what are the real world use cases of docker containers? [closed] - docker

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I understand docker containers features like app isolation, Server Consolidation, ... but I am wondering what are the real world use cases for Containers. How are you using containers in Production environment? Are they being used to host web services and web sites? Can you please give me some examples?
Thanks

First decoupling and distributing applications into microservices.
So I'll give you an example I work with where you have the old method of deploying an application lets say a rails application that's a monolith application, i.e with the db, web app, a background task scheduler like sidekiq(in the case of python RabbitMQ), and redis to hold temporal (key, value) data. All this services running on a single server would mean this application has a single point of failure at any given moment. If something were to fail means that your whole application is offline while you rush off to trace what failed. If you had taken your application split it into small pieces known as a micro-service where each part of your application is packed into a container with the libraries it needs then deployed independently and dynamically to form part your overall application. Decoupling your application into these manageable components and reducing the probability of your application ever failing entirely. Furthermore, decoupling allows container-based applications to be deployed easily and consistently, regardless of whether the target environment is a private data center, the public cloud, or even a developer’s personal laptop.
Dev and Ops separation of concerns
Take the part where most people build a release during deployment and may sometimes fail during deployment. With a container you get to build your image before release time which and you can run an environment similar to the one in production with no guesswork and this makes it easy for you to roll out more frequently without concern of failure/ or rather reduced. it also increases the consistency to which release/build your application.
Containerization provides a clean separation of concerns, as
developers focus on their application logic and dependencies, while IT
operations teams can focus on deployment and management without
bothering with application details such as specific software versions
and configurations specific to the app.
Just have a read on these two links and it should clear up some stuff on your end.
Containers 101 google and this
Kubernetes

Related

How to prevent an application from starting before its dependencies are available [duplicate]

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Docker Compose wait for container X before starting Y
(20 answers)
Closed 2 years ago.
My Dockerfile starts the application using the following command
CMD ["/home/app/start-app.sh"]
start-app.sh contains the following, it waits until RabbitMQ server is available. Is there a better way of achieving this for applications running using docker-compose, k8s
while ! nc -z "$RABBITMQ_HOSTNAME" "$SPRING_RABBITMQ_PORT"; do sleep 10; done
I guess not. Even though docker compose provides a depends_on it just starts the containers in the dependency order. It does not make sure that a specific service is available. The docker documentation explains it in this way that I can't do better:
The problem of waiting for a database (for example) to be ready is really just a subset of a much larger problem of distributed systems. In production, your database could become unavailable or move hosts at any time. Your application needs to be resilient to these types of failures.
To handle this, design your application to attempt to re-establish a connection to the database after a failure. If the application retries the connection, it can eventually connect to the database.
You already do what is needed if you have to wait for another service to become ready. But like they say, it is better to develop applications that can handle downtime of other services, because downtime can happen anytime. That's why netflix developed the chaos monkey. One might argue now that handling these possible states makes applications so much harder to develop. That's true, but it's just the complexity of distribution. One can either ignore it: "this will never happen" and I guarantee it will or accept that it can happen and do the right thing. Maybe this decision depends on the risk and the damage it will produce when it happens to your company.
Services or microservices give us a lot of decoupling and flexibility, but they come at a coast that we should keep in mind.

Is there a benefit to developing an iOS app against a docker instance?

Our backend is containerised with docker for use with minikube, I was wondering if as an iOS developer I can take advantage of this by running the backend locally on my laptop rather than having to communicate with a staging cloud based environment which can often be flaky.
Am I misunderstanding how this technology works, or would this be a viable and useful case for docker in iOS development, speeding up request and response times and allowing more control over the state of the backend I am building against?
Thanks for any clarity on this idea
What you’re explaining is possible and is something I do in my day job regularly so as to possibility, yes you can do this.
The question of whether this raises any benefit is broad and depends on every individuals needs. If you are finding that your cloud instance is extremely slow at the moment and you don’t have capacity to improve its performance, a locally run docker instance could very well help with this.
One thing to keep in mind though is that any changes you make to a local instance/server in order to make the app work as expected will need to be reflected into your production instance as soon as your app goes live to the public otherwise you will see undesired behaviour due to the app relying on non-existent server configs.

