An update to my microservices rant ...

I spent some time writing something more positive than my previous rant. I hope.

Types of microservices

I've started to post a few things over on the new Red Hat Developer Blog. My first entry was about microservices.

You keep using that word (REST) and I don't think it means what you think it does

A long time ago in a galaxy far, far away ... OK, not quite. But some time ago our industry spent a lot of time and effort on discussion the pros and cons of REST, SOA, SOAP (!) etc. I even had a few things to say on the subject myself. To misquote Jeff Wayne, "minds immeasurably superior to my own" on the topic of REST and HTTP at the time had a lot more to say and do in this area. It's something which is easily Googled these days. Covered in books too. Probably even several video master classes on the topic of REST and HTTP, let alone their relevance to SOA. And yet it seems that some people either have a very short memory, didn't understand what was said, or perhaps didn't do their homework?

I'm specifically talking about how REST plays into the recent microservices wave. Yes, I think there are some problem areas with microservices and yes, one of them is the dogmatic assertion by some that REST (they tend to really mean HTTP) is mandatory. I don't believe that. I do believe that different message exchange patterns may be suitable for a range of microservices and to limit ourselves to just one (HTTP) does not make sense.

Oh and yes, it still frustrates me to this day when people talk about REST and they're really talking about HTTP - my only consolation here is that if I find it frustrating it must really annoy the h*ll out of the RESTafarians! Not all REST is HTTP and likewise not everything which uses HTTP is necessarily REST. Simple, huh? Well you'd think ...

Anyway, putting that aside, what's got me more frustrated recently is that some people are suggesting that REST (really HTTP) can't do async for microservices and therefore can prevent you breaking apart your monolith. I'm not even going to attempt to explain in detail here how that is wrong except to suggest that a) those people should go and read some InfoQ articles from the early 2000's (yes, even theserverside had things to say on the topic), b) do a Google search, c) read something from my friend/colleague Jim Webber, Savas and others on the topic of REST (and maybe Restbucks - hint, hint), d) in case they're confused between REST and HTTP, maybe go and read the HTTP response codes and look at those in the early 200's range (again, another hint). As I said above, I'm not suggesting there aren't some issues with REST/HTTP for microservices. And as I've also said over the last decade or so, maybe there are some issues with building some types of distributed systems with REST/HTTP. But this isn't one of them!

And this then brings me to a related topic. And if he hadn't been saying it around REST, I'm pretty sure Inigo Montoya would've been saying "You keep using that word. I do not think it means what you think it means" about "asynchronous". Yes, some of the authors try to make the distinction between a blocking call within a single address space and a one way interaction with a service across the network, but that really doesn't instil me with confidence that they know what they're talking about. If they threw in a bit of Fischer, Lynch and Patterson, rather than the oft overused reference to CAP, then maybe I'd be slightly less concerned. But that'd require some homework again, which they don't appear to want to do! Oh well, good luck to those who follow them!

Note, I have deliberately not included many links to things in the post in the hopes it will encourage the reader to follow up.

Micromonoliths?

I'm not even sure it's a word, but I wrote something on micromonoliths elsewhere - basically just some words on architecture.

Some cross postings on microservices

As I mentioned earlier, I've had some time on holiday recently and spent some time musing on microservices amongst other things. I've written a couple of articles over on my JBoss.org blog, one on microservices and co-location, and one about the mad rush to make everything a microservice. As Rod Serling often said: submitted for your approval.

Poor scientific method

One of the nice things about being on holiday is that the mind can wander down paths that might otherwise not be trodden, particularly because to do so typically needs more available time. This holiday I spent some of that time pondering microservices, amongst other things. As I've mentioned and been quoted elsewhere, I'm not against the fundamental concepts behind microservices architectures (MSA) - I see them as embodying an evolution of services-based architectures which we've seen happening over several decades. And yet I have a few concerns or niggles about the way in which some groups are positioning it as so significantly different that it represents a fundamental new approach or wave.

