MongoDB is a NoSQL database and one of the main difference compared to relational DB is you can put in your collection documents with different structure. In fact you don’t really care about structure of documents and type of data you are storing.
This is particularly true when you start using your Mongo instance with langage like PHP or JS where the langage itself does not manage data type explicitly.
As a consequence your document format may not be optimized (like storing numbers in String and making search on them later) and once you decide to move your backend to a more structured language like Java you start to have to make this more robust and organized. At this point you may want to reformat your documents to match the right type, eventually update your previous documents to a new version.
This kind of operation can be done “easily” with Mongo scripting language. This post will details 2 of the current structure to manipulate and transform Documents.
The Adeunis Field Tester is a simple way to make test on a LoRaWan network. The device provide GPS information, temperature and an accelerometer to activate communications.
The device is big but it have a screen and you can have a direct feedback of the transmissions on the screen. It make it good for testing coverage manually. You can also program it to send messages periodically and easily put it in a car to create coverage maps thanks to the embedded GPS.
The following post explains how to set it to use it with TheThingsNetwork (as for any other network by-the-way).
When deploying a API in a scalable environment we usually try tom implement a stateless solution to avoid parallelism conflicts between the different nodes.
This works well for event management synchronously executed. But in some case these event need to have a part of the work managed asynchronously. It was my was my case when I had to process alarm report potentially generating multiple communications with execution time not predictable. To manage this I decided to process theses operation asynchronously. There are multiple architecture for managing this like Queuing (my preferred) of dedicate asynchronous engine. I’ve in fact preferred another way to do it for keeping my infrastructure more simple : adding in all of my nodes a batch function processing the alarms asynchronously.
The alarm events are written into the database and processed by the first of the batch taking it. This allow to preserve a fully redundant and simple architecture. That said I need to ensure only one of the process will execute this process at a time and potentially split the work to do between all the nodes. For making this I had to create a mutex solution.
This post describes the way to create a Mutex solution based on MongoDB with Spring Boot.
I have this board in my stock since some months and never taken time to play with it. As I’m starting some developments with STM32 it’s time to do it. I’ve tried to do some stuff using it at reception but even if there is some kind of Arduino mentions on the package the start is not as easy as on Arduino. Not regarding coding (it is more complicated but it is not the problem) but regarding the development environment. You need to use different tools and find yourself the way to use each of them. In my point of view ST would do a good thing simplify all this stuff. So in this post I’ll describe how to get started by creating your first led blink project. Hope it will save your time.
As I written this post for another target and it can be also useful for anyone, even if It is one more post on many of them, here are a couple of words about Meltdown and Spectre security issues. Read mode for details.
Following my previous post on bitcoin I’ve start mining with ASIC to continue playing the technology. I’ve started with a small USB ASIC providing 2GH/s. This is equivalent to 200 times the power of my Xeon server and it was really easy to install, running on a Raspberry Pi to simplify the usage.
This post details this experience and gives some advices for one wanted to experience mining.
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