I am becoming familiar with DigitalOcean and deployments and practicing horizontally scaling our application. I created a small droplet and set it up to run our app, and then took a snapshot of it and created two more droplets from that snapshot. When I deployed a new version of my app to the first droplet, the one I created a snapshot from, the other two received the same code, without me scp-ing files to them. Is this normal?
The answer to this question is "no."
My issue was with nginx configuration - I forgot to change the config files for the new servers and was proxying requests to the old one, thereby returning responses from only one server.
A DigitalOcean snapshot is a copy of the image file of your droplet at the time the snapshot was made. Essentially it is an exact copy of your droplet.
What this means is it has all the same coding for your application. So if anything was specific to the original droplet (IP for example) you might run into some issues. So if the duplicates had proxy coding that the new application is no longer using, it is likely to run into such issues.
Related
I'm automating app deployment to cloud foundry. So in the start command, I do a db migration. What can happen is that the migration would fail and as the result, the app will be dead. Is there some predefined strategy that can be used to rollback to the last working deployment, or I should manually store the last working version, check for failure and in that case redeploy the stored version?
The typical strategy used to deploy apps on Cloud Foundry is blue/green. This generally works like this:
Push the new app under a new name & host, like my-app-new.
Test the app & make sure it works.
When your satisfied, change the route mapping from the old app to the new app.
Delete the old app & optionally rename the new app.
Step #3 is where the cut-over happens. Prior to that all traffic keeps flowing to the old app.
This is documented more here.
https://docs.cloudfoundry.org/devguide/deploy-apps/blue-green.html
I'd say this often works well, but sometimes there are problems. Where this breaks down is with steps #1 & #2, if your app cannot have multiple instances of itself running or if migrations to your service are so different that the old app breaks when you update the database. It definitely helps if you keep this strategy in mind as you develop your app.
Aside from that, which has historically been the way to go, you could take a look at the new v3 API functionality. With v3, apps now retain multiple versions of a droplet. With this, you can rollback to a previous version of a droplet.
http://v3-apidocs.cloudfoundry.org/version/3.36.0/index.html#droplets
You can run cf v3-droplets to see the available droplets and cf v3-set-droplet to change the droplet being used.
That said, this will only rollback the droplet. It would not rollback a service like a database schema. If you need to do that, you'd need reverse migrations or perhaps even restore from a backup.
Hope that helps!
I work on very similar automation processes.
Daniel has explained the process very well. I think you're looking for the blue-green deployment methodology
1) Read up on blue green deploy here:
https://docs.cloudfoundry.org/devguide/deploy-apps/blue-green.html
2) Look at this plugin or implement blue green deploy manually:
https://github.com/contraband/autopilot
3) Blue-green restage plugin (a nice to have, in case you need to restage the app but not cause any downtime to the clients):
https://github.com/orange-cloudfoundry/cf-plugin-bg-restage
It works by creating a temporary app, copying the env vars/routes/code from the working app to he temp app.
The temp app now accepts traffic while the original app is being restaged.
the traffic moves on to the original app after it is restaged and the temporary app is deleted.
For an application I'm converting to the Cloud Foundry platform, I have a couple of template files. These are basically templates for documents that will be converted to PDF's. What are my options when it comes to having these available to my application? There are no persistent system drives, so I can't just upload them, it seems. Cloud Foundry suggests for you to save them on something like Amazon S3, Dropbox or Box, or simply having them in a database as blobs, but this seems like a very curious work-around.
These templates will change separately from application files, so I'm not intending to have them in the application Jar.
Cloud Foundry suggests for you to save them on something like Amazon S3, Dropbox or Box, or simply having them in a database as blobs, but this seems like a very curious work-around.
Why do you consider this a curious work-around?
One of the primary benefits of Cloud Foundry is elastic scalability. Once your app is running on CF, you can easily scale it up and down on demand. As you scale up, new copies of the app are started in fresh containers. As you scale down, app containers are destroyed. Only the files that are part of the original app push are put into a fresh container.
If you have files like these templates that are changing over time and you store them in the container's file system, you would need to make sure that all instances of the app have the same copies of the template file at all times as you scale up and down. When you upload new templates, you would have to make sure they get distributed to all instances, not just the one instance processing the upload. As new app instances are created on scale-up, you would need to make sure they have the latest versions of the templates.
Another benefit of CF is app health management. If an instance of your app crashes for any reason, CF will detect this and start a new instance in a fresh container. Again, only files that were part of the original app push will be dropped into the fresh container. You would need to make sure that the latest version of the template files got added to the container after startup.
Storing files like this that have a lifecycle separate from the app in a persistence store outside of the app container solves all these problems, and ensures that all instances of the app get the same versions of the files as you scale instances up and down or as crashed instances are resurrected.
