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4Sep/15Off

Containers – my experiences good and bad

TechOps Guy: Nate

This is a followup post to an earlier post I had responding to container hype (more specifically perhaps Docker hype).

I want to give some of my (albeit limited) real-world experience with containers(that play a part in generating well north of two hundred million a year in revenue) the good and the bad, and how I decided to make use of them and where I see using them in the future.

I wrote a lot of this in a comment on el reg not too long ago so thought to more formalize it here so I can refer people to it if needed. Obviously I have much better control over formatting on a blog than a comment box.

The case for containers

The initial use case for containers at my organization was very targeted at one specific web application. From a server perspective up until this point we were 100% virtualized under VMware ESXi Enterprise Plus.

This web application drives the core e-commerce engine of the business, it is a commercial product (though an open source version exists), and the license cost is north of $10,000/year per installation. So for example if you have a VMware server with 5 VMs on it, each running this application in production you will pay north of $50,000/year in license fees/support for those 5 VMs. There is no license model where they license per CPU, or per CPU core, or per physical host(at this time anyway).

The application can be very CPU hungry, and in the earliest days we ran the application stack in the Amazon cloud. In early 2012 we moved out and ran it in house on top of VMware. We allocated something like 4 vCPUs per web server running this application. We had 4 web servers active at any given time, though we had the ability to double that capacity very quickly if required.

Farm based software deployment

It was decided early on before I joined the company that the deployment model for the applications would be "farm" based. That is we would have two "banks" of servers "A" and "B". Generally one bank would be active at any given time, and to deploy code we would deploy to the inactive servers and then "flip farms", basically change load balancing routing to point users at the servers with the new code. While in Amazon the line of thinking is we would "spin up" (on demand) new servers, deploy to them, make them live, then terminate the original servers(to save $$). Rinse & Repeat. Reality set in and this never happened, the farms stayed up all the time (short of Amazon failures which were very frequent(relative to current failures anyway)).

This model of farm deployments is the same model used at my previous company (with the original Ops director being the same person so not a big surprise). Obviously it's not the only way to deploy (it's the only two places I've worked at that deploy in this manor), but it works fine. My focus really is not on application deployment so I have not had an interest in pushing to use another model.

When we moved to the data center, the cost of managing both farms was not much, inactive farms used very little CPU, disk space was a non issue(I have perfected log rotation and retention over the years combined with LVM disk management to maximize efficiency of thin provisioning on 3PAR, it runs really well). Memory was a factor to some degree but at the end of the day it wasn't a big deal.

Having the 2nd farm always running had another benefit. We could, on very short notice activate the 2nd farm and essentially double our production server capacity. We did this(and continue to) for high load events. Obviously it does impact the ability to deploy code when in this situation but we adapted to that a long long time ago.

One big benefit of the farm approach is it makes rollbacks of application code very quick(10-30 seconds). The applications involved generally aren't expected to operate with mixed versions of the application running simultaneously(obviously depends on the extent of the changes).

The process today which manages activating both "farms" simultaneously does perform a check of the application code on both farms and will not allow them both to go active if they do not match.

Scaling the application

As a year or two passed the CPU requirements of the application grew (in part due to traffic growth also in part due to bad code etc). We found ourselves during our high traffic time two years ago keeping both "farms" active for months at a time(making short exceptions for code deployment), to try to ensure we had sufficient capacity. This worked, but it wasn't the most cost effective model to grow to, as traffic continued to rise, I wanted something (much) faster without breaking the bank.

Moving to physical hardware

Although we were 100% virtualized I did think a good strategy for this application was to move to physical hardware, for two main reasons:

  • Eliminate any overhead from hypervisor
  • I wanted to dedicate entire physical servers to this application, paying VMware license fees for basically a single application on one server seemed like a waste of $

I did not entertain the option of using one of the free hypervisors for four reasons:

  • Didn't want overhead from the hypervisor
  • Nobody in the organization had solid experience with any other hypervisor
  • Didn't want another technology stack to manage separately, just needless complexity
  • Xen and KVM aren't nearly as solid as VMware, just not enough to consider using them for this use case anyway.

