Introduction

Currently CloudStack accepts only URL's to register a template/volume. If the user has a downloaded template/volume available, user has to host it either on dropbox etc. or run web server so as to get downloadable url. It is desirable to be able upload a volume or template directly through standard we browser.

This feature enables the users to directly upload the template/volume to CloudStack and eliminates the dependency on an external http server. This will be a complementary functionality and users can continue to register template/volume with URL as well.

use cases

  1. A user, who wants to upload a template from the browser and launch a vm with it on CloudStack
  2. A user, who want to upload a volume from the browser and attach it to a vm on CloudStack

Functional Requirements

This section will explain key requirement this feature shall address.

Assumptions & Out-of-Scope

  1. No unencrypted or http version of this will not be available

  2. Upload progress to the user (http://creativejs.com/tutorials/advanced-uploading-techniques-part-1/ )
  3. split upload and join in apache so as to not hit browser timeouts

  4. post url should be active only for one time call - return proper error message on subsequent calls - how do we determine if its already used?

  5. Admin to list all the uploads happening and cancel any if required

  6. Multiple files for the same template/volume will not be supported for now

Design

This section will explain how the feature shall be implemented in CloudStack

process flow

The browser-based uploading process will have four main steps:

  1. Management Server generates a unique pre-shared key (PSK) and shares it with the SSVM agent. 
  2. New API request "getUploadParams" encoded the usual CloudStack API way using api keys. Request parameters include format, hypervisor, md5 sum etc.
  3. Management Server response to (b) returns post url to upload the file, params to send to the url while uploading the file and a SHA1 signature generated using PSK and params json.  
  4. User should upload the file over https POST request to the url obtained in (c). The signature and params returned in (c) should be passed as is.
  5. The Apache web server on the SSVM matches the url, decrypts and passes on to the SSVM java agent as plain HTTP. The SSVM agent checks the signature against the params using the key PSK and SHA1. Once the params are verified, it writes to the NFS storage to the location encoded in the URL. 
  6. Once the upload completes, the MD5 checksum is compared (if available from step c). 

To increase the number of parallel uploads, multiple SSVMs needs to be created. This will be handled automatically by the management server using the system.vm.auto.reserve.capacity, secstorage.capacity.standby and secstorage.session.max configuration variables.

pre-shared key management

This section shall cover when and how the pre-shared key is generated by management server, how is it stored, how is it passed to SSVM

  1. key is saved in encrypted form in the configuration tables as hidden configuration with name upload.secret.key
  2. on start of management server, if the key doesnt exist, it generates one using sha1 and stores it in db
  3. when the management server sends StartCommand to SSVM agent, it shares this key with it. 
  4. SSVM agent stores this key in a file at /etc/cloudstack/agent/ms-psk.

API changes

A new API getUploadParams which takes all the params as the registertemplate/uploadvolume except for URL and  which returns all the required params plus a post URL to be used to uploadVolume/registerTemplate

POST url to post the data on to SSVM. This post url is returned from the getUploadParams api call Ex: https://ssvmpublicip/upload/key 

At any point, the api user should be able to call the listtemplates/listvolumes api to get the installation status of the template.

If the template failed to upload(401 or 500 above), the user should request for a new upload url and upload it again. He shouldn't be reusing the same upload URL again.

Example

management server api: 

request:

http://managementip:8080/client?command=getUploadParams&type=template&response=json&sessionkey=OXgYX%2BINFOOcxQgI2yzEzuA3xCg%3D&name=lxc1&displayText=lxc1&zoneid=-1&format=TAR&isextractable=false&passwordEnabled=false&isdynamicallyscalable=false&osTypeId=1b510c30-3352-11e4-aaca-a5c7f57670d0&hypervisor=LXC&requireshvm=false&_=1410847402478 

response:

{
"postURL":"https://ssvmpublicip/upload/uuid",
payload:{"store":{"com.cloud.agent.api.to.NfsTO":"nfs://10.147.28.7/export/home/rajani/lxc/secondary"}, "hvm":false,"description":"lxc1","maxDownloadSizeInBytes":53687091200,"id":207,"resourceType":"TEMPLATE","installPath":"template/tmpl/2/207", "format":"TAR","accountId":2,"name":"207-2-09c78adc-065f-3dc8-9621-9e7a036d7dc9"},
signature:de7c9b85b8b78aa6bc8a7a36f70a90701c9db4d9
}

file upload:

request:

curl -X POST "https://ssvmpublicip/upload/uuid" -F "template=@templatelocation.tar" -F "signature=de7c9b85b8b78aa6bc8a7a36f70a90701c9db4d9" -F "payload={'store':{'com.cloud.agent.api.to.NfsTO':'nfs://10.147.28.7/export/home/rajani/lxc/secondary'}, 'hvm':false,'description':'lxc1','maxDownloadSizeInBytes':53687091200,'id':207,'resourceType':'TEMPLATE','installPath':'template/tmpl/2/207', 'format':'TAR','accountId':2,'name':'207-2-09c78adc-065f-3dc8-9621-9e7a036d7dc9'}" -v

response:

