Software Development

Authenticating and encrypting MQTT to Mosquitto with SSL

(October 23, 2022) A huge part of modern Internet security is SSL/TLS, which encrypts data and authenticates connections. This is the technology behind HTTPS, and can be used to securely run MQTT on the Internet.

Deploying Mosquitto MQTT broker on Linux using Docker

(October 13, 2022) Getting started with Mosquitto is deceptively easy. We show you how to avoid the pitfalls.

Correct character encoding with DOMDocument implementing a Wordpress content filter

(July 6, 2017) Using DOMDocument in a Wordpress content filter lets you correctly manipulate the content as HTML. It might be that Wordpress filters are commonly using regular expressions or text search/replace functions. While that can be fast and powerful, correctly changing HTML elements requires an HTML-oriented API. The specifics of HTML elements are such that regular expressions and text search/replace functions just don't cut it due to the many pitfalls from highly specific details of HTML. With DOMDocument you simply load the HTML into the library, then you use DOM functions to manipulate the HTML, then you serialize the DOM to HTML text, and voila powerful HTML manipulations easily performed. Unfortunately that method comes with its own pitfalls you must be careful of.

Create hierarchical navigation for custom post types in Wordpress with PODS

(2015-06-20 23:27) On (longtailpipe.com) my Wordpress site I want to create "documentation" areas with a cluster of pages organized as a hierarchy, with an index to those pages showing as a sidebar. Many think of doing this for "Product Documentation", but I simply want to organize notes and additional material related to some books that I'm writing. Just as a book is organized by chapters and subsections, I want to hierarchically organize these pages.

How to customize the per-post authoring byline in Wordpress

(Mon Apr 06 2015 17:00:00 GMT-0700 (Pacific Daylight Time))

Nuxt.js overview, running Vue.js on the server to pre-render on the server

(September 4, 2018) Vue.js is an application framework for the front end running inside browsers. It supports building single-page-applications (SPA) or simply enhancing a web page with fancy interactivity. However it isn't always useful to have a big application running in the client. With Nuxt.js the Vue.js code is pre-rendered on the server so that the initial load of the page has already-rendered HTML. Subsequent interactivity on the page is still managed by client-side Vue.js code running in the browser.

Getting started with Vue.js application development

(July 20, 2018) Vue.js is an exciting new framework for developing front-end JavaScript applications. It promises to be a "Progressive" web framework, and I don't think they mean in a Political sense but means that Vue.js can be plugged into the part of an application which requires a richer experience. It is also supposed to be Approachable, works directly from HTML, CSS and JavaScript, while being Versatile and Performant. In this example we'll build a starter application, and embed it into an HTML web page. Specifically, this web page.

Rudimentary form validation in Vue.js with Buefy/Bulma

(July 21, 2018) As a follow-up to Software Development we want to study form validation. That example includes a little form in which we enter some information, and we want a little bit of validation to make sure we don't add bad entries.

Add/remove list items in Vue.js built with Bulma/Buefy

(July 21, 2018) Most applications with item lists you want to add or remove individual items. With Vue.js it's easy and obvious how to render an item list. What's not so obvious is how to manipulate the list afterwards. The Vue.js documentation doesn't say how to remove items or change items.

Showing a tree structure, like a file-system, in Vue.js

(July 26, 2018) Many kinds of applications show a tree structure of data items, such as files in a file system. Over the last couple weeks I implemented (blog.sourcerer.io) a simple Markdown editor in Vue.js/Electron - and while the sample application did not show a file-system tree a full version of the application would do so. We use this sort of widget all the time in programs and web applications, but do you know how to implement such a widget? Speaking for myself I could probably work it out - it's nested UL and LI elements with some custom styling and whatnot - but I'd rather use a pre-baked tree component for Vue.js instead. The application shown here demonstrates using one such tree component.

InfluxDB CLI and Configuration Options

(Jul 27, 2016) Influx DB is an easy-to-use time-series database, that uses a familiar query syntax, allows for regular and irregular time series, and is part of a broad stack of platform components. The TICK stack is a set of four components that together make it quick and easy to collect time series data and graph it for users. One uses the CLI because it's always there, and is much easier than using CURL on the REST API.

Introduction to Time Series and InfluxDB

(May 30, 2017) Influx DB is an easy-to-use time-series database, that uses a familiar query syntax, allows for regular and irregular time series, and is part of a broad stack of platform components. This video goes over what Time Series Data is, a comparison of different Time Series Databases, and more.

