As mentioned here, one of the differences that caught my eye is "Web server instances share content and configuration, which means you don't have to redeploy or reconfigure as you scale." which is marked NOT possible for cloud services.
If cloud service is set to autoscale/has more instances (scale-out), won't they share the same content (code base I'm assuming) and configuration (.csdef/.cscfg) settings?
Azure Cloud Services (web/worker role instances) share code when code is deployed (based on what's in the .cspkg along with any content downloaded+installed as instructed in your startup script). Each instance is a fresh VM image, overlaid with your software bits. The same software bits are placed on each scaled instance. They have no shared data space, unless they are attached to something like Azure File Storage (an SMB share atop Azure Storage). Any local disk is per-instance (and non-durable). Any attached drives are per-instance (and durable, backed by Azure Storage).
Azure Web App instances have a shared-disk (durable) between all instances of your web app. This is how, for example, you can run something like Ghost, where the Sqlite database is shared amongst instances. The size of this shared disk area changes based on the App Service Plan tier chosen. Alternatively, Web Apps may access Azure File Storage. Similar to web/worker role instances, every instance of a Web App gets the same code bits deployed.
Related
SUMMARY: Can I use an Azure Storage Plan as additional storage that is available to an Azure Web App?
DETAILS: We have a very simple Web App using a low amount of CPU and large amount of storage (all it does is list and allow you to download files). I need at least 50GB of storage for video and audio files for this app and to get that amount of storage on a plan pushes me up to unreasonable CPU and other resources that I don't need with the consequences of a much higher price.
My plan (hope) is that I could create a Web App and remap the root directory of the Web App to a Storage Plan that is 50GB. Two challenges that I have spent the last day researching but at this point, I have not been able to find an answer.
I have created the Web App. I see that /wwwroot is on the D: drive of the Web App. I also created a storage plan and have created a sharable area of 50GB on the storage plan.
So... Can anyone give me some insight into the following:
How do I tell the Web App to use the 50GB of storage which is now available to it?
How can I map a drive letter to the area in the storage plan?
How do I tell the Web App that it should use the 50GB area on the storage plan as the root drive instead of using D:/Webroot
Many Thanks!
Refer this feedback link on a similar request: https://feedback.azure.com/forums/169385-web-apps/suggestions/13536996-the-ability-to-store-iis-logs-in-azure-file-storag - it has been denied.
By default, on Azure WebApps, all files are stored in the file system with the application, including the media files. You may wish to know about the main types of files (https://github.com/projectkudu/kudu/wiki/Azure-runtime-environment) that are dealt on Azure WebApp (Persisted files, Temporary files and Machine level read-only files)
Refer to the article (https://github.com/projectkudu/kudu/wiki/File-structure-on-azure) File structure on azure to know the sets of files & dirs on Azure WebApp, and check the directories which include the possible increasing files, such as LogFiles, site/repository, site/deployments(for deployment slots) and your directory for uploading files.
To verify you can go to your scm site's debug console
(https://{sitename}.scm.azurewebsites.net/DebugConsole) and query for the free space on d:\local. The “Disk Space” depends on the App Service plan you're using. It's 1 GB for Free, 10 GB for Basic, 50 GB for Standard and 250 GB for Premium, refer the document for more details on these limits: https://azure.microsoft.com/en-us/pricing/details/app-service/.
If your requirement fits you may use ASE - Azure App Service Environment is an Azure App Service feature that provides a fully isolated and dedicated environment for securely running App Service apps at high scale.
https://learn.microsoft.com/en-us/azure/app-service/environment/app-service-web-how-to-create-a-web-app-in-an-ase
According to Microsoft Azure Support:
"... since the Product Group confirmed that it is not possible to mount
additional storage to the web app, you can integrate Azure storage
with the Azure SDK or rest API. But you can't mount the drive and use
it as storage.
Another option that you have would be to replicate the scenario on a
Virtual Machine where you can choose its capabilities (Number of
cores, RAM, and Storage Memory)."
So there you have it. It appears that WebApps are pretty fixed configurations which means that when you scale up a Web App, you get more CPU resources AND more Disk storage. It's a packaged deal most likely designed for ease of deployment. Nothing, it appears, you can do about that.
The best alternative, it seems, is to spin up a VM with your chosen OS and then add additional disk storage as needed. It's a "do-it-yourself" approach but the best solution that seems to be available.
I'm developing an app in in Azure Web Apps (formerly Websites) and want to be sure I understand how the local disk is used in a multiple instance scenario. When I scale to multiple instances, do they share a single virtual disk with all of the app files?
