Automating SlipStream

Although the SlipStream web interface provides a great interface for humans, there are cases where programmatic access is more appropriate. These cases include the need for bulk operations, programmatic control for continuous integration systems, and in a few cases access to features that don’t yet appear in the web interface.

In this chapter, you’ll learn about programmatic access to SlipStream through the command line client and through the REST API. The text and exercises will concentrate on the management of components and applications.

The REST API is documented on the http://ssapi.sixsq.com website. It provides the full list of SlipStream resources. Although we strive for complete documentation, there may be some holes in the API docs. If you run into trouble, please contact support and we’ll give you a hand.

Setup

Command Line Client

The SlipStream client is installed by default on all machines started through SlipStream. To install it on your local machine, it can be installed with pip, the python installer.

You will need to have python (v2.6+, not v3.x) installed on the machine as well as pip. See the Python and pip websites for installation of these tools on your machine.

Once python and pip are available, just running the following should work:

$ pip install slipstream-client

for a system-level installation. If you don’t have administrator access to your machine, you can also perform a user-level installation:

$ pip install --user slipstream-client

In this case, be sure to modify your PYTHONPATH and PATH to include the directories used by the pip user-level installation.

cURL

The REST API uses the standard HTTP protocol, so any HTTP library can be used to access the API. A ubiquitous tool for quick HTTP requests is cURL. This is available natively on most operating systems.

If it is not available and you want to use it, see the cURL website.

If you’re going to use the cURL command line extensively, you will probably want to define the following alias:

$ alias ss-curl="curl --cookie-jar ~/cookies -b ~/cookies -sS"

This avoids having to repeat the options that you’ll need for every command. The following text, will assume that this alias has been defined.

Advanced REST Client

The Advanced REST Client (ARC) extension to the Chrome web browser allows a more graphical method of sending HTTP requests and visualizing the responses. To be able to reuse authentication cookies with ARC, you will have to install ARC cookie exchange Chrome extention as well.

Consult the referenced web sites for installation of Chrome and the REST client along with its cookie exchange on your machine.

Authentication

Just like with the web interface, you must be authenticated to use most of the SlipStream features through the command line or the REST API. At the moment, SlipStream supports both basic authentication and cookie-based authentication.

Command Line Client

The command line client uses primarily basic authentication. When using the client, you must supply your SlipStream username and password either via environmental variables or via command line options.

The environmental variables to set are:

$ export SLIPSTREAM_USERNAME=ssuser
$ export SLIPSTREAM_PASSWORD=sspass

substituting the ssuser and sspass values with your own username and password. You can also set these values explicitly on the command line with the -u or --username options for the username and with the -p or --password options for the password.

You can quickly test the authentication by listing your user account information:

$ ss-user-get ssuser

again changing ssuser to your username. This should return an XML representation of your user account.

cURL

It is strongly recommended to use cookie-based authentication when using the REST API; the basic authentication method will be removed at some point in the near future.

To obtain a valid authentication cookie, you must login to SlipStream, much like you’d do with the web interface. To do this, execute a POST request to the login resource with a form that includes the username and password parameters.

Doing this with cURL (and the alias defined above!):

$ ss-curl https://nuv.la/auth/login \
    -D - \
    -o /dev/null \
    -XPOST \
    -d "username=ssuser" \
    -d "password=sspass"

This should return only the headers from the response, which should include a “Set-Cookie” header with a value and a redirect response code. The cookie should also end up in the ~/cookies file.

Advanced REST Client

Doing this with the Advanced REST Client in Chrome, you can fill in the form for the login request, which should look like the following screenshot.

REST Login Request

and which should return something like the following screenshot.

REST Login Response

As for cURL, the “Set-Cookie” header should have a value. To automatically reuse the cookie for the next requests in the Advanced REST Client, you need to have the ARC cookie exchange extension installed and enabled in Chrome and also enabled in ARC: in the right corner the Use XHR should be turned on.

Note

If you want to logout by destroying your access cookie, then you can either delete the cookie manually or send a HTTP DELETE request to the logout resource http://nuv.la./logout.

Managing an Application

Command Line Client

To deploy an application or a component via the command line client use the ss-execute command. To deploy the web server and client application defined earlier:

$ ss-execute --parameters="server:title=Great Title" \
             --kill-vms-on-error \
             Training-2015-11/nginx-test-app

This will return the URL of the created run.

This is essentially a “shoot and forget” feature intended for deploying test applications. There are no comparable commands for finding the application’s status or terminating it. Those actions either need to be done through the web interface or REST API.

cURL

The REST API allows complete control over the application lifecycle.

To start an application with cURL, you must use the following command:

$ ss-curl https://nuv.la/run \
  -X POST \
  -d refqname=Training-2015-11/nginx-test-app \
  -d keep-running=always \
  -d parameter--node--server--title='Great Title' \
  -H 'Accept: application/xml' \
  -D - \
  -o response-body.txt

This will send a POST request to the “run” resource to start an application. The “Location” header will contain the run identifier if the command completes successfully.

The command shows how parameter values are encoded for the REST API. You can also specify other parameters such as the “keep-running” value. The “refqname” is required as it identifies the application to run.

You can see the full state of the run by performing a GET request on the given run URL:

$ ss-curl https://nuv.la/run/815a8f66-fc9d-4444-849c-d12e883982c1

All of the responses related to the applications and runs are in XML. Newer resources such as events and usage are in JSON. All of the resources will eventually be migrating toward JSON in the future.

You can then terminate the run by sending a DELETE request to the given run URL:

$ ss-curl -X DELETE \
  https://nuv.la/run/815a8f66-fc9d-4444-849c-d12e883982c1

This will immediately terminate the application, so be careful when using DELETE requests.

Advanced REST Client

You can perform the same lifecycle with the Advanced REST Client. Start with deploying the application.

Start Application with REST

If successful, it will return a 201 response with the run identifier in the “Location” header.

Start Application with REST

Performing a GET on the returned URL will give you the status.

Application Status Request Application Status Response

And finally the application can be terminated with a DELETE request.

Application Termination Request

A successful termination will return a “No Content 204” response.

Application Termination Response

EXERCISES

  1. Start your web test application with the ss-execute command.
  2. Perform a full lifecycle of your web test application with the REST API.
  3. Perform a full lifecycle of your web component with the REST API.