So my line of thinking early on wasn't containers, it was more likely a single OS image, with custom application configurations, and directory structures, two apache instances (one for each "farm") on each server, and the load balancer would just switch between the apache instances when "flipping farms". I have done this before to some extent as mentioned in the previous article on containers. It didn't take long for me to kinda-sorta rule this out as a good idea for a couple of reasons:

  • The application configuration was going to be somewhat unique relative to all other environments (unless we changed all of them which was possible, quite a bit more work though)
  • Not entirely sure how easy it was going to be to get the application to run from two different paths and ensure that it operates correctly (maybe it would of been easy I don't know)

So at some point the ideas of containers hit me and I decided to explore that as an option.

Benefit of containers for this use case

  • LXC being built into our existing Ubuntu 12.04 LTS operating system
  • Easily runs on physical hardware
  • "Partitions" the operating system into multiple instances so that they have their own directory structures eliminating the need to have to reconfigure applications to work from a funky layout.
  • Allows me to scale a single container to the entire physical CPU horsepower of the server automatically, while limiting memory usage so the physical host does not run out of memory
  • Allows me to maintain two containers on each host (one for each "farm"), and eliminates the need to "activate both farms" for capacity since all of the capacity is already available.
  • Eliminates $10,000+ fee of VMware licensing
  • Slashes $10,000+/year fee of application by slashing the number of systems required to run it in production now and in the future.
  • Eliminates overhead of hypervisor
  • Eliminates dependency on SAN storage
  • Massive increase in available capacity, roughly 8 X the capacity of the previously virtualized "farm" of servers (or 4X the capacity of both farms combined). Means years of room to grow into without having to think about it.

Limited use case

This is a very targeted deployment for containers. This is a highly available production web application where each server is basically an exact copy of each other. Obviously this means if one physical host or container fails the others continue processing without skipping a beat. There are three physical hosts in this case (HP DL380Gen8 with dual Xeon 2695v2 CPUs (24 cores / 48 threads)- I find it amusing to run top, and tell it to show me all CPUs and it says "Sorry, terminal is not big enough"), and only one is required for current production loads(even on a high traffic day).

These systems are dedicated to this application. You might think when launching these on day one and seeing the CPU usage of the application go from ~45% to under 5% would make me say, oh what a waste of hardware resources let's pile more containers on this. No way. We saved an enormous amount of costs in licensing for this application by doing this, well enough to pay for the servers quite quickly. We also have capacity for a long time to come, and can handle any bursts in traffic without a worry.  It was a concept that turned into a great success story for containers at my organization.

I gave a benefit of eliminating dependency on SAN storage as a bonus, these are the first physical servers that this organization has deployed with internal storage. Everything else is boot from SAN(Like I am going to trust a $5 piece crap USB flash memory stick for a hypervisor when I have multipath fibre channel available likewise goes for having internal disks in the servers just for a tiny hypervisor). Obviously the big benefit of shared storage is being able to vmotion between hosts. Can't do that with containers(as far as I am aware anyway), so we put 5 disks in each server 4 of them in RAID 10 with one hot spare and 1GB of battery backed write cache.

So while I love my SAN storage, in this case it wasn't needed, so we aren't using it. Saved some costs and complexity on fibre channel cards and connectivity etc(not really an iSCSI fan for production systems).

I did somewhat dread the driver situation going to physical hardware, my last experiences with physical hardware with Linux several years ago were kind of frustrating with the drivers, I remember many times having to build custom kickstart disks for NIC drivers or storage drivers etc.. Fortunately this time around the stock drivers worked fine.

We also saved costs on networking, all of our VMware hosts each have two dual port 10GbE cards, along with 2x1Gbps ports for management(total 11 cables coming out of each server). The container hosts since they really only have one container active at a time rely just on the 2x1Gbps ports, more than enough for a single container(total 5 cables coming out of each server).

No rapid build up or tear down

The original containers have been running continuously (short of a couple of reboots, and some OS patches) for well over a year at this point. They do not have a short life span.