Why do people use Heroku when AWS is present? What distinguishes Heroku from AWS? [closed]

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I'm a beginner RoR programmer who's planning to deploy my app using Heroku. Word from my other advisor friends says that Heroku is really easy, good to use. The only problem is that I still have no idea what Heroku does...
I've looked at their website and in a nutshell, what Heroku does is help with scaling but... why does that even matter? How does Heroku help with:
Speed - My research implied that deploying AWS on the US East Coast would be the fastest if I am targeting a US/Asia-based audience.
Security - How secure are they?
Scaling - How does it actually work?
Cost efficiency - There's something like a dyno that makes it easy to scale.
How do they fare against their competitors? For example, Engine Yard and bluebox?
Please use layman English terms to explain... I'm a beginner programmer.
First things first, AWS and Heroku are different things. AWS offer Infrastructure as a Service (IaaS) whereas Heroku offer a Platform as a Service (PaaS).
What's the difference? Very approximately, IaaS gives you components you need in order to build things on top of it; PaaS gives you an environment where you just push code and some basic configuration and get a running application. IaaS can give you more power and flexibility, at the cost of having to build and maintain more yourself.
To get your code running on AWS and looking a bit like a Heroku deployment, you'll want some EC2 instances - you'll want a load balancer / caching layer installed on them (e.g. Varnish), you'll want instances running something like Passenger and nginx to serve your code, you'll want to deploy and configure a clustered database instance of something like PostgreSQL. You'll want a deployment system with something like Capistrano, and something doing log aggregation.
That's not an insignificant amount of work to set up and maintain. With Heroku, the effort required to get to that sort of stage is maybe a few lines of application code and a git push.
So you're this far, and you want to scale up. Great. You're using Puppet for your EC2 deployment, right? So now you configure your Capistrano files to spin up/down instances as needed; you re-jig your Puppet config so Varnish is aware of web-worker instances and will automatically pool between them. Or you heroku scale web:+5.
Hopefully that gives you an idea of the comparison between the two. Now to address your specific points:
Speed
Currently Heroku only runs on AWS instances in us-east and eu-west. For you, this sounds like what you want anyway. For others, it's potentially more of a consideration.
Security
I've seen a lot of internally-maintained production servers that are way behind on security updates, or just generally poorly put together. With Heroku, you have someone else managing that sort of thing, which is either a blessing or a curse depending on how you look at it!
When you deploy, you're effectively handing your code straight over to Heroku. This may be an issue for you. Their article on Dyno Isolation details their isolation technologies (it seems as though multiple dynos are run on individual EC2 instances). Several colleagues have expressed issues with these technologies and the strength of their isolation; I am alas not in a position of enough knowledge / experience to really comment, but my current Heroku deployments consider that "good enough". It may be an issue for you, I don't know.
Scaling
I touched on how one might implement this in my IaaS vs PaaS comparison above. Approximately, your application has a Procfile, which has lines of the form dyno_type: command_to_run, so for example (cribbed from Heroku Architecture - The Process Model):
web: bundle exec rails server
worker: bundle exec rake jobs:work
This, with a:
heroku scale web:2 worker:10
will result in you having 2 web dynos and 10 worker dynos running. Nice, simple, easy. Note that web is a special dyno type, which has access to the outside world, and is behind their nice web traffic multiplexer (probably some sort of Varnish / nginx combination) that will route traffic accordingly. Your workers probably interact with a message queue for similar routing, from which they'll get the location via a URL in the environment.
Cost Efficiency
Lots of people have lots of different opinions about this. Currently it's $0.05/hr for a dyno hour, compared to $0.025/hr for an AWS micro instance or $0.09/hr for an AWS small instance.
Heroku's dyno documentation says you have about 512MB of RAM, so it's probably not too unreasonable to consider a dyno as a bit like an EC2 micro instance. Is it worth double the price? How much do you value your time? The amount of time and effort required to build on top of an IaaS offering to get it to this standard is definitely not cheap. I can't really answer this question for you, but don't underestimate the 'hidden costs' of setup and maintenance.
