Using EEM (w/Python, Tcl, etc.) to Call an External API (REST)

[rcarrara]

Hello,

I'm not sure if this is possible but wanted to ask the question before asking specifics. Here's what I'm trying to do:

Have EEM w/IP SLA monitor an existing network connection. In the event the remote side becomes unreachable I need to run a script (or something) that will make external REST API calls to an external device. The REST API calls will tell the external device to dynamically create a second circuit (it cannot be up and running concurrently with the first). Then I want to move traffic over to the new connection. The secondary interface on the router/switch will be preconfigured on the Cisco router/switch. The actual layer 2 circuit providing transport (on an external device) is what needs to be created dynamically.

Is this possible? I know the EEM portion will work, what I don't know is if it's possible to make external calls via REST to an external device. (Via Python, EEM Applet, EEM Script, Tcl or something else.) Note, the external device is a provider switch and not Cisco but supports REST for circuit creation.

Any information is greatly appreciated.

Regards,

[Carlos T]

Hi,

Have you found the solution? I need to run something similar on IOS and IOS XE nodes to make rest api calls to other vendor devices, triggered by EEM events.

[jawicks]

Hi Carlos, yes you should be able to do this as part of your PnP Python script using the urllib module and at the end of your script once a routable IP-address and other identification has been provisioned which initiates a post-operation toward your automation engine depending upon which object your tool is listening to………………..for regular IOS devices we don’t have a GuestShell to be able to run the Python scripting (which is part of the reason that the IOS-XE devices are more expensive, as they have additional CPU/Memory to be able to operate Linux GuestShell, etc).

[guestshell@guestshell /]$ ls -l /usr/lib64/python3.6/urllib

total 154

-rw-r--r--. 1 root root      0 Nov 21  2019 __init__.py

drwxr-xr-x. 2 root root   1024 Sep 23 12:31 __pycache__

-rw-r--r--. 1 root root   2641 Dec 23  2018 error.py

-rw-r--r--. 1 root root  38327 Nov 21  2019 parse.py

-rw-r--r--. 1 root root 100028 Nov 21  2019 request.py

-rw-r--r--. 1 root root   2299 Dec 23  2018 response.py

-rw-r--r--. 1 root root   8832 Dec 23  2018 robotparser.py

ISR4431#guestshell run python3

Python 3.6.8 (default, Nov 21 2019, 19:31:34)

[GCC 8.3.1 20190507 (Red Hat 8.3.1-4)] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> import cli

>>> import urllib                                            ß import all the requests module

>>> from urllib import request                   ß or import just the request module

>>> 

>>> help(request)

Help on module urllib.request in urllib:

NAME

    urllib.request - An extensible library for opening URLs using a variety of protocols

DESCRIPTION

    The simplest way to use this module is to call the urlopen function,  which accepts a string containing a URL or a Request object (described below).  It opens the URL and returns the results as file-like object; the returned object has some extra methods described below.

    The OpenerDirector manages a collection of Handler objects that do all the actual work.  Each Handler implements a particular protocol or option.  The OpenerDirector is a composite object that invokes the Handlers needed to open the requested URL.  For example, the HTTPHandler performs HTTP GET and POST requests and deals with  non-error returns.  The HTTPRedirectHandler automatically deals with HTTP 301, 302, 303 and 307 redirect errors, and the HTTPDigestAuthHandler deals with digest authentication.

    urlopen(url, data=None) -- Basic usage is the same as original urllib.  pass the url and optionally data to post to an HTTP URL, and get a file-like object back.  One difference is that you can also pass a Request instance instead of URL.  Raises a URLError (subclass of OSError); for HTTP errors, raises an HTTPError, which can also be treated as a valid response.

snip.............

Rgds, Jim.W.