Downsides to containers

No technology is perfect of course, and I did fairly quickly come across some very annoying limitations of container technology inside the Linux kernel, which prevents me from making containers a more general purpose replacement for VMs. Maybe now some of these issues are resolved, I am not sure, I don't run bleeding edge kernels etc.

  • autofs does not function inside containers. We use autofs for lots of NFS mount points, and not having it operate is very annoying. It was a documented kernel limitation when we deployed containers last year, since we are on the same general kernel version today I don't believe that has changed for us anyway.
  • Memory capacity is not correctly reported by the container. If the host has 64GB of memory, and the container is limited to 32GB of memory, all of the general linux tools inside the container all report 64GB of memory available, again, annoying, and I imagine this means the container doesn't handle out of memory situations too gracefully as it has no idea it is about to run out before it hits the wall.
  • Likewise querying per-container CPU usage using standard linux tools is impossible. Everything reports the same CPU usage whether it is the host, the active container on the host, or the idle container on the host.
  • Running containers that span multiple subnets simultaneously is extremely difficult and complicated. I have probably a dozen different VLANs on VMware hosts each on different subnets, each with different default gateways etc. The routing exists in the Linux kernel and having more than one default gateway is a real pain. I read last year it seemed to be technically possible, but the solution was not at all a practical one. So in the meantime, a host has to be dedicated to a single subnet.
  • Process listings on the container host is quite confusing, as it lists the processes for all of the containers as well, identifying which process is from where is confusing and annoying. Having to have custom monitors configured to say, on these hosts having 6 postfix processes is ok but everywhere else 1 is required, is annoying too. I'm sure there is probably lxc-specific tools that can do it but the point is the standard linux tools don't handle this well at all.
  • Lack of ability to do things like move containers between hosts, some applications, and some environments can be made fully redundant so you can lose a VM/container and be ok. But many others are not. I literally have several hundred VMs each of which are single points of failure because most are development VMs and it is a waste to build redundancy into every development environment the resource requirements would explode. So having things like vmotion & VMware high availability, and even DRS for host affinity rules is very nice to have.

Any one of the above I would consider a deal breaker for large(r) scale deployments of containers at organizations I have worked for. Combine them all? What a mess.

There are other limitations as well, those are just the most severe I see.

Future uses of containers at my organization

I can see future uses of containers at my organization expanding in the production environment, targeting CPU hungry applications and putting them on physical hardware. Maybe even feel brave enough to host multiple applications on the same hardware knowing that I have no good insight into how much each application is using CPU wise(since all current monitoring is performed at the OS level not the application level). Time will tell.

I said earlier we continue to activate "both farms" even though we use containers. In the case of the container hosted application we do not ever activate both farms anymore, but we do have other production web applications that are farm based and living in VMware still, so those we do activate both farms for in anticipation(hopefully) or response to sudden increases in traffic.

Containers inside a hypervisor are a waste of time

In case it isn't obvious it is my belief that the main point of using containers is to leverage the underlying hardware of server platform you are on, and removing the overhead and costs associated with the hypervisor where possible. Running containers within a hypervisor to me is a misguided effort. Of course I am sure there are people doing this in public clouds because they want to use containers but they are limited by what the "cloud" will give them (hence the original pro-docker article talking about this specific point).

I do not believe that containers themselves have any bearing on deployment of applications in any scenario. They are completely independent things. A container, from a high level (think CxO level) is functionally equivalent to a virtual machine, a concept we have had in the server world for over a decade at this point.

Deep down technically they are pretty different but the concept of segmenting a physical piece of hardware into multiple containers/VMs so that things don't run over each other is nothing new (and it's really really old if you get outside of the x86 world I believe IBM has been doing this kind of thing for 30+ years on big iron).

Good use cases for containers at hyper scale

At hyperscale (never having worked at such a scale but I get the gist of how some things operate), all math changes. Every decision is magnified 10,000x.

  • Suddenly saving 5 watts of power on a server is a big deal because you have 150,000 servers deployed.
  • Likewise the few percent of CPU and memory overhead provided by hypervisors can literally cost an organization millions of $ at high scale.
  • Yet alone licensing costs from the likes of VMware etc even with volume/enterprise deals.
  • The time required to launch a VM really is slow compared to launching a container, which again at scale that time really adds up.