(A bit of an aside, but if I connect to a dyno from here (heroku run bash), a cursory look shows 4 cores in /proc/cpuinfo and 36GB of RAM - this leads me to believe that I'm on a "High-Memory Double Extra Large Instance". The Heroku dyno documentation says each dyno receives 512MB of RAM, so I'm potentially sharing with up to 71 other dynos. (I don't have enough data about the homogeny of Heroku's AWS instances, so your milage may vary))
How do they fare against their competitors?
This, I'm afraid I can't really help you with. The only competitor I've ever really looked at was Google App Engine - at the time I was looking to deploy Java applications, and the amount of restrictions on usable frameworks and technologies was incredibly off-putting. This is more than "just a Java thing" - the amount of general restrictions and necessary considerations (the FAQ hints at several) seemed less than convenient. In contrast, deploying to Heroku has been a dream.
Conclusion
Please comment if there are gaps / other areas you'd like addressed. I feel I should offer my personal position. I love Heroku for "quick deployments". When I'm starting an application, and I want some cheap hosting (the Heroku free tier is awesome - essentially if you only need one web dyno and 5MB of PostgreSQL, it's free to host an application), Heroku is my go-to position. For "Serious Production Deployment" with several paying customers, with a service-level-agreement, with dedicated time to spend on ops, et cetera, I can't quite bring myself to offload that much control to Heroku, and then either AWS or our own servers have been the hosting platform of choice.
Ultimately, it's about what works best for you. You say you're "a beginner programmer" - it might just be that using Heroku will let you focus on writing Ruby, and not have to spend time getting all the other infrastructure around your code built up. I'd definitely give it a try.
Note, AWS does actually have a PaaS offering, Elastic Beanstalk, that supports Ruby, Node.js, PHP, Python, .NET and Java. I think generally most people, when they see "AWS", jump to things like EC2 and S3 and EBS, which are definitely IaaS offerings
AWS / Heroku are both free for small hobby projects (to start with).
If you want to start an app right away, without much customization of the architecture, then choose Heroku.
If you want to focus on the architecture and to be able to use different web servers, then choose AWS. AWS is more time-consuming based on what service/product you choose, but can be worth it. AWS also comes with many plugin services and products.
Heroku
Platform as a Service (PAAS)
Good documentation
Has built-in tools and architecture.
Limited control over architecture while designing the app.
Deployment is taken care of (automatic via GitHub or manual via git commands or CLI).
Not time consuming.
AWS
Infrastructure as a Service (IAAS)
Versatile - has many products such as EC2, LAMBDA, EMR, etc.
Can use a Dedicated instance for more control over the architecture, such as choosing the OS, software version, etc. There is more than one backend layer.
Elastic Beanstalk is a feature similar to Heroku's PAAS.
Can use the automated deployment, or roll your own.
As Kristian Glass Said, there is no comparison between IaaS(AWS) and PaaS(Heroku, EngineYard).
PaaS basically helps developers to speed the development of app,thereby saving money and most importantly innovating their applications and business instead of setting up configurations and managing things like servers and databases. Other features buying to use PaaS is the application deployment process such as agility, High Availability, Monitoring, Scale / Descale, limited need for expertise, easy deployment, and reduced cost and development time.
But still there is a dark side to PaaS which lead barrier to PaaS adoption :
Less Control over Server and databases
Costs will be very high if not governed properly
Premature and dubious in current day and age
Apart from above you should have enough skill set to mange you IaaS:
Hardware acquisition
Operating System
Server Software
Server Side Scripting Environment
Web server
Database Management System(Mysql, Redis etc)
Configure production server
Tool for testing and deployment
Monitoring App
High Availability
Load Blancing/ Http Routing
Service Backup Policies
Team Collaboration
Rebuild Production
If you have small scale business, PaaS will be best option for you:
Pay as you Go
Low start up cost
Leave the plumbing to expert
PaaS handles auto scaling/descaling, Load balancing, disaster recovery
PaaS manages all security requirements
PaaS manages reliability, High Availability
Paas manages many third party add-ons for you
It will be totally individual choice based on requirement. You can have details on my PPT Hosting Rails Apps.
There are a lot of different ways to look at this decision from development, IT, and business objectives, so don't feel bad if it seems overwhelming. But also - don't overthink scalability.
Think about your requirements.
I've engineered websites which have serviced over 8M uniques a day and delivered terabytes of video a week built on infrastructures starting at $250k in capital hardware unr by a huge $MM IT labor staff.
