python.prov

#! /usr/bin/python

import json
import sys
import os

# Example of a JSON provider written in Python. To turn this into a real
# provider you will need to:
# - change the METADATA
# - change the do_get implementation
# - change the do_set implementation

METADATA="""
---
provider:
  type: example
  invoke: json
  actions: [get,set]
  suitable: {suitable}
  attributes:
    name:
      desc: the resource name
    ensure:
      desc: what state the resource should be in
      type: enum[absent, present]
"""

#
# Provider actions
#
def do_describe():
    # Determine if the provider can work on this system and set
    # suitable accordingly
    suitable=True
    print(METADATA.format(suitable=str(suitable).lower()))

def do_get(inp):
    res = []
    names=inp["names"]

    for name in names:
        ens = "present"
        if name.startswith("a"):
            ens = "absent"
        res.append({ "name": name, "ensure": ens })

    # Add some fake resources that are always there. It's totally fine to
    # report back more than was asked for via names
    fake_names=[ "python1", "python2" ]
    for name in fake_names:
        if name not in names:
            res.append({ "name": name, "ensure": "present" })

    return { "resources": res }

def do_set(inp):
    upds=inp["updates"]
    noop=inp["ral"]["noop"]

    result = { "changes": [] }
    for upd in upds:
        name = upd["name"]
        ensure = upd["should"]["ensure"]
        is_ensure = upd["is"]["ensure"]
        if ensure != is_ensure:
            # This is the point where we would make changes to the system
            # to reflect the change in ensure value.
            change = { "name": name,
                       "ensure": { "was": is_ensure, "is": ensure } }
            result["changes"].append(change)
    return result

# This is all boilerplate that should not require any changes
def parse_stdin():
    inp=json.load(sys.stdin)
    # Checking isn't strictly necessary as libral will make sure that all
    # these things are set up right, but it helps when monkeying around
    # from the command line
    if not isinstance(inp, dict):
        die("input must be a dict")
    return inp

def dump(obj):
    print(json.dumps(obj))

def main():
    if len(sys.argv) < 2:
        progname = os.path.basename(sys.argv[0])
        print("usage: %s ral_action=<action>" % progname)
        sys.exit(1)
    action=sys.argv[1].split("=")[-1]
    if action == "describe":
        do_describe()
    elif action == "get":
        dump(do_get(parse_stdin()))
    elif action == "set":
        dump(do_set(parse_stdin()))
    else:
        print("unsupported action: '%s'" % action)
        sys.exit(1)

if __name__ == '__main__':
    main()