There was an article I read last year that said google launches 2,000,000,000 containers per week. Maybe I have launched 4,000 VMs in the past decade - average 7.7 VMs per week(that is aiming really high too). So perspective is in order here. (yes I wanted to write out the 2 billion number that way, nicer perspective). 2 billion per week vs 8 per week, yeah, just slightly different scale here.

At scale you can obviously overcome the limitation of requiring multiple subnets on a server because you have fleets of systems, each fleet probably on various subnets, you're so big you don't need to be that consolidated. You probably have a good handle on application-level CPU and memory monitoring(not relying on monitoring of the VM/container as a whole), you probably don't rely too much on NFS, but instead applications probably use a lot of object storage. You probably never login to the servers so you don't care what the process list looks like. Your application is probably so fault tolerant that you don't care about losing a host.

All of these are perfectly valid scenarios to have at a really big scale. But again most organizations will never, ever get to that scale. I'll say again I believe firmly that trying to build for that level of scale from the outset is a mistake because you will very likely do it wrong, even if you think you know what you are doing.

I'll use another example here, again taking from one of my comments from el reg recently. I had a job interview back in 2011 at a mid sized company in Seattle, they probably had a few hundred servers, and a half dozen to dozen or so people in the operations group(s). They had recently hired some random guy(random to me anyway) out of Amazon who proclaimed he was a core part of building the Amazon cloud (yet his own linkedin profile said he was just some random engineer there). He talked the talk, I obviously didn't know him so it was hard to judge his knowledge based on a 1-2 hour interview with him. Our approaches were polar opposite to each other. I understood his approach(the Amazon way), and I understood my approach(the opposite). Each has value in certain circumstances. It was the only interview I've ever had where I was really close to just standing up and walking out. My ears were hot, I could tell I would not get along with this person. I kept my BS going though because I was looking for a new job.

The next day or the day after they offered me the job(apparently this guy liked me a lot), I declined politely and accepted the position I am at now and relocated to the bay area a couple of months later.

I had friends who knew this company and kept me up to date on what was going on over there. This guy wanted to build an Amazon cloud at this company. An ambitious goal to be sure, I believed firmly they weren't going to be able to do it, but this guy believed they could. So they went down the procurement route, and it was rough going. At one point their entire network team quit en-masse because they did not agree with what this guy was doing. He was basically trying to find the cheapest hardware money could buy and wanted to make it "cloud". He was clueless but their management bought into his BS for some time. He wrecked the group, and within a year I want to say I was informed that not only was he fired but he was escorted out of the building. The company paid through the nose to hire a new team because word got around, nobody wanted to work there. Last I heard they were doing well, had long abandoned the work this person had tried to do.

He had an idea, he had some experience, he knew what he wanted to do. He didn't realize the organization lacked the ability to execute on that vision. I realized this during my one day interview there but he had no idea, or didn't care (maybe he thought if they just work hard enough they can make it work).

Anyway perhaps an extreme example, but one that remains fresh in my mind.

Conclusion

Simply trying to do something just because Amazon, or Google(hello hipster Hadoop users from the past decade) or even Microsoft is doing it doesn't automatically make it a good idea for your organization, you've got to have the ability to execute on it, and in many cases execution turns out to be much harder than it appears(I once had one VP tell me he wanted to use HDFS for vmware storage, are you kidding me? At the same company the CTO wanted to entertain the idea of using FreeNAS for their high volume data processing TBs of data per day hundreds of megabytes of throughput per second for their mission critical data, the question was so absurd I didn't know how to respond at the time).

I re-read what I wrote in the original container hype article many times(as I always re-read many times and make corrections). I realized pretty quickly that the person who wrote the original pro-docker container article I was quoting really seemed to me like a young developer who lacked experience working on anything other than really toy applications. One of the system administrators I know outright said at one point he just stopped reading that (pro-docker) article because the arguments were just absurd. But those points did seem to me to be along the lines of what I have been hearing for the past year so I believed it was a well formed post that I could leverage to respond to.