But I've also had smaller websites which were designed to generate $10-$20k per year, didn't have very high traffic, db or processing requirements, and I ran those off a $10/mo generic hosting account without compromise.
In the future, deployment will look more like Heroku than AWS, just because of progress. There is zero value in the IT knob-turning of scaling internet infrastructures which isn't increasingly automatable, and none of it has anything to do with the value of the product or service you are offering.
Also, keep in mind with a commercial website - scalability is what we often call a 'good problem to have' - although scalability issues with sites like Facebook and Twitter were very high-profile, they had zero negative effect on their success - the news might have even contributed to more signups (all press is good press).
If you have a service which is generating a 100k+ uniques a day and having scaling issues, I'd be glad to take it off your hands for you no matter what the language, db, platform, or infrastructure you are running on!
Scalability is a fixable implementation problem - not having customers is an existential issue.
Actually you can use both - you can develop an app with amazon servers ec2. Then push it (with git) to heroku for free for awhile (use heroku free tier to serve it to the public) and test it like so. It is very cost effective in comparison to rent a server, but you will have to talk with a more restrictive heroku api which is something you should think about. Source: this method was adopted for one of my online classes "Startup engineering from Coursera/Stanford by Balaji S. Srinivasan and Vijay S. Pande
Well, people usually ask this question: Heroku or AWS when starting to deploy something.
My experiment of using both of Heroku & AWS, here is my quick review and comparison:
Heroku
One command to deploy whatever your project types: Ruby on Rails, Nodejs
So many 1-click to integrate plugins & third parties: It is super easy to start with something.
Don't have auto-scaling; that means you need to scale up/down manually
Cost is expensive, especially, when system needs more resources
Free instance available
The free instance goes to sleep if it is inactive.
Data center: US & EU only
CAN dive into/access to machine level by using Heroku run bash (Thanks, MJafar Mash for the advice) but it is kind of limited! You don't have full access!
Don't need to know too much about DevOps
AWS - EC2
This just like a machine with pre-config OS (or not), so you need to install software, library to make your website/service go online.
Plugin & Library need to be integrated manually, or automation script (public script & written by you)
Auto scaling & load balancer are the supported services, just learn how to config & integrate to your system
Cost is quite cheap, depends on which services and number of hours you use it
There are several free hours for T2.micro instances, but usually, you will pay few dollars every month (if still using T2.micro)
Your free instance won't go to sleep, available 24/7 (because you may pay for it :) )
Data center: around the world. Pick the region which is the best fit for you.
Dive into machine level. So you can enjoy it
Some knowledge about DevOps, but it is okay, Stackoverflow is helpful there!
AWS Elastic Beanstalk an alternative of Heroku, but cheaper
Elastic Beanstalk was announced as a public beta from 2010; it helps we easier to work with deployment. For detail please go here
Beanstalk is free, the cost you will pay will be for the services you use & number of hours of usage.
I use Elastic Beanstalk for a long time, and I think it can be the replacement of Heroku and cheaper!
Summary
Heroku: Easy at beginning, FREE instance, but expensive later
AWS: Not easy, free hours available, kind of cheaper, Beanstalk should be concerned to use
So in my current system, I use Heroku for staging and Beanstalk for production!
The existing answers are broadly accurate:
Heroku is very easy to use and deploy to, can be easily configured for auto-deployment a repository (eg GitHub), has lots of third party add-ons and charges more per instance.
AWS has a wider range of competitively priced first party services including DNS, load balancing, cheap file storage and has enterprise features like being able to define security policies.
For the tl;dr skip to the end of this post.
AWS ElasticBeanstalk is an attempt to provide a Heroku-like autoscaling and easy deployment platform. As it uses EC2 instances (which it creates automatically) EB servers can do everything any other EC2 instance can do and it's cheap to run.
Deployment with EB is very slow; deploying an update can take 10-15 minutes per server and deploying to a larger cluster can take the best part of an hour - compared to just seconds to deploy an update on Heroku. Deployments on EB are not handled particularly seamlessly either, which may impose constraints on application design.