200 OK

DB Changes

No db changes.

Sequence Diagram

Agent Commands

  1. DownloadProgressCommand will be used the check the download progress (from Management server to Agent)
  2. DownloadCommand will be used to start the download(SSVM Apache to SSVM Agent)

fault scenarios & cleanup

This section shall describe how the management server shall detect a failed volume/template upload.

management server and SSVM agent interaction

When the management server receives getUploadParams api call, it selects SSVM and secondary store in the zone requested by the user and returns a POST url to that SSVM. There can be multiple SSVMs in the same zone. Management servers decides which SSVM to handle this based on the load. SSVM agent will be able to return the status of the upload at any point using the in memory hash map if the download is in progress or by the file status on the secondary storage. If the template/volume is selected to be cross-zone, it will uploaded to one zone and then copied to other zones from it. 

management server owns the state machine of the volume/template. It polls the SSVM agent(using DownloadProgressCommand of the agent) to get the status and updates it. Failure at any point during the form upload to ssvm apache would return error to the user and UPLOAD_ERROR when the management server pings for download status.

Polling starts after the successful return of the getUploadParams. The polling starts after an initial delay of 100ms and in intervals of 1000ms. The management server polls 5 times before it changes the state to ERROR. (we may need to add new configurations to handle this polling)

If the management server itself goes down during the upload, if the timeout hasnt crossed, it will poll for the status once its up. Otherwise the state of the template will be transitioned to ERROR. In a load balanced situation where the management server handling the ssvm upload goes down, the status wont be updated unless the SSVM is connected to a new management server.

status update

detecting failures

The below failures can happen while the agent is receiving the template. When management server asks for the status of the tempalte/volume, if any of these below errors happen, the agent returns ERROR state and management server updates the state accordingly.

successful completion

If the template install is successful within the polling timeout, when the management server asks for the status of it, agent returns a success state and it is updated by the management server accordingly.

State machine 

Template/Volume go through below state machine state transitions, when it goes through the browser based upload.

States:

NOT_UPLOADED: getUploadParams API was successful and the template is registered. But, upload hasnt started yet

UPLOAD_IN_PROGRESS: User has initiated the POST request SSVM Apache and the validation/download is in progress

UPLOADED: SSVM Agent successfully Downloaded the template to secondary storage

UPLOAD_ERROR: Any Failure in between user initiating a post request and template being downloaded

ABANDONED: the post request isnt called in the stipulated time (check sequence diagram point 4)

State Transitions:

All these errors will result in the same state for the template/volume as there isnt any way to recover from them or the handling isnt different for these. Additional error information will be provided in the form of a message for respective errors. 

Cleanup

Of the error categories defined in the failures above,

recovery mechanisms

There isnt any recovery or retry mechanism as this is a POST request. Once errored, template/volume will remain in the error state and admin will be able to troubleshoot it based on the appropriate log messages in management server log, agent log, apache access/error log files.

Security

SSVM public ip will be given to the end user in the response to getUploadParams. This is required as it is the location to which the template/volume has to be uploaded.

The NFS Store url, path and some other information are exposed to the end user in the response to getUploadParams. This is done so that agent gets all the information required to download the template with the POST request.

UI Changes

A new register template and upload volume UI which should be able to accept "browse and upload" file. 

UI flow:

  1. Browser UI requests the upload form by doing the getUploadParams api call. 
  2. Management Server returns a upload url, params json string which should be passed on to the upload url while doing the upload
  3. UI shows an upload dialog with a way to browse and upload file.
  4. User chooses a file and posts on the url.
  5. The post request completes once the template is downloaded/errored. 
  6. The user can close the dialog(Post request should still be active) and use list page to check the status of it.

Open Issues

  1. SSL CA certificates - what kind of certificates will be used?

Bug Reference & Branch

CLOUDSTACK-....

template-upload branch off master