Tagged as: 2 Comments
27Aug/15Off

Container Hype

TechOps Guy: Nate

(You can see part two of my thoughts on containers here.)

I'll probably regret this post for a little while at least. Because I happened to wake up at about 3AM this morning and found myself not really falling back asleep quickly and I was thinking about this article I read last night on Docker containers and a couple skype chats I had with people regarding it.

Like many folks, I've noticed a drastic increase in the hype around containers, specifically Docker stuff over the past year or so. Containers are nothing new, there have been implementations of them for a decade on Solaris anyway. I think Google has been using them for about a decade, and a lot of the initial container infrastructure in Linux (cgroups etc) came from Google. Red Hat has been pushing containers through their PaaS system Openshift I want to say for at least five years now since I first started hearing about it.

My personal experience with containers is limited - I have deployed a half dozen containers in production for a very specific purpose a little over a year ago using LXC on Ubuntu. No Docker here, I briefly looked into it at the time and saw it provided no value to what I do so I went with plain LXC. The containers have worked well since deployment and have completely served their purpose. There are some serious limitations to how containers work(in the Linux kernel) which today prevent them from being used in a more general sense, but I'll get to that in another post perhaps (this one ended up being longer than I thought). Perhaps since last year's deployment some of those issues have been addressed I am not sure. I don't run bleeding edge stuff.

I'll give a bit of my own personal experience here first so you get an idea where I am coming from. I have been working in technical operations for organizations (five of them at this point) running more or less SaaS services (though internally I've never heard that term tossed about at any company, we do run a hosted application for our customers) for about 12 years now. I manage servers, storage, networking, security to some degree, virtualization, monitoring etc(the skills and responsibilities have grown over time of course). I know I am really good at what I do(tried to become less modest over recent couple of years). The results speak for themselves though.

My own personal experience again here - I can literally count on one hand the number of developers I have worked with over the years that stand out as what I might call "operationally excellent". Fully aware of how their code or application will work in production and builds things with that in mind, or knows how to engage with operations in really productive way to get questions answered on to how best to design or build things. I have worked with dozens of developers(probably over 100 at this point), some of them try to do this, others don't even bother for some reason or another.  The ones I can count on one hand though, truly outstanding, a rare breed.

Onto the article. It was a good read, my only real question is does this represent what a typical Docker proponent thinks of when they think of how great Docker is or how it's the future etc. Or is there a better argument. Hopefully this represents what a typical Docker person thinks so I'm not wasting my time here.

So, to address point by point, try to keep it simple

Up until now we’ve been deploying machines (the ops part of DevOps) separately from applications (the dev part). And we’ve even had two different teams administering these parts of the application stack. Which is ludicrous because the application relies on the machine and the OS as well as the code, and thinking of them separately makes no sense. Containers unify the OS and the app within the developer’s toolkit.

This goes back to experience. It is quite ludicrous to expect the developers to understand how to best operate infrastructure components, even components to operate their own app (such as MySQL) in a production environment. I'm sure there are ones out there that can effectively do it(I don't claim to be a MySQL expert even myself having worked with it for 15 years now I'll happily hand that responsibility to a DBA as do most developers I have worked with), but I would wager that number is less than 1 in 50.

Operating things in a development environment is one thing, go at it, have a VM or a container or whatever that has all of your services. Operating correctly in production is a totally different animal. In a good production environment (hopefully in at least one test environment as well) you have significantly more resources to throw at your application to get more out of it. Things that are just cost prohibitive or even impossible to deploy at a tiny scale in a development environment(when I say development environment I imply that it runs on a developer laptop or something). Even things like connectivity to external dependencies likely don't exist in a development environment. For all but the most basic of applications production will always be significantly different in many ways. That's just how it is. You can build production so it's really close to other environments or even exactly the same but then you are compromising on so much functionality, performance, scalability that you've really just shot yourself in the foot and you should hope you don't get to any kind of thing resembling scale (not "web scale" mind you) because it's just going to fall apart.

