Trifork Blog

Posts Tagged ‘Microservices’

Using Axon with PostgreSQL without TOAST

October 9th, 2017 by

The client I work for at this time is leveraging Axon 3. The events are stored in a PostgreSQL database. PostgreSQL uses a thing called TOAST (The Oversized-Attribute Storage Technique) to store large values.

From the PostgreSQL documentation:

“PostgreSQL uses a fixed page size (commonly 8 kB), and does not allow tuples to span multiple pages. Therefore, it is not possible to store very large field values directly. To overcome this limitation, large field values are compressed and/or broken up into multiple physical rows”

As it happens, in our setup using JPA (Hibernate) to store events, the DomainEventEntry entity has a @Lob annotation on the payload and the metaData fields (via extension of the AbstractEventEntry class):

For PostgreSQL this will result in events that are not easily readable:

SELECT payload FROM domainevententry;

| payload |
| 24153   |

The data type of the payload column of the domainevententry table is OID.

The PostgreSQL JDBC driver obviously knows how to deal with this. The real content is deTOASTed lazily. Using PL/pgSQL it is possible to store a value in a file. But this needs to be done value by value. But when you are debugging your application and want a quick look at the events of your application, this is not a fun route to take.

So we wanted to change the data type in our database to something more human readable. BYTEA for example. Able to store store large values in, yet still readable. As it turned out, a couple changes are needed to get it working.

It took me a while to get all the pieces I needed. Although the solution I present here works for us, perhaps this could not be the most elegant of even the best solution for everyone.
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Heterogeneous microservices

July 13th, 2017 by

Heterogeneous microservices

Microservices architecture is increasingly popular nowadays. One of the promises is flexibility and easier working in larger organizations by reducing the amount of communication and coordination between teams. The thinking is, teams have their own service(s) and don’t depend on other teams, meaning they can work independently, thereby reducing coordination efforts.

Especially with multiple teams and multiple services per team, this can mean there are quite a few services with quite different usage. Different teams can have different technology preferences, for example because they are more familiar with the one or the other. Similar different usage can mean quite different requirements, which might be easier to fulfill with the one or the other technology.

The question I’m going to discuss in this blog post, how free or constrained should technology choices be in such an environment?

Spaghetti freedom

If you’ve ever worked in a hectic startup environment where quickly building features is more important than clean sustainable code, you probably know how that ends. People just build things and it all becomes a big spaghetti mess. There is lots of technical debt..

The combination of freedom and high pressure means choices are short-term focussed and there is little attention to keeping things tidy.


Large organizations can have the opposite policy, any project or change need to be approved by multiple boards, architects and committees. There are strict rules about exactly what technologies should be used.

This can mean there might be some shoe-horning to implement things with a sub-optimal technology, or over engineering because complex technology is used for simple problems.

This can also be de-motivating to engineers, as they’re not allowed to pick their favorite technology.


I think the right approach is a middle ground. Some standardization and preferred languages, frameworks and solutions are very helpfull to promote software being built the same way. This helps engineers working on new services, for example when switching teams or when onboarding new people.

I think this preferred way of working should evolve also and be open for discussion. New insights or new ways of building can be integrated if they prove beneficial.

In my opinion such a preferred approach should serve as a starting point for teams building new services and be open for discussion. Teams should try and build software in a common way, but when needed it should be fine to diverge and do things differently.


I’ve shared my opinion – how can technology be standardized in larger microservice environments. How does this work in your company? What’s your insight on this topic?

Service Discovery using Consul & Spring Cloud

December 14th, 2016 by


In one of our customer projects we are heavily using Spring Boot in combination with other Spring projects for our microservices.

One of the more complex parts of microservices, especially when you are using them as fine-grained as meant to be, will be the fact that you need to setup and maintain the connections between all those services. In Spring you are typically doing this using some way of externalized configuration like property files. But even then, it can become quite a challenge when you need to connect with for instance 20 other microservices.

To make it even more complex you definitely want, especially in cloud based solutions, something like scalability. Actually, this should be accomplished by running just another instance of your microservice. They are self-contained, so they just need some basic configuration like setting the port-number. But then you also need something to load-balance the different microservices serving the same purpose. And to be honest: I don’t care about the location and port! I just want a service which offers me a certain contract. And at runtime, when needed, I want them to behave differently depending on configuration.

So what we are actually looking for is a solution which provides an easy way to do service discovery and even better, can act as a load-balancer and even better, can provide my services with their configuration.

This is where comes to the rescue. According to their website Consul is a solution which makes service discovery and service configuration easy and is distributed, highly available and datacenter-aware.

So let’s discover how Consul plays nicely with Spring Boot!

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