It wasn't until I read the recent NIST document that I managed to put my finger on at least one of these concerns: they're making data fit their own definitions of SOA and MSA, whilst conveniently ignoring those facts which don't fit. Any good scientist knows that goes against scientific method, whereby we come up with a theory based upon all of the available data and that theory lasts until some new data appears which blows a hole in it (yes, I'm paraphrasing). The NIST document is particularly guilty of this by choosing a definition of SOA which is conveniently at odds with their definition of MSA - it's not even the one that the standards, such as the OASIS SOA Reference Model, define! The table they have to compare and contrast is so badly flawed - go read the SOA-RM and look at the NIST MSA definition to see how close SOA and MSA are!

Look, I'm not suggesting there's nothing different in MSA than what we've been doing in the past with service oriented architectures. But let's please be objective, stick to the facts and define theories or models based upon all of the available data. Then also be prepared to change if new data appears. But please don't select data to match your own preconceived notions. In our more fully connected world there's really no excuse for being selective of the available data or ignorant of what is available!

Holiday thoughts ...

I just got back from a week of holidaying with family in Tenerife. We did lots of great things together, such as whale watching, snorkeling, visiting the local volcano (great mountain roads with barely enough space for one car let alone two lanes!) and generally soaking up the sunshine! It also gave me an opportunity to catch up on some articles and work related videos I'd been saving up on for a while, which resulted in me also being able to write down some of my own thoughts on a few related areas. I'm taking a bit of a down-day today before back to work tomorrow so it may take me a few days to upload the entries here or to my JBoss.org account.

Frameworks versus stacks - cross posting

Wasn't really sure if I should put this on my JBoss.org blog or here, so cross posting.

SRC-IoT 2016

I have had the honour of working with Professor Paul Watson to create the System Research Challenges Workshop. For the first year we focussed on IoT and it's possible we may keep that high-level theme next time. But it really great to see and hear the attendees embrace the underlying issues which are presented by large-scale distributed systems, which IoT embodies: reliability, fault tolerance, security, trustworthiness, data management etc. Of course all of the presentations had an IoT focus, but even there we had a wide range of examples, from field devices through gateways and including wearables (yes, there were a lot of side discussions about whether some of these IoT devices would ever really take off.)

We had attendees from industry (e.g., Red Hat, IBM and ARM) as well as SMEs and arcademia (e.g., Newcastle University, Lyon and Cambridge). It was a great mix of practical and theoretical, highlighting some of the challenges we have ahead of us in research and development. And as with many of these kinds of events, it was the discussions around the sessions that generated as much interesting conversation as during the presentations.

As well as 2 days of 30 minute presentations (maybe we'll try and get the agenda published somewhere), we also held a 2 hour lightning talk session on the first evening. Here anyone attending, whether they had a formal presentation or not during the event, was encouraged to present on a topic for 5 minutes. There hadn't been much preparation for this beforehand, so there was a little concern about whether we'd be able to fill the time. We needn't have worried - we could have gone much longer than the allotted 2 hours. It was a lot of fun. In fact my favourite talk of the entire event was probably here when Jonathan Halliday gave a presentation onf Big Data over the centuries, going back hundreds of years and managing to also touch on open source 400 years ago!

In conclusion, I thought the event went well. I'm hoping we can do it again next year, perhaps with the same theme or maybe we need to change it. We'll know closer to the time.

Elite

Back when I was just starting at university Elite came out for the Beeb. I remember going into my local town and walking to the computer shop to buy the game, then getting the slow bus home, waiting with apprehension for the time when I could put the tape into the cassette drive and slowly load up the game! By today's standards the graphics were basic, but in 1984 they were ground breaking. And I spent the next couple of years playing Elite at every opportunity. Even when I upgraded to the Atari 520 STM I longed for Elite on it but it never arrived.