Time-series data with InfluxDB, overview

(May 17, 2017) Time-series databases are used for scenarios involving collecting time-stamped data. You probably want to generate summaries (rollups and aggregations), data retention policies, and so forth. That every datum is time-stamped makes it immediately different from regular SQL databases. InfluxDB is an open source time-series database.

Easily launch RDS and EC2 instance, with SSH access, using Terraform

(April 6, 2020) We commonly must deploy on AWS both running code and a database service. AWS offers a cloud based database system, RDS, and in this tutorial we will look at launching an AWS EC2 instance along with an RDS database inside a custom-built AWS Virtual Private Cluster (VPC). The RDS database will not be reachable from the public Internet, and only from within the VPC we will create. Our tool for this will be Terraform, a powerful tool for configuring infrastructure on a long list of cloud-based systems

Configuring Terraform to use for deploying AWS Infrastructure

(August 13, 2020) Terraform is a powerful tool for configuring infrastructure on a long list of cloud-based systems. Since AWS is such a complex system we look for simpler ways to do anything on AWS. Get started means installing and configuring the AWS CLI before using Terraform to simplify AWS deployment.

Introduction to Node.js with the Serverless framework on AWS Lambda

(May 19, 2018) AWS Lambda lets programmers focus on their code, with AWS taking care of all the deployment drama issues.

Introduction to Node.js with the Serverless framework on AWS Lambda

(May 19, 2018) AWS Lambda has excellent support for Node.js code. As of this writing Lambda supports Node.js 8.10, meaning we have excellent async function support and other modern ES2015+ language features.

Getting started with using Node.js and the Serverless framework on AWS Lambda

(June 3, 2018) While Amazon's AWS platform is excellent, there are other similar platforms from Google, IBM, Microsoft and others. Why should our code be written solely to support the AWS infrastructure? The Serverless framework makes it easy to reuse the same application code on any of these functions-as-a-service platforms. Perhaps more importantly, it simplifies coding against these platforms. The AWS platform is incredibly complex, and using the Serverless framework is simplifies developing applications for the AWS platform.

Solving Http Message NotWritable Exception, Could not write JSON: Could not set field value in Spring Boot

(October 16, 2017) My experience of programming on the Spring platform is that you'll be coding along, everything is going great, until an inscrutable complex error message emerges from the depths of who knows where. This message seemed to involve some module or another having created a round peg to fit into a square hole. That is, I'd sent a GET request to retrieve a large object tree, and it seemed that while filling data into a field of a subsidiary object Spring/Hibernate/etc chose the wrong data type, and it threw up an error. The specific type of error was receiving no discussion anywhere, so it was impossible to see how others had solved the problem. The documentation was of no use in explaining anything about this. But, after a couple days of trials and errors and more errors, a solution was found. And, indeed, Spring/Hibernate had chosen the wrong data type to fill into one of the fields, and the solution is fairly simple.

A fix for "Persistent Object Exception - detached entity passed to persist" in Spring Boot

(September 6, 2017) Error messages coming out of Spring can be more than inscrutable. As discussed in my solution to transient unsaved properties, I'm defining a REST API using Swagger/OpenAPI targeting a Spring Boot implementation. The object models are complex, with lots of nested objects. Today's inscrutable message, "detached entity passed to persist", doesn't make much sense as a phrase does it? Detached? Detached Entity? Say what? Turns out it's not that hard a problem to fix.

Accessing the Spring H2 database console when X-Frame-Options says deny

(January 5, 2018)

You're coding a Spring Boot application, need a database, and quickly configure in the H2 in-memory database thinking it'll be easy. Rerun the application, do a few things, then try to get into the H2 console, and it's a blank screen. The JavaScript console says "Refused to display ... in a frame because it set 'X-Frame-Options' to 'deny'." and there's a sinking feeling, it's another one of those obtuse error messages from the bowels of somewhere you've never heard of. Fortunately the solution is easy.