Consider this example:
An app running on 5 instances
A page in the app that uploads a file to the local disk, say to Server.MapPath("~/Content") (I know Storage would be better, but just for concept)
Will all 5 instances have access to this file, or will it only exist on the instance where it was uploaded?
Yes, all your instances will be sharing the same persistent state, which includes everything under d:\home (your site bits are in d:\home\site\wwwroot).
There is also temp space under d:\local which is not shared, but this won't hurt your scenario.
See this for more detail on this topic.
I am trying to a deploy an app which has a frontend app and a backend worker. The worker runs a CPU intensive process. Now my requirements are to run the web app in a Azure A0 instance while the CPU intensive process runs in a D2 instance. Now both the instance must be able to share the files. I have read at places where they spoke of SBS.
I tried creating the linux VMs in same cloud services but couldnt figure out how to ssh into them separately since they use the same cloud service url. i followed this http://azure.microsoft.com/en-us/documentation/articles/cloud-services-connect-virtual-machine/
to create the 2nd vm.
Can anyone suggest me as how to achieve this setup? Also if possible how do i check if the disks are available to both the instances?
Azure docs aren't as helpful as aws. :(
If the two VMs just want to share files and you don't want to go to the extra effort of coding for blob storage then consider Azure Files which exposes an SMB share against a blob storage back end. This allows you to do standard file IO operations instead of custom blob storage code. See http://blogs.msdn.com/b/windowsazurestorage/archive/2014/05/12/introducing-microsoft-azure-file-service.aspx which shows how to create the file share in Windows and Linux VMs.
[Probably easier to give an answer here]
BlobStorage is a universal storage container that can effectively act as the common drive you are looking for. Access to the blob storage container is made over HTTP / HTTPS either through a BlobStorage Client or over REST, where you will have functions to upload, download, list objects, etc.
For Python, you'll hopefully find this article sufficient although I've no experience with Python on Azure to comment, or if choosing REST and http requests - that should work fine.
HTH
My understanding of the VMs involved in Azure Cloud Services is that at least some parts of it are not meant to persist throughout the lifetime of the service (unlike regular VMs that you can create through Azure).
This is why you must use Startup Tasks in your ServiceDefinition.csdef file in order to configure certain things.
However, after playing around with it for a while, I can't figure out what does and does not persist.
For instance, I installed an ISAPI filter into IIS by logging into remote desktop. That seems to have persisted across deployments and even a reimaging.
Is there a list somewhere of what does and does not persist and when that persistence will end (what triggers the clearing of it)?
See http://blogs.msdn.com/b/kwill/archive/2012/10/05/windows-azure-disk-partition-preservation.aspx for information about what is preserved on an Azure PaaS VM in different scenarios.
In short, the only things that will truly persist are things packaged in your cscfg/cspkg (ie. startup tasks). Anything else done at runtime or via RDP will eventually be removed.
See - How to: Update a cloud service role or deployment - in most cases, an UPDATE to an existing deployment will preserve local data while updating the application code for your cloud service.
Be aware that if you change the size of a role (that is, the size of a virtual machine that hosts a role instance) or the number of roles, each role instance (virtual machine) must be re-imaged, and any local data will be lost.
Also if you use the standard deployment practice of creating a new deployment in the staging slot and then swapping the VIP, you will also lose all local data (these are new VMs).
I have a local storage folder, called TempStore, set up on my Web Role instances.
Is it possible to expose files as a URI from my local storage?
E.g:
http://myapplication.cloudapp.net/TempStore/helloworld.jpg
I understand that I could use blobs for this, but I would prefer to use local storage in this case.
There is. However I really do not understand the reason for doing this? The only reason I see is some misunderstanding or not fully understanding the capabilities of the Windows Azure Platform Services (Storage, Cloud Service / Web Roles).
You have to know that local storage is not synced between role instances. Also if hardware failure happens, a role healing process will instantiate an entirely new VM with fresh image from your cloud service package. This will lead to an absolutely empty local storage resource. Windows Azure Load Balancer (the thing that sits in front of your web and worker roles, more here) uses Round Robin algorithm. Meaning that even if with one request user uploads file to your web role. The next request (that you will probably want to show preview) might go to another instance that has no idea of user uploaded.
If, after knowing all these facts, you still want to "shoot yourself in the foot" here is the solution:
Implement VirtualPathProvider
register it for desired public URL Path
Use the RoleEnvironment.GetLocalResource method in your VPP to obtain the full path to the local storage resource
don't blame anyone else when you realize this was a mistake ;)