Up until now, we’ve been running our service-oriented architectures on AWS and Heroku and other IaaSes and PaaSes that lack any real tools for managing service-oriented architectures. Kubernetes and Swarm manage and orchestrate these services

First off I'm happy to admit I've never heard of Kubernets and Swarm, I have heard of Heroku but no idea what it does. I have used AWS in the past (for about 2 years - worst experience of my professional career, I admit I do have PTSD when it comes to Amazon cloud).

I have worked with service-oriented architectures for the past 12 years. My very first introduction to SaaS was an EXTREMELY complicated Java platform that ran primarily on Weblogic+Oracle DB on the back end, with Apache+Tomcat on the front end. Filled with Enterprise Java Beans(EJB), and just dozens of services. Their policy was very tight, NOTHING updates the DB directly without going through a service. No "manual" fixes or anything via SQL(only company I've worked at with that kind of policy). Must write an app or something to interface with a service to fix issues. They stuck to it from what I recall while I was there anyway, I admire them for that.

At one point I took my knowledge of the app stack, and proposed an very new architecture for operational deployment, it was much more expensive, because this was before wide spread use of VM technology or containers in general. We split the tomcat tiers up for our larger customers into isolated pools(well over 200 new physical servers! that ran at under 5% cpu in general!). The code on all systems was the same but we used the load balancer to route traffic for various paths to different sets of servers. To some extent this was for scaling but the bigger problem this "solved" was something more simple operationally (but was not addressed to-date in the app) - logging. This app generated gobs of logging from tons of different subsystems (all of it going to centralized structure on each system) making it very difficult to see what log events belonged to what subsystem.  It could take hours to trace transactions through the system. Something as simple as better logging, which developers ignored forever, we were able to address by splitting things out. The project started out small scale but ballooned quickly as other people piled in. Approvals came fast and hard for everything. My manager said  "aim for the sky because they will reject some things". I aimed for the sky and got everything I asked for(several million $ worth). I believe eventually they moved to a VM model a few years after I left. We tried to get the developers to fix the code, it never happened, so we did what we had to do to make things more manageable. I recall most everyone's gleeful reaction the first time they started using the new systems. I know it's hard to believe, you had to be there to see what a mess it was.

Though the app itself was pretty terrible. I remember two members of my team quit within a month and both said something along the lines of "we've been at the company 6-9 months and still don't understand how the application works" (and their job was in part supporting production issues like mine was, I was as close to an expert in the operation of that application as one could get, it wasn't easy). The data flows of this application were a nightmare, it was my first experience working in SaaS, so as far as I knew it was "normal". But if I were exposed to that today I would run away screaming. So. many. outages. (bad code, and incredibly over designed) I remember one developer saying "why weren't you in our planning meeting last year when we were building this stuff?" I said back something like "I was too busy pulling 90 hour weeks just keeping the application running, I had no time for anything else". I freely admit these days I burned out hard core at that company, took me more than three years to recover. I don't regret it, it was a good experience, I learned a lot, I had some fun. But it cost me a lot as well. I would not do it again at this point in my career, but if I had the ability to talk to my 2003 self I would tell me to do it.

My first exposure to "micro services" was roughly 2007 at another SaaS company, these services specifically were built with Ruby on Rails of all things. There were a few different ways to approach deploying it. By this time I had started using VMware ESX (my first production deployment of VMware was GSX 3.0 in 2004 in a limited scope production deployment at the previous company I referred to).

Perhaps the most common way would of just been to have an apache instance and the various applications inside of it, keep it simple. Another approach might of been to leverage VMware in a larger scope and build VMs for each micro service (each one had a different code base in subversion, not like it was a bunch of services in a single code base). I took a different approach though, an approach I thought was better(at the time anyway, I still think it was a good choice). I decided to deploy each service on it's own apache instance(each listening on a different port) on a single OS image (CentOS or Fedora at the time) running on physical hardware. We had a few "web" servers each running probably 15 apache instances with custom configurations managed by CFengine. The "micro services" talked to each other through a F5 BigIP load balancer. We had other services on these boxes as well, the company had a mod_perl based application stack, and another Tomcat-based application, these all ran on the same set of servers.