Persisting complex Embeddable/Embedded objects in Spring/Hibernate

(October 8, 2017) Hibernate and Spring and the Java Persistence packages make for a powerful combination. You can define a complex tree of objects, and the system automagically creates the database schema, and automagically saves and retrieves that object tree from the database. It means you can innocently code away, until one day you try to include an Embedded object but it silently fails to be saved to the database, Hibernate silently fails to create database columns for that object, and when retrieving the object for which the Embedded object is a field, the object is null. No error messages are printed in the log. Instead you're left wondering, why didn't Hibernate persist this object? What's presented here is a solution using EntityListener methods to convert values in and out of shadow values stored in the Entity.

A fix for org hibernate TransientPropertyValueException in Spring Boot

(September 1, 2017)

Error messages coming out of Spring can be more than inscrutable. In this case I'm defining a REST API using Swagger/OpenAPI targeting a Spring Boot implementation. The object models are complex, with lots of nested objects. It turns out you can POST a big blob of JSON with all kinds of structure, and Spring/JPA/Hibernate will swallow the whole thing and automatically parcel everything out to the corresponding database table. If you define the JPA annotations correctly, that is.

Get an annotation incorrect, and you'll be left scratching your head over what the heck you're being told by the error message. The Spring Team promises on a huge stack of bibles that Spring Boot automatically takes care of zillions of things for you, and it's so easy to write your code. In my experience it's instead a matter of papering complexity over complexity over a system containing about a thousand kitchen sinks worth of excess capabilities. There's no amount of papering-over that kind of complexity that will make the system simpler. But, the boss-man says to use Spring Boot, so here goes.

Implementing MySQL style AUTOINCREMENT in SQLite3

(Fri Jan 06 2012 16:00:00 GMT-0800 (Pacific Standard Time))

Converting a MySQL enum for use in SQLite3

(2012-01-06 21:11) I've got a database & website I want to move from using MySQL to using SQLite3.  Well, I think I want to use SQLite3.  Their document saying what sorts of uses make sense for SQLite3 are directly in line with my website, and I do want to remove some of the load off of my MySQL server so that it can have  cycles free for more important purposes.

However I've run into a couple troubles converting the schema so that it fits within SQLite3's limited SQL support.  Turns out that it doesn't support some column types and indexes.  And that the SQL produced by mysqldump contains some MySQLisms which SQLite3 just doesn't understand.

Easily launch EC2 instance, with SSH access, using Terraform

(April 4, 2020) Terraform is a powerful tool for configuring infrastructure on a long list of cloud-based systems. Since AWS is such a complex system we look for simpler ways to do anything on AWS. Terraform promises to make AWS deployments much simpler. To test that let's learn how to deploy some EC2 instances on AWS using Terraform.

Bare-metal Rust for AVR/Arduino and ARM microcontrollers coming soon

(April 28, 2018) In contemplating a project for an embedded microcontroller product, the customer is suggesting C++ and I'm having bad memories of memory allocations gone haywire. I've heard good things about Rust, being a modern language with the same mindset of C/C++ in terms of doing low level operations. Would Rust make a good choice for embedded device programming? Seems that it's still early days for that dream, as the tools aren't all lined up. Important thing is that folks are thinking in that direction and working towards that result. For some specific embedded CPU's it is possible to configure a Rust/LLVM toolchain that works fine.

Compiling Rust for Raspberry Pi

(June 28, 2018) Instructions for cross-compiling Rust code to ARMv7, such as the Raspberry Pi.

An iframe from googlesyndication.com tries to access the Camera and Microphone

(December 14, 2021) The last thing we want is for an advertising network to access the Camera or Microphone on our computer. But, while looking for something else, I stumbled upon messages in the Safari JavaScript console saying that an iframe loaded from safeframe.googlesyndication.com tried to do exactly that.

Easily use Let's Encrypt to HTTPS-protect your own server, for free

(2017-04-11 14:47 PDT) The search engines and browser makers are telling us to encrypt all websites. A driving factor is to protect everyone from not only miscreants wanting to hijack the web for nefarious goals, but the government security agencies who are snooping into everything. If everything on the Web is encrypted, then we'll all be better off. Until Let's Encrypt came along, the requirement to encrypt carried with it a high cost of paying for SSL certificates, and therefore many website owners would be unable to keep going. The free Lets Encrypt service opens HTTPS up to regular folk, allowing all website owners to encrypt their web traffic irregardless of how deep their pockets are. With that in mind, let's look into what it takes to set up HTTPS using Let's Encrypt.