You can use all the services ElasticBeanstalk uses behind the scenes to build your own bespoke system (with CodeDeploy, Elastic Load Balancer, Auto Scaling Groups - and CodeCommit, CodeBuild and CodePipeline if you want to go all in) but you can definitely spend a good couple of weeks setting it up the the first time as it's fairly convoluted and slightly tricker than just configuring things in EC2.
AWS Lightsail offers a competitively priced hosting option, but doesn't help with deployment or scaling - it's really just a wrapper for their EC2 offering (but costs much more). It lets you automatically run a bash script on initial setup, which is nice touch but it's pricy compared to the cost of just setting up an EC2 instance (which you can also do programmatically).
Some thoughts on comparing (to try and answer the questions, albeit in a roundabout way):
Don't underestimate how much work system administration is, including keeping everything you have installed up to date with security patches (and occasional OS updates).
Don't underestimate how much of a benefit automatic deployment, auto-scaling, and SSL provisioning and configuration are.
Automatic deployment when you update your Git repository is effortless with Heroku. It is near instant, graceful so there are no outages for end users and can be set to update only if the tests / Continuous Integration passes so you don't break your site if you deploy broken code.
You can also use ElasticBeanstalk for automatic deployment, but be prepared to spend a week setting that up the first time - you may have to change how you deploy and build assets (like CSS and JS) to work with how ElasticBeanstalk handles deployments or build logic into your app to handle deployments.
Be aware in estimating costs that for seamless deployment with no outage on EB you need to run multiple instances - EB rolls out updates to each server individually so that your service is not degraded - where as Heroku spins up a new dyno for you and just deprecates the old service until all the requests to it are done being handled (then it deletes it).
Interestingly, the hosting cost of running multiple servers with EB can be cheaper than a single Heroku instance, especially once you include the cost of add-ons.
Some other issues not specifically asked about, but raised by other answers:
Using a different provider for production and development is a bad idea.
I am cringing that people are suggesting this. While ideally code should run just fine on any reasonable platform so it's as portable as possible, versions of software on each host will vary greatly and just because code runs in staging doesn't mean it will run in production (e.g. major Node.js/Ruby/Python/PHP/Perl versions can differ in ways that make code incompatible, often in silent ways that might not be caught even if you have decent test coverage).
What is a good idea is to leverage something like Heroku for prototyping, smaller projects and microsites - so you can build and deploy things quickly without investing a lot of time in configuration and maintenance.
Be sure to factor in the cost of running both production and pre-production instances when making that decision, not forgetting the cost of replicating the entire environment (including third party services such as data stores / add ons, installing and configuring SSL, etc).
If using AWS, be wary of AWS pre-configured instances from vendors like Bitnami - they are a security nightmare. They can expose lots of notoriously vulnerable applications by default without mentioning it in the description.
Consider instead just using a well supported mainstream distribution, such as Ubuntu or Debian (or CentOS if you need RPM support).
Note: Amazon offer have their own distribution called Amazon Linux, which uses RPM, but it's EC2 specific and less well supported by third party/open source software.
You could also setup an EC2 instance on AWS (or Lightsail) and configure with something like flynn or dokku on it - on which you could then deploy multiple sites easily, which can be worth it if you maintain a lot of services or want to be able to spin up new things easily. However getting it set up is not as automagic as just using Heroku and you can end up spending a lot of time configuring and maintaining it (to the point I've found deploying using Amazon clustering and Docker Swarm to be easier than setting them up; YMMV).
I have used AWS EC instances (alone and in clusters), Elastic Beanstalk and Lightsail and Heroku at the same time depending on the needs of the project I'm working on.
I hate spending time configuring services but my Heroku bill would be thousands per year if I used it for everything and AWS works out a fraction of the cost.
tl;dr
If money was never an issue I'd use Heroku for almost everything as it's a huge timesaver - but I'd still want to use AWS for more complicated projects where I need the flexibility and more advanced services that Heroku doesn't offer.
The ideal scenario for me would be if ElasticBeanstalk just worked more like Heroku - i.e. with easier configuration and quicker and a better deployment mechanism.
An example of a service that is almost this is now.sh, which actually uses AWS behind the scenes, but makes deployments and clustering as easy as it is on Heroku (with automatic SSL, DNS, graceful deployments, super-easy cluster setup and management).