Suppose I create a site in Wordpress, which is running on Elastic Beanstalk. Now, on the running app I will create posts /pages, upload images, etc. That is, some data, videos, files and records in a database will be added to the running application.
3 questions:
If WordPress is running on Elastic Beanstalk with multiple Amazon EC2 instances actually running my WordPress install, then will those files propagate automatically to all running instances? And will this also happen, if a new EC2 instance is fired up - for example, to handle increased load?
From what I see in AWS console, I can deploy different versions of an app-- but as per scenario above, if I deploy a new version, wont I lose all the files uploaded directly into running app (i.e. files and database records)? How do I keep those and at the same time deploy a new version of my app?
The WordPress team keeps issuing upgrades. Can I directly upgrade my running WordPress install, through the web interface? Or do I have to first upgrade my local version of WordPress, and then upload the new version of the app to Beanstalk? If I have to upgrade my local version and then upload, then again I am back to point 1, i.e. changes made by users directly to the older version of running app. How do I preserve those changes?
I've been working on this as well, and have learned a couple of things that are relevant here -- your question about uploads in particular has been on my mind:
(1) The best way to handle uploads, it seems to me, is to either go the NFS/NAS route like you suggest, but one better than that is to use an Amazon S3 plugin for WordPress, so that any uploads automatically copy up to S3 and the URLs in your WordPress media library reflect the FQDN of your bucket and not your specific site. That way you could have one or ten WP nodes in your Beanstalk and media/images are independent of any one of those servers.
(2) You should absolutely be using RDS here. Few things are easier to work with and as stress-free as a Multi-AZ, reserved MySQL RDS instance. Either that or your own EC2 running MySQL that is independent of the Beanstalk, but why run that when RDS is so much easier?
(3) Yes you definitely have to commit changes to your Git repository or local file first (new plugins, changes to themes, WP upgrades) and then upload/install as a revision to the Beanstalk code. Otherwise, all the changes you make via the web interface to one node will never be in the new load for a new node -- in fact you'll have an upgraded database but an older set of code in the Beanstalk application, so it's likely to create errors of some kind or another.
I took an AWS architecture course, and their advice for EC2 and the Beanstalk is to start to think about server instances as very disposable -- so you should try to think about easy ways for your boxes to provision themselves in the bootstrapping process and to take over work for one another without any precious resources on just one box. So losing an instance should never be a big deal. (This is definitely not how we thought in the world of physical servers, where we got everything tweaked 'just so'.)
Good luck!
Well, I'm no expert, but since no one has answered, I'll give it my best shot.
You are absolutely right--kind of. While each EC2 instance does have some local storage, it is destroyed and reset with each new instance. Because of this, Amazon has things like Elastic Block Storage and S3 for persistent files. I don't know how one would configure WP to utilize this, but that will likely be the solution.
I think this problem is solved by my answer to #1. As for the database, all of your EC2 instances should be pulling from the same RDS location. Again, while you could have MySQL running on each EC2 instance, in the interest of persistence, having a separate database makes more sense.
You, again, have most everything right. Local development should always precede live deployment. Upgrading locally then pushing to the live servers will make sure all of your instances remain identical.
Truth-be-told, I am still in the process of learning all of this too, as I said, I'm not an expert. Hopefully someone else will come along and give a more informed answer. However, the key conceptual hurdle here is the idea of elastic scalability--and the salient point of this idea is the separation of elements between what is elastic/scalable/disposable and what is persistent.
Hopefully that helps.
I have deployed a small Wordpress site on EB, S3 and RDS. S3 holds all static data, such as media uploads. This works through a plugin. RDS holds the database. EB holds the latest deployed application. The application is deployed from my dev environment, with a build script. This way, I just have to press one button and I redeploy.
I wrote an article about it here: http://www.cortexcode.com/wordpress-to-aws-code-example/
While it was at first annoying to work with, the speed of AWS is nice and now it's easier than ever. It used to be that I had to upload a bunch of files over FTP, this is way more efficient. :-)
As an addition to all the great answers already:
1) I can highly recommend EFS but also S3 for media files, so they are served from high availability regions in combination with cloudfront. For Wordpress there is one plugin that really speeds up this ( not affiliated to them, just really like the plugin ). There is also an assets plugin, if you'd like to serve JS, CSS files from S3. For the EFS solution, take a look at the AWSlabs docs on git, and specifically this file on how they mount the uploads file.
In general, EBS is really great for Wordpress, but you'll need to think in a different mindset as compared to other hosting solutions ( shared hosting, managed hosting ).