Building Node.js REST API servers from OpenAPI specifications

(May 24, 2022) OpenAPI specifications are meant to assist creating either server or client API implementations. In this article we will explore quickly implementing server code from an OpenAPI spec, running on Node.js, preferably using TypeScript.

Create a Spring Boot REST API using Swagger, OpenAPI, to "Generate Swagger OpenAPI REST API documentation for Spring Boot application"

(July 31, 2017)

The Swagger tools, and the OpenAPI format, are an excellent way to document REST API's and even to generate client or server stub libraries to ease implementation. The technology serves two purposes -- a) standardized documentation for REST API's, b) generating code from API documentation in several programming languages. An OpenAPI file is fairly simple to write, you declare REST endpoints, describe the parameters and the request type, and then describe responses. It allows you to define complex object models that can be used either as input to a service, or its output.

Unfortunately the Swagger website doesn't have adequate documentation of using the tools. And it proved difficult to find clear straight-forward tutorials showing how to get started. Even the most powerful tool can be hampered if folks are unable to use it.

The following tutorial is a complete demonstration of, starting from scratch, developing a small Spring Boot service using OpenAPI and the Swagger tools. We show how to go from an OpenAPI spec to generated Spring Boot code, and also how to generate an OpenAPI spec from running Spring Boot code. There are several issues with the workflow of generating code from the OpenAPI spec. It's more effective to instead write the service code, and add in the annotations required for the Swagger tools to generate the OpenAPI spec for you.

With the OpenAPI spec it's easy to produce interactive API documentation that programmers can try out directly in their web browser.

Displaying Swagger UI in an HTML page without using server-side services

(May 19, 2022) Among the Swagger Tools is Swagger UI, an excellent tool for browsing an OpenAPI specification, the methods it defineds, and the data models it defines. Swagger UI turns the YAML or JSON specification file into an interactive browsing of the API. In this article we'll go over deploying the Swagger UI documentation viewer in a regular web page.

Setup Google Recaptcha v2 in PHP scripts

(June 9, 2018)

Recaptcha has been around a long time, fighting the good fight against spammers. One of my sites has been using Recaptcha for years, long enough to require updating to new API implementations a couple times. Google has updated to Recaptcha v2 and soon v3, and somehow my site stopped enforcing Recaptcha's with the subsequent Spammer intrusions. Fixing the implementation proved to be difficult, especially as the available tutorials missed some details.

Installing Composer on a Dreamhost VPS, or perhaps other VPS's

(January 12, 2018)

Modern PHP software development has been modernized by Composer. My exposure to Composer is because the Drupal team adopted the Symfony framework, which in turn is based on Composer. Installing Drupal any longer seemingly requires to first install Composer. Which isn't installed by default on Dreamhost VPS's, but it's not too hard to get it going.

Understanding how Python classes work

(September 26, 2019) Python classes allow programmers to define new data types to use in their programs. They act like a blueprint with which a program creates objects. Objects can contain both methods and attributes, giving us a useful higher-level abstraction over the built-in Python data types.

Easily edit or view OpenAPI 3 API specifications using free tools

(May 20, 2022) OpenAPI documents are written in either YAML or JSON and are editable with any programmer's editor. Tools like the Swagger Editor interactively assist with writing OpenAPI specifications by immediately showing errors and interactive API documentation. Since OpenAPI is an open specification, the door is open for any company to develop OpenAPI tools. In this post, we'll go over using the Swagger Editor on the swagger.io website and try some alternatives that will run on your laptop.

Fixing 'Enter passphrase for /dev/fd/63' in a Gitlab CI job

(2016-06-30 16:53) If you're a Gitlab user you're probably hoping to use Gitlab CI to automate builds and deployments. You probably want to deploy something using rsync, using an SSH key for security. Unfortunately (in my opinion) the official Gitlab documentation is confusing. While the Gitlab team does provide example .gitlab-ci.yml files that are supposed to work, the actual specifics of what to do are sketchy, and I found myself puzzling over a curious error message: "Enter passphrase for /dev/fd/63" ... WTF?

Make your own Raspberry Pi git repository server with Gogs and Docker

(2016-10-09 13:38) The Raspberry Pi is an amazing little computer that, while it's targeted at the DIY Hardware Maker, it is a full-fledged Linux computer that can be used to run services that used to require much bigger and more expensive computers. How long ago were office servers required to be $4000 systems from the likes of Dell Computers? It seems that the Raspberry Pi (and other tiny computers) can perform the same tasks at a low cost with minuscule energy requirements. To this end I'm setting up Gogs (a github-like server for Git repositories) on a Raspberry Pi. As I worked on the project it seemed most straightforward to use Docker to manage the Gogs process, and therefore the project became setting up Docker on Raspberry Pi to run other services.