I've used it quite lot for both Node.js app and Docker image deployments, the major caveat is the instances are shared (something reflected in their lower cost) and currently no option to buy dedicated instances. However their open source deployment tool 'now' can also be used to deploy to dedicated instances on AWS as well as Google Cloud and Azure.
It's been a significant percentage of our business migrating people from Heroku to AWS. There are advantages to both, but it's gets messy on Heroku after a while... once you need a certain level of complexity no longer easy to maintain with Heroku's limitations.
That said, there are increasingly options to have the ease of Heroku and the flexibility of AWS by being on AWS with great frameworks/tools.
Funny thing is Heroku actually uses AWS on the backend. It takes away all the overhead and does architecture management on EC2 for you. (Got that knowledge from a senior engineer at a Big Company during an Interview)
Sometimes, I wonder why people compare AWS to Heroku. AWS is an IAAS( infrastructure as a service) it clearly speaks how robust and calculative the system is. Heroku, on the other hand, is just a SAAS, it is basically just one fraction of AWS services. So why struggle with setting up AWS when you can ship your first product to the prime using Heroku.
Heroku is free, simple and easy to deploy almost all types of stacks to the web. Heroku is specifically built to bypass all the hassles of shipping your application to a live server in less than no time.
Nevertheless, you may want to deploy your application using any of the tutorials from both parties and compare
AWS DOCS and Heroku Docs
Well Heroku uses AWS in background, it all depends on the type of solution you need. If you are a core linux and devops guy you are not worried about creating vm from scratch like selecting ami choosing palcement options etc, you can go with AWS. If you want to do things on surface level without having those nettigrities you can go with heroku.
Even though both AWS and Heroku are cloud platforms, they are different as AWS is IaaS and Heroku is PaaS
Well! I observer Heroku is famous in budding and newly born developers while AWS has advanced developer persona. DigitalOcean is also a major player in this ground. Cloudways has made it much easy to create Lamp stack in a click on DigitalOcean and AWS. Having all services and packages updates in a click is far better than doing all thing manually.
You can check out completely here: How to Host PHP on Amazon AWS EC2
Amazon Web Services (AWS) offers lots of services from IaaS to PaaS with assured 99.9999999% durability and availability of data and infrastructure. AWS offers infrastructure automation along with several tools for developers to pipeline their application deployment process.
On the other hand, Heroku is just PaaS which offers services to manage your platform on their cloud. It nowhere stands with AWS whether it is infrastructure or security.
Heroku is like subset of AWS. It is just platform as a service, while AWS can be implemented as anything and at any level.
The implementation depends on what the business requirement. If it fits in either, use accordingly.

Selecting a Rails host [closed]

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I'm close to picking a Rails host. I think I need a VPS solution, because (1) my Rails app has gems and plugins that I need to install to get it working, and (2) I need an SMTP server to send emails from my rails app out to users.
But then it occured to today...
1) Do I actually need VPS and root access to get my app up and running, just because I need to install gems, or can I just copy my Rails app folder up to a Rails-supporting hosting server and start it?
2) If I get a Google Apps account, which would include a business-class GMail solution, would that give me an SMTP server which I could use to send emails to users?
I'm looking for least-support-needed-solution. I can afford to pay for VPS hosting, and a Google Apps account, but I just wonder if this is really my best option.
UPDATE: It's now been just over three years since I first posted this question and answer. I still prefer AWS for all new deployments of a professional or serious horsepower nature (that is, if I don't self-host), but I also regularly deploy demo and tutorial apps to Heroku. I haven't tried any of the many VPS providers that have popped up such as Linode or DigitalOcean, but generally hear good things about them.
The key thing that keeps me from choosing Heroku for all my apps is cost. Since most of my indie projects outside of work are things where I'd prefer to absolutely minimize costs, AWS remains the better deal between AWS vs. Heroku. AWS (or any VPS provider for that matter) has the nice side effect of teaching you the OS along the way, which turns out to be hugely valuable in the long term.
=======================
So, two years later, here's my update. I've used three services for hosting, and here's my take on each of them (I actually love them all, but for various reasons).
Slicehost (now part of Rackspace Cloud Hosting)
This was the first VPS host I tried, and I loved them. The people there were amazing, support was awesome, and it had a really cool grassroots kind of feel. Now that VPS as a solution is more mainstream, and Rackspace has long since purchased Slicehost, I feel that the service offering is still awesome. If you want a simple way to setup a server, plenty of Linux distro choices, and control over your server, this is an awesome option.