A common theme for this for me is, twelve years of working with services oriented architectures, and eight years of working with "micro services" and I've never needed special sauce to manage them.

Up until now, we have used entire operating systems to deploy our applications, with all of the security footprint that they entail, rather than the absolute minimal thing which we could deploy. Containers allow you to expose a very minimal application, with only the ports you need, which can even be as small as a single static binary.

This point seems kind of pointless to me. Operating systems are there to provide the foundation of the application. I like the approach of trying to keep things common. That is the same operating system across as many of the components as possible - keeping in mind there are far more systems involved than just the servers that "run the application". While saying minimal exposure is a nice thing to have, at the end of the day it really doesn't matter(it doesn't noticeably or in most cases measurably impact operation of the application, but it does improve manageability).

Up until now, we have been fiddling with machines after they went live, either using “configuration management” tools or by redeploying an application to the same machine multiple times. Since containers are scaled up and down by orchestration frameworks, only immutable images are started, and running machines are never reused, removing potential points of failure.

I'll preface this by saying I have never worked for an organization that regularly or even semi regularly scaled up and scaled down their infrastructure(even while working in Amazon cloud). Not only have they never really done it, but they've never really needed to. I'm sure there are some workloads that can benefit from this, but I'm also sure the number is very small. For most you define a decent amount of headroom for your application to burst into and you let it go, and increase it as required(if required) as time goes on with good monitoring tools.

I'll also say that since I led the technical effort behind moving my current organization out of Amazon cloud in late 2011(that is what I was hired to do, I was not going to work for another company that used them on a regular basis. Per earlier point we actually intended to auto scale up and down but at the end of the day it didn't happen), we have not had to rebuild a VM, ever.  Well over three years now with never having had to rebuild a VM (well there is one exception where we retired one of our many test environments at one point only to have a need for it again a few months later, NOTHING like our experience with public cloud though). So yeah, the lifetimes of our systems are measured in years, not in hours, days, or weeks. Reliability is about as good as you can get in my opinion(again record speaks for itself). We've had just two sudden hardware failures causing VMs to fail in the past 3 and a half years. In both cases VMware High availability automatically restarted the affected VMs on other hosts within a minute, and HP's automatic server recovery rebooted the hosts in question (in both cases had to get system boards replaced).

Some people when thinking of public cloud say "oh but how can we operate this better than Amazon, or Microsoft etc". I'm happy to admit now that I KNOW I can operate things better than Amazon, Microsoft, Google etc. I've demonstrated it for the past decade, and will continue to do so. Maybe I am unique, I am not sure (I don't go out of my way to socialize with other people like me). There is a big caveat to that statement that again I'm happy to admit to. The "model' of many of the public cloud players is radically different from my model. The assumptions they make are not assumptions I make (and vise versa). Their model in order to operate well you really have to design your app(s) to handle it right. My model you don't. I freely admit my model would not be good for "web scale", just like their model is not good for the scale any company I have worked at for the past 12 years. Different approaches to solve similar issues.

Up until now, we have been using languages and frameworks that are largely designed for single applications on a single machine. The equivalent of Rails’ routes for service-oriented architectures hasn’t really existed before. Now Kubernetes and Compose allow you to specify topologies that cross services.

I'll mostly have to skip this one as it seems very code related, I don't see how languages and frameworks have any bearing on underlying infrastructure.

Up until now, we’ve been deploying heavy-weight virtualized servers in sizes that AWS provides. We couldn’t say “I want 0.1 of a CPU and 200MB of RAM”. We’ve been wasting both virtualization overhead as well as using more resources than our applications need. Containers can be deployed with much smaller requirements, and do a better job of sharing.

I haven't used AWS in years, in part because I believe they have a broken model, something I have addressed many times in the past. I got upset with HP when they launched their public cloud and launched with a similar model. I believe I understand why they do things this way (because doing it "right" at "large scale" is really complicated).