OK I researched a lot on this particular issue, and this is what I learned--
(1) If a wordpress user uploads some files, then his files will be uploaded only to the virtual machine that is actually serving his request at that time. Eg if currently the wordpress site is cloud-deployed and is using 5 virtual machines, now when user makes request he is directed to one virtual machine-- the one with the lowest load at that point... His uploads are stored only on that server. Current Platform-as-a-service solutions (like Amazon Elastic Beanstalk and App Fog) do not have the ability to propagate the changes to all the running instances. Either that (propagate changes to all servers) or use a common storage by all running instances-- these are the only 2 solutions to this problem. (Eg of common storage would be all 5 running virtual machines using Network-Attached-Storage (NAS)... )
(2) With ref to platforms available currently like Amazon Elastic Beanstalk and App Fog, for example, even if user made changes directly to running app- these platforms rely on the local version of code (which the admin deployed initially to cloud)- and there is no way to update the local version of code (on admin's PC) with the changes made by a user to running app-- hence these changes viz, files are lost-- Similarly, changes in database by user to running app are also lost-- unless the admin is using exactly the same database for his local app (that he deployed to cloud)
(3) Any changes to running apps first have to be made to the local app on admin's PC and then pushed to cloud.
I am working on a Cloud PaaS that addresses all these concerns-- viz updates can be made to running apps, code changes made to running app are also updated in code repository accessible by user...The Proof of concept is ready, hopefully it will be as good as I hope it should be :) -- currently the only thing that is actually there is the website (anyacloudpanel.com) -- design work is going on :)
If there is some rule that I should not mention my website( Anya Cloud Panel) -- then I am sorry -- pls feel free to edit and remove my website URL from my answer :)
Thanks,
Arvind.
Deploying WordPress to AWS Elastic Beanstalk does require some change to the normal WordPress deployment as mentioned here a few times. To answer your questions, here is a great tutorial explaining stateless applications and how to deploy to Elastic Beanstalk:
Deploying WordPress to Amazon Web Services AWS EC2 and RDS via ElasticBeanstalk
Be careful if you use a theme from themeforest for example. Some of them are incompatible with wordpress S3 plugin. Then you're screwed, you can not deploy your wordpress on the cloud.
Windows 2008 Server R2 64bit, ColdFusion8 Enterprise Edition (multi-server configuration), Plesk
Recently purchased dedicated hosting on Hostgator and set up a website with help from a server guy. I'm doing a second site on my own this time. I've successfully created the new site in plesk, pointed the domain etc, but now need to set up a new instance of ColdFusion for this new site and I'm not sure how to go about it. From my googling, I'm guessing it's simply a case of setting up a new "instance", which can be done via the coldfusion administrator. Is this correct? Is there anything else I need to know? Any gotchas waiting to bite me?
Thanks in advance for any help.
Well you don't need to set up a new CF instance for a new website: there's not a one-to-one relationship between the two ideas.
The minimum you really need to do is to set up the new website, in a directory within the CF application root, or within a CF-mapped directory if the dir is outside that root, and then run the web server connector (wsconfig.exe) to configure the website to pass requests for CF files to CF.
On a standard install, wsconfig.exe is located in the [coldfusion]/runtine/bin dir, and on a multiserver install it's in [JRun]/bin.
If you do add a new instance, you still need to run wsconfig to connect the website to the CF instance.
user460114, new instance == new "server", so when first instance crashes for some reason, second will still run because it uses separate heap space and lives it's own life.
You could use this for some other purpose like failover instance, or cluster, or staging instance. It's not needed in your case.
You need to need to make new directory in webroot, here's example:
C:\inetpub\www\old_site
C:\inetpub\www\new_site
And set new_domain.com to point to ..\new_site, and leave old_site.com point to ..\old_site.
Cheers
I'm having a django project that should be deployed on Amazon's EC2. There are various tutorials on installing django on EC2, but I think it'll always be a time consuming step to generate a new AMI image with your whole application... So I was thinking that it should also be possible to deploy it on the persistent storage, EBS?
But I'm wondering if that would have any disadvantages because there are no tutorials describing that out there... So if anybody is having some ideas on that or having any other tutorials on how to deploy new versions in an easy fast way to EC2 please let me know!
I used Bitnami Djangostack 1.2.3 (I'm not associated with bitnami in any way).
http://bitnami.org/stack/djangostack
The EC2 image is "ami-18fb0f71", described as "bitnami-djangostack-1.2.3-0-linux-ubuntu-10.04-ebs".
This is an EBS backed instance, but I can't comment on advantages/disadvantages of this.
I found some of the pertinent configuration files in these locations:
/opt/bitnami/apache2/conf/httpd.conf
/opt/bitnami/apps/django/conf/django.conf
The file served by default (as configured in httpd.conf) is '/opt/bitnami/apache2/htdocs/index.html'.
You can get a bit of support here:
http://bitnami.org/forums/forums/djangostack
I think it should be fine. At the least, you can experiment: get an EBS-backed instance, install django, stop the instance (not terminate!) and snapshot the volume (for backup).
Restart the instance, and see.