CodeAnywhere - fast and flexible in-browser developers code editor

(2014-04-17 12:30:58 -0700) Codeanywhere is a code editor in a browser with an integrated ftp client, and all popular web formats are supported (HTML, PHP, JavaScript, CSS, and XML).

With ARM servers becoming a thing, developers may need ARM PC's

(February 23, 2019) ARM-based CPU's are going into not just mobile devices. ARM is popular in cell phones and the like because it is low power. That, and heat dissipation, is proving popular in server computers as the world moves towards cloud computing. Linus Torvalds recently suggested that software developers need ARM-based PC's to go along with ARM-based servers.

These github alternatives give you powerful git hosting, on your own terms

(January 8, 2018)

Git is a powerful source code revision control system, letting teams large and small track changes between team members. Github is an excellent service for hosting Git repositories. The Github corporation offers powerful free features, and even more powerful paid features, and software teams around the world are using Github to collaborate. But what if you want to, or must, host your repositories yourself? Some corporate security teams require no use of 3rd party services. Are you stuck using bare git?

Fortunately several Bitbucket and Github alternatives exist letting you create source repositories similar to Github, with most of the capabilities of Github. These open source Github/Bitbucket alternatives can be installed on your own hardware.

Fixing could not read Username for 'https://github.com': No such device or address in Jenkins

(August 12, 2020) You might have a successfully executing build task in Jenkins, then suddenly need that build task to push to a Github repository. For example, it might render a statically generated website to push to the gh-pages branch for display using Github Pages. But this inscrutable error message comes up. There is a fairly simple fix, especially if you're using an HTTPS URL to access the Github repository.

Throwing away local changes in Git workspace, allowing 'git pull' to proceed

(August 8, 2017)

Git is a powerful source code revision control system, letting teams large and small track changes between team members. It is widely used and very flexible. However, it's easy to get into an inscrutable state where it's not clear how to proceed.

Just now I found myself wishing to update my local repository with changes from co-workers. The repository contains UML models designed with Enterprise Architect, hence the primary thing in the repository is a large binary file. I'd been running Enterprise Architect on my local file, and there must have been some changes made to that file. As such Git told me there were local changes which I must merge before I could fetch the upstream changes. (specifically: Your local changes to the following files would be overwritten by merge) But I knew any change that had been made was unimportant, unneeded, and should be tossed away. Leaving me wondering how to throw away changes to a local Git repository.

How and why to use Git Submodules

(December 10, 2021) Sometimes we need to use the contents of one Git repository inside another. A typical example is using the source for a shared library in multiple applications. With Git Submodules, we configure one or more other repositories to check out as child repositories.

What is In-memory Computing?

(December 5, 2017)

Traditional computer architecture has a performance bottleneck due to the slow speed of persistent data storage on disk. We've developed complex systems like databases, and even distributed databases, to manage the data used in computations. The key limitation is the latency between requesting data, and getting the result. With in-memory computing the data is right there in quickly accessed memory, which greatly amplifies system performance.

How to read array of values from browser DOM using jQuery, or in Node.js using Cheerio

(March 12, 2019) Typically with jQuery or Cheerio we read or write strings and numbers to/from the DOM, but what if we must use objects or arrays of data? The jQuery documentation mentions data-* attributes, but the documentation is not entirely clear how to use this for reading/writing objects or arrays to/from the DOM.

Forbidding multiple heads in a shared mercurial repository

(Thu Oct 09 2008 17:00:00 GMT-0700 (Pacific Daylight Time))

Multiple headed Mercurial problems

(2008-11-20 20:37) Supposedly people who imbibe mercury become crazy as, well, a madhatter (so named because old-style hat-making practices involve the use of mercury). So maybe it sounds crazy to talk about multiple heads but in this case the mercury is the Mercurial source code management system. In Mercurial a 'head' is the endpoint of a chain of changes and it becomes downright inconvenient when there are multiple endpoints in the chain of changes in your source repository.

