About

OpenFaaS Python function example for the VMware Event Router.

Usage

Requirements

These steps require a running environment with:

• OpenFaaS
• vSphere (vCenter)
• VMware Event Router

Note: Alternatively, the vCenter Event Broker Appliance can be used to ease the deployment.

Deployment

• Add the OpenFaaS gateway: <URL or IP> information under provider or export it as an environment variable used by faas-cli (export OPENFAAS_URL=http://...)
  • The faas-cli documentation can be found here
• vCenter credentials and information about the tag ID and operation to be performed is stored in vcconfig.toml
  • This is for security reasons to not expose sensitive data
  • If you follow the steps below how to pass this information as a secret into OpenFaaS you only need to change the pre-defined key/value pairs in vcconfig.toml
  • Please see below how to retrieve the TAG URN parameter
• A key-value annotation under topic defines which VM event should trigger the function
  • A list of VM events from vCenter can be found here
  • Multiple topics can be specified using a "," delimiter, e.g. "topic: "VmPoweredOnEvent,VmPoweredOffEvent""

Note: OpenFaaS provides some useful debugging configured via environment variables write_debug and read_debug.

Here's an example for stack.yml:

provider:
  name: openfaas
  gateway: http://127.0.0.1:8080
functions:
  pytag-fn:
    lang: python3
    handler: ./pytag-fn
    image: embano1/pytag-fn:0.3
    environment:
      write_debug: true
      read_debug: true
    secrets:
      - vcconfig
    annotations:
      topic: VmPoweredOnEvent

Now create pass the vCenter and TAG information defined in vcconfig.toml into OpenFaaS as a secret:

# depending on your OpenFaaS requirement you might need to log into OpenFaaS before this step
$ faas-cli secret create vcconfig --from-file=vcconfig.toml

Next deploy the function:

$ faas deploy -f stack.yml
Deployed. 202 Accepted.

How to retrieve the TAG_URN

The TAG_URN can be retrieved from the ID field in the object, e.g. with govc:

$ govc tags.info <tag>            # example uses "vmon" as the tag name
Name:           vmon
  ID:           urn:vmomi:InventoryServiceTag:4c57977e-27fa-4392-b344-0a90a502f524:GLOBAL
  Description:  VM powered on
  CategoryID:   urn:vmomi:InventoryServiceCategory:ee941e4d-56ce-4ebf-86ab-0f615828d585:GLOBAL
  UsedBy: []

Link to govc: https://github.com/vmware/govmomi/tree/master/govc

Invoke the Function

If the event topic is VmPoweredOnEvent the function can be triggered via the vCenter Client UI or using govc:

# be careful as this wildcard will power on all VMs in your environment
$ govc vm.power -on '*'

Development/Contributions (Python >=3.4)

After you've cloned the code you can easily create a virtual Python environment to make changes/contribute:

$ cd <cloned_directory>
$ python -m venv .
$ source bin/activate
$ pip install -r pytag-fn/requirements.txt
<make changes>

If you add new dependencies pipreqs is a useful tool to only reflect used packages in requirements.txt:

$ pipreqs --savepath ./pytag-fn/requirements.txt pytag-fn/

Read more about it here.