autocommit.py

def autocommit(fn):
    def wrapper(*args, **kwargs):
        self = args[0]
        cmd = fn(*args, **kwargs)
        if isinstance(self, Transaction):
            self.commands.append(cmd)
            return cmd
        else:
            return cmd.execute()
    return wrapper


class Command(object):
    def __init__(self, cmd, name):
        self.cmd = cmd
        self.name = name

    def execute(self):
        return (self.cmd, self.name)


class API(object):
    def __init__(self, context):
        self.context = context

    @autocommit
    def br_exists(self, name):
        return Command('br_exists', name)

    @autocommit
    def db_list(self, name):
        return Command('db_list', name)


class Transaction(API):
    def __init__(self):
        self.commands = []
        self.results = []

    def commit(self):
        for cmd in self.commands:
            cmd.result = cmd.execute()
            self.results.append(cmd.result)
        return self.results

    def __enter__(self):
        return self

    def __exit__(self, *args, **kwargs):
        return self.commit()

    def __str__(self):
        return "Transaction results: %s" % self.results


API.transaction = Transaction


class BaseOVS(object):
    def __init__(self):
        self.ovsdb = API(self)

    def bridge_exists(self, name):
        # Look ma, no execute!
        return self.ovsdb.br_exists(name)

    def db_list(self, name):
        # Look ma, no execute!
        return self.ovsdb.db_list(name)

    def multi_cmd(self, name1, name2):
        with self.ovsdb.transaction() as txn:
            # instead of:
            # a = txn.add(self.ovsdb.br_exists('mybridge'))
            # b = txn.add(self.ovsdb.db_list('mydblist'))
            a = txn.br_exists(name1)
            b = txn.db_list(name2)
        print "a returned:", a.result
        print "b returned:", b.result
        return txn.results

if __name__ == '__main__':
    ovs = BaseOVS()

    a = ovs.bridge_exists('mybridge')
    b = ovs.db_list("mydblist")
    c = ovs.multi_cmd("mybridge", "mydblist")

    print [a, b]
    print c