I learned about Elite Dangerous back in 2012 and that it was available on Steam earlier this year. I wasn't a Steam player at the time, preferring to do my gaming on a PlayStation 3 or 4, or perhaps an XBox 360. However, I made the plunge this morning and for my first game purchase of 2016 I decided to install Steam on my laptop and buy Elite. I'm sure I'll have hours of fun ahead if it's anything like the original game!

HPTS 2015

I've been so busy travelling to conferences and customer engagements that I haven't had a chance to write about my trip to HPTS 2015. I've written several times about previous trips to this workshop and how it's my favourite of them all, so won't repeat. The workshop had the usual high standard of presentations and locating it at Asilomar is always a great way to focus the mind and conversations.

Because of its highly technical nature of the workshop I always like to use this event to try out new presentations - I know the feedback I receive will be constructive and worth hearing. This time my submission was essentially about what I'd written earlier this year concerning the evolution of application servers (application containers) driven by immutability and operating system containers, such as Docker. And I threw in a smattering of microservices since the topic is obviously relevant and I figured Adrian would be there! My presentation was well received and the feedback clearly showed that many people at the event agreed with it.

One other positive thing to come from the workshop and my presentation was that my co-traveller and long time friend/colleague, Professor Shrivastava, saw the presentation for the first time at the event. He understood it and whilst much of what was said I and others take for granted, he believes that there are groups of people that would find it interesting enough that we should write a paper. Writing papers with Santosh is something I enjoy and it has been a very fruitful collaboration over the years, so I look forward to this!

I also want to thank James because it was our discussions after I started my initial entries on the evolution of application servers that helped to focus and clarify my thinking.

High Integrity Software 2015 conference

I was asked to give one of the keynotes at this year's High Integrity Software Conference and I have to say that I enjoyed the entire event. It's probably one of the best technical conferences that I've been to for a while and I've been thinking about why that was the case. I think it's partly due to the fact that it was a very focussed themed event with multiple tracks for just a small part (4 talks) of the day so everyone at the event was able to concentrate on that main theme. In many ways it was similar to how conferences and workshops were "back in the day", before many of them seemed to need to try to appeal to everyone with all of the latests hot topics at the time.

The other thing that appealed to me was that I was asked to give a talk I hadn't given before: dependability issues for open source software. The presentation is now available and it was nice to be forced to put into a presentation things I've taken for granted for so many years. The feedback from the audience was very positive and then we were straight into a panel session on open source, which was also well attended with lots of great questions. Definitely a conference I'll remember for a long time and one I hope to go back to at some point.

Finally there was one presentation that stuck in my mind. It was by Professor Philip Koopman and worth reading. There's a video of a similar presentation he did previously and despite the fact it's not great quality, I recommend watching it if you're at all interested in dependable software for mission critical environments.

Heisenberg's back!

A long time ago (longer than I care to remember), I made the analogy between Heisenberg's Uncertainty Principle and large-scale data consistency (weak/eventual consistency). It got reported by InfoQ too. Over the weekend I came across a paper from friend/colleague Pat Helland where he made a similar analogy, so I figured I'd mention it here. What's that they say about "great minds" ;) ?

The modern production stack

Over a year ago I wrote the first of what was supposed to be the start of a series of articles on how research our industry had been doing years (decades) ago was relevant today and even in use today, i.e., had moved from blue-sky research into reality. I never got round to updating it, despite several valiant attempts. However, thanks to James I got to see a nice article called Anatomy of a Modern Production Stack, I probably don't need to, or at least not as much as I'd expected. And before anyone points out, yes this stuff is very similar to what James, Rob and the team have been doing with Fabric8, OpenShift etc.

Proud ...

I have two sons. They both make me proud on a daily basis. I've been away for a week at Summit and whilst there my youngest son, who's not quite 13, did something brave that made me very proud of him. I can't go into what it was except to say that he did it through the medium of social media - that annoyed me slightly but it seems to be the way of things today for a certain generation. I've told him that what he did was brave and made me proud but I figured I would also put it here so he can refer to it in the future; it's the closest I can get to social media.