Using Mercurial patch queues

(Wed Nov 19 2008 16:00:00 GMT-0800 (Pacific Standard Time))

Solve 'Drive has not been shared' error with Docker on Windows

(May 5, 2020) We often mount folders into a Docker container to ensure data is persistent while letting us freely destroy and recreate the container. But on Windows you might get a head-scratching error message saying "Unhandled exception: Drive has not been shared". The most common advice that might come up when searching the Internet is not about this situation, but about general file sharing in Windows. In this case the error refers to configuration settings in Docker.

Correctly launch MySQL on Docker for Windows, avoiding 'Bind on unix socket' error

(May 6, 2020) Docker is an excellent tool for launching Linux-containerized applications, and it even runs on Windows. But running Docker containers on Windows has a few unexpected rough edges. One will come if you try the default way to launch MySQL doesn't work on Windows. Instead of the expected successful launch you might instead be told Can't start server : Bind on unix socket and asked whether there is another MySQL server running. That misleading error can send you on a tangential wild goose chase.

Self-hosting services using Docker

(May 12, 2022) Self-hosting is the opposite of using a 3rd party cloud service like Dropbox or Google Drive, and instead to host an equivalent service, like Nextcloud, on their own hardware. For every popular cloud service there is probably an independently developed open source equivalent one can host on their own hardware. Self-hosting gives one control, and peace of mind that their private information is not being sold to others, and it can save a lot of money from service fees that aren't paid. The personal security implications are huge, since it is known that governments around the world are pressuring internet services for data on user activity. While there is a legitimate need to know about criminal activities, do we really need to risk our data being snooped upon?

Comprehensive NextCloud installation using Docker Compose the smart way

(May 16, 2022) NextCloud primarily focuses on storing files, making it an open source equivalent to Google Drive, Dropbox, and the like. Beyond file sharing, it supports document editing, calendars, email, and more, matching up against commercial cloud services. But, as an open source self-hosted service your privacy is protected.

Why self-host web services for more control and lower cost than cloud-based web services

(December 17, 2021) Self-hosting is about hosting Internet services on your computers, controlled by you. This is different from just Using the Cloud by signing up for services like Dropbox, Github, Travis, or other 3rd party controlled services. Instead of taking the easy path, just using cloud services, self-hosters have control over their data, and enjoy lower costs. For most commercial services there are equivalent open source alternatives you can host on your own hardware.

Avoid 'could not be accessed' error when deploying a Service to a Docker Swarm on AWS

(May 30, 2020) Launching a Docker Swarm on EC2 instances is relatively easy, but of course there are pitfalls. One involves deploying a service to the swarm, but getting an error message about being unable to access the container image from the ECR registry.

Creating a Docker Swarm using Multipass and Ubuntu 20.04 on your laptop

(May 21, 2020) Docker is a cool system for deploying applications as reusable containers, and Docker Swarm is a Docker Orchestrator that let's us scale the number of containers across multiple machines. Multipass is a very light weight virtual machine manager application running on Windows, Linux and macOS, that let's us easily set up multiple Ubuntu instances on our laptop at low performance impact. Therefore Multipass can serve as a means to easily experiment with Docker Swarm on your laptop, learning how it works, setting up networks, etc.

How to share a Docker network between Stacks deployed to a Docker Swarm

(September 20, 2020) How do you handle a system deployed to Docker Swarm, with multiple Stacks, where a container in one Stack must communicate with a container in another Stack? For example, you may have a database Stack, and an application layer Stack, where the application needs to communicate with the database. It's simplest to put both into the same Stack. But it's a best practice for the database to stay running, and to separately bring the application up and down to deploy updates. Therefore it's best to use separate Stacks for each layer, raising the question of how will the application containers find the database containers.

Self-hosted metasearch engine protects against tracking from Google, Bing, etc

(July 13, 2022) Are you worried that Google/Bing/etc know too many details about you? These companies collect data about us, to then sell advertising targeting us. This can be avoided using search tools that protect privacy. One, SearXNG, is an open source metasearch engine that guarantees complete anonymity.

Self-hosted DMARC report viewer to aid your anti-SPAM effort

(July 12, 2022) DMARC is an important tool for websites that send e-mails to do so legitimately. Implementation requires catching e-mails containing DMARC reports then using a tool to parse/summarize/report on their content. We look at a simple DMARC reporting tool that is easily deployable using Docker.