So this point is kind of moot. I mean people have been able to share CPU resources across VMs for well over a decade at this point(something that isn't possible in all major public cloud providers). I also share memory to an extent(this is handled transparently with the hypervisor). There is certainly overhead associated with VM, and with a "full" operating system image, but that is really the price you pay for the flexibility, and manageability that those systems offer. It's a price I'm willing to pay in a heartbeat, because I know how to run systems well.

Up until now, we’ve been deploying applications and services using multi-user operating systems. Unix was built to have dozens of users running on it simultaneously, sharing binaries and databases and filesystems and services. This is a complete mismatch for what we do when we build web services. Again, containers can hold just simple binaries instead of entire OSes, which results in a lot less to think about in your application or service.

(side note, check the container host operating system, yeah that one that is running all of the native processes in the same kernel - yes a multi user operating system running dozens of services on it simultaneously, a container is just a veil..)

This is another somewhat moot point. Having a lot less to think about, certainly from an OS perspective to me makes things more complicated. If your systems are so customized that each one is different that makes life more difficult. For me I can count on a common set of services and functionality being available on EVERY system. And yes, I even run local postfix services on EVERY system(oh, sorry that is some overhead). To be clear postfix is there as a relay for mail which is then forwarded to a farm of load balanced utility services which then forward onto external SMTP services. This is so I can do something as simple as "cat some file| mail my.email.address" and have it work.

Now we do limit what services run, e.g. Chef(current case) or CFengine(prior companies) only runs our core services, extra things that I never use are turned off. Some services are rare or special. Like FTP for example. I do have a couple of uses cases for running a FTP server still, and in those cases FTP services only run on the systems that need it. And obviously from an application standpoint not all apps run on all app servers.  But this kind of stuff is pretty obvious.

At the end of the day having these extra services provides convenience not only to us, but to the developers as well. Take postfix as an example. Developers came to me one day saying they were changing how they send email, instead of interfacing with some external provider via web API their new provider they will interface with SMTP. So where do they direct mail to? My answer was simple - in all cases, in all environments send mail to localhost, we'll handle it from there. Sure you can put custom logic in your application or custom configurations for each environment if you want to send directly to our utility servers, but we sure as hell don't want you to try to send mail directly from the web servers to the external parties, that's just bad practice (for anything resembling a serious application assuming many servers supporting it and not just a single system running all services). The developers can easily track progress of the mail as it arrives on the locahost MTA, and is then immediately routed to the appropriate utility server farm (different farms for different environments due to network partitioning to prevent QA systems for example from talking to production, also each network zone(3 major zones) has a unique outbound NAT address, which is handy in the event of needing IP filters or something).

So again, worrying about these extra services is worrying about nothing in my opinion. My own experience says that the bulk of the problems with applications are code based, sometimes design, sometimes language, sometimes just bugs. Don't be delusional and think that by deploying containers that will somehow magically make the code better and the application scale and be highly available. It's addressing the wrong problem, it's a distraction.

Don't get me wrong though, I do believe containers do  have valid use cases, which I may cover in another post this one is already pretty long. I do use some containers myself (not Docker). I do see value in providing an "integrated" experience (download one file and get everything - even though that has been a feature in virtualized environments for probably close to a decade with OVF as well). That is not a value to me, because as an experienced professional it is rare that something works properly "out of the box", at least as far as applications go. Just look for example at how Linux distributions package applications, many have their own approach on where to put files, how to manage things etc. That's the simplest example I can give. But I totally get it for constrained environments it's nice to be able to get up to speed quickly with a container. There are trade offs certainly once you get to "walking" (thinking baby step type stuff here).

There is a lot of value that operating systems and hypervisors and core services provide. There is overhead associated with them certainly. In true hyper scale setups this overhead is probably not warranted (Google type scale). I will be happy to argue till I am somewhat blue in the face that 99.99% of organizations will never be at that scale, and trying to plan for that from the outset is a mistake(and I'd wager almost all that try, fail because they over design or under design), because there is not one size that fits all. You build to some reasonable level of scale, then like anything new requirements likely come in, and you re evaluate, re-write, re-factor or whatever.

It's 5AM now, I need to hit the gym.

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