Heroku
Love these guys too. I built a hobby app that is hosted there, rpglogger.com (which as of Nov. 2012 has actually migrated to Amazon Web Services), and developing and deploying to Heroku is a no-brainer. I really like working on Heroku for two reasons:
It's dead simple to setup. It really is as easy as they say, in my experience, to get an app running on their platform.
A single dyno (web server instance) is free. So hobby apps, and smaller apps basically get free hosting. It's not just for hobbies though - their plugin architecture is second-to-none, making the addition of 3rd party plugins such as NewRelic, Exceptional, and anything else on their platform a matter of just a few clicks.
You absolutely cannot beat Heroku for ease of use. Deploying an updated version of your app is literally as simple as pushing to your git repo. Heroku isn't necessarily cheap (for anything other than the small app), but if you're in a situation where you believe developer time is more valuable than having control over the server, then this is an amazing option. You can always migrate your app to any other platform anyhow, if it gets big, or the needs of the app vs. the cost of Heroku no longer make sense for you.
Amazon Web Services
I do quite a few small apps, and AWS reserved instances are awesome. For $60 I can basically get a reserved instance for an entire year. That one server is enough to run 3-4 small apps on the same machine, with more optimized memory usage, and the ability to run multiple web server instances (vs. Heroku's one free dyno, though I hear you can custom config your Heroku dyno using unicorn to get more scalability). Basically, AWS scales really well, and lets you share a server among multiple small apps, or spread a larger app across multiple servers.
On top of that initial cost for the reserved instance, I only have to pay for bandwidth and other AWS usage (S3, for example). I think AWS is an amazing mix of ultimate scalability, great costs, ultimate control, and for enterprise customers who want to build their entire infrastructure in the sky, it can't be beat. Rackspace Cloud Hosting provides similar services, and they're probably comparable for most things. But if what you want is the Swiss army knife of cloud services, I think AWS is still way ahead of everyone else.
===============
So, that being said, I started on Slicehost, then went to AWS, then tried Heroku, and today I spend most of my time back on AWS.
AWS is the kind of platform that, after you invest a little time in setting up your collection of VPS machines, it often makes sense to stay on this platform and leverage their ever increasing set of tools.
Granted, it took me two years of trying several options, and trying every level of management from fully managed servers (i.e. Heroku, where you don't even think of the server, just the app) to fully controlled servers (Slicehost and AWS). After all that I've come to this point where I'm ready to manage my own machines in order to get the flexibility and low costs that I want.
Through automation, the actual management of the servers on AWS becomes a non-event, so I don't spend my time constantly patching my machines, or doing other sysadmin tasks. I just check periodically to see if my servers need reboots, I set them to automatically install all security updates (I happen to deploy to Ubuntu servers), which means I spend 99% of my time (at least day-to-day) writing the application - not managing the servers (managing services is instead an occasional task of a few day's work, and then nothing else for months) - which is where I want to spend my time as a developer.
Neither of your requirements are VPS-specific. I use shared hosting from Site5 and currently run two rails apps through the account, both with gems that are not installed on the server by default and sending email. Installing gems does not require root access.
If you want to use a VPS anyway, both Slicehost and Linode are often recommended for Rails apps. A few more are listed under Deploy on the Rails site. I would encourage you to do some research on your choice in either case. Good luck!
You could check out Ruby on Rails Hosting, What is a good Ruby on Rails hosting service?, Good Ruby on Rails free hosting, and What is a good Ruby on Rails and PHP hosting?.
I personally prefer Heroku which has offers free low-scale hosting and is very easily upgraded. Also, they allow you to install gems (similarly to the gem dependencies and rake gems:install, but with different syntax/files), and send a few free emails (200, but it is easily upgraded).
I hate Heroku, it gives you no control over services you want to use and it's massively over priced. Just try to make use of a gem or service they don't specifically support and you will quickly find the limitations and the horrendous pricing.
Heroku is my host of choice.
You can send messages using GMail SMTP as well as the commercial SMTP plugin.
I have also used Slicehost, Linode, Dreamhost and RailsMachine.
