about Software Engineering and life in general on my Twitter account. If you have liked this article or if it did help you, feel free to share, 👏 it and/or leave a comment. This is the currency that fuels amateur writers.