Kids and asynchronous messaging

We've heard a lot recently about asynchronous frameworks. Typically what these really do is prevent or discourage blocking (synchronous) calls; such calls may be made, e.g., making an RPC to a remote service, but the sender thread/process either doesn't block (so doesn't actually make the call directly), or gets back some kind of token/promise that it can later present (locally or back to the receiver) in order to get the response when it needs it. Of course there's a lot more to this which I'm deliberately glossing over, but the point I'm trying to make it that most of these frameworks don't use the term "asynchronous" in the way we might understand it elsewhere. The FLP problem is a reality yet not one with which they tend to be concerned.

It's strange how the mind wanders when you're doing other things because this was precisely the problem I started to think about whilst cooking dinner the other day. With a lot of people believing that "asynchronous" is the way to go (and in many cases they're not necessarily wrong) I'm more often than not unsure as to whether they really understand the full implications. And whilst cooking I was getting frustrated with my kids, both of whom I'd tried contacting by SMS and neither of whom had responded.

So my mind wandered and I made the not-so-huge leap: I'm trying to communicate with them asynchronously. I sent each of them an SMS and I had no idea of it had arrived. Of course I could have added the SMS-delivery ack request to the messages but that can be disabled by the receiver. Therefore, until and unless they responded, I had absolutely no way to know if they'd got the message and were ignoring me, or if it had gone missing en route (SMS isn't reliable, after all). I sent more SMS messaged but with no responses I was left in the same quandary from before.

Now of course I could ring them but if they don't answer then all that does is mean I've deposited a message (voice) into some semi-persistent queue that they may or may not look at later. Another option would be to find someone who knows them and talk with them, asking for messages to be forwarded. By increasing the number of people I ask I increase the chances that one of them will eventually get through and I may receive a response (gossip protocols). However, ultimately until and unless they or a proxy (friend) for them responded (or came home) I couldn't really know directly whether or not they'd received my messages and acted upon them. Asynchronous is a bitch!

To conclude the story - they came home, had received the messages and didn't believe a response had been needed. Dinner was very tasty though!

A little more on transactions and microservices

I had some interesting discussions this week which made me want to write something more on transactions (really XA) and microservices.

Monoliths and a bit of a history lesson

Just another cross-post for those interested.

Update: one thing I forgot to make explicit but hopefully comes through in the above post and the earlier one on web-scale is that to suggest is that to suggest application servers (Java or something else) aren't sufficient for web-scale is difficult to justify since many high profile sites do run today quite well on them.

Web-scale: I do not think it means what you think it means!

When I blogged about transactions recently one of the comments referenced "web-scale" and how application servers aren't well suited for web-scale distributed applications. I'm going to write something specific about this later but it got me to thinking: what does that actually mean? To paraphrase Inigo Montoya "You keep using that term, I do not think it means what you think it means." Many people and groups use the term but there really isn't a common (agreed) definition. It's a cop out to claim that we don't need such a definition because everyone who is sufficiently "in the know" will "know it when they see it".

The web has been around now for a long time. Over the years it has grown considerably and yet many sites back in the late 1990's would not be considered "web-scale" today. But back then they almost certainly were. Despite what many people may suggest today, sites then and now got by well using "traditional" (or dated?) technologies such as relational databases, CORBA, probably even COBOL! Coping will millions of requests, terabytes of data etc.

It's only fair that our definition of "web-scale" should change over time in much the same way as our definition of things like "personal transport" change from "horse" to "car", or even "jet pack". But we don't even have a definition of "web-scale" that we can all get behind and then evolve. It's subjective and therefore fairly useless as a way of signifying whether anything is or is not suitable for the kinds of applications or services people develop for the web. Ideally we'd fix this before anyone (person, group, company) used the term again, but I doubt that'll happen.

Slightly frustrating article ...

I came across an article the other day from last year which tried to poke holes in transactions. I kept putting off writing about it but eventually decided I had to say something. So ... here it is.