Slicehost/Linode are awesome if you can set up the box yourself.
Dreamhost is cheap-as and great for staging. Sites are ponderously slow at times though.
RailsMachine is second to none as a managed service. Highly recommended for the support and the well-tuned stack.
I prefer linode, aws or so.
linode : is a standard linux server. you can login, install 3rd party dependencies and play around just like in your own server. Installing nginx/rails/ruby is the same way as what you did on your own pc/laptop/server.
heroku : is a service. I have to learn lots of stuffs that are not valuable at all if one day you switch to another platform(e.g. linode) or you have your own real server, for example, check the logs, install databases, or install gems. I have printed out most of its documents and read them in 1/2 days, and then I realize that I can't use these knowledges in my working server( that my company offered to me)
linode is cheap enough, $20 per month.
heroku is not always free. and I don't think it's stable enough for demonstration purpose.(e.g. your free heroku app will fall in sleep in spare time, and will cost you several seconds to wake up. this SEVERAL seconds is long enough to make you lost your customers if they want FAST web app )
so, forget heroku, buy or setup your own VPS, use it for years, then you will be an linux expert.
I use HawkHost for all my hosting needs, and I'm 90% sure they meet all your criteria. They provide web hosting and VPS services for very good prices, and their basic web host plan lets you have Rails applications running as well.
I'm used Joyent host- http://www.joyent.com. It's good Rails host.

Auto-update a Windows Service [closed]

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I am about to develop a program which will be installed and run as a Windows Service on the back-end servers (with internet access) of several clients. I do not have physical access to the servers. What I am working on is a scheme for reliably rolling out updates to the program.
I have spend quite a lot of time looking for best practices for Windows Service auto-updates, but have found very little useful information. Most techniques, such as ClickOnce, seem to cater primarily for Windows Forms-based applications.
My current plan is:
When updates are available, have the running service download, install, and start an update service.
The update service will download the new version of the main service and install it side-by-side of the current, still active version.
The update service next stops the old version and then starts the new version of the service.
The new version disables the update service during startup.
Some important concerns for me are:
Being able to handle updates both to the main service and the update service
Being able to handle interruptions such as power failure or a connection failure at any point during the update process
What am wondering is if this a common way to solve this problem and/or if I am missing anything crucial. Is it too complicated, or perhaps far too simplistic? How would you have done it (or, even better, how have you done this successfully)?
Thanks!
I was faced with the same problem last year and I wrestled with a lot of the same questions. A few bits of advice:
Since either service may be updated,
both services will function as
updaters of the other. Service A will
update Service B and vice versa. For
this reason, I suggest simply running
both services at all times. Unless
you are worried about really loading
down your server with
does-update-exist calls, the
enable/disable service management
isn't worth the overhead.
Like services can't be installed on a
single machine. In other words, you
can't install new and old versions of
the service side-by-side if they have
the same name. Unless you want to
complicate your update process, I
suggest you uninstall the old version
and then install the new version.
For example, Service A would download
Service B Installer, uninstall
Service B, install new version of
Service B and then run. Service B
would do the same for Service A.
Since each service is managing the
other, they should not only check for
available updates but they should
verify each other's health. For
example, Service A would check to see
if Service B exists and if it is
running. If the health check fails,
a list of steps to resolve the issue
and get the service running would be
completed by Service A. Executing the
health check and recovery operations
will cover you now matter what issue
arises with the update, initial
install or general operations.
Do ample logging on both the client
and the server. You'll want to track
what actions were taken and when.
For example, Service A might when it
is checking for updates, when it is
executing the health check and
associated actions. On the service
(assuming you are calling into a web
service looking for updates) track
the calls made by each Service. If
your Services aren't getting updated
at least you'll have a trail of
breadcrumbs (or lack of breadcrumbs)
pointing you to the problem.
There are literally bunches of potential gotchas with a solution of this sort: services not running at startup, UAC getting in the way, not being able to install and uninstall the services with the same user, ensuring user installing the service has ample permissions, connectivity loss, getting the .NET Framework installed on the client machine, handling reboot after install if necessary, etc.
Best of luck. It's a fun problem to solve, but it doesn't go without it's frustration -- especially since, as you said, there isn't a lot of documented information available.

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