Monthly Archives: October 2022

JMESPath is represented using Railroad diagrams

31 Monday Oct 2022

Posted by in development, General, railroad diagrams, Technology

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JMESPath is a mature syntax for traversing and manipulating JSON objects. The syntax is also supported with multiple language implementations available through GitHub (and other implementations exist). As a result, it has been very widely adopted; just a few examples include:

  • Azure CLI
  • AWS CLI and Lambda
  • Oracle Cloud WAF
  • Splunk

As the syntax is very flexible and recursive in its use following the documented notation can be a little tricky to start with. So following the syntax can be rather tricky. The complete definition runs to 97 lines, of which 32 lines focus on the syntactical structure. The others describe the base types such as numbers, characters, accepted escaped characters, and so on. Nothing wrong with this, as the exhaustive definition is necessary to build parsers. But for the majority of the time it is those 32 lines that we need to understand.

As the expression goes – ‘a picture says a thousand words’, there might not be a thousand words, but there is enough to suggest a visual representation will help. Even if the visual only helps us traverse the use of the detailed syntax. So we’ve use our favoured visual representation – the railroad diagram and the tool produced by Tab Akins to create the representation. We’ve put the code and created images for the syntax in my GitHub repository here, continuing the pattern previously adopted.

Here is the resulting diagram …

To make it easy to trace back to the original syntax document we’ve included groupings on the diagram that have names from the original speciofication.

Parts of the diagram make the expressions look rather simple, but you’ll note that it is possible for the sections to be iterative which allows for the expression to traverse a JSON object of undefined depth. But what can be really challenging is that an in many areas it is possible to nest expressions within expressions. Visually there is no simple way to represent the expression possibilities of this in a linear manner. Other than be clear about where the nesting can take place.

LogSimulator New Feature – Custom Targets with OCI Logging example

14 Friday Oct 2022

Posted by in Cloud, development, General, logsimulator, Oracle, Technology

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Those who have been using my Logging in Action book will know that to help test the configuration of monitoring tools including Fluentd we have built a LogGenerator that can very easily play and replay logging events into a variety of destinations and formats. all written in Groovy to make the utility easy to run as a script and extend without needing to set up a proper Java development environment.

With the number of different destinations built into the script and the logic to load the source log events and format them the utility is getting rather large for a single file. Rather than letting it continue to grow as we add more destinations to pump log events too, I’ve extended the implementation so you can point to a Groovy file that implements the logic to send the log events. It only requires three simple methods to be implemented.

To demonstrate the feature we have created a custom extension and fully documented it. The extension allows you to send log events to the OCI Logging service. This includes an optional crude aggregation mechanism as sending individual log events is a little inefficient over REST. By doing this we can send synthetic or playback logs as if we’re an application in real-life to ensure that any alerting or routing for the logging works properly before we get anywhere production and do not need to run the application and induce error events.

Beyond this, we’re also thinking about creating a plugin to fire log events at Prometheus so we can send events using the Prometheus pushgateway. As a result, we can tune Prometheus’ configuration.

More improvements – refactoring the existing code

We will refactor the existing code to use the same approach which should make the code more maintainable, but the changes won’t stop the utility from working as it always has (so we won’t break out the existing output channels from the core).

We have also started to improve the code commenting – so hopefully it will make the code a bit more navigable.

Practical Steps when it comes to writing a technical book

11 Tuesday Oct 2022

Posted by in Books, General, manning, Oracle Press, Packt, Technology

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Following my article on Software Engineering Daily, here are some practical things that will help you if you’re considering taking on a technical book project.

Identifying a Publisher

While it is easy to self-publish today. The recognition comes from having worked with a traditional publisher as they have processes that ensure a level of quality. Not all publishers are equal, and some publishers are attributed with more prestige than others. In addition to this, some publishers are willing to take a risk on a subject and/or author. Have a look at the titles already published, and whether there are any publishers you can connect to.

When comes to contacting the publishers, most of their websites will have a page for recruiting authors. Some are easier to find than others. Here are a couple:

If, or when you get to talk to a publisher it is worth ensuring you understand how their editorial process works and what is expected from you? Plus what happens if you find yourself in the position of not being able to work to the original schedule. Day-to-day work can get in the way which you hadn’t expected.

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Contributing to Software Engineering Daily

10 Monday Oct 2022

Posted by in General, Technology

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For a long time, I’ve tracked and read articles on Software Engineering Daily. We’ll day represents what is hopefully the first of many articles that we will write for them. The article is about the kind of people that make technical book authors, and the perception we have of authors – so if you’re interested check it out here.

Some more content on the subject of books …

Is The 12 Factor App right about Logging?

05 Wednesday Oct 2022

Posted by in development, Fluentd, General, Technology

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The 12 Factor App definition is now ten years old.  In the world of software that is a long time. So perhaps it’s time to revisit and review what it says.  As I have spent a lot of time around Logging – I’ve focussed on Factor 11 – Logging.

I have been fortunate enough to present at the hybrid JAX London conference on this subject. It was great to get out and see people at a conference rather than just with a screen and a chat console of online-only events.

You can see my presentation here:

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