Apparently there’s this new distributed architecture thing called microservices out and about – so last week I went ahead and read Martin Fowler’s & James Lewis’s extensive article on the subject . and my reaction to this was basically:
I guess it is easier to use a new name (Microservices) rather than say that this is what SOA actually meant – re http://t.co/gvhxDfDWLG
— Arnon Rotem-Gal-Oz (@arnonrgo) March 16, 2014
Similar arguments (nothing new here) were also expressed after Martin’s tweet of his article e.g. Clemens Vasters’ comment:
— Clemens Vasters (@clemensv) March 16, 2014
Or Steve Jones’ post “Microservices is SOA, for those who know what SOA is.”
Autonomy, smart endpoints, events etc. that the article talks about are all SOA concepts – If you happen to have read my book and you read this article you’ve probably identified these as patterns like inversion of communication, Service Host,Service Instance, Service Watchdog and others.
So microservices as they appear from Martin’s & James’s article is pretty much service orientation without some of the bad misconception that tied into the SOA moniker like WS*, ESBs as a must, etc. -perhaps that’s a good enough reason for a new name but personally I doubt it.
However, the story doesn’t end here there are various other opinions as to what microservices are such as Chris Ford’s view who says that
“My own opinion is that microservice architectures can be understood through a single abstract architectural constraint which can be interpreted along many different degrees of freedom.
X can be varied independently of the rest of the system.”
The idea that something is separate and can be varied independently from the rest of the system is good but I would hardly say it is a definition of anything or at least anything new. CSCI (Computer Software Configuration Item) which I first heard of as part of DOD-STD-2167A (published in 1988) essentially means the same thing a CSCI is a component that can be varied independently from the rest of the system. In 2167A eyes it also means a very detailed , waterfall, documentation laden process, which isn’t what anyone thinks service or microservices should entail but it does demonstrate that “being varied independently” doesn’t mean much.
I am sure some reader goes something like “but wait, we’re talking about micro-services here – so they should also be small” – indeed there are posts like James Hughes’s on microservice with a quote like
“First things first what actually is a micro service? Well there really isn’t a hard and fast definition but from conversations with various people there seems to be a consensus that a micro service is a simple application that sits around the 10-100 LOC mark.”
(truth be told is that in the next sentence James says that LOC is an atrocious way to compare implementations but I thought it was worth repeating due to the use of the words “there seems to be a consensus”)
So how can you have 100 LOC services? you can get there if you rely on frameworks (like Finagle or Sinatra James mention) generate serialization/deserialization code (protobuff, thrift, avro etc.) – this is essentially building on a smart service host. Another example for this would be developing in Erlang with its supervisor hierarchies which also brings us to another way to reduce LOC by use languages that are less verbose (like the aforementioned Erlang, python or scala vs. say, Java).
I would say., however, that if you find you have a 10 lines of code service, you are more likely than not, implementing a function as a service and you don’t have a real service micro or not- e.g. I can’t see you having a decentralized storage (and autonomy) as mentioned in Martin’s and Lewis’s article above or having monitoring and instrumentation that Hughes mention.
You should also keep in mind that while better and cheaper networks allow us to push the limits – the fallacies of distributed computing still exist furthermore having a lot of small services that you need to manage along with the performance hits for serializations and deserializations, security etc. may very well mean that you moved from valid smaller “micro” services into the realm of headache which I called “Nano services”
“Nanoservice is an antipattern where a service is too fine-grained. A nanoservice is a service whose overhead (communications, maintenance, and so on) outweighs its utility.”
So there we have it, for the most part microservices is just another name for the principle of SOA, anther name might have been appropriate in the hype days of SOA, but I think these days most of that vapor has cleared and people understand better what’s needed. Furthermore if we do want to name proper SOA by a new name I think microservices is a poor term as it leads toward the slippery slope into nano-services and 10 lines of code which are just your old web-service method executed by a fancy chic host using a hot serialization format.
Micro or not, services should be more useful than the overhear they incur.